Article pubs.acs.org/jnp Proteasome Inhibitors from Neoboutonia melleri Christophe Long,† Joséphine Beck,† Frédéric Cantagrel,† Laurence Marcourt,† Laure Vendier,‡ Bruno David,† Fabien Plisson,† Fadila Derguini,† Isabelle Vandenberghe,§ Yannick Aussagues,† Frédéric Ausseil,† Catherine Lavaud,⊥ François Sautel,† and Georges Massiot*,† † USR CNRS-Pierre Fabre No. 3388 ETaC, Centre de Recherche et Développement Pierre Fabre, 3 Avenue Hubert Curien, 31035 Toulouse Cedex 01, France ‡ UPR CNRS No. 8241, Laboratoire de Chimie de Coordination, 205 Route de Narbonne, 31077 Toulouse Cedex 04, France § Institut de Recherche Pierre Fabre, Centre de Recherche en Oncologie Experimentale, Centre de Recherche et Développement Pierre Fabre, 3 Avenue Hubert Curien, 31035 Toulouse Cedex 01, France ⊥ UMR CNRS-Université Reims Champagne-Ardenne No. 6229, Institut de Chimie Moléculaire de Reims, Laboratoire de Pharmacognosie, 51097 Reims, France S Supporting Information * ABSTRACT: Thirty new cycloartane derivatives (1−3, 5−12, 14−32) have been isolated from the leaves of Neoboutonia melleri. Their novelty stems from the loss of one of the C-4 methyl groups (1−3, 5−12, 14−25, and 32) and from the presence of an “extra” carbon atom in the side chain (1−3, 5−12, 14−20, 26−29, and 30−32). Furthermore, compound 32 possesses a rare triterpene skeleton with the cyclopropane ring fused onto C-1 and C-10, instead of C-9 and C-10. The structures were determined by spectrometric means, chemical correlations, and X-ray crystallography of derivative 1c. The substitution pattern in ring A, with a cyclopropyl ring conjugated with an α,β-unsaturated carbonyl moiety, confers to the molecule a particular reactivity, giving rise to a formal inversion of the stereochemistry of the cyclopropane ring under UV irradiation. These compounds showed an interesting level of activity on the proteasome pathway, thus motivating their evaluation as possible anticancer agents. The large number of isolated compounds permitted a structure−activity relationship analysis, which showed that the presence of the two enone functions was a requirement for the activity. F or the past decade, proteasome inhibitors have been considered as potentially useful drugs in the treatment of cancer, and this has culminated in the approval of bortezomib for the treatment of multiple myeloma.1 Epoxomycin, lactacystin, and, the most promising, salinosporamide A, presently in phase 1 clinical trials, are examples of natural products that inhibit the proteasome catalytic functions.2 In order to find new inhibitors that do not particularly target proteolysis but the whole ubiquitin−proteasome pathway, we have developed an assay based on a human colon cancer cell line that stably expresses a 4-ubiquitin luciferase reporter protein (4Ub-Luc DLD-1).3 Under normal conditions, the fusion protein (4Ub-Luc) is produced and, due to the ubiquitin tag's presence, it is addressed to and degraded by the proteasome, while inhibitors of the proteasome pathway lead to protein accumulation and luminescence observation.4 The assay was applied to a collection of over 12 000 plant extracts and 62 000 pure compounds including natural products and derivatives. An extract from Neoboutonia melleri (Muell. Arg.) Prain and two pure compounds isolated from it (1 and 2) inhibited the proteasome pathway. The plant was collected in Cameroon, in the late 1980s, following ethnopharmacological observations. Its leaves were locally used to wrap fish, hence, its name © 2011 American Chemical Society and American Society of Pharmacognosy Koutencha, “fish leaves” in the Bamum language. Neoboutonia is an African tropical genus of the Euphorbiaceae, which, according to the latest classifications, represents numerous varieties combined into three species: N. melleri, N. diaguissensis Beille, and N. macrocalyx Pax.5 N. melleri, a small tree (4−8 m) growing in swamp areas from Cameroon/Angola to Sudan/ Mozambique, exhibits alternate, stipulate leaves, broadly ovate or subcircular. It is locally considered as toxic and of interest against diabetes. N. melleri was the subject of a single phytochemical investigation,6 and articles on the genus are rare.7 Here we describe the isolation and structural characterization of 30 new compounds, evaluation of their biological activity on the proteasome pathway, and discussion of their structure− activity relationship. RESULTS AND DISCUSSION The CH2Cl2 extract of N. melleri was dominated by two compounds, which differed by the presence of an acetyl group and ■ Received: May 30, 2011 Published: December 14, 2011 34 dx.doi.org/10.1021/np200441h | J. Nat. Prod. 2012, 75, 34−47 Journal of Natural Products Article Table 1. 13C NMR Data of Compounds 1-8 a carbon 1a 2a 3b 4b 5b 6b 7a 8a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 16a 16b 17 18 19 20 21 22 22a 22b 23 24 24a 25 26 26a 26b 27 28 30 153.7, CH 128.3, CH 202.0, C 46.9, CH 42.5, CH 23.4, CH2 23.5, CH2 44.3, CH 26.0, C 31.9, C 27.4, CH2 32.1, CH2 47.4, C 46.0, C 46.0, CH2 76.0, CH 170.1, C 21.7, CH3 50.3, CH 17.8, CH3 27.0, CH2 32.4, CH 12.8, CH3 77.6, CH 170.6, C 20.7, CH3 198.7, C 149.3, C 123.7, CH2 37.2, CH 66.9, CH2 153.9, CH 128.2, CH 202.1, C 46.9, CH 42.6, CH 23.6, CH2 23.6, CH2 44.7, CH 26.1, C 31.9, C 27.5, CH2 32.1, CH2 47.4, C 45.8, C 46.2, CH2 76.9, CH 170.1, C 21.8, CH3 50.1, CH 18.2, CH3 27.4, CH2 35.9, CH 11.7, CH3 74.8, CH 155.3, CH 128.5, CH 202.3, C 47.5, CH 43.1, CH 23.9, CH2 23.8, CH2 43.6, CH 27.4, C 33.3, C 28.4, CH2 32.8, CH2 44.8, C 52.4, C 41.7, CH2 82.5, CH 33.5, CH 41.5, CH 213.3, C 50.5, CH 47.0, CH 26.5, CH2 26.2, CH2 48.6, CH 25.4, C 30.3, C 27.4, CH2 33.5 CH2 46.7, C 47.9, C 47.8, CH2 77.5, CH 171.3, C 22.1, CH3 51.5,CH 19.5, CH3 28.0, CH2 36.3, CH 12.2, CH3 75.8, CH 205.6, C 149.1, C 126.5, CH2 37.6, CH 66.7, CH2 154.4, CH 127.4, CH 202.5, C 43.8, CH 45.7, CH 65.6, CH 31.9, CH2 40.1, CH 25.3, C 29.6, C 27.1, CH2 32.3, CH2 46.3, C 46.7, C 46.8, CH2 76.2, CH 170.1, C 21.7, CH3 50.5, CH 19.0, CH3 32.6, CH2 32.4, CH 12.7, CH3 77.6, CH 170.6, C 20.7, CH3 198.6, C 149.2, C 123.8, CH2 37.1, CH 66.9, CH2 154.6, CH 127.3, CH 202.7, C 43.8, CH 45.7, CH 65.6, CH 31.9, CH2 40.2, CH 25.4, C 29.7, C 27.2, CH2 32.3, CH2 46.1, C 46.7, C 46.9, CH2 77.1, CH 170.2, C 21.8, CH3 50.4, CH 19.3, CH3 32.7, CH2 35.8, CH 11.5, CH3 74.8, CH 77.8, CH 153.3, C 114.2, CH2 38.3, CH 69.0, CH2 33.5, CH 41.5, CH 213.2, C 50.5, CH 47.0, CH 26.5, CH2 26.2, CH2 48.6, CH 25.4, C 30.3, C 27.4, CH2 33.3, CH2 46.8, C 48.0, C 47.6, CH2 76.9, CH 171.3, C 22.1, CH3 51.4, CH 19.3, CH3 28.0, CH2 33.2, CH 13.2, CH3 78.5, CH 171.7, C 20.9, CH3 199.6, C 150.3, C 124.6, CH2 37.9, CH 66.4, CH2 16.3, CH3 10.8, CH3 19.6, CH3 16.5, CH3 10.8, CH3 19.6, CH3 155.5, CH 128.4, CH 202.4, C 47.6, CH 43.6, CH 24.3, CH2 24.3, CH2 45.2, CH 27.2, C 32.9, C 28.1, CH2 32.9 CH2 46.9, C 48.4, C 46.7, CH2 76.7, CH 171.3, C 22.1, CH3 51.3, CH 18.3, CH3 27.6, CH2 33.2, CH 13.3, CH3 78.3, CH 171.6, C 20.9, CH3 198.9, C 149.2, C 125.6, CH2 34.9, CH 67.8, CH2 171.6, C 21.1, CH3 17.3, CH3 11.3, CH3 20.0, CH3 17.8, CH3 11.3, CH3 19.3, CH3 17.2, CH3 11.2, CH3 20.6, CH3 17.2, CH3 11.2, CH3 20.7, CH3 16.3, CH3 10.8, CH3 20.3, CH3 16.5, CH3 10.8, CH3 20.3, CH3 204.5, C 148.0, C 125.7, CH2 36.7, CH 67.0, CH2 60.4, CH 21.3, CH3 26.5, CH2 38.2, CH 15.8, CH3 111.4, C 204.4, C 147.9, C 125.8, CH2 36.6, CH 67.0, CH2 In CDCl3. bIn CD3CN. were named neoboutomellerone (1) and 22-de-O-acetylneoboutomellerone (2). Compound 1 showed a pseudomolecular ion peak at m/z 591.3 [M + Na]+ in the positive ESI mode that analyzed for C34H48O7Na. The UV spectrum exhibited two maxima at 228 and 266 nm; the IR spectrum displayed strong OH vibrations at 3430 cm−1 and carbonyl bands at 1735, 1665, and 1602 cm−1. Analysis of the 13C NMR spectrum (DEPTQ and HSQC) permitted identification of seven methyl, eight methylene, ten methine, and nine quaternary carbons, thus accounting for a C34H47 partial formula and, therefore, a single OH group. Among the deshielded signals, two were clearly assignable to ketocarbonyls (δC 198.7 and 202.0), two ester carbonyls (δC 170.1 and 170.6), and an oxymethylene carbon at δC 66.9. The esters were identified as acetates on the basis of HMBC correlations between the CO and methyls at δH 2.08 and 2.16. The composition determined by HRMS was thus fully explained by NMR. A cyclohexenone moiety with a quaternary carbon atom γ to the CO, a conjugated exomethylene, two acetates, two methyl groups on sp3 quaternary carbons, and three methyl doublets were particular features of the molecule.The observation of an isolated methylene with its most upfield proton at δH 0.58, showing a small geminal coupling constant (J = 4.3 Hz), suggested the presence of a cyclopropane ring. Given the C30 composition of the basic skeleton (C34 minus two acetyl moieties), the first structural hypothesis for 1 was that of a diacetylated cycloartane derivative. On this basis, the two methyl singlets were assigned to C-18 and C-30, and the HMBC experiment permitted detection of the two quaternary carbons C-13 and C-14 (shared correlations with the methyls, see Table 1 for chemical shifts) as well as C-8, C-17 (CH), C-12, and C-15 (CH2). The cyclohexenone moiety was located in ring A to account for the observed long-range couplings between the ketocarbonyl (C-3), H-1, H-4, H-5, and CH3-28; the most upfield cyclopropane proton showed a correlation with H-1. Contrary to most described cycloartanes,8 1 had a proton on C-4 and therefore a single methyl group at this position. Analysis of the HMBC and HSQC experiments permitted identification of all the carbon atoms. The acetates were located on C-16 and C-22, and the alcohol function was located on the methyl group that terminates the chain. The location of the second enone moiety and the 30th carbon atom was determined by the couplings observed between the carbonyl at δC 198.7, the exo-methylene, and H-22, on one hand, and between the exo-methylene protons and C-26 (or -27), on the other. The extra carbon atom was thus placed at C-24, a common alkylation site in the cycloartane series.9 The planar 35 dx.doi.org/10.1021/np200441h | J. Nat. Prod. 2012, 75, 34−47 Journal of Natural Products Article structure of neoboutomellerone (1) is thus 16,22-di-O-acetyl-26hydroxy-29-nor-24-methylcycloarta-1,24(24a)-diene-3,23-dione. The second most abundant molecule was straightforwardly identified as 22-de-O-acetylneoboutomellerone (2), H-22 appearing shielded at δH 4.74 instead of 5.57. Upon acetylation, compounds 1 and 2 yielded the same 26-acetylneoboutomellerone (3), also isolated as a minor natural product, thus demonstrating that the three compounds had the same configuration. The latter was established through a ROESY experiment and by the preparation of Mosher esters. The cyclopropyl hydrogen atoms (H-19) were distinguished by the observation that the exo hydrogen showed ROESY correlations with H-1 and H-11eq, and the endo hydrogen with H-4, H-6, and H-8. These observations showed that the A/B ring junction was trans (H-5α) and that the C-4 methyl was equatorial (H-4β). In ring D correlations between the angular methyl-18, H-8, and H-20 on one hand and between CH3-30, H-16, and H-17, on the other, permitted assignment of a C/D trans ring junction with OAc-16 and the side chain in a β-orientation. The configuration of C-25 was determined by examination of the Mosher esters of 1 (1a and 1b), according to the method of Ivanchina.10 Ester 1a, prepared with S-α-methoxy-α-trifluoromethylphenylacetic acid chloride, showed 0.12 ppm nonequivalence between the diastereotopic H-26, while this value was 0.04 ppm for ester 1b prepared with the R-acid chloride, thus implying a 25R configuration. The configuration of C-22 was established similarly on diol 2 by considering the chemical shifts of H-20; in this case H-20 in the ester 2a, prepared from the S-acid chloride, was found at higher field than in the ester 2b made with the R-reagent (δH 2.57 vs 2.64). Finally, the configuration of C-20 was determined by the examination of the NMR spectra of compound 4, a saponification product of 1, in which a cis- fused five-membered ring is formed following hydrolysis of the acetate at C-16, α-ketol rearrangement, and ring closure as a hemiketal. In this compound, NOE correlations are observed between H-20 and CH3-18, between H-17 and CH3-21, and between CH3-30, H-16, and H-17, thus establishing a 20S configuration. Compounds 1 and 2 could not be crystallized for X-ray analysis. However, phenylcarbamate 1c was obtained in crystalline form in the course of a chemical modification program. The crystal structure determination confirmed these assignments as depicted in the formulas (see Experimental Section and Supporting Information for details). These molecules show a high degree of novelty, and their highly functionalized side chain is unique. Furthermore, there are only a few examples of nor-29-cycloart-1-en-3-ones.11 With these two major compounds and a valuable biological activity at hand, it was decided to enlarge the panel of molecules in order to evaluate the structural requirements for activity. A derivatization program was thus undertaken,12 as well as a systematic search for related natural products contained in this particular plant and in a few plants well known as sources of cycloartanes (Cimicif uga simplex, Musa sapientum, and Mangifera indica). Two minor compounds, 5 and 6, respectively the 1,2-dihydro derivatives of 1 and 2, were first isolated. Their HR-MS compositions were in agreement with the expected formulas (C34H50O7 and C32H48O6), and their 1H NMR spectra did not exhibit a deshielded AX system for H-1 and H-2. Both molecules showed a strong shielding of C-28 (δC 11.2), as a result of its equatorial position, β to a carbonyl group. All other 13C NMR signals except those of rings A and B were similar to those of 1−3 (see Table 1). On the basis of these data, the structures of 5 and 6 were identified as 1,2-dihydroneoboutomellerone and 1,2-dihydro22-de-O-acetylneoboutomellerone. HR-MS and NMR demonstrated that the pair of new compounds 7 and 8 contained an extra oxygen atom compared to their respective parent compounds 1 and 2. The 1H NMR spectra showed a broad singlet (W1/2 = 10 Hz) at δH 4.20 in the new compounds, corresponding to a CH at δC 65.6. In the COSY experiment, this signal displayed couplings to upfield CH and CH2, but the HMBC failed to yield any useful correlations. Assuming that the basic skeleton of the neoboutomellerones was conserved, C-6 was left as the unique position for the hydroxylation. In agreement, the neighboring C-5 and C-7 were downfield shifted (4 and 9 ppm, respectively), while C-8 exhibited a γ shielding effect (3 ppm). This substitution also induced a strong deshielding of C-19 (Δδ +6, δ effect) and, most importantly, of the endo proton of the cyclopropane (ΔδH +0.63) moiety, which could be explained by the presence of a 6β-OH group in 7 and 8. A ROESY experiment led to the same conclusion with the observation of interactions between H-6 and CH3-28, and between H-4 and H-19 endo, thus supporting the configurations of C-4, C-5, and C-6. Consequently, the structures of 7 and 8 were respectively determined to be 6βhydroxyneoboutomellerone and 6β-hydroxy-22-de-O-acetylneoboutomellerone. Along with compound 7, another isomer (9) was isolated, in which either CH3-18 or CH3-30 was replaced by a hydroxymethylene function. No HMBC correlations were observed between this CH2 and the backbone atoms, but the remaining methyl singlet displayed four long-range CH correlations, including one with CH2-15 (identified by scalar coupling with H-16). The OH was therefore placed at C-18, and this accounted for the chemical shift of the remaining CH3 at δH 1.00 (CH3-18 at δH >1.15, CH3-30 at δH <1). Compound 9 was thus assigned the structure of 18-hydroxyneoboutomellerone. Compound 10 appeared to belong to the same series as 1, displaying NMR signals for two O-acetyl groups, the γ,δcyclopropyl-α,β-unsaturated carbonyl, and the full and unmodified side chain. The HRMS indicated a C34H46O8 composition corresponding to the formula of compound 7 plus one degree of unsaturation. Analysis of the 1H NMR data was facilitated by the absence of signal overlap, with the sequence CH3-28, H-4, H-5, H-6, H-7, H-8 giving rise to wellseparated signals, in which H-6 and H-7 appeared as a doublet 36 dx.doi.org/10.1021/np200441h | J. Nat. Prod. 2012, 75, 34−47 Journal of Natural Products Article with C-7 being almost 7 ppm downfield (Table 2). In acetonitrile-d3, the 1H NMR spectrum displayed several wellseparated signals, including H-17, H2-12, H-15, and endo H-19, while H-5 was masked by the broad acetonitrile residual signal, and exo H-19 partially overlapped with H3-30. A ROESY experiment showed a correlation between H-5 and the endo H-19, suggesting that these atoms were cofacial, thus offering two possibilities: H-5β in a “normal” series or H-5α with H2-19 α-oriented. The presence of a cis-fused decalin moiety was deduced by the observation of an NOE correlation between H-1 and exo H-19, a feature not observed in any product in the trans series. The decision between the two hypotheses came in a serendipitous manner with the observation of a slow conversion of 1 into 14 upon storage in acetonitrile or by irradiation under a UV lamp, which could only be explained by opening of the cyclopropane (cleavage of the C-9/C-10 bond activated by the enone system) and ring closure to yield the thermodynamically more favorable cis isomer.13 The configuration of all stereogenic centers was assumed to be as in compound 1, and the proposed structure for 14 was 9,10-di-epi-25ξ-neoboutomellerone. Compound 15 is isomeric to 2 and was assigned the structure 9,10di-epi-25ξ-22-de-O-acetylneoboutomellerone owing to the strong similarity between the 13C NMR spectra of 15 and 2. of doublets at δH 3.15 and 3.00. These two protons were attached to carbon atoms resonating at δC 52.8 and 55.0, respectively, suggesting that they were incorporated in an epoxide ring. In this particular compound, H-5 was distinguished as an isolated broad doublet with J = 11.3 Hz (δH 2.45), thus proving its axial position and the trans-fusion of the A/B rings. The cyclopropane endo proton showed an Overhauser interaction with H-8 but not with H-6/7, allowing assignment of a β-configuration for the epoxide moiety. Shielding of the cyclopropane exo-proton, possibly as a result of interaction with the epoxide, is noteworthy. Compound 10 is thus 6β,7β-oxidoneoboutomellerone. The last compound in the “regular” series, 11, had a C32H48O7 molecular formula, as established by HR-MS, indicative of a hydroxylated analogue of 2. Absence of the AB system for H-1 and H-2 in the enone, as well as significant differences in the UV spectrum, suggested a 1,4-Michael addition of water to the enone functionality. An HMBC correlation between the exo-cyclopropane H-19 and the hydroxymethine allowed the hydroxy group to be placed at C-1. H-1 appeared as a broad triplet with J = 3 Hz (δH 3.80), characteristic of an equatorial proton, and, consequently, the hydroxy group was deduced to be axial. This was confirmed by the observation of an NOE interaction between H-1 and the exo-cyclopropane proton. Compound 11 was thus identified as 1,2-dihydro-1α-hydroxy22-de-O-acetylneoboutomellerone. At this point, all isolated compounds could be considered as being derived from 1 and 2 and thus were assigned the same configuration as evidenced by the series of related 13C NMR chemical shifts presented in Tables 1 and 2. Among the minor compounds, several isomers were isolated, including 12, in which the 1H and 13C NMR spectra were almost superimposable with the corresponding spectra of 1. The compounds were, however, quite different, with 12 being slightly less polar on reversedphase HPLC. Since minor differences were observed for the signals of CH-25 and CH2-26, 12 was proposed to be the C-25 epimer of 1, i.e., 25-epi-neoboutomellerone. This hypothesis was supported by the Dess-Martin oxidation of 1 into aldehyde 13, which was found to be unstable, rapidly converting into isomers at C-25. Compound 14, another isomer of 1, gave a 13 C NMR spectrum remarkably different from that of 1, despite the presence of all the functionalities, i.e., the two enones, the cyclopropane, and the esters (see Table 2). The most significant chemical shift differences were found for the signals of ring B, The next set of new compounds (16−20) shared the same side chain as before but without oxidation at C-26. As for 1 and 2, the difference between 16 and 17 was an acetyl group at C-22. The absence of a deshielded signal for H-26 and the presence of two diastereotopic methyl doublets for H3-26 and H3-27 suggested that these compounds were 26-deoxyneoboutomellerone (16) and 22-de-O-acetyl-26-deoxyneoboutomellerone (17), respectively. Compound 18 belonged to the 22-OAc series, but its molecular weight was 16 amu higher than observed for 16 (m/z 591.3287 for [M + Na]+). The 1H NMR spectrum of 18 showed similarity to that of 7, including a broad deshielded singlet for H-6 and characteristic deshielding for endo H-19 37 dx.doi.org/10.1021/np200441h | J. Nat. Prod. 2012, 75, 34−47 Journal of Natural Products Article Table 2. 13C NMR Data of Compounds 9−16 a carbon 9a 10b 11b 12a 13b 14a 15a 16b 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 16a 16b 17 18 19 20 21 22 22a 22b 23 24 24a 25 26 27 28 30 153.5, CH 128.3, CH 202.0, C 47.0, CH 43.0, CH 23.5, CH2 24.0, CH2 45.0, CH 25.8, C 32.0, C 27.5, CH2 27.7, CH2 47.5, C 51.0, C 46.2, CH2 76.6, CH 169.4, C 21.6, CH3 49.6, CH 64.9, CH2 28.5, CH2 32.8, CH 13.4, CH3 77.4, CH 170.5, C 20.7, CH3 198.5, C 149.3, C 123.6, CH2 37.4, CH 66.8, CH2 16.4, CH3 10.8, CH3 21.7, CH3 154.2, CH 128.4, CH 202.1, C 45.6, CH 41.5, CH 52.8, CH 55.0, CH 38.9, CH 27.2, C 31.8, C 27.4, CH2 32.1, CH2 47.1, C 47.3, C 44.7, CH2 76.3, CH 171.3, C 22.1, CH3 49.7, CH 15.2, CH3 22.1, CH2 33.2, CH 13.7, CH3 78.6, CH 171.7, C 20.9, CH3 199.6, C 150.3, C 124.7, CH2 38.0, CH 66.4, CH2 17.2, CH3 11.3, CH3 19.6, CH3 74.0, CH 49.3, CH2 212.2, C 50.5, CH 39.5, CH 26.1, CH2 26.2, CH2 48.7, CH 26.0, C 34.0, C 26.5, CH2 33.3, CH2 46.6, C 47.9, C 47.9, CH2 77.5, CH 171.3, C 22.1, CH3 51.5, CH 19.6, CH3 28.1, CH2 36.3, CH 12.2, CH3 75.8, CH 153.7, CH 128.3, CH 202.0, C 46.9, CH 42.5, CH 23.4, CH2 23.5, CH2 44.3, CH 26.0, C 31.9, C 27.4, CH2 32.1, CH2 47.4, C 46.0, C 46.0, CH2 75.9, CH 170.1, C 21.7, CH3 50.3, CH 17.8, CH3 27.0, CH2 32.2, CH 12.7, CH3 77.8, CH 170.7, C 20.7, CH3 198.6, C 149.2, C 124.3, CH2 37.9, CH 66.8, CH2 15.5, CH3 10.8, CH3 19.6, CH3 155.5, CH 128.4, CH 202.4, C 47.6, CH 43.6, CH 24.3, CH2 24.3, CH2 45.2, CH 27.2, C 33.4, C 28.1, CH2 33.0, CH2 46.9, C 48.3, C 46.7, CH2 76.8, CH 171.2, C 22.1, CH3 51.2, CH 18.3, CH3 27.6, CH2 33.8, CH 13.4, CH3 78.2, CH 171.6, C 20.9, CH3 198.3, C 145.8, C 128.6, CH2 48.9, CH 201.7, CH 13.8, CH3 11.3, CH3 20.0, CH3 155.4, CH 126.5, CH 200.6, C 47.7, CH 39.4, CH 20.6, CH2 31.2, CH2 40.7, CH 33.7, C 26.6, C 29.8, CH2 32.1, CH2 47.8, C 46.1, C 43.8, CH2 76.0, CH 170.1, C 21.7, CH3 49.5, CH 15.1, CH3 31.3, CH2 32.5, CH 13.2, CH3 77.7, CH 170.6, C 20.6, CH3 198.8, C 149.3, C 123.7, CH2 37.2, CH 66.9, CH2 16.3, CH3 12.2, CH3 18.6, CH3 155.7, CH 126.3, CH 200.7, C 47.8, CH 39.4, CH 20.6, CH2 31.2, CH2 40.7, CH 33.9, C 26.6, C 29.9, CH2 32.1, CH2 47.8, C 46.0, C 44.0, CH2 76.9, CH 170.1, C 21.8, CH3 49.3, CH 15.3, CH3 31.4, CH2 35.9, CH 12.1, CH3 75.0, CH 155.6, CH 128.4, CH 202.5, C 47.6, CH 43.6, CH 24.3, CH2 24.3, CH2 45.2, CH 27.7, C 32.9, C 28.1, CH2 32.9, CH2 46.8, C 48.4, C 46.7, CH2 76.6, CH 171.3, C 22.1, CH3 51.3, CH 18.2, CH3 27.7, CH2 33.0, CH 13.2, CH3 78.5, CH 171.7, C 20.9, CH3 199.5, C 154.3, C 122.3, CH2 29.7, CH 21.6, CH3 22.4, CH3 11.3, CH3 20.0, CH3 205.6, C 149.1, C 126.5, CH2 37.6, CH 66.7, CH2 17.2, CH3 11.0, CH3 20.7, CH3 204.6, C 148.0, C 125.6, CH2 36.7, CH 67.0, CH2 16.4, CH3 12.2, CH3 18.6, CH3 In CDCl3. bIn CD3CN. 22 were shown by 13C NMR to belong to the normal A/B trans series, 23 displayed a markedly different spectrum, characteristic of the cis α-series. Consequently, its structure was deduced to be 9,10-di-epi-24a-nor-24,25-didehydro-26-deoxyneoboutomellerone (see Table 3). Compounds 24 and 25 had molecular weights of 412 and 428, respectively, corresponding to molecular formulas C26H36O4 and C26H36O5. Although six carbon atoms were missing, the 1H NMR spectra of both compounds showed strong resemblance with those of the neoboutomellerones and displayed signals for an acetate, an α,β-unsaturated carbonyl, a cyclopropane, and the angular methyl groups. Initially, it was proposed that these compounds were lacking C-23 to C-27 of the “regular” series side chain. A formyl proton doublet at δH 9.58 (J = 1.8 Hz) coupling with a doublet of doublets of quartets (δH 2.86) suggested that truncation had happened between C-22 and C-23. Since the 13C NMR spectrum showed that the tetracyclic core was intact, 24 was proposed to be 23,24,24a,25,26,27-hexa-norneoboutomelleron-22-al. This was confirmed by the high-yield oxidation of 2 into 24 by MnO2. It is worth noting that 1 was recovered unchanged under the same conditions. The 13C NMR spectra of 24 and 25 could barely be distinguished except for the formyl carbonyl carbon, which was replaced by a signal at δC 182.0. It was deduced that 25 was the corresponding acid (δH 1.81). This feature, as well as the overall concordance between the spectra of 7 and 18, indicated that 18 was 6β-hydroxy-26deoxyneoboutomellerone. Compound 19, like the preceding compounds, was characterized by four methyl doublets and therefore lacked oxidation at the terminus of the side chain. This compound had a molecular weight of 512, corresponding to a C32H48O5 composition. This confirmed the absence of an oxygen atom and suggested that 19 was a dihydro analogue of a derivative of 2. Since the characteristic signals for the ring A double bond were missing, it was deduced that 19 was 1,2dihydro-22-de-O-acetyl-26-deoxyneoboutomellerone. Compound 20 was an isomer of 16 (C34H48O6), and, given the previous analyses, it was readily identified as the cyclopropyl isomer of 16, i.e., 9,10-di-epi-26-deoxyneoboutomellerone. Compounds 21−23 differed from the previous compounds by the absence of the C-24 exo-methylene group. Examination of the NMR spectra showed that C-24a was replaced by a proton (δH 6.15 ± 0.2) and that the chain was terminated by a 3-methyl-2-butenoyl moiety. In these three compounds, the tetracyclic cycloartane core was intact, and, as for compounds 1 and 2, 21 and 22 differed only by the presence of a C-22-O-acetyl moiety. Compound 21 was thus 24a-nor-24,25-didehydro-26deoxyneoboutomellerone, and 22 was 22-de-O-acetyl-24a-nor24,25-didehydro-26-deoxyneoboutomellerone. While 21 and 38 dx.doi.org/10.1021/np200441h | J. Nat. Prod. 2012, 75, 34−47 Journal of Natural Products Article Table 3. 13C NMR Data of Compounds 17−24 a carbon 17a 18a 19a 20a 21a 22a 23a 24a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 16a 16b 17 18 19 20 21 22 22a 22b 23 24 24a 25 26 27 28 30 155.7, CH 128.3, CH 202.5, C 47.6, CH 43.6, CH 24.3, CH2 24.3, CH2 45.3, CH 27.2, C 33.0, C 28.1, CH2 33.1, CH2 46.7, C 48.3, C 46.9, CH2 77.3, CH 171.3, C 22.1, CH3 51.4, CH 18.5, CH3 27.7, CH2 36.2, CH 12.3, CH3 75.8, CH 156.2, CH 127.5, CH 203.4, C 44.9, CH 46.6, CH 65.6, CH 32.7, CH2 41.1, CH 26.5, C 30.8, C 27.7, CH2 33.1, CH2 47.1, C 47.7, C 47.5, CH2 76.8, CH 171.3, C 22.1, CH3 51.5, CH 19.4, CH3 33.0, CH2 33.0, CH 13.1, CH3 78.5, CH 171.7, C 20.9, CH3 199.4, C 154.3, C 122.3, CH2 29.7, CH 22.4, CH3 21.7, CH3 11.0, CH3 20.7, CH3 33.5, CH2 41.5, CH2 213.3, C 50.5, CH 47.0, CH 26.5, CH2 26.2, CH2 48.6, CH 27.4, C 33.5, C 27.4, CH2 33.5, CH2 46.7, C 47.9, C 47.8, CH2 77.5, CH 171.3, C 22.1, CH3 51.6, CH 19.5, CH3 28.0, CH2 36.2, CH 12.2, CH3 75.7, CH 157.3, CH 126.5, CH 201.0, C 48.5, CH 40.4, CH 21.3, CH2 31.9, CH2 41.5, CH 27.7, C 34.9, C 30.4, CH2 32.9, CH2 47.0, C 48.8, C 44.6, CH2 76.5, CH 171.3, C 22.1, CH3 50.6, CH 15.4, CH3 31.6, CH2 33.0, CH 13.6, CH3 78.6, CH 171.7, C 20.9, CH3 199.6, C 154.3, C 122.3, CH2 29.7, CH 21.6, CH3 22.4, CH3 12.6, CH3 18.9, CH3 155.7, CH 128.4, CH 202.6, C 47.6, CH 43.5, CH 24.2, CH2 24.2, CH2 44.9, CH 27.0, C 32.9, C 28.0, CH2 32.7, CH2 46.7, C 48.7, C 46.1, CH2 76.1, CH 171.3, C 21.8, CH3 51.1, CH 18.1, CH3 27.4, CH2 32.7, CH 13.2, CH3 81.5, CH 171.7, C 21.2, CH3 196.9, C 120.5, CH 155.7, CH 128.4, CH 202.5, C 47.6, CH 43.5, CH 24.3, CH2 24.2, CH2 45.0, CH 27.1, C 32.8, C 28.1, CH2 32.9, CH2 46.2, C 48.2, C 46.3, CH2 76.5, CH 171.3, C 21.8, CH3 51.2, CH 18.3, CH3 27.4, CH2 34.4, CH 12.2, CH3 79.0, CH 155.4, CH 128.5, CH 202.3, C 47.6, CH 43.3, CH 24.1, CH2 24.0, CH2 44.3, CH 27.3, C 33.0, C 28.0, CH2 32.6, CH2 46.5, C 48.4, C 45.3, CH2 75.1, CH 170.9, C 21.3, CH3 50.7, CH 18.4, CH3 26.9, CH2 45.1, CH 13.4, CH3 205.2, CH 202.5, C 120.3, CH 157.3, CH 126.5, CH 201.0, C 48.5, CH 40.4, CH 21.3, CH2 31.9, CH2 41.4, CH 27.6, C 31.5, C 30.4, CH2 32.7 46.8, C 48.8, C 44.1, CH2 76.1, CH 171.3, C 21.8, CH3 50.2, CH 15.4, CH3 31.6, CH2 32.8, CH 13.5, CH3 81.6, CH 171.6, C 21.2, CH3 196.9, C 120.5, CH 159.8, C 28.0, CH3 21.0, CH3 11.3, CH3 19.8, CH3 159.9, C 28.1, CH3 21.3, CH3 11.3, CH3 19.9, CH3 159.7, C 28.0, CH3 21.0, CH3 12.6, CH3 18.8, CH3 205.4, C 153.1, C 124.3, CH2 29.5, CH 22.0, CH3 22.6, CH3 11.3, CH3 20.1, CH3 205.4, C 153.1, C 124.3, CH2 29.5, CH 22.0, CH3 22.6, CH3 11.3, CH3 20.8, CH3 11.3, CH3 19.4, CH3 In CD3CN. of 24, i.e., 23,24,24a,25,26,27-hexa-nor-neoboutomelleron-22oic acid. Six more compounds (26−31) were isolated and, although devoid of any biological activity (vide inf ra), are interesting from a biosynthetic standpoint. They all shared common functionalities in rings A and B: a hydroxy group at C-3 and a quaternary C-4 bearing a hydroxycarbonyl or ester function. These compounds could be considered as the precursors for the aforementioned compounds, undergoing oxidation of a C-4 methyl group of a cycloartane, oxidation of C-3, followed by decarboxylation and introduction of the Δ1,2 double bond, paralleling the well-known biosynthesis of the steroids. All six compounds had a 3S configuration (3β-OH) based on the large vicinal coupling between H-3 and H-2α (ca. 11 Hz) and a 4S configuration to account for the strong shielding of the axial C-28 methyl group (δC ca. 10). In the 1H NMR spectrum of 27, H-5 was observed as a doublet of doublets with J = 12.2 and 3.4 Hz and was therefore α-axially oriented. Configurations of the other ring junctions, and of C-16, C-20, and C-22, were most likely the same as for the major compounds given the similarities in chemical shift values. Compounds 26 and 27 were isomers with a C33H50O7 molecular formula, and comparison of their NMR spectra showed that they differed in the location of the side chain hydroxy group: C-22 for 27 and C-25 for 26. However, it was not possible to define the configuration of C-25 in compound 26 due to a paucity of material. Compound 29 was not oxidized at C-16 nor C-22, as shown by the presence of two methylene resonances at δC 29.3 and 46.5. The C-22 methylene group gave rise to two well-separated doublets of doublets, with 15.6 Hz geminal couplings and vicinal couplings 39 dx.doi.org/10.1021/np200441h | J. Nat. Prod. 2012, 75, 34−47 Journal of Natural Products Article bond was evident, with H-11 being a broad doublet coupling with H2-12. This assignment was supported by an HMBC correlation to C-18. A broad hydroxymethine singlet [δH 4.16 (δC 73.2)] showed HMBC couplings with the methine, the methylene, and the quaternary carbon of the cyclopropane moiety. The COSY experiment showed a weak but definite coupling between this proton and the cyclopropane proton at δH 1.88. Consequently, the hydroxy group was placed at C-2, and the cyclopropane bridge between C-1 and C-10. A NOESY experiment showed a correlation between H-2 and the exocyclopropane proton, suggesting that this proton and the cyclopropane moiety were β-cofocially oriented, and therefore the 2-OH group must be α-oriented. This molecule is another member of a rare family of triterpenes that are linked to the parent compounds through acidic rearrangements, for example, simplexol and O-methylcinicimol, arising from cimigenol.15 In our case, the putative epoxide 33, an oxidation product of 1, should be the intermediate between 32 and the regular cycloartanes, and the rearrangement should be favored by an anti relationship between the cyclopropane and the oxirane, hence giving further support to the 2α-OH configuration. On the basis of the above evidence, the structure of 32 was proposed to be 16,22-diacetyl-2,26-dihydroxy-29-nor-24methyl-19(9→1)-abeo-cycloart-9(11),24(24a)-diene-3,23dione. of 3.1 and 10.1 Hz, the smaller constant being close to that observed in all the HO-22 derivatives. The mass spectrum of compound 28 indicated a molecular formula of C31H46O5, corresponding to the loss of HOAc with regard to 26 and 27. Accordingly, no signal was observed for an acetate group in the 1H NMR spectrum. A noteworthy feature of the 13C NMR spectrum was the presence of a quaternary carbon at δC 108, which showed HMBC couplings with two exo-methylene protons, sp2 C-24a, and an oxymethylene corresponding to C-26. These characteristics were best accounted for by a ketal derived from a precursor possessing a C-23 carbonyl group and hydroxy groups at C-16 and C-26. No NOE correlations between protons of the spiroketal rings were evident, and we could not assign configurations to C-23 and C-25. Compounds 30 and 31 shared with 29 the absence of oxidation of C-16 and C-22, but analysis of the NMR spectra suggested that these highly polar compounds were glycosides. In both compounds, the sugar was tentatively identified as an α-L-rhamnose. The difference between the two compounds was in the side chain, with 31 having the same side chain as 16 and 17, and 30 having the truncated chain of 21 and 22. Therefore, the respective structures of these compounds were 16-acetyl-3β,26-dihydroxy-24-methyl-25ξ-cycloart-24(24a)-en-23-on-29-oic acid (26), 16-acetyl-3β,22βdihydroxy-24-methylcycloart-24(24a)-en-23-on-29-oic acid (27), 3β,16β,22β-trihydroxy-24-methyl-(16,23:23,26)-diepoxycycloart-24(24a)-en-29-oic acid (28), 3β-hydroxy-24-methylcycloart-24(24a)-en-23-on-29-oic acid (29), 3β-hydroxy-29-O(α-L-rhamnopyranosyl)cycloart-24-en-23-on-29-oic acid (30), and 3β-hydroxy-29-O-(α-L-rhamnopyranosyl)-24-methylcycloart-24(24a)-en-23-on-29-oic acid (31). Structure−Activity Relationship Analysis. Twenty-four of the isolated compounds the two non-natural derivatives, 4 and 13, were evaluated in the cellular proteasome assay (Table 5). Cimiracemosides F and G,16 cycloeucalone,17 28-nor-cycloeucalone, mangiferonic, and mangiferolic acids,18 isolated from Cimicif uga simplex, Musa sapientum, and Mangifera indica, were also tested, but none were found to be active. Table 5 lists the induction factors (IFs) observed for the cycloartanes. The IF is defined as the increase in luciferase signal measured in the 4UB-Luc-DLD-1 cells, after 7 h exposure to the test compound, as compared to untreated cells.3b Epoxomycin was used as reference with an IF of 100 at 0.5 μM. Due to the cytotoxicity of the compounds and/or the accumulation of proteasome substrates (known to produce cytotoxic effects), it was not possible to observe luminescence at the highest concentrations. It also explains why a maximum on the induction factor (IF) versus concentration plots is observed (bell-shaped curve). The two major compounds (1, 2) from the plant were also the most active, with IF values of 48 and 45 at 1 μM, respectively, and the activity decreased with the acylation level at the C-26 hydroxy group, with 1, 2 > 3. The integrity of the side chain seemed to be another requirement since compounds such as 4 or 24 showed no activity. Simple modifications, such as the removal of the exo-methylene in this side chain (21 and 22) or the alteration of CH3-18 into a hydroxymethlene (9), also reduced the biological activity. However, a C-6 hydroxy group (7, 8), an epoxy moiety on C-6/C-7 (10), a configurational change at C-25 (12), a cyclopropyl isomerism (14, 15), or substitutions at C-26 (13, 16, 17) represent structural modifications that do not significantly affect biological activity. Compound 32 was an isomer of 7, with its 1H NMR spectrum displaying all the signals corresponding to rings C and D and of the side chain. However, the enoyl AB system in 7 was missing and the usual upfield doublet for H-19 was replaced by a doublet of doublets at δH 0.41 (J = 9.9, 4.7 Hz) and 0.94 [broad triplet (J = 4.7 Hz)], with both signals coupled to a broadened doublet of doublets at δH 1.88 (J = 9.9, 4.7 Hz). The values of the vicinal coupling constants in the cyclopropane ring indicated that the most upfield proton was endo, since it is known that in such systems Jtrans > Jcis.14 A trisubstituted C-9/C-11 double 40 dx.doi.org/10.1021/np200441h | J. Nat. Prod. 2012, 75, 34−47 Journal of Natural Products Article Table 4. 13C NMR Data of Compounds 25−32 a carbon 25a 26a 27c 28c 29c 30c 31c 32a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 16a 16b 17 18 19 20 21 22 22a 22b 23 24 24a 25 26 27 28 29 30 1′ 2′ 3′ 4′ 5′ 6′ 153.7, CH 128.3, CH 202.0, C 46.8, CH 42.3, CH 23.4, CH2 23.3, CH2 43.4, CH n.d.c 32.0, C 27.4, CH2 32.0, CH2 45.2, C 47.5, C 44.0, CH2 75.0, CH 171.8, C 21.1, CH3 52.0, CH 18.0, CH3 26.5, CH2 38.7, CH 17.5, CH3 182.0, C 31.4, CH2 29.4, CH2 75.4, CH 54.5, C 44.0, CH 22.8, CH2 25.6, CH2 47.7, CH 19.7, C 25.1, C 26.0, CH2 32.3, CH2 45.9, C 47.1, C 45.7, CH2 75.1, CH 171.0, C 21.2, CH3 54.7, CH 18.5, CH3 30.2, CH2 27.3, CH 19.2, CH3 44.8, CH2 32.8, CH2 30.5, CH2 76.3 CH 56.0, C 45.7, CH 24.1, CH2 26.9, CH2 49.7, CH 20.8, C 26.6, C 27.1, CH2 33.8, CH2 46.9, C 48.3, C 48.1, CH2 78.1, CH 172.3, C 21.9, CH3 51.8, CH 19.5, CH3 31.3, CH2 36.2, CH 12.1, CH3 76.0, CH 32.8, CH2 30.5, CH3 76.3, CH 55.9, C 45.5, CH 23.9, CH2 27.1, CH2 49.1, CH 20.8, C 26.8, C 27.0, CH2 34.1, CH2 45.7, C 47.4, C 44.7, CH2 74.0, CH 32.8, CH2 30.5, CH2 76.3, CH 55.8, C 45.6, CH 24.1, CH2 26.7, CH2 49.3, CH 21.1, C 26.4, C 27.4, CH2 34.0, CH2 46.6, C 50.1, C 36.5, CH2 29.3, CH2 32.7, CH2 30.4, CH2 75.9, CH 56.5, C 46.0, CH 23.9, CH2 26.5, CH2 49.3, CH 21.2, C 26.3, C 27.4, CH2 33.9, CH2 46.6, C 50.1, C 36.5, CH2 29.3, CH2 32.7, CH2 30.4, CH2 75.9, CH 56.5, C 46.0, CH 23.9, CH2 26.5, CH2 49.3, CH 21.2, C 26.3, C 27.4, CH2 33.9, CH2 46.6, C 50.1, C 36.5, CH2 29.3, CH2 57.7, CH 20.9, CH3 31.3, CH2 26.8, CH 21.0, CH3 43.8, CH2 53.8, CH 18.5, CH3 30.7, CH2 35.2, CH 19.8, CH3 46.5, CH2 53.8, CH 18.6, CH3 30.8, CH2 34.9, CH 19.7, CH3 52.7, CH2 53.8, CH 18.6, CH3 30.8, CH2 35.1, CH 19.7, CH3 46.4, CH2 203.1, C 151.8, C 123.8, CH2 36.6, CH 67.6, CH2 16.1, CH3 9.1, CH3 180.8, C 20.0, CH3 205.1, C 154.2, C 123.2, CH2 29.9, CH 22.6, CH3 21.9, CH3 10.2, CH3 181.7, C 20.7, CH3 108.0, C 159.2, C 106.2, CH2 38.7, CH 72.7, CH2 14.3, CH3 10.1, CH3 181.4, C 20.0, CH3 205.0, C 157.1, C 122.6, CH2 29.1, CH 22.3, CH3 22.4, CH3 10.0, CH3 181.2, C 19.7, CH3 23.6, CH 73.2, CH 213.2, C 40.4, CH 47.6, CH 26.6, CH2 29.5, CH2 44.2, CH 140.4, C 30.0, C 116.1, CH 36.2, CH2 45.1, C 45.2, C 45.0, CH2 76.2, CH 170.1, C 21.7, CH3 49.1, CH 15.1, CH3 15.8, CH2 32.4, CH 12.8, CH3 77.6, CH 170.6, C 20.7, CH3 198.7, C 149.3, C 123.7, CH2 37.2, CH 66.9, CH2 16.3, CH3 10.8, CH3 10.8, CH3 19.0, CH3 204.2, C 125.3, CH 157.0, C 27.7, CH3 20.9, CH3 9.9, CH3 176.2, C 19.7, CH3 94.9, CH 71.2, CH 72.4, CH 73.3, CH 72.4, CH 17.9, CH3 204.9, C 157.1, C 122.6, CH2 29.1, CH 22.3, CH3 22.4, CH3 9.9, CH3 176.2, C 19.8, CH3 94.9, CH 71.2, CH 72.4, CH 73.3, CH 72.4, CH 17.9, CH3 19.4, CH3 In CDCl3 cIn methanol-d4. cn.d., not detected. species such as N. melleri. Cursory investigation of the terpenes from the twigs did not show the presence of cycloartanes but rather daphnanes, as observed in the only published investigation on similar material.6 Despite the ubiquity of these triterpenes, the oxidation level of the molecules discussed here is most peculiar, with the rare combination of an α,β-unsaturated carbonyl with a cyclopropane giving rise to photochemical reactivity. The two Michael acceptors in ring A and in the side chain add further biological properties to the neoboutomellerones. In fact, the two moieties may act as reversible or irreversible inhibitors across the ubiquitin−proteasome pathway. From a medicinal point of view, the novelty of the isolated compounds and their interesting pharmacological properties motivate the antitumor activity evaluation of the most abundant molecules 1 and 2.19 Moreover, minor changes in ring A were tolerated; the 1,2dihydro derivatives (5, 6) and 1-hydroxy derivative (11) showed some activity, possibly due to reoxidation in vivo. Compounds lacking the A-ring enone function (26−28, 30−32) or the C-16-ester moiety (4, 28) were also found to be weakly active. Acetylation of the C-22-hydroxy group results in minor decreases of activity among comparable structures (1/2, 5/6, 7/8, 16/17, and 21/22). Finally, enone functionalities associated with the side chain and in ring A appear to be crucial to maintain the biological activity, thus leaving the C-16-ester group and the C-22-hydroxy function as possible points of modification. CONCLUSION From a phytochemical standpoint, it is not surprising to find cycloartanes as major secondary metabolites in a Euphorbiaceae ■ 41 dx.doi.org/10.1021/np200441h | J. Nat. Prod. 2012, 75, 34−47 Journal of Natural Products Article reference RBL-273 in the Pierre Fabre Botanical Conservatory in Cambounet-sur-le-Sor (France). The plant was collected again by one of us (B.D.) at the same location and identified by comparison of the vouchers at the National Herbarium of the Museum National d’Histoire Naturelle in Paris. HPLC of the extracts showed similar profiles. Extraction and Isolation. The dried leaves (1 kg) of N. melleri were powdered and extracted at room temperature with CH2Cl2 (15 L) overnight. After filtration, the extract was concentrated under reduced pressure. The residue (45 g) was dissolved in CH2Cl2 (1 L) and stirred for 1 h with 100 g of activated vegetable charcoal. After filtration and concentration under reduced pressure, the extract (32 g) was partitioned between MeOH and cyclohexane. The MeOH fraction (15 g) was subjected to silica gel CC (600 g, 57 × 420 mm) using cyclohexane−EtOAc (50:50) to give 50 fractions of 150 mL. All the fractions were analyzed by TLC on silica gel using the solvent mixture CH2Cl2−MeOH (97:3) and pooled according to TLC into four fractions (F1−F4). Fraction F1 (6.0 g) was purified by semipreparative HPLC RP-18 chromatography, eluting with a linear gradient (80 to 100% B), to give after repeated HPLC purification 17 (84 mg), 19 (53 mg), 23 (6 mg), 3 (5 mg), 22 (25 mg), 21 (18 mg), 16 (76 mg), 24 (7 mg), 20 (3 mg), and 18 (1 mg). Fractions F2 (5.5 g) and F3 (1.5 g) were purified by semipreparative RP-18 chromatography, eluting with a linear gradient (45−100% B). After repeated HPLC purification of F2, compounds 1 (2.5 g, 0.25%), 6 (180 mg, 0.018%), and 5 (107 mg, 0.0107%) were obtained. Fraction F3, after repeated HPLC purification, afforded the second most abundant compound, 2 (600 mg), 10 (11 mg), and 15 (63 mg). Fraction F4 (1.0 g) was purified by semipreparative RP-18 chromatography, to give after repeated HPLC purification with a linear gradient (90−100% B and 50−100% B) the most polar compounds, 26 (3 mg), 30 (5 mg), 27 (7 mg), 29 (23 mg), 28 (17 mg), 11 (12 mg), 25 (3 mg), 31 (2 mg), 7 (34 mg), 8 (18 mg), 14 (80 mg), 12 (5 mg), 32 (1 mg), and 9 (1 mg). Neoboutomellerone (1): white fluffy solid, [α]20D −55 (c 0.16, CHCl3); UV (MeOH) λmax (log ε) 224 (3.77), 266 (3.83) nm; IR (film) νmax 3430, 1735, 1665, 1602, 1230 cm−1; 1H NMR (CDCl3, 500 MHz) δ 6.85 (1H, d, J = 10.1 Hz, H-1), 6.13 (1H, s, H-24a), 6.02 (1H, d, J = 10.1 Hz, H-2), 5.89 (1H, br s, H-24a), 5.57 (1H, d, J = 2.1 Hz, H-22), 5.09 (1H, dt, J = 4.6, 7.6 Hz, H-16), 3.59 (2H, d, J = 5.8 Hz, 2 H-26), 2.88 (1H, sext, J = 6.5 Hz, H-25), 2.60 (1H, dqd, J = 11.0, 7.0, 2.1 Hz, H-20), 2.31 (1H, dd, J = 14.0, 7.9 Hz, H-15a), 2.28 (1H, dd, J = 11.1, 7.5 Hz, H-17), 2.19 (1H, dq, J = 12.7, 7.9 Hz, H-4), 2.16 (3H, s, OAc-22), 2.08 (3H, s, OAc-16), 1.75−1.65 (3H, m, H-6, 2 H-12), 1.54 (1H, m, H-11), 1.47 (1H, m, H-7), 1.32 (1H, dd, J = 13.7, 4.6 Hz, H15b), 1.20 (1H, d, J = 4.3 Hz, H-19a), 1.18 (3H, s, H-18), 1.12 (3H, d, J = 7.0 Hz, H-27), 1.10 (3H, d, J = 6.7 Hz, H-28), 0.95 (3H, s, H-30), 0.90 (3H, d, J = 6.7 Hz, H-21), 0.58 (1H, d, J = 4.3 Hz, H-19b); 13C NMR, see Table 1; HR-ESIMS m/z 591.3297 (calcd for C34H48O7Na 591.3292). Preparation of Compound 1c. To a stirred solution of 1 (53 mg, 0.093 mmol) in 1 mL of CH2Cl2 were added DMAP (6 mg, 0.047 mmol, 0.5 equiv), phenyl isocyanate (11 μL, 0.102 mmol, 1.1 equiv), and Et3N (11 μL, 0.102 mmol, 1.1 equiv). The mixture was stirred at room temperature, and after 22 h, it was diluted with EtOAc and the organic solution was successively washed with 4% aqueous HCl, NaHCO3, and brine. The organic solution was dried over MgSO4 and concentrated under vacuum. The residue was purified by chromatography on silica gel (elution: cyclohexane−EtOAc, 1:0 to 0:1) to give 1c as a white solid (30 mg, 47%): 1H NMR (500 MHz, CD3CN) δ 7.68 (1H, br s, H-26b), 7.41 (2H, br d, J = 8.3 Hz, H-26d, H-26 h), 7.29 (2H, dd, J = 7.6, 8.3 Hz, H-26 g, H-26e), 7.03 (1H, tt, J = 7.6, 1.2 Hz, H-26f), 6.94 (1H, d, J = 10.1 Hz, H-1), 6.15 (1H, s, H-24a), 6.02 (1H, d, J = 0.6 Hz, H-24a), 5.90 (1H, d, J = 10.1 Hz, H-2), 5.54 (1H, d, J = 2.1 Hz, H-22), 5.09 (1H, dt, J = 4.4, 7.7 Hz, H-16), 4.13 (1H, dd, J = 10.7, 7.0 Hz, H-26a), 4.06 (1H, dd, J = 10.7, 6.4 Hz, H-26b), 3.07 (1H, sext, J = 7.0 Hz, H-25), 2.61 (1H, ddq, J = 2.3, 10.9, 7.0 Hz, H-20), 2.30 (1H, dd, J = 11.0, 7.3 Hz, H-17), 2.10 (3H, s, OAc-22), 2.03 (3H, s, OAc-16), 1.55 (1H, ddd, J = 6.6, 9.0, 14.8 Hz, H-11b), 1.37 (1H, dd, J = 13.9, 4.1 Hz, H-15b), 1.24 (1H, d, J = 4.6 Hz, H-19a), 1.18 (3H, s, H-18), 1.11 (3H, d, J = 7.0 Hz, H-27), 1.02 Table 5. Induction Factors for Cycloartanes induction factor (4Ub Luc DLD-1 cell) at dose (μM) ■ compound 10 5 1 0.5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 21 22 24 26 27 28 30 31 32 4.4 2.9 37 28 48 1.0 45 10 31 35 12 72 11 71 70 84 9.1 74 65 34 5.2 1.3 1.3 1.3 1.3 1.0 1.0 1.9 48 45 12 0.9 0.9 1.2 5.1 1.1 1.2 2.8 1.6 1.5 1 2 0.9 7.2 2.4 1.1 1.1 1.1 1.0 1.2 1.2 1.0 1.1 1.2 2.1 1.4 1.1 2.6 48 77 1.1 15 74 60 31 24 19 20 44 53 3.0 2.8 1.8 1.3 1.1 1.1 15 1.2 1.3 1.0 1.4 0.9 EXPERIMENTAL SECTION General Experimental Procedures. Optical rotations were determined on a Perkin-Elmer 341 automatic polarimeter. UV spectra were obtained in MeOH using a UV MC2 Safas spectrophotometer. An FT-IR Bruker Tensor 27 spectrophotometer was used for scanning IR spectroscopy. The NMR spectra were recorded on a Bruker Avance II spectrometer equipped with a 13C cryoprobe at 500 MHz for 1H and 125 MHz for 13C; 2D experiments were performed using standard Bruker programs. The ESIMS and MS/MS were performed using a Bruker Esquire-LC ion trap mass spectrometer; the samples were introduced by infusion in a solution of MeOH. HR-ESIMS were obtained on a Bruker MicrOTOF. TLC was carried out on precoated silica gel 60F254 (Merck) with CH2Cl2−MeOH (97:3), and spots were visualized by heating after spraying with 3% H2SO4 + 1% vanillin. CC was carried out on a prepacked Kieselgel cartridge (40−60 μm) with cyclohexane−EtOAc (50:50). Analytical HPLC was performed on a Merck-Hitachi apparatus equipped with an L-7200 automated sample injector, an L-7100 pump, a L-7450 diode array detector, a D-7000 interface, and Lachrom HSM or EZChrom software. A prepacked C18 reversed-phase column (Lichrospher 100 RP-18, 4 × 125 mm, 5 μm) was used for analytical HPLC with a binary gradient elution (solvent A: H2O; solvent B: MeCN) and a flow rate of 1 mL·min−1. Semipreparative HPLC was performed on an apparatus equipped with a VWR International LaPrep pump P110, a VWR LaPrep P314 Dual λ absorbance detector, and EZChrom software. A 50 × 250 mm column (NW 50, Merck) with LiChroprep RP-18 (15−25 μm) and a prepacked C18 reversed-phase column (Hibar-Lichrospher 100 RP-18, 25 × 250 mm, 5 μm) were used for semipreparative HPLC with a binary gradient elution (solvent A: H2O; solvent B: MeCN) and a flow rate of 100 or 30 mL.min−1, and the chromatogram was monitored at 210 and 270 nm. Plant Material. The original plant sample was collected by René Bellé (Pierre Fabre Research Institute) in Malantouen (Cameroon) on June 21, 1988, and an herbarium specimen was deposited under 42 dx.doi.org/10.1021/np200441h | J. Nat. Prod. 2012, 75, 34−47 Journal of Natural Products Article 2-(S)-MTPA ester (2b): 1H NMR (methanol-d4, 500 MHz) δ 4.40 (2H, m, H-26), 2.65 (1H, m, H-20); ESIMS m/z 981 [M + Na]+. 26-Acetylneoboutomellerone (3): yellow gum; [α]20D −61 (c 0.05, CHCl3); UV (MeOH) λmax (log ε) 222 (3.78), 266 (3.74) nm; IR (film) νmax 3299, 2933, 2874, 1736, 1699, 1596, 1372, 1230, 1022 cm−1; 1 H NMR (CD3CN, 500 MHz) δ 6.94 (1H, d, J = 10.1 Hz, H-1), 6.10 (1H, s, H-24a), 5.95 (1H, d, J = 0.6 Hz, H-24a), 5.88 (1H, d, J = 10.1 Hz, H-2), 5.52 (1H, d, J = 2.1 Hz, H-22), 5.09 (1H, dt, J = 4.6, 7.6 Hz, H-16), 4.04 (1H, dd, J = 7, 11 Hz, H-26a), 3.99 (1H, dd, J = 6.5, 11 Hz, H-26b), 3.00 (1H, sext, J = 6.9 Hz, H-25), 2.57 (1H, ddq, J = 11.0, 2.1, 7.0 Hz, H-20), 2.28 (1H, dd, J = 11.0, 7.6 Hz, H-17), 2.08 (3H, s, OAc-22), 2.05 (3H, s, OAc-16), 1.96 (3H, s, OAc-26), 1.56 (1H, ddd, J = 6.3, 8.5, 15 Hz, H-11b), 1.45 (1H, m, H-7a), 1.37 (1H, dd J = 14.5, 4.5 Hz, H-15b), 1.24 (1H, d, J = 4.6 Hz, H-19a), 1.19 (1H, m, H-7b), 1.18 (3H, s, H-18), 1.07 (3H, d, J = 7.0 Hz, H-27), 1.02 (3H, d, J = 6.7 Hz, H-28), 0.95 (3H, s, H-30), 0.94 (1H, m, H-6b), 0.84 (3H, d, J = 7.0 Hz, H-21), 0.57 (1H, d, J = 4.6 Hz, H-19b); 13C NMR, see Table 1; HR-ESIMS m/z 633.3399 (calcd for C36H50O8Na 633.3398). Preparation of Compound 3. To a stirred solution of compound 2 (50 mg, 0.088 mmol) in 4 mL of CH2Cl2 at 0 °C were added pyridine (300 μL, 3.7 mmol) and acetyl chloride (60 μL, 0.88 mmol, 10 equiv). The mixture was stirred overnight, MeOH (0.5 mL) was added, and the mixture was concentrated under vacuum. The crude material was purified by chromatography on silica gel (elution: from cyclohexane− EtOAc, 7:3 to 6:4) to yield 3 (52 mg, 75%), identical by all means with the natural product. Preparation of 22,23,26-Trihydroxy-29-nor-24-methyl-16,22-epoxycycloarta-1,24(24a)-diene-3,23-dione (4). To a stirred solution of compound 1 (20 mg, 0.038 mmol) in CH3CN (300 μL) was added NaOH (570 μL, 0.437 mmol, c = 1 mol/L, 15 equiv). The mixture was stirred for 22 h at room temperature, then diluted with EtOAc, and filtered over Celite. After concentration under vacuum, the product was purified by chromatography on silica gel (elution: cyclohexane− EtOAc, 1:1) to obtain 4 as a translucent film (3 mg, 17%): 1H NMR (CD3CN, 500 MHz) δ 6.96 (1H, d, J = 10.1 Hz, H-1), 5.91 (1H, d, J = 10.1 Hz, H-2), 5.24 (1H, s, H-24a), 5.11 (1H, s, H-24a), 4.66 (1H, dt, J = 7.2, 8.5 Hz, H-16), 3.97 (1H, d, J = 5.6 Hz, H-23), 3.79 (1H, d, J = 5.6 Hz, OH-23), 3.48 (1H, s, OH-22), 3.47 (1H, m, H-26a), 3.40 (1H, ddd, J = 9.6, 8.7, 4.6 Hz, H-26b), 3.23 (1H, t, J = 4.7 Hz, OH-26), 2.63 (1H, sext, J = 7.0 Hz, H-25), 2.47 (1H, quint, J = 6.8 Hz, H-20), 1.31 (1H, d, J = 4.6 Hz, H-19a), 1.27 (1H, m, H-7b), 1.13 (3H, s, H-18), 1.03 (3H, d, J = 6.7 Hz, H-28), 1.00 (3H, d, J = 7.0 Hz, H-27), 0.95 (3H, d, J = 6.7 Hz, H-21), 0.92 (3H, s, H-30), 0.50 (1H, d, J = 4.6 Hz, H-19b); 13C NMR, see Table 1; ESIMS m/z 507.3 [M + Na]+, 991.6 [2M + Na]+. 1,2-Dihydroneoboutomellerone (5): yellow gum; [α]20D +36 (c 0.08, CHCl3); UV (MeOH) λmax (log ε) 216 (3.78), 290 (2.63) nm; IR (film) νmax 3513, 2965, 2871, 1734, 1705, 1452, 1376, 1231 cm−1; 1H NMR (CD3CN, 500 MHz) δ 6.05 (1H, s, H-24a), 5.90 (1H, d, J = 0.9 Hz, H-24a), 5.53 (1H, d, J = 2.1 Hz, H-22), 5.08 (1H, dt, J = 4.3, 7.6 Hz, H-16), 3.53 (1H, dt, J = 10.6, 5.8 Hz, H-26a), 3.39 (1H, dt, J = 10.6, 6.1 Hz, H-26b), 2.77 (1H, sext, J = 6.7 Hz, H-25), 2.68 (1H, t, J = 5.6 Hz, OH-26), 2.60 (1H, ddq, J = 10.7, 1.8, 6.7 Hz, H-20), 2.43 (1H, td, J = 13.6, 6.4 Hz, H-2a), 2.20 (1H, dd, J = 14.0, 7.9 Hz, H-15a), 2.09 (3H, s, OAc-22), 2.11 (1H, m, H-11a), 2.03 (3H, s, OAc-16), 1.82 (1H, m, H-1a), 1.60−1.55 (2H, m, H-1b, H-5), 1.36 (1H, dd, J = 14.5, 4.1 Hz, H-15b), 1.23 (3H, s, H-18), 1.10 (1H, m, H-7b), 1.03 (3H, d, J = 7.0 Hz, H-27), 0.97 (3H, s, H-30), 0.91 (3H, d, J = 6.7 Hz, H-28), 0.84 (3H, d, J = 7.0 Hz, H-21), 0.75 (1H, dq, J = 2.4, 12.6 Hz, H-6b), 0.65 (1H, br d, J = 4.0 Hz, H-19a), 0.47 (1H, d, J = 4.0 Hz, H-19b); 13C NMR, see Table 1; HR-ESIMS m/z 593.3451 (calcd for C34H50O7Na 593.3449). 1,2-Dihydro-22-de-O-acetylneoboutomellerone (6): yellow gum; [α]20D +11 (c 0.12, CHCl3); UV (MeOH) λmax (log ε) 214 (3.74), 262 (3.23) nm; IR (film) νmax 3435, 2932, 2873, 1731, 1705, 1700, 1452, 1376, 1237, 1022, 997 cm−1; 1H NMR (CD3CN, 500 MHz) δ 6.12 (1H, s, H-24a), 5.99 (1H, d, J = 0.9 Hz, H-24a), 5.20 (1H, dt, J = 4.4, 7.6 Hz, H-16), 4.72 (1H, dd, J = 6.1, 2.1 Hz, H-22), 3.56 (1H, dt, J = 10.5, 5.8 Hz, H-26a), 3.54 (1H, d, J = 6.1 Hz, OH-22), 3.41 (1H, dt, (3H, d, J = 6.7 Hz, H-28), 0.95 (3H, s, H-30), 0.85 (3H, d, J = 7.0 Hz, H-21), 0.57 (1H, d, J = 4.6 Hz, H-19b); 13C NMR (125 MHz, CD3CN) δ 202.4 (C-3), 198.8 (C-23), 171.8 (C-22a), 171.3 (C-16), 155.5 (C-1), 149.2 (C-24), 139.9 (C-26c), 129.9 (C-26e, 26 g), 128.4 (C-2), 125.7 (C-24a), 123.9 (C-26f), 119.5 (C-26d, 26 h), 78.5 (C-22), 76.7 (C-16), 68.5 (C-26), 51.3 (C-17), 48.3 (C-14), 47.6 (C-4), 46.8 (C-13), 46.7 (C-15), 45.2 (C-8), 43.6 (C-5), 35.0 (C-25), 33.4 (C-20), 32.9 (C-12), 28.1 (C-11), 27.6 (C-19), 27.2 (C-9), 24.3 (C-6, 7), 22.1 (C-16b), 21.0 (C-22b), 20.0 (C-30), 18.3 (C-18), 17.1 (C-27), 13.4 (C-21), 11.3 (C-28); ESIMS m/z: 688.24 [M + H]+. X-ray Crystallographic Analysis of Compound 1c. Data were collected at low temperature (180 K) on a Bruker Kappa Apex II diffractometer using graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) and equipped with an Oxford Cryosystems Cryostream cooler device. The structure was solved by direct methods using SHELXS-8620 and refined by means of least-squares procedures on F2 with the aid of the program SHELXL9720 included in the software package WinGX version 1.63.21 The atomic scattering factors were taken from International Tables for X-ray Crystallography.22 All hydrogen atoms were placed geometrically and refined by using a riding model, except for the atoms H30A and H30B, which were located by Fourier differences. All non-hydrogen atoms were anisotropically refined, and in the last cycles of refinement, a weighting scheme was used, where weights were calculated from the following formula: w = 1/[σ2(Fo2) + (aP)2 + bP] where P = (Fo2 + 2Fc2)/3. Drawing was performed with the program ORTEP32 with 30% probability displacement ellipsoids for non-hydrogen atoms.23 Crystal Data for 1c: orthorhombic, C41H53NO8, space group P212121 with a = 11.5565(7) Å, b = 14.6892(10) Å, c = 22.0210(15) Å, V = 3738.2(4) Å3, Z = 4, Dcalcd 1.222 g/cm3, m = 0.084 mm−1, F(000) = 1480. Crystal size: 0.35 × 0.2 × 0.08 mm3. Independent reflections: 6975 with Rint = 0.0333. The final agreement factors are R1 = 0.0394 and wR2 = 0.0972 [I > 2σ(I)]. Crystallographic data are deposited at the Cambridge Crystallographic Data center (deposition no. CCDC 826141). 22-De-O-acetylneoboutomellerone (2): [α]20D −55 (c 0.16, CHCl3); UV (MeOH) λmax (log ε) 228 (3.71), 266 (3.86) nm; IR (film) νmax 3453, 1725, 1661, 1601, 1245, 1043 cm−1; 1H NMR (CDCl3, 500 MHz) δ 6.85 (1H, d, J = 10.1 Hz, H-1), 6.18 (1H, s, H-24a), 6.02 (1H, s, H-24a), 5.99 (1H, d, J = 10.1 Hz, H-2), 5.35 (1H, dt, J = 4.6, 7.5 Hz, H-16), 4.74 (1H, dd, J = 5.5, 1.5 Hz, H-22), 3.65 (2H, d, J = 6.1 Hz, H-26), 3.52 (1H, d, J = 5.8 Hz, OH-22), 2.96 (1H, sext, J = 6.7 Hz, H-25), 2.52 (1H, dd, J = 11.0, 7.3 Hz, H-17), 2.46 (1H, m, H-20), 2.35 (1H, dd, J = 14.0, 7.9 Hz, H-15a), 2.19 (1H, dq, J = 12.5, 6.7 Hz, H-4), 2.10 (3H, s, OAc-16), 2.05 (1H, m, H-11a), 1.99 (1H, dt, J = 5.2, 13.4 Hz, H-5), 1.97 (1H, dd, J = 10.5, 6.9 Hz, H-8a), 1.65 (1H, m, H-12a), 1.34 (1H, dd, J = 14.0, 4.4 Hz, H-15b), 1.18 (1H, d, J = 4.5 Hz, H-19a), 1.18 (3H, s, H-18), 1.14 (3H, d, J = 7.0 Hz, H-27), 1.10 (3H, d, J = 7.0 Hz, H-28), 0.99 (3H, s, H-30), 0.88 (1H, m, H-6b), 0.66 (3H, d, J = 7.0 Hz, H-21), 0.57 (1H, d, J = 4.5 Hz, H-19b); 13C NMR, see Table 1; HR-ESIMS m/z 549.3179 (calcd for C32H46O6Na 549.3187). Preparation of Mosher Ester Derivatives 1a, 1b, 2a, and 2b. Compounds 1 and 2 (10 mg) in dry pyridine (2.0 mL) were transferred into an HPLC vial (2 mL) capped with a septum and were treated with 30 μL (175 μmol) of (S)-(+)-α-methoxy-α-trifluoromethylphenylacetyl chloride (MTPA chloride). The mixtures were stirred at room temperature for 2 h. After concentration under reduced pressure, they were purified by semipreparative HPLC RP-18 chromatography, eluting with a linear gradient (55−100% B) to afford 1a and 2a. Derivatives 1b and 2b were prepared in a similar fashion by using (R)-(−)-α-methoxy-α-trifluoromethylphenylacetyl chloride. 1-(R)-MTPA ester (1a): 1H NMR (CD3CN, 500 MHz) δ 4.39 (1H, dd, J = 6.2, 10.9 Hz, H-26a), 4.27 (1H, dd, J = 5.7, 10.9 Hz, H-26b); ESIMS m/z 807 [M + Na]+. 1-(S)-MTPA ester (1b): 1H NMR (CD3CN, 500 MHz) δ 4.34 (2H, AB part of an ABX system, H-26); ESIMS m/z 807 [M + Na]+. 2-(R)-MTPA ester (2a): 1H NMR (methanol-d4, 500 MHz) δ 4.44 (1H, dd, J = 6.0, 10.9 Hz, H-26a), 4.35 (1H, dd, J = 5.1, 10.9 Hz, H26b), 2.59 (1H, m, H-20); ESIMS m/z 981 [M + Na]+. 43 dx.doi.org/10.1021/np200441h | J. Nat. Prod. 2012, 75, 34−47 Journal of Natural Products Article J = 10.5, 5.8 Hz, H-26b), 2.83 (1H, sext, J = 6.7 Hz, H-25), 2.67 (1H, t, J = 5.8 Hz, OH-26), 2.07 (1H, m, H-11a), 2.03 (3H, s, OAc-16), 1.82 (1H, m, H-1a), 1.37 (1H, ddd, J = 14.2, 4.4, 0.9 Hz, H-15b), 1.22 (3H, s, H-18), 1.12 (1H, dq, J = 2.7, 12.8 Hz, H-7b), 1.05 (3H, d, J = 7.3 Hz, H-27), 0.97 (3H, d, J = 0.6 Hz, H-30), 0.91 (3H, d, J = 6.7 Hz, H-28), 0.75 (1H, dq, J = 2.4, 12.5 Hz, H-6b), 0.65 (1H, m, H-19a), 0.64 (3H, d, J = 6.4 Hz, H-21), 0.47 (1H, d, J = 4.0 Hz, H-19b); 13C NMR, see Table 1; HR-ESIMS m/z 551.3342 (calcd for C32H48O6Na 551.3343). 6β-Hydroxyneoboutomellerone (7): yellow gum; [α]20D −43 (c 0.13, CHCl3); UV (MeOH) λmax (log ε) 212 (3.84), 220 (3.84), 266 (3.87) nm; IR (film) νmax 3409, 2937, 2876, 1733, 1662, 1454, 1374, 1232, 1022 cm−1; 1H NMR (CDCl3, 500 MHz) δ 6.76 (1H, d, J = 10 Hz, H-1), 6.14 (1H, s, H-24a), 5.96 (1H, d, J = 10 Hz, H-2), 5.90 (1H, s, H-24a), 5.59 (1H, d, J = 2.1 Hz, H-22), 5.10 (1H, dt, J = 4.4, 7.7 Hz, H-16), 4.20 (1H, br s, H-6), 3.60 (2H, d, J = 5.8 Hz, H-26), 2.89 (1H, sext, J = 6.4 Hz, H-25), 2.35 (1H, dd, J = 14.0, 7.9 Hz, H-15a), 2.20 (1H, m, H-11a), 2.16 (3H, s, OAc-22), 2.08 (3H, s, OAc-16), 1.99 (1H, m, H-5), 1.86 (1H, d, J = 3.7 Hz, H-19a), 1.76 (2H, m, 2 H-12), 1.56 (1H, m, H-7a), 1.48 (1H, dt, J = 1.7, 13.3 Hz, H-7b), 1.25 (3H, s, H-18), 1.24 (3H, d, J = 7.0 Hz, H-28), 1.13 (3H, d, J = 7.0 Hz, H-27), 1.0 (3H, s, H-30), 0.91 (3H, d, J = 6.7 Hz, H-21), 0.72 (1H, d, J = 3.7 Hz, H-19b); 13C NMR, see Table 1; HR-ESIMS m/z 607.3243 (calcd for C34H48O8Na 607.3241). 6β-Hydroxy-22-de-O-acetylneoboutomellerone (8): yellow gum; [α]20D −8 (c 0.14, CHCl3); UV (MeOH) λmax (log ε) 210 (3.94), 266 (3.78) nm; IR (film) νmax 3435, 2934, 2876, 1729, 1666, 1453, 1375, 1236, 1023 cm−1; 1H NMR (CDCl3, 500 MHz)) δ 6.76 (1H, d, J = 10 Hz, H-1), 6.18 (1H, s, H-24a), 6.03 (1H, s, H-24a), 5.94 (1H, d, J = 10 Hz, H-2), 5.35 (1H, dt, J = 4.4, 7.1 Hz, H-16), 4.74 (1H, s, H-22), 4.19 (1H, br s, H-6), 3.64 (2H, d, J = 6.1 Hz, H-26), 3.59 (1H, d, J = 5.5 Hz, OH-22), 2.96 (1H, sext, J = 6.4 Hz, H-25), 2.58 (1H, m, H-4), 2.52 (1H, m, H-17), 2.45 (1H, m, H-20), 2.37 (1H, dd, J = 13.7, 7.9 Hz, H-15a), 2.30 (1H, dd, J = 12.7, 4.4 Hz, H-8), 2.22 (1H, m, H-11a), 2.09 (3H, s, OAc-16), 1.99 (1H, dd, J = 12.8, 2.4 Hz, H-5), 1.84 (1H, d, J = 3.1 Hz, H-19a), 1.75 (2H, m, 2 H-12), 1.58 (1H, dt, J = 4.4, 12.9 Hz, H-7a), 1.48 (1H, t, J = 13.1 Hz, H-7b), 1.40−1.20 (2H, m, H-15b, H-11b), 1.24 (3H, d, J = 7.3 Hz, H-28), 1.23 (3H, br s, H-18), 1.14 (3H, d, J = 7.0 Hz, H-27), 1.04 (3H, s, H-30), 0.70 (1H, d, J = 3.1 Hz, H-19b), 0.67 (3H, d, J = 6.4 Hz, H-21); 13C NMR, see Table 1; HRESIMS m/z 565.3133 (calcd for C32H46O7 Na 565.3136). 18-Hydroxyneoboutomellerone (9): yellow gum; [α]20D −16 (c 0.03, CHCl3); UV (MeOH) λmax (log ε) 214 (3.14), 266 (2.96) nm; 1H NMR (CDCl3, 500 MHz) δ 6.80 (1H, d, J = 10 Hz, H-1), 6.07 (1H, s, H-24a), 5.98 (1H, d, J = 10 Hz, H-2), 5.86 (1H, br d, H-24), 5.57 (1H, d, J = 2.1 Hz, H-22), 5.18 (1H, dt, J = 4.3, 7.6 Hz, H-16), 4.06 (1H, m, H-18a), 3.94 (1H, d, J = 12.2 Hz, H-18b), 3.58 (2H, m, 2 H-26), 2.86 (1H, sext, J = 7.0 Hz, H-25), 2.72 (1H, m, H-20), 2.36 (1H, dd, J = 11.3, 7.6 Hz, H-17), 2.28 (1H, dd, J = 14.3, 7.9 Hz, H-15a), 2.19 (1H, m, H-4), 2.14 (3H, s, OAc-22), 2.09 (3H, s, OAc-16), 2.03 (2H, m, H-5, H-8), 1.85 (1H, m, H-12a), 1.70 (1H, m, H-6a), 1.63 (1H, m, H12b), 1.60 (1H, m, H-15b), 1.35 (2H, m, H-7a, H-11b), 1.19 (1H, d, J = 4.3 Hz, H-19a), 1.16 (1H, m, H-7b), 1.11 (3H, d, J = 7.3 Hz, H-27), 1.09 (3H, d, J = 6.9 Hz, H-28), 1.00 (3H, s, H-30), 0.93 (3H, d, J = 6.7 Hz, H-21), 0.90 (1H, m, H-6b), 0.60 (1H, d, J = 4.3 Hz, H-19b); 13C NMR, see Table 2; HR-ESIMS m/z 607.3216 (calcd for C34H48O8Na 607.3241). 6β,7β-Oxidoneoboutomellerone (10): yellow gum; [α]20D −86 (c 0.16, CHCl3); UV (MeOH) λmax (log ε) 224 (3.92), 262 (3.93) nm; IR (film) νmax 3411, 2966, 2878, 1735, 1669, 1375, 1233, 1022 cm−1; 1 H NMR (CD3CN, 500 MHz) δ 6.94 (1H, d, J = 10 Hz, H-1), 6.06 (1H, s, H-24a), 5.91 (1H, d, J = 10.0 Hz, H-2), 5.90 (1H, br s, H-24a), 5.54 (1H, d, J = 2.1 Hz, H-22), 5.16 (1H, dt, J = 4.7, 7.7 Hz, H-16), 3.53 (1H, dd, J = 10.4, 6.4 Hz, H-26a), 3.39 (1H, dd, J = 10.4, 6.6 Hz, H-26b), 3.15 (1H, dd, J = 4.3, 1.5 Hz, H-6), 3.00 (1H, dd, J = 4.3, 1.8 Hz, H-7), 2.83 (1H, br d, J = 1.2 Hz, H-8), 2.77 (1H, sext, J = 6.7 Hz, H-25), 2.70 (1H, br s, OH-26), 2.63 (1H, ddq, J = 10.8, 2.1, 7.0 Hz, H-20), 2.55 (1H, dq, J = 12.5, 7.0 Hz, H-4), 2.45 (1H, br d, J = 11.3 Hz, H-5), 2.33 (1H, dd, J = 13.4, 7.9 Hz, H-15a), 2.28 (1H, dd, J = 10.8, 7.8 Hz, H-17), 2.08 (3H, s, OAc-22), 2.06 (3H, s, OAc-16), 2.04 (2H, m, H-11a, H-19a), 1.40 (1H, ddd, J = 15.9, 3.1, 1.6 Hz, H-11b), 1.23 (3H, d, J = 7.0 Hz, H-28), 1.20 (3H, s, H-18), 1.03 (3H, d, J = 7.0 Hz, H-27), 0.94 (3H, s, H-30), 0.86 (3H, d, J = 7.0 Hz, H-21), 0.03 (1H, d, J = 4.0 Hz, H-19b); 13C NMR, see Table 2; HRESIMS m/z 605.3091 (calcd for C34H46O8Na 605.3085). 1,2-Dihydro-1α-hydroxy-22-de-O-acetylneoboutomellerone (11): yellow gum; [α]20D +30 (c 0.12, CHCl3); UV (MeOH) λmax (log ε) 216 (3.920) nm; IR (film) νmax 3401, 2934, 2876, 1707, 1669, 1376, 1237, 1021 cm−1; 1H NMR (CD3CN, 500 MHz) δ 6.12 (1H, s, H-24a), 5.99 (1H, d, J = 0.9 Hz, H-24a), 5.21 (1H, dt, J = 4.3, 7.5 Hz, H-16), 4.72 (1H, dd, J = 5.3, 1.7 Hz, H-22), 3.80 (1H, t, J = 3.1 Hz, H1), 3.55 (2H, dd, J = 10.9, 6.1 Hz, H-26a + OH-22), 3.42 (1H, dd, J = 10.9, 7 Hz, H-26b), 2.83 (1H, sext, J = 6.4 Hz, H-25), 2.80 (1H, br s, OH-1), 2.69 (1H, br s, OH-26), 2.64 (1H, ddd, J = 14.0, 3.7, 0.5 Hz, H-2a), 2.46 (1H, ddq, J = 11.0, 2.1, 6.7 Hz, H-20), 2.42 (1H, dd, J = 11.0, 7.0 Hz, H-17), 2.14 (1H, m, H-5), 2.03 (3H, s, OAc-16), 1.74 (1H, m, H-6a), 1.21 (3H, s, H-18), 1.05 (3H, d, J = 7.0 Hz, H-27), 1.01 (3H, s, H-30), 0.92 (3H, d, J = 6.4 Hz, H-28), 0.80 (1H, dq, J = 2.4, 12.6 Hz, H-6b), 0.73 (1H, d, J = 4.3 Hz, H-19a), 0.64 (3H, d, J = 6.6 Hz, H-21), 0.48 (1H, d, J = 4.3 Hz, H-19b), 13C NMR, see Table 2; HR-ESIMS m/z 567.3296 (calcd for C32H48O7Na 567.3292). 25-Epi-neoboutomellerone (12): yellow gum; [α]20D +9 (c 0.03, CHCl3); UV (MeOH) λmax (log ε) 210 (3.54), 264 (3.54) nm; IR (film) νmax 3386, 2927, 1732, 1667, 1570, 1375, 1233, 1022 cm−1; 1H NMR (CDCl3, 500 MHz) δ 6.82 (1H, d, J = 9.8 Hz, H-1), 6.11 (1H, s, H-24a), 5.98 (1H, d, J = 9.8 Hz, H-2), 5.83 (1H, d, J = 0.9 Hz, H-24a), 5.52 (1H, d, J = 2.1 Hz, H-22), 5.07 (1H, dt, J = 4.4, 7.7 Hz, H-16), 3.56 (2H, t, J = 6.0 Hz, 2 H-26), 2.96 (1H, sext, J = 6.7 Hz, H-25), 2.59 (1H, m, H-20), 2.28 (1H, dd, J = 7.4, 14.4 Hz, H-17), 2.25 (1H, m, H-15a), 2.18 (1H, m, H-4), 2.14 (3H, s, OAc-22), 2.06 (3H, s, OAc16), 1.45 (1H, m, H-7), 1.30 (1H, dd, J = 14.2, 4.7 Hz, H-15b), 1.18 (1H, d, J = 4.6 Hz, H-19a),1.16 (3H, s, H-18), 1.09 (3H, d, J = 7.0 Hz, H-27), 1.08 (3H, d, J = 6.7 Hz, H-28), 0.93 (3H, s, H-30), 0.89 (3H, d, J = 7.0 Hz, H-21), 0.55 (1H, d, J = 4.6 Hz, H-19); 13C NMR, see Table 2; HR-ESIMS m/z 591.3291 (calcd for C34H48O7Na, 591.3292). Preparation of 25ξ-Neoboutomelleron-26-al (13). To a stirred solution of 1 (100 mg, 0.18 mmol) in CH2Cl2 (3.5 mL) was added 350 μL of pyridine (2 mL/mmol), and the mixture was cooled to 0 °C. The Dess-Martin reagent (1.76 mL, 0.528 mmol, c = 3 mol/L, 3 equiv) was added dropwise, and the mixture was allowed to warm. After 3 h, the mixture was diluted with EtOAc, and a saturated solution of Na2S2O3 was added. The aqueous layer was extracted three times with EtOAc (10 mL), and the combined organic layers were washed successively with NaHCO3 (10 mL) and brine. The organic solution was dried over MgSO4 and concentrated under vacuum. The residue was purified by chromatography on silica gel (cyclohexane−EtOAc, 7:3 to 6:4) to give 13 (66 mg, 66%). 1H NMR (500 MHz, CD3CN) δ 9.52 (1H, d, J = 0.6 Hz, H-26), 6.94 (1H, d, J = 10.1 Hz, H-1), 6.31 (1H, s, H-24a), 6.06 (1H, s, H-24), 5.90 (1H, d, J = 10.1 Hz, H-2), 5.58 (1H, d, J = 2.1 Hz, H-22), 5.10 (1H, dt, J = 4.4, 7.7 Hz, H-16), 3.45 (1H, q, J = 7.2 Hz, H-25), 2.64 (1H, m, H-20), 2.31 (1H, dd, J = 11.0, 7.6 Hz, H-17), 2.09 (3H, s, OAc-22), 2.04 (3H, s, OAc-16), 1.38 (1H, dd, J = 13.7, 4.0 Hz, H-15b), 1.25 (1H, d, J = 4.4 Hz, H-19a), 1.18 - 1.22 (7H, m, H-7, -27, -18), 1.03 (3H, d, J = 6.7 Hz, H-28), 0.96 (3H, s, H-30), 0.94 (1H, qd, J = 12.8, 3.7 Hz, H-6b), 0.85 (3H, d, J = 7.0 Hz, H-21), 0.58 (1H, d, J = 4.4 Hz, H-19b);); 13C NMR, see Table 2; ESI-MS m/z 567.3 [M + H]+. 9,10-Di-epi-25ξ-neoboutomellerone (14): yellow gum; [α]20D −48 (c 0.13, CHCl3); UV (MeOH) λmax (log ε) 210 (3.73), 270 (3.93) nm; IR (film) νmax 3417, 2937, 2875, 1734, 1666, 1373, 1233, 1022 cm−1; 1H NMR (CDCl3, 500 MHz) δ 6.39 (1H, d, J = 10.4 Hz, H-1), 6.13 (1H, s, H-24a), 5.99 (1H, d, J = 10.4 Hz, H-2), 5.88 (1H, d, J = 0.6 Hz, H24a), 5.58 (1H, d, J = 2.1 Hz, H-22), 5.15 (1H, dt, J = 5.0, 7.7 Hz, H16), 3.60 (2H, t, J = 5.5 Hz, 2 H-26), 2.88 (1H, sext, J = 6.4 Hz, H-25), 2.62 (1H, m, H-20), 2.28 (1H, dd, J = 11.9, 7.3 Hz, H-17), 2.26 (1H, m, H-15a), 2.20 (1H, m, H-4), 2.16 (3H, s, OAc-22), 2.10 (3H, s, OAc-16), 1.96 (1H, m, H-8), 1.85 (1H, dt, J = 5.0, 13.0 Hz, H-12a), 1.6 (1H, dd, J = 13.0, 4.1 Hz, H-12a), 1.28 (1H, d, J = 5.0 Hz, H-19a), 1.14 (3H, s, H-18), 1.12 (3H, d, J = 6.1 Hz, H-28), 1.10 (3H, s, H-27), 0.93 (3H, br s, H-30), 0.91 (3H, d, J = 7.0 Hz, H-21), 0.88 44 dx.doi.org/10.1021/np200441h | J. Nat. Prod. 2012, 75, 34−47 Journal of Natural Products Article (1H, d, J = 5.0 Hz, H-19b); 13C NMR, see Table 2; HR-ESIMS m/z 591.3295 (calcd for C34H48O7Na, 591.3292). 9,10-Di-epi-22-de-O-acetyl-25ξ-neoboutomellerone (15): yellow gum; [α]20D −53 (c 0.13, CHCl3); UV (MeOH) λmax (log ε) 210 (4.12), 270 (4.20) nm; IR (film) νmax 3421, 2937, 2877, 1732, 1666, 1609, 1453, 1376, 1240, 1024 cm−1; 1H NMR (CDCl3, 500 MHz) δ 6.39 (1H, d, J = 10.1 Hz, H-1), 6.19 (1H, s, H-24a), 6.02 (1H, s, H-24a), 5.99 (1H, d, J = 10.1 Hz, H-2), 5.39 (1H, dt, J = 5.0, 7.6 Hz, H-16), 4.73 (1H, br s, H-22), 3.64 (1H, d, J = 5.8 Hz, 2 H-26), 3.54 (1H, br s, OH-22), 2.96 (1H, sext, J = 6.7 Hz, H-25), 2.53 (1H, dd, J = 11.0, 7.6 Hz, H-17), 2.48 (1H, m, H-20), 2.31 (1H, dd, J = 13.3, 7.8 Hz, H-15), 2.11 (3H, s, OAc-16), 1.84 (1H, dt, J = 4.7,, 13.4 Hz, H-12), 1.60 (1H, ddd, J = 13.4, 4.0, 1.5 Hz, H-12b), 1.33 (1H, m, H-15), 1.28 (1H, d, J = 4.9 Hz, H-19a), 1.13 (6H, d, J = 7.0 Hz, H-27, H-28); 1.12 (3H, s, H-18), 0.97 (3H, s, H-30), 0.88 (1H, d, J = 4.9 Hz, H-19b), 0.67 (3H, d, J = 6.4 Hz, H-21); 13C NMR, see Table 2; HRESIMS m/z 549.3190 (calcd for C32H46O6Na, 549.3187). 26-Deoxyneoboutomellerone (16): yellow gum; [α]20D −102 (c 0.08, CHCl3); UV (MeOH) λmax (log ε) 220 (3.95), 264 (3.77) nm; IR (film) νmax 3437, 2962, 2931, 2873, 1734, 1669, 1599, 1455, 1407, 1237 cm−1; 1H NMR (CD3CN, 500 MHz) δ 6.94 (1H, d, J = 10 Hz, H-1), 5.94 (1H, s, H-24a), 5.90 (1H, d, J = 10.0 Hz, H-2), 5.83 (1H, d, J = 1.2 Hz, H-24a), 5.51 (1H, d, J = 2.4 Hz, H-22), 5.09 (1H, dt, J = 4.3, 7.6 Hz, H-16), 2.81 (1H, dsept, J = 0.9, 7.0 Hz, H-25), 2.56 (1H, ddq, J = 11.0, 2.1, 7.0 Hz, H-20), 2.29 (1H, dd, J = 11.0,, 7.3 Hz, H-17), 2.18 (2H, m, H-4, H-15a), 2.09 (3H, s, OAc-22), 2.02 (3H, s, OAc-16), 1.56 (1H, ddd, J = 7.0, 9.0, 15.0 Hz, H-11b), 1.44 (1H, ddt, J = 7.0, 13.5, 4.0 Hz, H-7a), 1.36 (1H, ddd, J = 14.0, 4.3, 0.9 Hz, H-15b), 1.24 (1H, d, J = 4.6 Hz, H-19a), 1.18 (3H, s, H-18), 1.07 (3H, d, J = 6.7 Hz, H-26), 1.02 (3H, d, J = 7.0 Hz, H-28), 1.00 (3H, d, J = 7.0 Hz, H-27), 0.95 (3H, s, H-30), 0.85 (3H, d, J = 7.0 Hz, H-21), 0.58 (1H, d, J = 4.6 Hz, H-19b); 13C NMR, see Table 2; HR-ESIMS m/z 575.3341 (calcd for C34H48O6Na, 575.3343). 22-De-O-acetyl-26-deoxyneoboutomellerone (17): yellow gum; [α]20D −91 (c 0.12, CHCl3); UV (MeOH) λmax (log ε) 220 (3.87), 266 (3.86) nm; IR (film) νmax 3457, 2933, 2931, 2873, 1734, 1669, 1456, 1375, 1237 cm−1; 1H NMR (CD3CN, 500 MHz) δ 6.93 (1H, d, J = 10.0 Hz, H-1), 6.02 (1H, s, H-24a), 5.93 (1H, d, J = 1.2 Hz, H-24a), 5.89 (1H, d, J = 10.0 Hz, H-2), 5.20 (1H, dt, J = 4.4, 7.6 Hz, H-16), 4.71 (1H, d, J = 5.8 Hz, H-22), 3.54 (1H, d, J = 5.8 Hz, OH22), 2.85 (1H, dsept, J = 0.9, 6.9 Hz, H-25), 2.42 (2H, m, H-17, H-20), 2.22 (1H, dd, J = 13.9, 7.8 Hz, H-15a), 2.17 (1H, dq, J = 12.7, 6.9 Hz, H-4), 2.02 (3H, s, OAc-16), 1.54 (1H, ddd, J = 7.0, 8.5, 15.0 Hz, H-11), 1.45 (1H, ddt, J = 7.0, 14.0, 4.0 Hz, H-7a), 1.37 (1H, ddd, J = 13.9, 4.4, 1.0 Hz, H-15), 1.23 (1H, d, J = 4.3 Hz, H-19a), 1.17 (3H, s, H-18), 1.09 (3H, d, J = 7.0 Hz, H-26), 1.03 (3H, d, J = 6.7 Hz, H-28), 1.02 (3H, d, J = 6.7 Hz, H-27), 0.96 (3H, d, J = 0.6 Hz, H-30), 0.64 (3H, d, J = 6.4 Hz, H-21), 0.57 (1H, d, J = 4.3 Hz, H-19b); 13C NMR, see Table 3; HR-ESIMS m/z 533.3234 (calcd for C32H46O5Na, 533.3237). 6β-Hydroxy-26-deoxyneoboutomellerone (18): yellow gum; [α]20D −61 (c 0.12, CHCl3); UV (MeOH) λmax (log ε) 220 (3.83), 266 (3.74) nm; IR (film) νmax 3414, 2965, 2939, 2876, 1737, 1668, 1600, 1376, 1232 cm−1; 1H NMR (CD3CN, 500 MHz) δ 6.84 (1H, d, J = 9.9 Hz, H-1), 5.95 (1H, s, H-24a), 5.84 (1H, d, J = 1.2 Hz, H-24a), 5.82 (1H, d, J = 9.9 Hz, H-2), 5.53 (1H, d, J = 2.1 Hz, H-22), 5.10 (1H, dt, J = 4.3, 7.6 Hz, H-16), 4.05 (1H, br s, H-6), 2.81 (1H, dsept, J = 1.0, 6.7 Hz, H-25), 2.61 (1H, d, J = 3.4 Hz, OH-6), 2.57 (1H, ddq, J = 2.2, 10.0, 6.9 Hz, H-20), 2.48 (1H, dq, J = 13.1, 6.7 Hz, H-4), 2.32 (1H, dd, J = 11.0, 7.6 Hz, H-17), 2.29 (1H, dd, J = 12.8, 4.9 Hz, H-8a), 2.22 (1H, dd, J = 13.7, 7.9 Hz, H-15a), 2.21 (1H, m, H-11), 2.10 (3H, s, OAc-22), 2.03 (3H, s, OAc-16), 1.81 (1H, d, J = 3.1 Hz, H-19a), 1.75 (2H, m, 2 H-12), 1.52 (1H, dt, J = 13.4, 4.7 Hz, H-7), 1.24 (3H, s, H-18), 1.14 (3H, d, J = 6.7 Hz, H-28), 1.08 (3H, d, J = 6.7 Hz, H-26), 1.01 (3H, d, J = 7.0 Hz, H-27), 1.00 (3H, s, H-30), 0.86 (3H, d, J = 7.0 Hz, H-21), 0.67 (1H, d, J = 3.4 Hz, H-19b); 13C NMR, see Table 3; HR-ESIMS m/z 591.3287 (calcd for C34H48O7Na, 591.3292). 1,2-Dihydro-22-de-O-acetyl-26-deoxyneoboutomellerone (19): yellow gum; [α]20D +19 (c 0.09, CHCl3); IR (film) νmax 3401, 2930, 2871, 1734, 1707, 1453, 1377, 1240 cm−1; 1H NMR (CD3CN, 500 MHz) δ 6.03 (1H, s, H-24a), 5.94 (1H, d, J = 1.1 Hz, H-24a), 5.20 (1H, td, J = 4.2, 7.7 Hz, H-16), 4.70 (1H, d, J = 1.4 Hz, H-22), 2.86 (1H, dsept, J = 0.9, 7.0 Hz, H-25), 2.03 (3H, s, OAc-16), 1.86−1.78 (2H, m, H-1, H-12), 1.22 (3H, s, H-18), 1.10 (3H, d, J = 6.7 Hz, H-27), 1.02 (3H, d, J = 6.7 Hz, H-26), 0.97 (1H, d, J = 0.6 Hz, H-30), 0.91 (3H, d, J = 6.8 Hz, H-28), 0.76 (1H, dq, J = 2.3, 12.5 Hz, H-6b), 0.64 (1H, m, H-19a), 0.64 (3H, d, J = 6.1 Hz, H-21), 0.47 (1H, d, J = 4.0 Hz, H-19b); 13C NMR, see Table 3; HR-ESIMS m/z 535.3393 (calcd for C32H48O5Na, 535.3394). 9,10-Di-epi-26-deoxyneoboutomellerone (20): yellow gum; [α]20D −98 (c 0.11, CHCl3); UV (MeOH) λmax (log ε) 212 (4.08), 270 (4.21) nm; IR (film) νmax 3451, 2936, 2873, 2876, 1734, 1667, 1609, 1452, 1374, 1238 cm−1; 1H NMR (CD3CN, 500 MHz) δ 6.50 (1H, d, J = 10.2 Hz, H-1), 5.95 (1H, s, H-24a), 5.88 (1H, d, J = 10.2 Hz, H-2), 5.82 (1H, d, J = 1.2 Hz, H-24a), 5.52 (1H, d, J = 2.0 Hz, H-22), 5.14 (1H, dt, J = 4.5, 7.7 Hz, H-16), 2.81 (1H, dsept, J = 1.0, 7.0 Hz, H-25), 2.57 (1H, ddq, J = 10.9, 2.1, 6.9 Hz, H-20), 2.29 (1H, dd, J = 10.8, 7.7 Hz, H-17), 2.22 (2H, m, H-4, H-8a), 2.09 (3H, s, OAc-22), 2.04 (3H, s, OAc-16), 2.00 (1H, m, H-7), 1.83 (1H, dt, J = 4.4, 12.5, H-12a), 1.63 (1H, ddd, J = 2.0, 5.0, 13.0 Hz, H-12b), 1.42 (1H, ddd, J = 2.2, 5.0, 14.0, H-11b), 1.36 (1H, dd, J = 4.7, 14.0 Hz, H-15b) 1.30 (1H, d, J = 4.7 Hz, H-19a), 1.13 (3H, s, H-18), 1.07 (3H, d, J = 7.0 Hz, H-26), 1.04 (3H, d, J = 6.6 Hz, H-28), 1.00 (3H, d, J = 6.9 Hz, H-27), 0.93 (3H, s, H-30), 0.92 (1H, m, H-19), 0.86 (3H, d, J = 6.9 Hz, H-21); 13C NMR, see Table 3; HR-ESIMS m/z 575.3338 (calcd for C34H48O6Na, 575.3343). 24a-Nor-24,25-didehydro-26-deoxyneoboutomellerone (21): yellow gum; [α]20D −73 (c 0.03, CHCl3); UV (MeOH) λmax (log ε) 242 (3.96) nm; IR (film) νmax 3433, 2932, 2931, 2874, 1735, 1671, 1615, 1378, 1234 cm−1; 1H NMR (CD3CN, 500 MHz) δ 6.94 (1H, d, J = 10.1 Hz, H-1), 6.14 (1H, sept, J = 1.3 Hz, H-24), 5.90 (1H, d, J = 10.1 Hz, H-2), 5.10 (1H, dt, J = 4.6, 7.8 Hz, H-16), 4.85 (1H, d, J = 1.8 Hz, H-22), 2.59 (1H, ddq, J = 10.9, 1.5, 7.0 Hz, H-20), 2.12 (3H, d, J = 1.2 Hz, H-27), 2.09 (3H, s, OAc-22), 2.08 (3H, s, OAc-16), 1.98 (3H, m, H-26), 1.26 (1H, d, J = 4.3 Hz, H-19a), 1.20 (3H, s, H-18), 1.02 (3H, d, J = 6.7 Hz, H-28), 0.93 (3H, d, J = 0.9 Hz, H-30), 0.85 (3H, d, J = 7.0 Hz, H-21), 0.56 (1H, d, J = 4.3 Hz, H-19b); 13C NMR, see Table 1; HR-ESIMS m/z 561.3182 (calcd for C33H46NaO6, 561.3187). 22-De-O-acetyl-24a-nor-24,25-didehydro-26-deoxyneoboutomellerone (22): yellow gum; [α]20D −80 (c 0.04, CHCl3); UV (MeOH) λmax (log ε) 242 (3.95) nm; IR (film) νmax 3464, 2933, 2874, 1732, 1671, 1618, 1449, 1378, 1237 cm−1; 1H NMR (CD3CN, 500 MHz) δ 6.94 (1H, d, J = 10 Hz, H-1), 6.17 (1H, sept, J = 1.3 Hz, H-24), 5.89 (1H, d, J = 10.0 Hz, H-2), 5.19 (1H, dt, J = 4.7, 7.9 Hz, H-16), 3.99 (1H, dd, J = 4.9, 1.2 Hz, H-22), 3.54 (1H, d, J = 5.2 Hz, OH-22), 2.47 (1H, ddq, J = 11.3, 1.8, 7.0 Hz, H-20), 2.35 (1H, dd, J = 11.0, 7.6 Hz, H-17), 2.18 (1H, m, H-4), 2.17 (3H, d, J = 1.2 Hz, H-27), 2.05 (3H, s, OAc-16), 1.94 (3H, m, H-26), 1.56 (1H, ddd, J = 7.5, 8.5, 14.0 Hz, H-11), 1.47 (1H, m, H-7), 1.39 (1H, dd, J = 13.6, 5.0 Hz, H-15), 1.25 (1H, d, J = 4.6 Hz, H-19a), 1.20 (3H, s, H-18), 1.02 (3H, d, J = 6.7 Hz, H-28), 0.95 (3H, d, J = 0.6 Hz, H-30), 0.65 (3H, d, J = 6.7 Hz, H-21), 0.56 (1H, d, J = 4.6 Hz, H-19b); 13C NMR, see Table 3; HR-ESIMS m/z 519.3076 (calcd for C31H44O5Na, 519.3081). 9,10-Di-epi-24a-nor-24,25-didehydro-26-deoxyneoboutomellerone (23): yellow gum; [α]20D −55 (c 0.07, CHCl3); UV (MeOH) λmax (log ε) 210 (3.77), 244 (3.98) nm; IR (film) νmax 3409, 2936, 2874, 1734, 1669, 1612, 1447, 1374, 1235 cm−1; 1H NMR (CD3CN, 500 MHz) δ 6.50 (1H, d, J = 10.1 Hz, H-1), 6.15 (1H, sept, J = 1.2 Hz, H-24), 5.88 (1H, d, J = 10.1 Hz, H-2), 5.16 (1H, dt, J = 4.8, 7.7 Hz, H-16), 4.86 (1H, d, J = 1.7 Hz, H-22), 2.62 (1H, ddq, J = 11.0, 1.5, 6.9 Hz, H-20), 2.12 (3H, d, J = 1.1 Hz, H-27), 2.10 (6H, 2 s, OAc-16, OAc-22), 1.44−1.35 (2H, m, H-11, H-15), 1.30 (1H, d, J = 4.9 Hz, H-19a), 1.15 (3H, s, H-18), 1.05 (3H, d, J = 6.8 Hz, H-28), 0.93 (1H, m, H-19b), 0.91 (3H, d, J = 1.0 Hz, H-30), 0.86 (3H, d, J = 7.0 Hz, H-21); 13C NMR, see Table 3; HR-ESIMS m/z 561.3187 (calcd for C33H46O6Na, 561.3187). 23,24,24a,25,26,27-Hexa-nor-neoboutomelleron-22-al (24): yellow gum; [α]20D −74 (c 0.11, CHCl3); UV (MeOH) λmax (log ε) 210 45 dx.doi.org/10.1021/np200441h | J. Nat. Prod. 2012, 75, 34−47 Journal of Natural Products Article (3.51), 266 (3.83) nm; IR (film) νmax 3640, 2938, 2874, 1732, 1669, 1603, 1455, 1375, 1238 cm−1; 1H NMR (CD3CN, 500 MHz) δ 9.58 (1H, d, J = 1.8 Hz, H-22), 6.95 (1H, d, J = 10.0 Hz, H-1), 5.90 (1H, d, J = 10.0 Hz, H-2), 5.24 (1H, dt, J = 5.5, 8.2 Hz, H-16), 2.86 (1H, ddq, J = 11.0, 2.0, 7.3 Hz, H-20), 2.39 (1H, dd, J = 11.0, 8.2 Hz, H-17), 2.16 (1H, m, H-4), 1.89 (3H, s, OAc-16), 1.47 (1H, m, H-7), 1.33 (1H, ddq, J = 13.4, 5.6, 1.1 Hz, H-15), 1.27 (1H, d, J = 4.3 Hz, H-19a), 1.17 (3H, s, H-18), 1.09 (3H, d, J = 7.3 Hz, H-21), 1.02 (3H, d, J = 6.7 Hz, H-28), 0.96 (3H, d, J = 0.9 Hz, H-30), 0.55 (1H, d, J = 4.3 Hz, H-19b); 13C NMR, see Table 3; HR-ESIMS m/z 435.2503 (calcd for C26H36O4Na, 435.2506). 23,24,24a,25,26,27-Hexa-nor-neoboutomelleron-22-oic acid (25): yellow gum; [α]20D −57 (c 0.06, CHCl3); UV (MeOH) λmax (log ε) 208 (3.52), 266 (3.74) nm; IR (film) νmax 3406, 2930, 2875, 1725, 1666, 1456, 1376, 1247 cm−1; 1H NMR (CDCl3, 500 MHz) δ 6.86 (1H, d, J = 10.0 Hz, H-1), 6.01 (1H, d, J = 10.0 Hz, H-2), 5.46 (1H, br q, J = 7.3 Hz, H-16), 2.73 (1H, m, H-20), 2.42 (1H, dd, J = 10.2, 9.1 Hz, H-17), 2.20 (1H, dq, J = 12.0, 6.9 Hz, H-4), 2.00 (3H, s, OAc-16), 1.75 (1H, m, H-12), 1.35 (1H, m, H-15), 1.23 (1H, d, J = 4.5 Hz, H-19a), 1.21 (3H, d, J = 7.0 Hz, H-21), 1.16 (3H, s, H-18), 1.10 (3H, d, J = 6.8 Hz, H-28), 0.96 (3H, s, H-30), 0.55 (1H, d, J = 4.5 Hz, H-19b); 13C NMR, see Table 4; HR-ESIMS m/z 451.2428 (calcd for C26H36O5Na, 451.2455). 16-Acetyl-3β,26-dihydroxy-24-methyl-25ξ-cycloart-24(24a)-en23-on-29-oic acid (26): yellow gum; [α]20D −7 (c 0.04, CHCl3); UV (MeOH) λmax (log ε) 220 (3.57) nm; IR (film) νmax 3310, 2933, 2871, 1732, 1669, 1555, 1378, 1247, 1028 cm−1; 1H NMR (CDCl3, 500 MHz) δ 6.03 (1H, s, H-24a), 5.75 (1H, s, H-24a), 5.26 (1H, dt, J = 4.9, 7.8 Hz, H-16), 4.07 (1H,br d, J = 7.9 Hz, H-3), 3.55 (1H, dd, J = 10.6, 5.2 Hz, H-26a), 3.49 (1H, dd, J = 10.6, 7.0 Hz, H-26b), 2.95 (1H, sext, J = 6.5 Hz, H-25), 2.52 (3H, m, H-20, 2 H-22), 2.11 (1H, dd, J = 13.7, 8.2 Hz, H-15), 1.95 (3H, s, OAc-16), 1.89 (1H, dd, J = 9.9, 8.1 Hz, H-17), 1.80 (1H, m, H-2), 1.17 (3H, s, H-18), 1.13 (3H, br.s, H-28), 1.05 (3H, d, J = 7.0 Hz, H-27), 0.91 (3H, s, H-30), 0.88 (3H, d, J = 5.8 Hz, H-21), 0.62 (1H, d, J = 4.0 Hz, H-19a), 0.40 (1H, d, J = 4.0 Hz, H-19b); 13C NMR, see Table 4; HRESIMS m/z 581.3443 (calcd for C33H50O7Na, 581.3449). 16-Acetyl-3β,22β-dihydroxy-24-methylcycloart-24(24a)-en-23on-29-oic acid (27): yellow gum; [α]20D 0 (c 0.03, CHCl3); UV (MeOH) λmax (log ε) 216 (3.58) nm; IR (film) νmax 3302, 2929, 2864, 1732, 1671, 1542, 1454, 1385 cm−1; 1H NMR (methanol-d4, 500 MHz) δ 5.99 (1H, s, H-24a), 5.89 (1H, d, J = 1.2 Hz, H-24a), 5.27 (1H, dt, J = 4.0, 7.3 Hz, H-16), 4.71 (1H, d, J = 1.5 Hz, H-22), 4.03 (1H, dd, J = 11.3, 4.6 Hz, H-3), 2.87 (1H, dsept, J = 1, 6.7 Hz, H-25), 2.24 (1H, dd, J = 14.0, 7.9 Hz, H-15a), 2.06 (3H, s, OAc-16), 1.94 (1H, dd, J = 12.2, 3.4 Hz, H-5), 1.72 (1H, m, H-2), 1.19 (3H, s, H-18), 1.11 (3H, d, J = 7.0 Hz, H-27), 1.07 (3H, s, H-28), 1.03 (3H, d, J = 7.0 Hz, H-26), 0.99 (3H, s, H-30), 0.69 (3H, d, J = 6.1 Hz, H-21), 0.63 (1H, d, J = 4.1 Hz, H-19a), 0.42 (1H, d, J = 4.1 Hz, H-19b); 13C NMR, see Table 4; HR-ESIMS m/z 581.3455 (calcd for C33H50O7Na, 581.3449). 3β,16β,22β-Trihydroxy-24-methyl-(16,23:23,26)-diepoxycycloart24(24a)-en-29-oic acid (28): yellow gum; [α]20D −38 (c 0.05, CHCl3); UV (MeOH) λmax (log ε) 208 (3.41), 270 (2.74) nm; IR (film) νmax 3300, 2929, 2864, 1650, 1541, 1385 cm−1; 1H NMR (methanol-d4, 500 MHz) δ 5.24 (1H, d, J = 3.1 Hz, H-24a), 4.92 (1H, d, J = 3.1 Hz, H-24a), 4.27 (1H, dt, J = 8.6, 7.1 Hz, H-16), 4.03 (1H, dd, J = 11.3, 4.6 Hz, H-3), 3.94 (1H, t, J = 7.8 Hz, H-27a), 3.30 (1H, t, J = 7.8 Hz, H-27b), 2.75 (1H, m, H-25), 2.07 (1H, ddd, J = 15.3, 10.5, 5.3 Hz, H-7a), 1.95 (1H, dd, J = 12.4, 4.1 Hz, H-5), 1.90 (1H, m, H-20), 1.84 (1H, dd, J = 12.8, 7.9 Hz, H-15a), 1.78 (1H, dd, J = 13.7, 2.7 Hz, H-22a), 1.74 (1H, m, H-2a), 1.49 (1H, t, J = 13.7 Hz, H-22b), 1.41 (1H, br dd, J = 12.5, 6.7 Hz, H-15b), 1.18 (3H, s, H-18), 1.08 (3H, s, H-28), 1.07 (3H, d, J = 6.8 Hz, H-26), 0.93 (3H, d, J = 7.0 Hz, H-21), 0.92 (3H, s, H-30), 0.68 (1H, d, J = 4.0 Hz, H-19a), 0.41 (1H, d, J = 4.0 Hz, H-19b); 13C NMR, see Table 4; HR-ESIMS m/z 521.3230 (calcd for C31H46O5Na, 521.3237). 3β-Hydroxy-24-methylcycloart-24(24a)-en-23-on-29-oic acid (29): yellow gum; [α]20D −34 (c 0.06, CHCl3); UV (MeOH) λmax (log ε) 220 (3.78) nm; IR (film) νmax 3380, 2930, 2869, 1678, 1552, 1406, 1374 cm−1; 1H NMR (methanol-d4, 500 MHz) δ 6.05 (1H, s, H24a), 5.75 (1H, d, J = 0.9 Hz, H-24a), 4.02 (1H, dd, J = 11.4, 4.4 Hz, H-3), 2.87 (1H, dsept, J = 1.0, 6.8 Hz, H-25), 2.72 (1H, dd, J = 15.6, 3.1 Hz, H-22a), 2.48 (1H, dd, J = 15.6, 10.1 Hz, H-22b), 1.08 (3H, s, H-28), 1.04 (3H, s, H-18), 1.02 (3H, d, J = 6.7 Hz, H-27), 1.01 (3H, d, J = 7.0 Hz, H-26), 0.95 (3H, s, H-30), 0.84 (3H, d, J = 6.4 Hz, H-21), 0.62 (1H, d, J = 4.2 Hz, H-19a), 0.41 (1H, d, J = 4.2 Hz, H-19b); 13C NMR, see Table 4; HR-ESIMS m/z 507.3441 (calcd for C31H48O4Na, 507.3445). 3β-Hydroxy-29-O-(α-L-rhamnopyranosyl)cycloart-24-en-23-on29-oic acid (30): yellow gum; [α]20D −22 (c 0.17, CHCl3); UV (MeOH) λmax (log ε) 238 (4.27), 300 (3.09) nm; IR (film) νmax 3291, 2932, 2867, 1723, 1677, 1607, 1445, 1378, 1311 cm−1; 1H NMR (methanol-d4, 500 MHz) δ 6.16 (1H, sept, J = 1.2 Hz, H-24), 5.99 (1H, d, J = 1.8 Hz, H-1′), 4.03 (1H, dd, J = 11.3, 4.3 Hz, H-3), 3.86 (1H, dd, J = 3.4, 1.8 Hz, H-2’), 3.69 (1H, dd, J = 9.5, 3.4 Hz, H-3′), 3.61 (1H, dq, J = 9.5, 6.2 Hz, H-5′), 3.44 (1H, t, J = 9.5 Hz, H-4’), 2.52 (1H, dd, J = 15.0, 3.1 Hz, H-22a), 2.11 (3H, d, J = 0.9 Hz, H-27), 1.99 (1H, dd, J = 12.1, 3.8 Hz, H-5), 1.90 (3H, d, J = 0.9 Hz, H-26), 1.22 (3H, d, J = 6.1 Hz, H-6’), 1.13 (3H, s, H-28), 1.04 (3H, s, H-18), 0.94 (3H, s, H-30), 0.86 (3H, d, J = 6.4 Hz, H-21), 0.64 (1H, d, J = 4.1 Hz, H-19a), 0.44 (1H, d, J = 4.1 Hz, H-19b); 13C NMR, see Table 4; HRESIMS m/z 639.3856 (calcd for C36H56O8Na, 639.3867). 3β-Hydroxy-29-O-(α-L-rhamnopyranosyl)-24-methylcycloart-24(24a)-en-23-on-29-oic acid (31): yellow gum; [α]20D −16 (c 0.13, CHCl3); UV (MeOH) λmax (log ε) 220 (3.95) nm; IR (film) νmax 3291, 2935, 2865, 1725, 1659, 1462, 1376, 1248, 1147, 1105 cm−1; 1H NMR (methanol-d4, 500 MHz) δ 6.05 (1H, s, H-24a), 5.99 (1H, d, J = 1.8 Hz, H-1′), 5.76 (1H, d, J = 1.2 Hz, H-24a), 4.03 (1H, dd, J = 4.3, 11 Hz, H-3), 3.86 (1H, dd, J = 3.5, 1.8 Hz, H-2’), 3.70 (1H, dd, J = 9.5, 3.5 Hz, H-3′), 3.61 (1H, dq, J = 9.5, 6.2 Hz, H-5′), 3.45 (1H, t, J = 9.5 Hz, H-4’), 2.87 (1H, sept, J = 6.7 Hz, H-25), 2.72 (1H, dd, J = 15.6, 2.7 Hz, H-22a), 2.48 (1H, dd, J = 15.6, 9.8 Hz, H-22b), 1.22 (3H, d, J = 6.2 Hz, H-6’), 1.12 (3H, s, H-28), 1.04 (3H, s, H-18), 1.02 (3H, d, J = 7.0 Hz, H-27), 1.01 (3H, d, J = 7.0 Hz, H-26), 0.95 (3H, s, H-30), 0.84 (3H, d, J = 6.4 Hz, H-21), 0.64 (1H, d, J = 4.1 Hz, H-19a), 0.44 (1H, d, J = 4.1 Hz, H-19b); 13C NMR, see Table 4; HR-ESIMS m/z 653.4014 (calcd for C37H58O8Na, 653.4024). 16,22-Diacetyl-2,26-dihydroxy-29-nor-24-methyl-19(9→1)-abeocycloart-9(11),24(24a)-dien-3,23-dione (32): yellow gum; [α]20D +77 (c 0.13, CHCl3); UV (MeOH) λmax (log ε) 210 (3.97), 268 (3.17) nm; IR (film) νmax 3394, 2926, 2854, 1734, 1694, 1566, 1376, 1229, 1021 cm−1; 1 H NMR (CDCl3, 500 MHz) δ 6.12 (1H, s, H-24a), 5.87 (1H, d, J = 0.6 Hz, H-24a), 5.56 (1H, d, J = 2.1 Hz, H-22), 5.20 (1H, d, J = 6.1 Hz, H-11), 5.09 (1H, dt, J = 4.4, 7.6 Hz, H-16), 4.16 (1H, d, J = 2.1 Hz, H-2), 3.60 (3H, m, OH-2, 2 H-26), 2.88 (1H, sext, J = 6.5 Hz, H25), 2.56 (1H, m, H-20), 2.36 (1H, dd, J = 14.0, 7.9 Hz, H-15a), 2.27 (1H, dd, J = 11.1, 7.5 Hz, H-17), 2.15 (3H, s, OAc22), 2.07 (3H, s, OAc-16), 1.88 (1H, dd, J = 9.9, 4.7 Hz, H-1), 1.37 (1H, dd, J = 14.2, 4.1 Hz, H-15b), 1.11 (3H, d, J = 7.3 Hz, H-27), 1.05 (3H, d, J = 6.4 Hz, H-28), 0.94 (1H, bt, J = 4.7 Hz, H-19a), 0.88 (3H, d, J = 7.0 Hz, H-21), 0.81 (3H, s, H-30), 0.79 (3H, s, H-18), 0.41 (1H, dd, J = 9.9, 4.7 Hz, H-19b); 13C NMR, see Table 4; HR-ESIMS m/z 607.3245 (calcd for C34H48O8Na, 607.3241). Proteasome Assay. Experimental procedures for the assay are detailed in ref 3. ASSOCIATED CONTENT S Supporting Information * This material is available free of charge via the Internet at http://pubs.acs.org. ■ AUTHOR INFORMATION Corresponding Author *Tel: +33-5-34506517. E-mail: georges.massiot.externe@ pierre-fabre.com. ■ ACKNOWLEDGMENTS The authors are grateful to R. Bellé for historical plant collection, to P. Arimondo, C. Bailly, and N. Guilbaud for their ■ 46 dx.doi.org/10.1021/np200441h | J. Nat. Prod. 2012, 75, 34−47 Journal of Natural Products Article (18) Anjaneyulu, V.; Satyanarayana, P.; Viswanadham, K. N.; Jyothi, V. G.; Nageswara Rao, K.; Radhika, P. Phytochemistry 1999, 50, 1229− 1236. (19) Beck, J.; Guminski, Y.; Long, C.; Marcourt, L.; Derguini, F.; Plisson, F.; Grondin, A.; Vandenberghe, I.; Vispé, S.; Brel, V.; Aussagues, Y.; Ausseil, F.; Arimondo, P. B.; Massiot, G.; Sautel, F.; Cantagrel, F. Bioorg. Med. Chem., in press. (20) Sheldrick, G. M. Acta Crystallogr. 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