The Malaysian Journal of Analytical Sciences Vol 12 No 3 (2008): 633 - 637

 

 

MASS SPECTROMETRY OF UNNATURAL STILBENE DIMERS

 

Weber, J. F. F.¹, Thomas, N. F.², Abdul Wahab, I.¹, Feroz, F.  & Buniyamin, I¹*.

 

¹Faculty of Pharmacy, Universiti Teknologi MARA,

Shah Alam, Selangor Darul Ehsan.

²Department of Chemistry, Faculty of Science,  2

Universiti Malaya, Kuala Lumpur.

 

*Corresponding author: irmadany2u@yahoo.co.uk

 

Abstract

The dimerisation of  3,4-dimethoxy-12-benzyloxystilbene  1  with 15 equivalent of ferric chloride (FeCl₃ ) 60% w/v for 12 hours afforded  unnatural  products, a pallidol-like  compound  2  and  an  ampelopsin F analogue,  3  (molecular formula  2 ,  3  =    C₄₆H₄₂O₆). By using High Resolution-Electron Impact Mass Spectrometer (HR-EIMS) technique, we found that the mass spectrum of  2 showed significant mass peaks. This allows us to suggest several fragmentations, compatible to the peaks. The mass spectrum of  2  exhibited molecular ion peak as 713.2869, compatible with the presence of pallidol analogue (690) associated with sodium adduct (23). The loss of methyl group gave single oxygen which presumed unstable, followed by deformation with new bonding with proton thus giving m/z 676. m/z 508 was resulted from the loss of benzyloxybenzene.  The base peak was indicated by the m/z 294, where bis cyclopentane transformed to cycloocta-1,5-diene having two aromatic rings attached with methoxy and single oxygen. The presence of 1 during fragmentation was remarked as the fragment molecular formula compatible with m/z 242. Meanwhile, the protonated molecular ion peak of  3  was observed to give compatible molecular formula 690. The fragmentation of 3  exhibited the occurrence of highly stabilized tropylium cation (C₇H₇⁺). The loss of benzyloxybenzene and benzyloxy led to fragment having m/z 417. It was followed by the  cleavage of the benzyloxy to present fragment with m/z 401. We concluded that the spectra were more informative than those published from previous study.

 

Keywords : synthesis, stilbene, mass

 

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