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Paper | Regular issue | Vol 71, No. 11, 2007, pp.2347-2362
Published online, 27th July, 2007
DOI: 10.3987/COM-07-11114
Synthesis of 18-Hydroxyvincamines and Epoxy-1,14-secovincamines; A New Proof for the Aspidospermane-Eburnane Rearrangement

András Nemes,* Csaba Szántay Jr., László Czibula, and István Greiner

*Technological Research Laboratory No.I, Chemical Works of Gedeon Richter Ltd., H-1475 Budapest 10. POB 27., Hungary


Chemical transformations started from tabersonine were studied. A one-pot oxidative ring-transformation with permaleic acid in methanol yielded 17,18-dehydrovincamine. Hydroboration-oxidation of the latter compound led to alkaloid 17,18-dehydrovincamone. Hydroboration-oxidation of tabersonine resulted 14β-hydroxyvincadifformine and 15β-hydroxyvincadifformine. Allowing 14β- and 15β- hydroxyvincadifformines to react with permaleic acid/methanol provided 1,14-secovincamines, serving as new evidence for the mechanism of the aspidospermane-eburnane transformation. On the other hand 18β-hydroxyvincamine was obtained from 14β-hydroxyvincadifformine by reaction with 3-chloroperbenzoic acid and successive treatment with triphenylphosphine/aqueous acetic acid.