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■ Biomimetic Chemical Transformation of 3’,4’-Anhydrovinblastine to Vinblastine and Related Bisindole Alkaloids

James Peter Kutney,* Lewis Siu Leung Choi, Jun Nakano, and Hiroki Tsukamoto

*Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, B.C., V6T 1Z1, Canada

Abstract

Employing flavine co-enzyme mediated photooxidation and reduced nicotinamide-adenine dinucleotide (β-NADH) as reactant, 3’,4’-anhydrovinblastine (4) is transformed into vinblastina (5), 4’-deoxyleurosidins (14), vinamidine (8) and its reduction product (16). In this biomimetic transformation of 4 to the end products, unstable intermediates are recognized and their structures established by appropriate deuterium labelled experiments. The results obtained provide important information on the nature of biointermediates involved in the later stages of the biosynthetic pathway of vinblastine and related bisindols alkaloids. Contrary to earlier speculations proposed from various laboratories. 4 is not a biosynthetic precursor for the above-mentioned alkaloids. Its formation is the result of regiospecific 1,2-reduction of the true biosynthetic precursor, the highly unstable dihydropyridinium intermediate 3. The latter, after enzymatically controlled conversion to 10, 11 and 12, then affords routes to the alkaloids 5,8 and 14.