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Total Synthesis of Indole and Dihydroindole Alkaloids. IX Studies on the synthesis of bisindole alkaloids in the vinblastine‐ vincristine series. The biogenetic approach
Author(s) -
Kutney James P.,
Hibino Toshihiko,
Jahngen Edwin,
Okutani Tetsuya,
Ratcliffe Arnold H.,
Treasurywala Adi M.,
Wunderly Stephen
Publication year - 1976
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19760590824
Subject(s) - chemistry , vindoline , trifluoroacetic anhydride , indole test , vinblastine , reagent , total synthesis , alkaloid , stereochemistry , organic chemistry , surgery , medicine , chemotherapy
A detailed study of the reaction of catharanthine N‐oxide and vindoline has been carried out employing various conditions. Under optimum conditions, which involve low temperatures and trifluoroacetic anhydride as reagent, 3′, 4′‐dehydrovinblastine (XIII, R = COOCH 3 ), in reasonable yields is essentially the exclusive product. However two additional products, 18′ ( epi )‐ 3′, 4′‐dehydrovinblastine (XIV, R = COOCH 3 ) and 1′‐hydroxy‐ 3′, 4′‐dehydrovinblastine (XVI, R = COOCH 3 ) are also often isolated. The reaction, which follows the course of a Polonovski ‐type fragmentation process, has been extended to the N‐oxide derivatives of dihydrocatharanthine and decarbomethoxycatharanthine to provide again a series of bisindole alkaloid derivatives, also vinblastines. A mechanistic rationale is provided to explain the various results obtained.