The bicyclic gamma-ylidenetetronate motif found in several Stemona alkaloids was prepared in a stereoselective manner by addition of lithium methyl tetronate to an alkoxy oxonium ion formed from a lactone. The corresponding mixed alkyl ketal obtained was subjected to a Lewis acid-base-promoted dealkoxylation reaction to deliver the desired products.
Enzyme-catalysed baeyer–villiger oxidations of some substituted bicyclo[3.2.0]heptanones
作者:Andrew J. Carnell、Stanley M. Roberts、Vladimir Sik、Andrew J. Willetts
DOI:10.1039/c39900001438
日期:——
The ketones 1 and 4 are oxidized to γ-lactones 2 and 5 with low enantioselectivity by both Acinetobacter sp. NCIB 9871 and Pseudomonas sp. NCIB 9872; in contrast the ketones 7 and 10 are biotransformed to products 8/9 and 11 respectively of very high optical purity.