An enantioselective synthesis of (+)-polyoxamic acid via phase-transfer catalytic conjugate addtion and asymmetric dihydroxylation

Abstract

A new efficient stereoselective synthesis of (+)-polyoxamic acid, the major component of the polyoxin family of antifungal antibiotics, is reported. Starting from a commercially available glycine derived Schiff base, (+)-polyoxamic acid was obtained in 46% overall yield after 7 linear steps. Enantioselective phase-transfer catalytic Michael reaction (99% yield, 96% ee) and diastereoselctvie dihydroxylation (98% yield, 94% de) are very efficient key reactions. In both, cinchona derivatives were used as stereoselectivity control element, which make this synthesis more practical. was obtained in 46% overall yield after 7 linear steps. Enantioselective phase-transfer catalytic Michael reaction (99% yield, 96% ee) and diastereoselctvie dihydroxylation (98% yield, 94% de) are very efficient key reactions. In both, cinchona derivatives were used as stereoselectivity control element, which make this synthesis more practical.