Enantioselective Syntheses of 3-Substituted 4-(Alkoxycarbonyl)-2-azetidinones from Malic Acid

Article abstract of DOI:10.1021/jo00146a020

Enantioselective syntheses of 3-substituted 4-(alkoxycarbonyl)-2-azetidinones from malic acid have been developed.Alkylation of diesters of D-malic acid provided primarily the erythro products 15RS.Base-mediated inversion gave racemic threo isomers 15.Saponification of 15 and selective monoesterification provided the correspondingly substituted β-hydroxy acids 17, which could also be epimerized at the hydroxyl position.Separate conversion of the isomers 17 to the hydroxamates 18 followed by cyclization gave the desired β-lactams 19 with complete control of stereochemistry.