4-Propargyl-2-azetidinone as a Versatile Synthon for the Synthesis of β-Lactam Antibiotics : Hydrostannation and Its Reactivities

Abstract

An efficient preparation of 4-propargyl-2-azetidinone (6) from 4-phenylsulfonyl-2-azetidinone is described. This compound was converted to the ketones 14 and 16, which are the key intermediates for the synthesis of carbapenem and carbacephem antibiotics. In this transformation it was found that polar functional groups (β-lactam, OH, etc.) control the regiochemistry of hydrostannation of the internal alkyne. The reaction of epoxystannanes with formic acid to give the ketones is also described.