Synthesis of Some Biologically Important 3-Oxacepham Derivatives

Abstract

The 6H-oxathiazines 1a-e having imine moiety underwent [2+2] cycloaddition with phenoxyacetylchloride in the presence of Et₃N to give β-lactam derivatives 2a-e in high yield. The X-ray crystallographic analysis revealed the relative stereochemistry that the substituents at C-2 and C-4 were cis configurated. The subtituents at C-6 and C-7 were also cis to each other. However, the 6H-oxathiazines 1f-i containing tert-butyl or methyl group at C-4 did not undergo the cycloaddition.