A CONVENIENT ONE-POT ASYMMETRIC-SYNTHESIS OF CIS-BETA-LACTAMS - KEY PRECURSORS FOR OPTICALLY-ACTIVE 2-OXAISOCEPHEMS

Asymmetric annelation of the disilylated imine 3 generated in situ fro m D-threonine 2 with acid chlorides 4 and triethylamine followed by es terification provided cis-beta-lactams 5 and 6 in excellent yields wit h high diastereoselectivity under mild conditions. And conversion of c ompounds 5 into 15, derivatives of 2-oxaisocephems having a thio-subst ituted methyl group at the 3-position and a 2-aminothiazol-4-yl moiety at the 7-position, is described. Biological activities of the new com pounds are presented. In particular, 15b showed potent antibacterial a ctivity against Methicillin-resistant Staphylococcus aureus (MRSA) and Enterococcus faecalis which cause a serious clinical problem in antib acterial chemotherapy.