STEREOSPECIFIC SYNTHESIS OF A NOVEL BICYCLIC BETA-LACTAM

Reductive ozonization in methanol of suitably protected 1,2-glycals of readily available D-sugars led to 4-formates of lower sugars in the a ldehyde form. An aza-Wittig type reaction with 2-methoxyethoxymethyl ( MEM) azide converted these aldehydes to Schiff bases with multiple chi ral centers. Stereospecific cis beta-lactam formation was observed on reacting these Schiff bases with benzyloxyacetyl chloride and triethyl amine. Mild acid hydrolysis of the formate group in the C-4 side chain led to )-1,2,8-tribenzyloxy-3-benzyloxymethyl-4-oxanonam, a bicyclic beta-lactam containing a hexahydro-3-oxazepine ring. The structure and absolute configuration of this beta-lactam was determined by X-ray cr ystallography.