SYNTHESIS OF OPTICALLY PURE 2-AZETIDINONES HAVING N-DEHYDROAMINO ACIDSIDE-CHAINS

An efficient, three step synthesis of optically pure N-vinyl-2-azetidi nones 1 starting from alpha- or beta-amino ester imines has been devel oped. Staudinger reaction between amino ester derived imines and keten e precursors gave 2-azetidinones 2. Enolate formation on the amino est er moiety of the optically pure 2-azetidinones 2, selenylation and, fi nally, MCPBA treatment afforded N-vinyl-2-azetidinones 1 in good to ex cellent yields, with total retention of the stereochemistry of the sta rting material. Compounds 2 bear the functionality needed to place a c arboxy group contiguous to the lactam nitrogen, a structural Feature c ommon to all the active beta-lactam antibiotics.