Stereoselective cycloaddition of monosubstituted ketene to a methyl glyoxylate- and threonine-derived imine: Synthesis of optically pure beta-lactamic alpha-amino ester with high functionality.

The reaction of chloroacetyl chloride and triethylamine with a chiral imine derived from the combination of methyl glyoxylate and protected L-threonin e gave two optically active a-amino acid derivatives with a cis-substituted beta-lactam skeleton in a 72:28 ratio. The major product is obtained in 59 % yield by simple crystallisation.