Stereoselective reactions. IX. Synthetic studies on optically active .BETA.-lactams. I. Chiral synthesis of carbapenam and carbapenem ring systems starting from (S)-aspartic acid.

A chiral carbapenam ring system ((3R, 5R)-(+)-19 and -20) having the desired absolute configuration at C-5 was synthesized starting from (S)-aspartic acid, and the latter product was further transformed to a chiral carbapenem derivative ((5S, 2'R)-(+)-21) having an (R)-cysteine moiety as a side chain.