title: Studies related to penicillins and cephalosporins. I. The preparation of 4-alkylthio- -lactams in which the ring nitrogen atom is part of an  -amino-acid ester system.
mesh_terms: D000577:Amides / Q000138:chemical synthesis*; D000595:Amino Acid Sequence; D002511:Cephalosporins; D003500:Cyclization; D004952:Esters / Q000138:chemical synthesis; D007769:Lactams / Q000138:chemical synthesis; D008722:Methods; D008956:Models, Chemical; D009584:Nitrogen; D010406:Penicillins; D013329:Structure-Activity Relationship; D013844:Thiazoles / Q000138:chemical synthesis
chemical_list: D000577:Amides; D002511:Cephalosporins; D004952:Esters; D007769:Lactams; D010406:Penicillins; D013844:Thiazoles; D009584:Nitrogen