Synthesis of 2-Azetidinones Incorporating Carbenechromium(0) Moieties and Their Use in the Preparation of Penicillin- and Cephalosporin-Containing Peptides

A series of beta-lactams incorporating a carbenechromium(0) moiety in their structures have been prepared. These stable compounds are suitable precursors for the preparation of alpha-amino esters, dipeptides and tripeptides tethered to a 2-azetidinone ring. The methodology has also been extended to the synthesis of carbenechromium(0) complexes of penicillin G, cephalosporin and 6-aminopenicillanic acid. All these new metalla-beta-lactam derivatives are stable compounds and can be transformed into antibiotic structures with tripeptide side-chains. The methodology relies on the compatibility of the beta-lactam ring with the carbenechromium(0) moiety and on the stability of the four-membered ring during the photocarbonylation of the resulting chromium complex. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)