R. Keltjens et al., A new convenient synthesis of 3-carhoxycephems starting from 7-aminocephalosporanic acid (7-ACA), EUR J ORG C, (13), 2001, pp. 2529-2534
New convenient syntheses of 3-carboxycephems starting from 7-ACA are report
ed. All three possible cephem derivatives with respect to the position of t
he double bond in the six-membered ring and oxidation state of the sulfur a
tom have been synthesized in high overall yield.