Opening of the Cephalosporin Dihydrothiazine Ring

Abstract

2-Ethoxy-3-cephem-1β-oxide (3) was found to be thermally unstable and easily converted into isothiazolones (4, 5, 6, 9, 10), and the β-lactam derivative (8) under varying reaction conditions. Furthermore, 2-ethoxy-3-cephem (2) was treated with tert-butyl hypochlorite, giving the azetidinone-oxazoline acetate (14).