Dihydrothiazine Ring-Opening Reactions in 2-Alkoxycephalosporin Compounds

Abstract

2-Alkoxy-3-cephem-1-oxides 1b-c were found to be thermally unstable and easily converted into isothiazolones 5a-f, β-lactam 12 and thiazole 14 according to reaction conditions. Further, 2-alkoxy-3-cephem 4a-b was treated with tert-butyl hypochlorite to give azetidinone-oxazoline acetals 18a-b. Formation of these rearrangement products was interpreted via the sulfenic acid intermediate 6 or 17.