【Abstract】 The 7 (phenylacetamido)deacetoxycephalosporin acid was prepared by ring expansion of penicillin G sulfoxide via its trimethylsiliated intermediate(protective silylation with N,N  dimethylsilylurea) using HBr 4 methylpyridine as catalyst. The effects of catal yst amount, reaction temperature and time were examined. Under optimum reaction condi tions product in 94% yield was obtained. The product has been characterized by IR and MS.更多还原