Abstract
Reaction of penicillin sulfoxides with diethyl phosphorocyanidate (DEPC) was investigated. Treatment of benzylpenicillin (S)-sulfoxide methyl ester (4a) with a slight excess of DEPC in N, N-dimethylacetamide gave the 3-cephem (5a), the 2-cephem (6a). and the 3-methylenecepham (7a) in 22, 4, and 4% yields, respectively. Increase of the quantity of DEPC to a three or five fold excess increased the yield of the 3-cephem (5a). Phenoxymethylpenicillin (S)-sulfoxide methyl ester (4b) also afforded the 3-cephem (5b) and the 3-methylenecepham (7b) under analogous reaction conditions as above, while phthalimidopenicillin (R)-sulfoxide methyl ester (8) furnished the 3-cephem (9) and the isothiazolones (10 and 11).
