Studies On The Synthesis Of Intermediates Of Cephalosporins From Penicillin V

3-Hydroxycephem derivatives are important intermediates for the modification at C-3 position of cephalosporins. Kukolia ring expansion of penicillins was studied, the reaction conditions were optimized in the present paper while penicillin V was employed as starting material. p-Nitrobenzyl 6-(phenoxyacetamido)penicillanate sulfoxide was obtained by protection of carboxylic acid with paranitrobenzyl, followed by oxidation with peroxyacetic acid; then chlorination of compound (3) with NCP in certain conditions. The compound obtained was not needed to be purified, followed by ring expansion catalyzed by SnC14, afforded p-Nitrobenzyl 3-methylene-7-(phenoxyaceta-mido)cepham-4-carboxylate 1-oxide. Treatment of compound (5) with ozone at -60℃ yielded (6).Finally, reduction of (6) with acetyl bromide afforded the desired product p-Nitrobenzyl 3-hydroxyl-7-(phenoxyacetamido)cepham-4-carboxylate(7).