STUDIES ON β-LACTAM ANTIBIOTICS——Ⅲ. THE STEREOSPECIFIC SYNTHESIS OF 7-AMIDINOTHIOACETAMIDOCEPHALOSPORANIC ACID SULFOXIDE DERIVATIVES

In order to find more active new cephalosporins a series of R- and S-sulfoxides of 7-(N, N'-substituted amidinothioacetamido) cephalosporanic acid was synthesized stereospecifically. The S-form sulfoxides Ⅱ-S were Prepared by oxidation of intermediate V with hydrogen peroxide and acetic acid and then condensation with a Variety of substituted thiourea. The R-form sulfoxides Ⅱ-R were prepared by several steps. After conversion of 7-ACA Ⅲ into corresponding Schiff's base the R-form sulfoxide of the Schiff's base was formed by oxidation. The intermediate Ⅸ was obtained by hydrolysis and acylation. The dersired derivatives Ⅱ-R could be prepared by condensation conveniently with N, N'-substituted thiourea.The stereochemistry of new cephalosporanie acid derivatives and intermediates has been idendified by means of ¹H NMR.