| abstract |
Cephalosporin antibiotics of formula (I): where R = H, MeCO2, O alkyl or -SR7; R7 = alkyl, aryl or a heterocyclic residue, R1 and R2 = H, alkyl, aryl, aralkyl, O-aryl, cycloalkyl, or a heterocyclic, residue or R1 and R2 tog. form a ring, R3 = H, hal, OH, NH2, NH alkyl, N3, O alkyl, S alkyl, benzyloxycarbonyl, benzhydroxycarbonyl, beta-haloethoxycarbonyl, CHal3CH2OCO-, or alkylOCO, and n = 0 or 1, are prepd by reacting a 7-aminocephalosporanic acid with R4R5R6SiX and a t.amine, where R4 and R5 = alkyl, opt. substd by hal, aryl, or O-alkyl, O-alkyl opt. substd by hal or aryl, aryl, O aryl, or hal; R6 = O-alkyl opt. substd. by hal or aryl or O-aryl; and X = hal., condensing the inter. with R1(CR2R3)nCOZ and a base, where Z is a labile residue e.g. hal or O-acyl and solvolysing to remove the silyl gp. |