PROCESS FOR THE PREPARATION OF CEPHEM PRODRUG ESTERS

摘要

Process for the preparation of cephem prodrug esters The invention relates to a process for the preparation of cephem prodrug esters of the formula (see formula I) in which R1 is C1-C5-alkanoyloxy-C1-C3-alkyl or C1-C5-alkoxycarbonyloxy-C1-C3-alkyl and X is an inorganic or organic anion, and in which the hydroxyimino group is present in the syn-form, which comprises allowing a compound of the formula II (see formula II) in which R2 is a protective group which can be removed by acid hydrolysis, to react with a bis(benzothiazol-2-yl) disulfide of the formula VI (see formula III) in which R3 is hydrogen, C1-C5-alkyl, C2-C6-alkenyl, C3-C6-alkynyl, C1-C6-alkyloxy, C2-C6-alkenyloxy, C3-C6-alkynyloxy, hydroxyl, acetoxy, halogen, nitro, amino, carboxyl or the sulfo group, and triphenylphosphine in an inert solvent, in the presence of a tertiary amine, to give a compound of the formula V (see formula IV) in which R2 and R3 have the abovementioned meanings, then reacting this compound with a 7-aminoceph-3-em-4-carboxylic acid ester of the formula III (see formula V) in which R1 has the abovementioned meaning, in inert organic or dipolar aprotic solvents at temperatures between 0.degree. and +80.degree.C and treating the resulting oxime-protected compound of the formula IV (see formula VI) in which R1 and R2 have the abovementioned meanings and in which the protected oxime group is present in the syn-form, with inorganic acids or with aliphatic or aromatic sulfonic acids in organic solvents at temperatures between +20.degree. and +110.degree.C to form the compound of the formula I.