| abstract |
The invention relates to a process for the preparation of cephem prodrug esters of the formula wherein R 1 is C 1 -C 5 alkanoyloxy-C 1 -C 3 alkyl or C 1 -C 5 alkoxycarbonyloxy-C 1 -C 3 alkyl and X is an inorganic or organic anion, and wherein the hydroxyimino group in the syn Form is present, characterized in that a compound of formula II wherein R 2 is a protective group which can be split off by acid hydrolysis, with a bis (benzothiazol-2-yl) disulfide of the formula VI |