PROCESS FOR THE PREPARATION OF INTERMEDIATES USEFUL IN THE SYNTHESIS OF CEPHALOSPORINS

摘要

A process is described for preparing 3-exomethylene cephalosporanic acid derivatives for use in the synthesis of cephalosporin antibiotics such as ceftibuten. The process comprises electrochemical reduction of a compound of formula (IV), wherein: R3 is CH¿3?C(O)-; a is an optional sulfoxide group; n is 2 or 3; R?1¿ is H and R is H or NHR2, where R2 is H or a protecting group selected from C¿6?H5CH2OC(O)-, C6H5C(O)- or C1-C6 alkoxy-C(O)-; or wherein R and R?1¿ together with the carbon atom to which they are attached comprise -C(O)-, and produces the desired 3-exomethylene compounds with low levels of the corresponding 3-methyl tautomers.