A new method for the synthesis of 7.ALPHA.-methoxycephalosporins.

Bromination of the 7β-benzenesulfinylpropenylaminocephalosporin (1) with NBS followed by treatment with methanol and sodium borate yielded the 7α-methoxylated cephalosporins (4a∼d). Removal of the side chain of the 7β-amino group of 4d was achieved by treating it successively with PCl5 and Girard T.