7 alpha Methoxycephalosporin derivatives

A 7 alpha -methoxycephalosporin derivative represented by the formula (I): (I) wherein R1 represents a heterocyclic ring or an -S- heterocyclic ring; R2 represents a hydrogen atom, a carboxy group or a -COOR5 group wherein R5 represents a lower alkyl group, a dialkylamino-lower alkyl group or a group wherein R6 represents a lower alkyl group, a lower acyl group or a lower alkoxycarbonyl group and Y represents a hydrogen atom or a lower alkyl group; R3 represents a hydrogen atom, a carbamoyl group or a lower acyl group; R4 represents a hydrogen atom, a lower alkyl group, a dialkylamino-lower alkyl group or a group wherein R6 and Y are defined as above; A and B, which may be the same or different, each represents a straight chain or branched chain alkylene group having 1 to 5 carbon atoms; and x represents 0 or 1; or a pharmaceutically acceptable salt thereof and a process for producing the same.