Optically active cephalosporin analogs of the formula ##STR1## wherein R.sub.2 represents a hydrogen or a group represented by the formula ##STR2## wherein R.sub.3 is a straight or branched lower alkyl group having 1 to 6 carbon atoms, a straight or branched lower alkoxy group having 1 to 6 carbon atoms or a phenyl group and R.sub.4 is a hydrogen or a straight or branched lower alkyl group having 1 to 6 carbon atoms; and A.sub.2 represents a straight or branched lower alkyl group having 1 to 6 carbon atoms or a straight or branched lower alkyl group having 1 to 6 carbon atoms which is substituted with one or two carboxyl groups, are useful as antibacterial agents.