A compound of the formula:

OR A PHARMACEUTICALLY ACCEPTABLE NONTOXIC SALT THEREOF WHEREIN R1 is hydrogen, straight or branched chain alkyl of one to five carbon atoms, monoaralkyl of up to eight carbon atoms, monoaryl, substituted monoaryl, or thienyl; A is a moiety of the formula:

wherein R2, R3, R4, R5, R6 and R7 are the same or different and each is hydrogen, straight or branched chain alkyl of one to five carbon atoms, monoaralkyl of up to eight carbon atoms, monoaryl, substituted monoaryl, or thienyl; B is a moiety of the formula:

WHEREIN R8, R9 and R10 are the same or different and each is hydrogen, fluorine, chlorine, bromine, iodine, lower alkyl, lower alkoxy, lower alkylthio, lower alkylsulphonyl, sulphamyl, nitro, cyano, di(lower alkyl)amino, lower alkanoylamino, lower alkanoyloxy, lower alkylsulphonylamino, trifluoromethyl or hydroxy; E is oxygen or sulphur; and C* is a carbon atom constituting a center of chirality, ARE USEFUL FOR THEIR ANTIBACTERIAL ACTIVITY.