Compounds of the formula ##STR1## wherein A is phenyl, 4-hydroxy-phenyl, 2-thienyl, 2-furyl or 3,4-dihydroxy-phenyl;Y is hydrogen or methoxy;Het is 4H-5,6-dioxo-1,2,4-triazin-3-yl,4-methyl-5,6-dioxo-1,2,4-triazin-3-yl,2-methyl-5,6-dioxo-1,2,4-triazin-3-yl,1-vinyl-tetrazol-5-yl, 1-allyl-tetrazol-5-yl or ##STR2## where n is an integer from 1 to 3, inclusiveR.sub.1 is hydroxyl, amino, dimethylamino, acetylamino, aminocarbonyl, aminocarbonylamino, aminosulfonyl, aminosulfonylamino, methylcarbonyl, methylsulfonylamino, cyano, hydroxysulfonylamino, methylsulfonyl, methylsulfinyl, a carboxylic acid group or a sulfonic acid group, and--(CH.sub.2).sub.n --R.sub.1 may also be alkyl of 2 to 4 carbon atoms or 2,3-dihydroxy-propyl;R is cyclopropyl, 4'-hydroxycyclohexyl-amino ##STR3## where R.sub.2 is straight or branched, saturated or unsaturated hydrocarbyl of 1 to 4 carbon atoms or cycloalkyl of 3 to 6 carbon atoms;G is hydroxyl, aminocarbonyl, aminosulfonyl, aminocarbonylamino, acetylamino, methylsulfonylamino, methylsulfinyl or methylsulfonyl;m is 0 or 1; andR.sub.3 and R.sub.4, which may be identical to or different from each other, are each hydrogen, chlorine, fluorine, hydroxyl, methoxy, acetylamino, aminocarbonylamino, nitro, acetyl, methylcarbonyloxy, methoxycarbonyl, aminocarbonyl, cyano, methylsulfinyl, methylsulfonyl, aminosulfonyl, methylaminosulfonyl or methyl; andE is hydrogen or a protective group which is easily removable in vitro or in vivo;and, when E is hydrogen, non-toxic, pharmacologically acceptable salts thereof; the compounds as well as their salts are useful as antibiotics.