Compounds of the formula ##STR1## wherein Y is hydrogen or methoxy;A is ##STR2## or, when Y is methoxy, also phenyl, 4-hydroxy-phenyl, 2-thienyl, 3-thienyl of 3,4-dihydroxy-phenyl;A' is hydrogen, --COCH.sub.2 Cl, --COCH.sub.2 Br, --COOCH.sub.2 CCL.sub.3, formyl or trityl;D is hydrogen, acetoxy, aminocarbonyloxy, pyridinium, 4-aminocarbonyl-pyridinium or -S-Het, where Het is 3-methyl-1,2,4-thiadiazol-5-yl, 1,2,4-thiadiazol-5-yl, 1,3,4-thiadiazol-5-yl, 2-methyl-1,3,4-thiadiazol-5-yl, 4H-5,6-dioxo-1,2,4-triazine-3-yl, 4-methyl-5,6-dioxo-1,2,4-triazin-3-yl, 1-vinyl-tetrazol-5-yl, 1-allyl-tetrazol-5-yl or ##STR3## n is 1, 2 or 3; R.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; or--(CH.sub.2).sub.n R.sub.1 is alkyl of 1 to 4 carbon atoms or 2,3-dihydroxy-propyl;R.sub.2 is unsubstituted or monosubstituted 3-pyridyl, 5-pyrimidinyl, 2-thienyl, 2-furyl-methyl, 2-thienyl-methyl, 2-imidazolyl-methyl, 2-thiazolyl-methyl, 3-pyridyl-methyl or 5-pyrimidinyl-methyl, where the substituent is chlorine, methyl, acetylamino, hydroxyl, methylsulfinyl, methylsulfonyl, aminocarbonyl or aminosulfonyl; andE is hydrogen or a carboxyl-protective group which is easily removable in vitro or in vivo;and, E is hydrogen, non-toxic, pharmacologically acceptable salts thereof formed with inorganic or organic bases; the compounds as well as their salts are useful as antibiotics.