A compound selected from the group consisting of a compound of the formula ##STR1## wherein R is ##STR2## m and n are individually integers from 0 to 6, A and B are individually a member selected from the group consisting of hydrogen, halogen and alkyl of 1 to 8 carbon atoms, the double bond geometry being E or Z or E+Z or A and B form a third bond between the carbon atoms to which they are attached, Ar is selected from the group consisting of a) carbocyclic aryl of up to 18 carbon atoms optionally substituted with at least one member of the group consisting of free carboxy, alkoxycarbonyl, carboxy salified with a non-toxic, pharmaceutically acceptable base, amidified carboxy, --OH, halogen, --NO.sub.2, --CN, alkyl, alkenyl, alkynyl, alkoxy, alkenyloxy, alkynyloxy, alkylthio, alkenylthio and alkynylthio of up to 12 carbon atoms, N-alkyl, N-alkenyl and N-alkynyl of up to 12 carbon atoms and cycloalkyl of 3 to 12 carbon atoms, all optionally substituted with at least one halogen and ##STR3## R.sub.1 and R.sub.2 are individually selected from the group consisting of hydrogen, alkyl of 1 to 12 carbon atoms, carbocyclic aryl, aryloxy, arylthio, heterocyclic aryl and aryloxy and arylthio containing at least one heteroatom, all optionally substituted as above and b) heterocyclic aryl having at least one heteroatom optionally substituted with at least one of the above substituents, Z is hydrogen or acyl of an organic carboxylic acid of 1 to 18 carbon atoms and their non-toxic, pharmaceutically acceptable acid addition salts having antibiotic properties.