Abstract: Compounds of the formula ##STR1## wherein X and X' form C.dbd.O or C.dbd.NOR, R is selected from the group consisting of hydrogen, heterocycle, alkyl, alkenyl, alkynyl, all optionally substituted,or X is ##STR2## R.sub.a and R.sub.b are hydrogen or a hydrocarbon group or form together with the nitrogen a heterocycle, or with A forms a 9-N, 11-O ring, and X' is hydrogen, --Y and Y' have the same definition as X and X', B is hydrogen or OR.sub.4, R.sub.4 is hydrogen or forms together with A a carbonate or a carbamate, A forms with C a double bond or A is OR'.sub.4, R'.sub.4 is hydrogen or forms together with B a carbonate or ##STR3## R.sub.2 is alkyl or --CONH.sub.2, --CONHCOR.sub.11 or --CONHSO.sub.2 R.sub.11, R.sub.11 is a hydrocarbon up to 18 carbon atoms, R.sub.3 is hydrogen, ##STR4## and Z is hydrogen or a carboxylic acid remainder and their non-toxic, pharmaceutically acceptable acid addition salts, their preparation and intermediates useful as antibiotics.

Abstract: A compound of the formula ##STR1## wherein A and B are both hydrogen or A is hydrogen and B is --OH or A and B form a carbon-carbon double bond and Z is hydrogen or acyl of an organic carboxylic acid of 1 to 6 carbon atoms and their nontoxic, pharmaceutically acceptable acid addition salts having antibiotic activity.

Abstract: All possible stereoisomeric forms and mixtures thereof of a compound of the formula ##STR1## wherein the substituents are as defined in the specification and their non-toxic, pharmaceutically acceptable acid addition salts having antibiotic properties.

Abstract: A compound selected from the group consisting of a syn isomer of a compound of the formula ##STR1## in the R or S form or in the form of an R, S mixture wherein the substituents are defined as in the specification and their non-toxic, pharmaceutically acceptable acid addition salts having anti-bacterial activity.

Abstract: A compound selected from the group consisting of a syn isomer of a compound of the formula ##STR1## in the R or S form or in the form of an R, S mixture wherein R.sub.1, Rc, Rb, A and A' are defined as in the following specification and their non-toxic, pharmaceutically acceptable acid addition salts having anti-bacterial activity.

Abstract: The syn isomer of a compound of the formula ##STR1## in the R or S form or a mixture of R and S forms and their non-toxic, pharmaceutically acceptable acid addition salts wherein the substituents are defined as in the specification having antibacterial activity and their preparation.

Abstract: A compound selected from the group consisting of a syn isomer of a compound of the formula ##STR1## in the R or S form or in the form of a R, S mixture wherein the various substituents are defined as in the specification and their non-toxic, pharmaceutically acceptable acid addition salts having anti-bacterial activity.

Abstract: A compound selected from the group consisting of a syn isomer of a compound of the formula ##STR1## wherein R is selected from the group consisting of hydrogen, alkyl of 1 to 6 carbon atoms, alkenyl and alkynyl of 2 to 6 carbon atoms and cycloalkyl of 3 to 6 carbon atoms, all optionally substituted with at least one member of the group consisting of optionally esterified or salified carboxy, alkoxy carbonyl, carbamoyl, dimethylcarbamoyl, amino, alkylamino, dialkylamino, halogen, alkoxy and alkylthio of 1 to 4 carbon atoms, aryl, heterocyclic aryl, arylthio and heterocyclic arylthio optionally substituted by alkyl of 1 to 4 carbon atoms, R.sub.1 is selected from the group consisting of ##STR2## and A is selected from the group consisting of hydrogen, alkali metal, alkaline earth metal, magnesium, --NH.sub.4 and an organic amine or A is selected from the group consisting of the residue of an easily cleavable ester group or --COOA is --COO-- and the wavy line indicates --CH.sub.2 --R.sub.