A compound selected from the group consisting of a compound of the formula ##STR1## wherein R.sub.1 and R.sub.2 are individually selected from the group consisting of hydrogen and an optionally unsaturated hydrocarbon of up to 24 carbon atoms optionally interrupted by at least one heteroatom selected from the group consisting of oxygen, sulfur and nitrogen and optionally having at least one functional group or taken together form ##STR2## and R'.sub.1 and R'.sub.2 are individually selected from the group consisting of hydrogen and an optionally unsaturated hydrocarbon of up to 23 carbon atoms optionally interrupted by at least one heteroatom selected from the group consisting of nitrogen, oxygen and sulfur and optionally having at least one functional group, Z is hydrogen or acyl of an organic carboxylic acid of 1 to 18 carbon atoms and the wavy line indicates the 10-methyl may have R or S configuration or a mixture of R+S and their non-toxic, pharmaceutically acceptable acid addition salts having antibiotic properties.