Tetronomycin, a novel polyether of unusual structure.

Tetronomycin, C34H50O8, isolated from a strain of Streptomyces sp. nov. represents a novel polycyclic ionophore polyether. The crystal structure and absolute configuration were established by X-ray analysis of the mono-O-acetyltetronomycin silver salt. Tetronomycin is the first metabolic polyether which contains a tetronic acid moiety instead of the essential carboxylic acid function. A trisubstituted cyclohexane ring and an interesting molecular conformation of the silver salt represent additional unique structural features. Extensive NMR-studies enabled the assignment of chemical shifts and the correlation of the proton and carbon signals. Tetronomycin exhibits activity against Gram-positive bacteria.

Noboritomycins A and B, new polyether antibiotics.

Noboritomycins A and B, two new polycyclic ionophoric polyethers were isolated from a strain of Streptomyces noboritoensis. The crystal structure and absolute configuration of noboritomycin A were established by X-ray analysis of its silver salt C43/63O14Ag. Noboritomycin A is the first metabolic polyether possessing two carboxylic acid functions on the carbon backbone (C-31), namely a free acid and an additional carboxylic acid ethylester group. An unusual spiroketal system as well as a salicylic acid chromophore represent further remarkable elements. Noboritomycin A shows in this respect a structural relationship to salinomycin and lasalocid respectively. Comparison of physico-chemical data, in particular the interpretation of the 1H- and 13C-NMR spectra, revealed that noboritomycins A and B are structurally closely related, noboritomycin B carrying an ethyl substituent on the aromatic ring in the place of a methyl group present in noboritomycin A. Both metabolites exhibit activity against Gram-positive bacteria and against Eimeria tenella (chicken coccidiosis).

Septamycin, a polyether antibiotic. Taxonomy, fermentation, isolation and characterization.

Septamycin is a metal complexing polyether antibiotic produced by a strain of Streptomyces hygroscopicus NRRL 5678. The metabolite, a monocarboxylic acid, was isolated as the sodium salt C48H81NaO16. The crystal structure and absolute configuration were established by X-ray analysis of the p-bromophenacyl derivative. Septamycin has a thirty-carbon backbone and contains seven heterocyclic rings. Supported by direct comparison septamycin proved to be identical with antibiotic A28695 A isolated from Streptomyces albus NRRL 3883. The metabolite is active against gram-positive bacteria and Eimeria tenella (chicken coccidiosis).