Saccharomicins, novel heptadecaglycoside antibiotics effective against multidrug-resistant bacteria

Two novel heptadecaglycoside antibiotics, saccharomicins A (1) and B (2), were isolated from a new species of Saccharothrix. Their structures were determined by a combination of chemical degradation and spectroscopic methods. Saccharomicin B (2) was identified as N-(m,p-dihydroxycinnamoyl) taurine p-O-[alpha-4-epi-vancosaminopyranosyl( 1-4)-alpha-4-epi-vancosaminopyranosyl(1-->4)-alpha-digitoxopyranosyl(1-->4)-alpha-4-epi-vancosaminopyranosyl(1-->4)-alpha-digitoxopyranosyl(1-->3)-beta-fucopyranosyl(1-->4)-beta-saccharosaminopyranosyl(1-4)-alpha-digitoxopyranosyl( 1-->3)]-[-4-epi-vancosaminopyranosyl(1-->4)]-beta-fucopyranosyl(1-->4)-beta-saccharosaminopyranosyl(1-4)-alpha-rhamnopysyl(1-4)-beta-fucopyranosyl(1-4)-beta-saccharosaminopyranosyl(1-4)-beta-2-sulfate-fucopyranoside. Saccharomicin A (1) differs from saccharomicin B (2) only in the 10th sugar residue, where alpha-digitoxopyranosyl(1-3) is replaced with alpha-rhamnopyranosyl(1-->3). The novel amino sugar residue, designated saccharosamine, was identified by NMR spectroscopy and X-ray crystallography. Both saccharomicins A (1) and B (2) showed antimicrobial activity against Gram-positive bacteria.