The 1,4-diyl (2) generated from calicheamicin 7/ (1, CLM) by reductive activation1•2 34and rearrangemen ****9t3•4 is believed to initiate DNA cleavage by hydrogen atom abstraction from both strands of the helix to give the reduced form of the drug, CLM e (3).

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-[α-4-epi-vancosaminopyranosyl(1→4)-α-4-epi-vancosaminopyranosyl(1→4)-α-digitoxopyranosyl(1→4)-α- 4-epi-vancosaminopyranosyl(1→4)-α-digitoxopyranosyl(1→3)-β-fucopyranosyl(1→4)-β-saccharosaminopyranosyl(1→4)-α-digitoxopyranosyl(1→3)]-[α-4-epi-vancosaminopyranosyl(1→4)]-β-fucopyranosyl(1→4)-β- saccharosaminopyranosyl(1→4)-α-rhamnopyranosyl(1→3)-β-fucopyranosyl(1→4)-β-saccharosaminopyranosyl(1→4)-β-fucopyranosyl(1→4)-β-saccharosaminopyranosyl(1→4)-β-2-sulfate-fucopyranoside. Saccharomicin A (1) differs from saccharomicin B (2) only in the 10th sugar residue, where α-digitoxopyranosyl(1→3) is replaced with α-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.

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The effect of introducing hydrophobic groups onto the disaccharide portion of the mannopeptimycins has been examined. Under acid-catalyzed conditions dimethyl acetals and ketals react on the terminal mannose of the disaccharide moiety of mannopeptimycin-alpha and the cyclohexylalanyl analogue 2. The preferentially formed monofunctionalized 4,6-acetals and -ketals display potent antibacterial activities against Gram-positive microorganisms, including MRSA, PRSP, and VRE pathogens.