Sisomicin, the principal antibiotic produced in the fermentation of Micromonospora inyoensis, has been shown to be 0-2,6-diamino-2,3,4,6-tetradeoxy-a-D-gZycero-hex-4-enopyranosyl(l-4)-0-[3-deoxy-4-C-methyl-3-(methylamino)-/?-L-arabinopyranosyl(l-6)]-2-deoxy-D-streptamine (1). Sisomicin contains a novel unsaturated sugar unit, not previously encountered in any aminocyclitol antibiotic.Submerged fermentations of Micromonospora inyoensis (NRRL 3292) produce sisomicin,1 a novel unsaturated aminocyclitol antibiotic2•3 having broad spectrum antibacterial activity.4 Sisomicin is the major component of the crude antibiotic complex, which was isolated from the fermentation broth by ion-exchange chromatography.3 Column chromatography of the crude antibiotic on silica Preparative Routes to 4-Amino-4-deoxy-D-galactose1

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A mutant strain of Micromonospora purpurea, designated var. JI-33, produced an antibiotic complex consisting primarily of gentamicin Cla,. A further product of this fermentation was identical to a very minor component isolated from the fermentation of the parent organism and named gentamicin C22. Physical measurements indicated its structure to be 6'-N-methylgentamicin C1a, and this was confirmed by synthesis from gentamicin Cla. The in vitro antibacterial activity of gentamicin C2b was very similar to that of the gentamicin C complex. Antibiotic XK-62-2, produced by Micromonospora sagamiensis, appears to be identical to gentamicin C22. Fermentation of Micromonospora purpurea NRRL 2953 affords, as the major products, the important antibiotics gentamicins C1, C2 and C1a , (gentamicin C complex)2) as well as a host of minor components.') During the screening of this organism, in search of improved gentamicin producers, a novel variant, designated M. purpurea var. JI-33, was isolated. The strain, obtained by multiple nitrosoguanidine treatments and repeated strain selection, was found to possess similar morphology to that already described for gentamicin-producing strains of M.

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