G7063-2

Chromic acid oxidation of manumycin (1), an antibiotic produced by Streptomyces parvulus (strain Tü 64), led to the isolation of 2-(2-methyl-4-oxo-2-pentenoylamino)-5,6-epoxy-1,4-benzoquinone (3) and (-)-(R)-2-methylhexanoic acid (4). From the absolute configuration of 4, determined by comparing its optical rotation with published data, follows the absolute configuration at the center of chirality in the diene side chain of manumycin (1) to be (6'R). Based on the direct comparison of the CD spectra of the two chromic acid oxidation products 2 and 3 with those of the antibiotic G7063-2 (5) and (-)-terreic acid (6) the stereochemistry at C-5 and C-6 of 1 was determined as (5R, 6S). From the negative CD-couplet of manumycin (1) its stereochemistry at C-4 was assigned as (4R).

Antibiotic G7063-2, isolated from a Streptomyces species, is a new nitrogen-containing analogue of phyllostine and terreic acid. In vitro G7063-2 is moderately active against both Gram-positive and Gram-negative bacteria and weakly active against fungi. It is toxic to mice.

The absolute configuration of the ring system of the antibiotic G7063-2 has been established as being the same as that reported for terreic acid, based on circular dichroism data. During structure elucidation experiments, reaction with ethereal diazomethane gave an adduct whose structure is proposed.