Novel benzo[a]naphthacene quinones from an actinomycete, Frankia G-2 (ORS 020604)

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Abstract
Frankia sp. G2 (ORS 020604), grown for 1 mo. without shaking, produced a mixture of 2 quinonoid pigments. The structure of one, G-2N, was shown by chemical and physical methods to be 2-methyl-4,7,9,12-tetrahydroxy-5,6-dihydrobenzo[a]naphthacene-8,13-dione. The other, G-2A, has the same structure with the addition of a carboxyl group at position 10 or 11. Natural quinones with this ring system were not reported previously.