Biosynthetic Studies on a Myxobacterial Antibiotic, Cystothiazole A

Biosynthetic Precursors of the Carbon Skeleton

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Biosynthetic studies on cystothiazole A (1), a β-methoxyacrylate-type antifungal compound from a myxobacterium, were performed by feeding the producing organism, Cystobacter fuscus, with stable-isotope-labeled compounds including [2-¹³C]acetate, [1, 2-¹³C₂]acetate, [1-¹³C]propionate, L-[1-¹³C]serine, L-[methyl-¹³C]methionine, and DL-valine-d₈. The polyketide moiety of 1 was found to be derived from acetate and propionate, the bithiazole moiety from L-serine, the O-methyl groups from the S-methyl group of L-methionine, and the isopropyl moiety from L-valine, which should be the metabolic precursor of isobutyryl-CoA.