Phthoxazolin A, a specific inhibitor of cellulose biosynthesis from microbial origin. I. Discovery, taxonomy of producing microorganism, fermentation, and biological activity.

A new inhibitor of cellulose biosynthesis named phthoxazolin A was discovered as a metabolite of Streptomyces sp. OM-5714. A newly established screening method, which utilized a cellulose-containing fungus, Phytophthora sp. as a test organism, was successfully employed for discovery of the compound. Phthoxazolin A, C16H22N2O3 (MW of 290), is a lipophilic triene compound with an oxazole moiety. It has moderate antifungal activity against Phytophthora spp. only and has potent herbicidal activity. Phosphate-limited fermentation conditions favored production of the active compound.