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The antibiotic novobiocin2 has been shown to be 7-[4-(carbamoyloxy)-tetrahydro-3-hydroxy-5-methoxy-6,6-dimethylpyran-2-yloxy]-4-hydroxy-3-[4-hydroxy-3-(3-methyl-2-butenyl)-benzamido]-8-methylcoumarin (I).Novobiocin, elaborated by Streptomyces niveus, is a crystalline, acidic antibiotic of the composition CíiHmN,Ou. Studies on the fermentation,3-4 extraction, purification and properties,3 456•6 biological activity7 and clinical usefulness8 have been reported.Because of its interesting antibacterial action and its clinical efficacy, the structure of novobiocin is of particular significance. Evidence is presented in this paper to show that novobiocin possesses structure I. O ocnh2 oh ch3 I General Characteristics.-Novobiocin crystallized in two polymorphic modifications, one melting at 174-178°and the other at 152-1560.6-6 The dibasic acid properties of the compound were indicated by the preparation of both acid and neutral salts. Potentiometric titrations and ultraviolet spectral shifts confirmed these observations and showed novobiocin to be a dibasic acid with pK'& values of 4.3 and 9.1 in aqueous solution. The ultraviolet spectra in acid, neutral and alkaline solu-(1) Novobiocin.IV. The investigations upon which this paper is based were first reported in a series of preliminary communications. (a) (This Journal, 77, 6710 (1955); (b) 78, 1072; (c) 78, 2019 (1956)). These findings are in agreement with those reported independently by the Merck group (d) (ibid., 78, 1770 (1956)).(2) The Upjohn Co. Registered Trademark for novobiocin is Albamycin. Our former generic name, streptonivicin, has been aban-(3) C.

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