Application of Chromatography. XXXIII. V-Compound Isolated from the Mycelium of Eremothecium ashbyii.

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The purple fluorescent substance (V-compound) obtained by the authors from the mycelium of Er. ashbyii occurs as colorless needles, m. p. 263°(decomp.), [α]²⁰_D : +4.5°(in H_2O), +11.45°(in 0.1N NaOH). The molecular weight of this substance was found to be about 300 by Barger method, titration (as monobasic acid), and from the wave height in polarography. A molecular formula of C₁₂H₁₆O₇N₄ was assigned to the substance from its analytical value. From its ultraviolet and infrared spectra the presence of a pteridine ring, COOH, and OH was presumed. Since the substance gave urea by treatment with alkali solution, it was assumed to be a pteridine compound having a carbonyl group at 2-position, substituted by a group at one of the nitrogens in the pyrazine ring. From the fact that the acetylation product of the substance was in accord with its tetraacetate, and that it gave formaldehyde by oxidation with lead tetraacetate, the group was presumed to be ribityl. Photodecomposition of this substance furnished more important data. Although exposure of an aqueous solution of the substance to direct sunlight destroyed even the pteridine ring, irradiation of its alkaline solution with light from an electric lamp in the presence of hydrogen peroxide yielded crystals of m. p. >360°. The product exhibited the ultraviolet spectrum characteristic to pteridine compounds. Comparison of the product with lumazine-6-carboxylic acid by ionophoresis indicated that the former has lower negative charge than the latter. Therefore, the molecular formula, C₇H₆O₄N₄, calculated from the analytical value was concluded to be C₇H₄O₃N₄·H₂O. This may be due to the dehydrogenation of the parent ring during cleavage of the group at the nitrogen of the pyrazine ring by photodecomposition of the V-compound. From these results, the authors gave the following structure to the V-compound.