Studies in the biochemistry of micro-organisms. 107. Metabolites of Penicillium viridicatum Westling: viridicatic acid (ethylcarlosic acid)

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Abstract
From the culture filtrate of a strain of Penicillium viridicatum 834, 2 crystalline acids were obtained, namely terrestric acid and a new acid, viridicatic acid. Viridicatic acid, C12H16[degree]6, m.p. 174.5[degree], [[alpha]]205461 - 105[degree] in ethanol (c, 1), titrates as a dibasic acid, and has properties close to those of the tetronic acid derivative carlosic acid. Derivatives of viridicatic acid prepared were the mono-p-bromophenacyl ester, m.p. 188-5[degree], and semicarbazone, m.p. 198-199[degree]. Catalytic hydrogena-tion afforded (-)-[alpha]-hexyl-gamma-carboxymethyltetronic acid, m.p. 205[degree] (decomp.), and bromine in aqueous acetic acid gave (-)-[alpha]-bromo-gamma-carboxymethyltetronic acid. On short acid hydrolysis viridicatic acid affords CO2,n-hexanoic acid and[beta]-hydroxylaevulic acid; onprolonged hy-drolysis af urther molecule of CO2 and of acetoin are obtained by degrada-tion of the hydroxylaevulic acid. These facts and other properties such as light-absorption values establish the structure of viridicatic acid as (-)-[alpha]-hexanoyl-gamma-carboxymethyltetronic acid. The relationship between viridicatic acid and carlosic acid is thus similar to that between terrestric and carolic acid, since the 1st member of each pair differs from the 2d only by the presence of an additional ethyl group. The mycelium of strain G. A. 834 afforded mannitol, i-erythritol, ergosteryl palmitate and viridicatin.