Abstract
The unknown acid, which had been found to be produced by fluoroacetate-tolerant mutants of Candida lipolytica, (1) was isolated as its lactone in a yield of 21g from 1 liter of the culture broth of a mutant, No. R-2, grown on n-paraffins mixture. The lactone was recrystallized from ethyl acetate-chloroform (1:10) in long needles; C7H8O6, mp 153°C, [α]23D-26.2° (c=1.0, H2O), -24.4° (c=1.0, MeOH). It yielded derivatives and a salt: the dimethyl ester, needles from ethanol, mp 112°C, [α]28D-21° (c=1.0, MeOH); the triamide, prisms from water, mp 198°C, [α]16D-8° (c=0.2, H2O); the trisodium salt, powder, [α]25D+5° (c=1.8, 0.4N HCl), -29° (c=1.0, H2O).
The sodium salt was found to inhibit competitively NADP-linked isocitrate dehydrogenase from pig heart. The Ki value for the enzyme was determined to be 1.0×10-7M. The acute toxicity of this acid, as either its lactone or its salt, for mouse, however, was as low as that of threo-Ds-isocitric acid.
From these data and this results of spectral analyses, this acid was safely assumed to be threo-Ds-2-methylisocitric acid.
