Parent patent disclosed a process for preparing difficulty available or pure optical isomers of unsaturated cyclic, alpha,beta-dihydroxy-monocarboxylic acids; substd. unsaturated, aliphatic dicarboxylic acids and substd. unsaturated aliphatic mono-hydroxy-dicarboxylic acids and lactones, by (i) growing a bacterial strain on a nutrient medium contg., as C- and energy source, an aromatic cpd., (A), contg. a non-physiological substituent which is eliminated anionically during cell multiplication; (ii) adding a structurally analogous cpd. (B) which is metabolised and (iii) allowing the metabolite of (B) to accumulate in substrate. In this addn. the new cpd. (+)-2,5-dihydro-2,4-dimethyl-5-oxo-furan-2-acetic acid, (I), is prepd. by (a) cultivating bacterial species WR 912 (registration no. DSM 1138) on a mineral salt medium contg. a 3,4- or 3,5-. dichlorobenzoate as C- and energy source, up to cell density E546 = 1.5-2; (b) adding 3,5-dimethyl-benzoate up to concn. 5mM in medium; (c) recovering (I) formed by extn. and crystallisation from a diisopropyl ether/benzine. Yields of (I) exceed 50%.
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