A single-step synthesis of (R)-α-methyl- 4-pyridinemethanol from (RS)-α-methyl-4- pyridinemethanol by stereoinversion using whole cells of Candida parapsilosis is reported. Among the various strains of Candida species examined, C. parapsilosis demonstrated to have the best oxidoreductase system for stereoinversion of (RS)-α-methyl-4-pyridinemethanol. The effect of various physicochemical parameters on the stereoinversion process, were studied. Under optimized conditions approximately 97% enantiomeric excess of (R)-α-methyl-4-pyridinemethanol (eeR) was obtained with 99% yield was obtained. The optimized parameters were determined to be a substrate concentration of 5 mM, pH 8.0, 30°C incubation temperature, and a reaction time of 48 h. The reactions were also carried out in different organic solvents, and maximum stereoinversion was obtained in 1,4-dioxane with 78.4% eeR and 74.7% yield, which are lower than those in phosphate buffer. This whole cell catalysis for the preparation of (R)-α-methyl-4- pyridinemethanol is an example of a green, enantiopure synthesis of secondary alcohols.
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