Asymmetric reduction of (4R)-(−)-carvone catalyzed by Bakerʹs yeast in aqueous mono- and biphasic systems

(1R,4R)-dihydrocarvone (2), an important renewable building block, was prepared with good conversions and excellent diastereoisomeric excess through the reduction of the α,β-unsatured carbon–carbon double bond of (4R)-(−)-carvone (1) mediated by Bakerʹs yeast (BY) in aqueous mono- and biphasic systems. Some parameters that may alter this bioreduction reaction, such as the concentrations of yeast and substrate, temperature, and pH, were evaluated. The effect of the addition of different additives on the course of 1 biotransformation was also investigated. The results showed that the conversion and diastereoisomeric excesses were strongly dependent on these variables. The optimum reaction conditions were 100 g L−1 of BY, 16.6 mM of substrate, and pH 7.5 at 26 °C in the presence of DMSO, trehalose, or sucrose as additives. Under the optimum conditions, the (1R,4R)-dihydrocarvone was recovered with diastereoisomeric excesses of 92–99% and with conversions of 70–74%.