Asymmetric Synthesis of an (R)-Cyanohydrin Using Enzymes Entrapped in Lens-Shaped Gels

A novel synthesis of (R)-cyanohydrins is described which is based on the use of cross-linked and subsequently poly(vinyl alcohol)-entrapped (R)-oxynitrilases. These immobilized lens-shaped biocatalysts have a well-defined macroscopic size in the mm range, show no catalyst leaching, and can be recycled efficiently. Furthermore, this immobilization method is cheap and the entrapped (R)-oxynitrilases gave similar good results compared with those of free enzymes. The (R)-cyanohydrin was obtained in good yields and with high enantioselectivities of up to >99% ee.