PmHNL-Catalyzed Synthesis of Aliphatic(R)-Cyanohydrins

Significance

The use of PmHNL, an enzyme of the class of hydroxynitrile lyases, as catalyst for the enantioselective addition of cyanides to aldehydes is described. In a previous paper (Y. Asano et al. Tetrahedron 2005, 61, 10908-10916) aromatic aldehydes were reported as substrates for this enzyme. Attempting to widen the substrate scope, the authors have now employed several ali­phatic, unsaturated aliphatic, and cyclic aldehydes. It was found that short-chain aldehydes (e.g., propionaldehyde or pivaldehyde) are converted into the corresponding cyanohydrins with high enantioselectivity and moderate to good yield, while with increasing chain length both selectivity and yield decreased. Cyclic aldehydes, with the exception of cyclopropanecarbaldehyde, were found to give the desired products in excellent enantiomeric excess and good yield.