Different α-alkoxy and α, β-di-alkoxy substituted aldehydes have been submitted to the catalytic action of the oxynitrilases from almond (PaHNL) or from Hevea brasiliensis (HbHNL), in order to explore the possibility of using these enzymes for the preparation of complex cyanohydrins. The selectivity of both enzymes towards these compounds was found to be largely dependent on the substitutents, being low with the aldehydes carrying ...