Applying Biocatalysis to the Synthesis of Diastereomerically Enriched Cyanohydrin Mannosides

Fully acetylated D- and L-alpha-mannosylacetaldehydes have been prepared and used as substrates to produce the corresponding cyanohydrins or cyanohydrin acetates with (2S) or (2R) configuration, respectively, at the cyanohydrin moiety. The (R)-oxynitrilase-catalysed synthesis and lipase-catalysed diastereomeric kinetic and dynamic kinetic resolutions were investigated. Sequential catalysis with almond meal [ an economic source of (R)-oxynitrilase] and Burkholderia cepacia lipase was shown to be a straightforward method that yielded the four diastereomeric target cyanohydrins, the absolute configurations of which were confirmed by H-1 NMR analysis.