Enzyme Catalyzed Addition of Hydrocyanic Acid to Substituted Pivalaldehydes - A Novel Synthesis of (R)-Pantolactone
(R)-Cyanohydrins (R)-2b-h are obtained in good optical yields by (R)-oxynitrilase catalyzed enantioselective addition of HCN to β-substituted pivalaldehydes 1b-h.Under optimized reaction conditions with highly purified (R)-oxynitrilase, hydroxypivalaldehyde (1a) is converted to (R)-2a in satisfactory chemical and optical yields.By acid-catalyzed hydrolysis the cyanohydrins (R)-2a-h cyclize directly to give crude (R)-pantolactone (R)-3 with ee-values of 56-95percent which, after recrystallization, go up to >/=98 percentee in all cases.
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