Biotransformations of racemic 2,3-allenenitriles in biphasic systems: synthesis and transformations of enantioenriched axially chiral 2,3-allenoic acids and their derivatives.

Abstract

Catalyzed by Rhodococcus erythropolis AJ270 whole cells in an aqueous phosphate buffer-n-hexane biphasic system, racemic axially chiral 2,3-allenenitriles underwent hydrolysis to afford enantioenriched (aR)-2,3-allenamides and (aS)-2,3-allenoic acids with ee's up to >99.5%. Overall biotransformations proceeded through the nitrile hydratase-catalyzed efficient but nonselective hydration of nitriles followed by the amide hydrolysis catalyzed by the substrate-dependent enantioselective amidase. The application of the method has been demonstrated by the transformations of the resulting allene products into highly functionalized heterocyclic compounds with axial chirality of reactants being entirely transferred into or expressed as point chirality of products.