A novel class of fluorinated cinchona alkaloids as surface modifiers for the enantioselective heterogeneous hydrogenation of α-ketoesters

Abstract

Novel C-9 fluorinated cinchona alkaloid derivatives were investigated as chiral surface modifiers for the platinum-catalyzed asymmetric heterogeneous hydrogenation of α-ketoesters. Enantioselectivities approaching those observed with the parent alkaloids were obtained, and direct comparison with conformationally labile deoxycinchonidine confirmed that the C-9 fluorine atom is important for performance. In this study, the 9-fluoro derivative of cinchonidine was shown to effect the reduction of ketopantolactone to (R)-pantolactone in quantitative yield with good levels of enantioinduction (57% ee) providing preliminary validation for this novel class of surface modifiers.