ABSTRACT
Abstract The enantioselective hydrogenation of several a-ketoesters with varying alkyl substituents has been studied over cinchona alkaloid-modified Pt/Ah03 catalyst. The steric constraints caused by the bulky alkyl groups strongly affected the outcome of the catalytic reaction. The increasing substituent size, in the case of the ester group, however, resulted in only slight changes in the reaction rates and enantioselectivity. On the basis of the effect of the substituents an important contribution is proposed to refine the existing mechanistic picture.
