Valine-mediated borane reduction of ketones

Acetophenone, 3,3-dimethyl-2-butanone, 3-methyl-2-butanone, and 2-pentanone were reduced with (S)-valine-mediated borane in very good yields (86-91 %) giving predominantly alcohols of the (R)-configuration (80, 64, 55 and 36 % ee, respectively).