text: One of the more classic applications of DKR is Noyori's asymmetric hydrogenation. The presence of an acidic center between two carbonyl groups allows for easy epimerization at the chiral center under basic conditions.  To select for one of the four possible stereoisomers, a BINAP-Ru catalyst is used to control the outcome of the reaction through the steric bulk of the phosphorus ligand.  Some of the early transformations are shown below.
  To further understand the stereochemical outcome, one must look at the transition state geometry.
  The steric bulk of the BINAP ligand coupled with the coordination of ruthenium to the carbonyl oxygen atoms results in high selectivity for hydrogen insertion on one face.  This resulting stereochemistry of (R,S) and (R,R) is obtained in 94.5% yield while the other three stereoisomers range from 0.5-3% yield.  Noyori's accomplishments of 1990 paved the way for even more useful applications of DKR.