making this a dynamic kinetic resolution. In addition, lipases are used extensively for kinetic resolution in both academic and industrial settings. Lipases have been used to resolve primary alcohols, secondary alcohols, a limited number of tertiary alcohols, carboxylic acids, diols, and even chiral allenes. Lipase from Pseudomonas cepacia (PSL) is the most widely used in the resolution of primary alcohols and has been used with vinyl acetate as an acylating agent to kinetically resolve the primary alcohols shown below. For the resolution of secondary alcohols, pseudomonas cepecia lipase (PSL-C) has been employed effectively to generate excellent ee's of the (R)-enantiomer of the alcohol. The use of isopropenyl acetate as the acylating agent results in acetone as the byproduct, which is effectively removed from the reaction using molecular sieves. Oxidations and reductions Baker's yeast (BY) has been utilized for the kinetic resolution of α-stereogenic carbonyl compounds. The enzyme selectively reduces one enantiomer, yielding a highly enantioenriched alcohol and ketone, as shown below. Baker's yeast has also been used in the kinetic resolution of secondary benzylic alcohols by oxidation. While excellent ee's of the recovered alcohol have been reported, they typically require >60% conversion, resulting in diminished yields. Baker's yeast has also been used in the kinetic resolution via reduction of β-ketoesters. However, given the success of Noyori's resolution of the same substrates, detailed later in this article, this has not seen much use. Dynamic kinetic resolution Dynamic kinetic resolution (DKR) occurs when the starting material racemate is able to epimerize easily, resulting in an essentially racemic starting material mix at all points during the reaction. Then, the enantiomer with the lower barrier to activation can form in, theoretically, up to 100% yield. This is in contrast to standard kinetic resolution, which necessarily has a maximum yield of 50%. For this reason, dynamic kinetic resolution has extremely practical applications to organic synthesis. The observed dynamics are based on the Curtin-Hammett principle. The barrier to reaction of either enantiomer is necessarily higher than the barrier to epimerization, resulting in a kinetic well containing the racemate. This is equivalent to writing, for kR>kS, A number of excellent reviews have been published, most recently in 2008, detailing the theory and practical applications of DKR. Noyori asymmetric hydrogenation The Noyori asymmetric hydrogenation of ketones is an excellent example of dynamic kinetic resolution at work. The enantiomeric β-ketoesters can undergo epimerization, and the choice of chiral catalyst,