A number of enzymatic dynamic kinetic resolutions have been reported. A prime example using PSL effectively resolves racemic acyloins in the presence of triethylamine and vinyl acetate as the acylating agent. As shown below, the product was isolated in 75% yield and 97% ee. Without the presence of the base, regular kinetic resolution occurred, resulting in 45% yield of >99% ee acylated product and 53% of the starting material in 92% ee.
Another excellent, though not high-yielding, example is the kinetic resolution of (±)-8-amino-5,6,7,8-tetrahydroquinoline. When exposed to Candida antarctica lipase B (CALB) in toluene and ethyl acetate for 3–24 hours, normal kinetic resolution occurs, resulting in 45% yield of 97% ee of starting material and 45% yield of >97% ee acylated amine product. However, when the reaction is allowed to stir for 40–48 hours, racemic starting material and >60% of >95% ee acylated product are recovered.
Here, the unreacted starting material racemizes in situ via a dimeric enamine, resulting in a recovery of greater than 50% yield of the enantiopure acylated amine product.