We report a biocatalytic transamination method to prepare a broad range of b-branched a-amino acids that proceeds with high diastereo- and enantioselectivity. Mechanistic studies show that the transformation proceeds through a dynamic kinetic resolution process that is unique to the optimal enzyme. To highlight its utility and practicality, the biocatalytic reaction is applied to the synthesis of several cyclic fragments and in the first total synthesis of jomthonic acid A.