D-L Conversion Pathways between Optical Isomers of Alanine: Applications of the Scaled Hypersphere Search Method to Explore Unknown Reaction Routes in a Chiral System

摘要

D-L conversion pathways of alpha-alanine have been discovered by theoretical search of potential energy surfaces at the level of B3LYP/6-311++G(d,p).No direct conversion channel via only one transition state could be found between D and L optical isomers of alanine.It is demonstrated that there are four types of conversion channels in chiral amino acids.The interconversion of four functional groups(H,CH_3,NH_2,and COOH)around the asymmetric carbon atom can occur as rotation of a single-bonded pair of two groups involving either NH_2 or COOH together with H or CH_3.