Selective distortion of the planar group Cα C'(O)O to a chiral flat tetrahedron in the amino acid alanine.

Based on a Cambridge Structural Database (CSD) search, a meta-analysis of 116 structures of alanine H3 NCα H(CH3 )C'(O)O and its derivatives H3 NCα H(CH3 )C'(O)O(H/R/M), protonated, esterified, or coordinated at the carboxylic group, shows that in the first step of a chirality chain, the L configuration at Cα induces (M) and (P) conformations with respect to rotation around the central C'─Cα bond. In the second step, the (M) and (P) conformations selectively distort the planar carboxylic group Cα C'(Ocis )Otrans to asymmetric flat (R) and (S) tetrahedra. High diastereoselectivities are caused by the two players attraction N…Ocis and repulsion Otrans …CMe , which work together in (L,M,R) configurations but against each other in (L,P,S) configurations.