The effects of two different amino acid catalysts on the stereoselectivities in the direct Mannich reactions of cyclohexanone,p-anisidine and p-nitrobenzaldehyde were studied with the aid of density functional theory.Transition states of the stereo-determining C "C bond-forming step with the addition of enamine intermediate to the imine for the L-proline(·-amino acid) and (R)-3-pyrrolidinecarboxylic acid(·-amino acid)-catalyzed processes were reported.B3LYP/6-31G calculations provide a good explanation for the opposite syn vs.anti diastereoselectivities of these two different kinds of catalysts(syn-selectivity for the ·-amino acid catalysts,anti-selectivity for the ·-amino acid catalysts).Calculated and observed diastereomeric ratio and enantiomeric excess values are in reasonable agreement.
WANG Ying FU Ai-ping LI Hong-liang TIAN Feng-hui YUAN Shu-ping SI Hong-zong DUAN Yun-bo WANG Zong-hua
