Studies on the Synthesis of DMAP Derivatives by Diastereoselective Ugi Reactions

Diastereoselective Ugi reactions of DMAP-based aldehydes with alpha-amino acids and tert-butyl isocyanide were examined. The reactions of 4-(dimethylamino)-2-pyridine-carboxaldehyde with various alpha-amino acids afforded 2-substituted DMAP derivatives with low diastereoselectivity. On the contrary, reactions with 4-(dimethylamino)-3-pyridine-carboxaldehyde delivered 3-substituted DMAP derivatives with moderate to high diastereoselectivity. The combination of alpha-amino acid and DMAP-based aldehyde is thus important to achieve high diastereoselectivity. Kinetic resolution of a secondary alcohol using a chiral DMAP derivative obtained through these reactions was also examined.