A Versatile and practical solvating agent for enantioselective recognition and NMR analysis of protected amines

摘要

The 3,5-dinitrobenzoyl-derived 1-naphthylethyl amide 3 is an attractive CSA for NMR analysis of protected amines. It is readily prepared in a single step and combines practical resolution of diastereomeric complexes due to signal sharpness and effective signal separation. Crystallographic analysis shows that 3 forms a chiral cleft that can selectively bind one enantiomer of a substrate through hydrogen bonding, π-π stacking, and CH/π interactions. The enantioselective complex formation causes strong upfield shifts in the ~1H NMR spectrum even in the presence of only 5 mol % of 3.