Novel chiral imidazole cyclophane receptors: synthesis and enantioselective recognition for amino acid derivatives

Novel chiral imidazole cyclophane receptors were synthesized by highly selective N-alkylation of the imidazolyl 1N-position of the bridged histidine diester 2 with the dibromide in the presence of NaH; these receptors exhibit good chiral recognition toward the enantiomers Of L- and D-amino acid derivatives (up to K-D/K-L = 3.52, Delta DeltaG(0) = -3.11 kJ mol(-1)) in CHCl3 at 25.0 degreesC.