CYCLO[-HIS-HIS] DERIVED C2-SYMMETRIC DIKETOPIPERAZINE AS CHIRAL LIGAND FOR ASYMMETRIC DIELS-ALDER REACTIONS

摘要

A cyclic dipeptide based chiral ligand, cyclo[-His(Tr)-His(Tr)-] (Tr = triphenylmethyl), was designed and prepared through bis-N(τ)-tritylation of two imidazole rings of cyclo[-His-His-]. The complex prepared in situ by mixing Cu(OTf)2 with equimolar amount of this ligand successfully catalyzed asymmetric Diels-Alder reactions in fair to good yields and moderate selectivities.