Chirality Transfer in a Calixarene-Based Directional Pseudorotaxane Complex

Hexamethoxycalix[6]arene 3 forms a directional pseudorotaxane complex with the chiral axle (S)-(α-methyl-benzyl)benzylammonium 2+. Between two (endo-chiral)-2+@3 and (exo-chiral)-2+@3 stereoisomers, former is preferentially formed. This result confirms validity of “endo-α-methyl-benzyl rule”, previously reported by us. DFT calculations suggest that C-H···π interactions between methyl group 2+ calixarene aromatic rings, determine stereoselectivity threading process toward preference”. An amplification optical rotation observed upon formation respect to free Thus, specifical 1:1 mixture 2+∙B(ArF)4− salt achiral was augmented were used rationalize this result.