Rotaxanes with unidirectional cyclodextrin array

We report here construction of pseudo-rotaxanes of α-cyclodextrin (α-CD) with axle molecules bearing pyridyl end caps via kinetic control of threading of α-CD onto axle molecules. A single substituted pyridyl group attached to the ends of the axle molecule regulates the rate for α-CD passing them. Two methyl substituents can clearly govern the degree of complex formation of α-CD with guest molecules and result in the distinction of face direction of CD molecules entering the axle ends. α-CDs are arranged in one direction at two station units of the axle molecule to give a face-selective pseudo-[3]rotaxane.