Specific inclusion of 1,2-dimethoxybenzene derivatives by crystalline (R)-arylglycyl-(R)-phenylglycines and its structure

The crystallization of (R)-arylglycyl-(R)-phenylglycine (1, aryl = phenyl; 2, aryl = 1-naphthyl) in the presence of 1,2-dimethoxybenzene or its derivatives affords an inclusion compound. A single-crystal X-ray analysis has shown that, in a 1,2-dimethyoxybenzene inclusion compound, dipeptide molecules arrange in a sheet and the 1,2-dimethoxybenzene lies at the end in a void between the sheets by being anchored to an ammonio hydrogen on the sheet via three-center hydrogen bonding. The distance between the sheets was found to be variable according to the length of the guest 1,2-dimethoxybenzene derivatives, as if they were pillars that support the sheets.