Synthesis and structural characterization of 6I,6II-diamino-6I,6II-dideoxy-cyclomaltoheptaose, a difunctionalized β-cyclodextrin

6I,6II-Diamino-6I,6II-dideoxy-cyclomaltoheptaose was prepared using the regioselective procedure described by Tabushi. The difunctionalized β-cyclodextrin crystallizes as hexadecahydrate in the orthorhombic space group P212121, with a = 11.395(3), b = 32.989(9), c = 17.560(5) Å, V = 6601 Å3, Z = 4. The structure was solved by molecular replacement techniques using the program PATSEE and was refined to a conventional final R = 0.058 for the 5031 observed reflections with I ⩾ 3σ(I). The β-CD macrocycle presents only slight differences with respect to uncomplexed hydrated or methylated β-CD. The macrocycle structure maintains an approximate seven-fold symmetry. The round shape of the cyclodextrin ring is stabilized by intramolecular OH … O H-bonds between the secondary hydroxyl groups of neighbouring glucose residues. Along the a axis, the β-CD molecules are arranged in columns; the macrocycles form a herring-bone pattern, so that the cavity of each β-CD molecule is closed at each end by neighbouring molecules. The macrocycles are directly linked to each other by H-bonds involving either primary and secondary hydroxyl or amino groups of symmetry-related molecules. The resulting layers are connected to each other by a dense intermolecular hydrogen-bond network, in which solvent molecules participate.