A γ-cyclodextrin duplex connected with two disulfide bonds: synthesis, structure and inclusion complexes

Per(2,3,6-tri-O-benzyl)-γ-cyclodextrin was debenzylated by DIBAL-H to produce a mixture of C6^I,C6^IV and C6^I,C6^V isomeric diols, which were separated and isolated. The C₂-symmetrical C6^I,C6^V diol was transformed into dithiol and dimerized to produce a γ-cyclodextrin duplex structure. A crystal structure revealed tubular cavity whose peripheries are slightly elliptically distorted. The solvent accessible volume of the cavity of the γ-CD duplex is about 740 ų. Due to this large inner space the duplex forms very stable inclusion complexes with steroids; bile acids examined in this study show binding affinities to the γ-cyclodextrin duplex in the range of 5.3 × 10⁷ M⁻¹–1.9 × 10⁸ M⁻¹.