Intramolecular complexation in modified β-cyclodextrins:† a preparative, nuclear magnetic resonance and pH titration study
Abstract
The reactions of 4-nitrophenyl trinorbornane-2-acetate and 4-nitrophenyl noradamantane-1-carboxylate with 6A-(6-aminohexylamino)-6A-deoxy-β-cyclodextrin 1 produce 6A-{6-(bicyclo[2.2.1]heptan-2-ylacetylamino)hexylamino}-6A-deoxy-β-cyclodextrin 2 (pKa = 8.98) and 6A-deoxy-6A-{6-(tricyclo[3.3.1.0]nonan-3-ylcarbonylamino)hexylamino}-β-cyclodextrin 4 (pKa = 8.47), respectively, in good yield together with 4-nitrophenolate. The reaction of 2,3-dimethyl-1,8-bis-(4-nitrophenoxycarbonyl)cubane with two moles of 1 produces dimeric 1,8-bis-[6-(6A-deoxy-β-cyclodextrin-6A-ylamino)hexylaminocarbonyl]-2,3-dimethylcubane 7 (pKa = 8.80) in good yield together with two moles of 4-nitrophenolate. The pKas in brackets are those of the single protonated