Size discrimination in intramolecular complexation of modified #alpha#-cyclodextrins: a preparative and nuclear magnetic resonance study

摘要

Acylation of the primary amine group of 6~A-(6-aminohexylamino)-6~A-deoxy-a-cyclodextrin 1 by 4-nitrophenyl trinorbornane-2-acetate 6, 1-methoxycarbonyl-8-(4-nitrophenoxycarbonyl)cubane 7.1-methoxycarbonyl-2,3-dimethyl-8-(4-nitrophenoxycarbonyl)cubane 8. and 1-(4-nitrophenoxycarbonyl) adamantane 9. respectively, gives 6~A-deoxy-[6-(trinorbornan-2-ylacetylamino)hexylamino]-#alpha#-cyclodextrin 2.6~A-[6-(8-carboxycuban-1-ylcarbonyl-aminohexylamino)]-6~A-deoxy-#alpha#-cyclodextrin 3.6~A-[6-(8-carboxy-2.3-dimethylcuban-1-ylcarbonylamin) hexylamino]-6~A-deoxy-#alpha#-cyclodextrin 4. and 6~A-[6-(adamantan-1-ylcarbonylamino)hexylamino]-6~A-deoxy-#alpha#-cyclodextrin 5, in good yields together with 4-nitrophenolate. In basic D_2O, the substituents of 1-4 complex intramolecularly within the #alpha#-cyclodextrin annulus, whereas that of 5 does not due to its larger size, as shown by ~1H ROESY NMR spectroscopy. This facilitates a mechanistic comparison with the formation of #beta#CD analogues of 2-5.