FUNCTIONALIZED CYCLODEXTRINS - SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF BONYL-2-AMINOETHYL]-IMIDAZOLYL)-CYCLOMALTOHEPTAOSE

The synthesis and the structural characterization by X-ray diffraction analysis of a monofunctionalized beta-cyclodextrin (beta-CD), the bon yl-2-aminoethyl]-imidazolyl}cyclomaltoheptaose, are reported, It cryst allizes in the orthorhombic space group P2(1)2(1)2(1), with a = 17.250 (9)Angstrom, b = 19.45(1)Angstrom, c = 23.24(1)Angstrom, d(calc) = 1.3 04 g/cm(3) and Z = 4. The structure was refined to final indices R1 = 0.083 and wR2 = 0.24 (based on F-o(2)) for the 4843 observed reflectio n with I greater than or equal to 2 sigma(I). At the end of the refine ment the presence of 12 water molecules per beta-CD molecule distribut ed over 16 sites was detected, In the solid state the monofunctionaliz ed beta-CD molecule shows a 'sleeping swan'-like shape with the covale ntly bonded Boc-amino-ethyl-imidazolyl moiety forming a folded structu re with its terminal part inserted inside the hydrophobic cavity of th e beta-CD ring. The beta-CD macrocycle presents only small differences with respect to the conformation observed in hydrated uncomplexed or methylated beta-CDs. The macrocycle structure maintains an approximate seven-fold symmetry. The substituted beta-CD molecules pack in layers parallel to the be plane, The layers are stacked in an head-to-tail a rrangement of the monomeric units, with formation of columns of molecu les along the a axis, The layers are connected to each other by H-bond s through water molecules, Channels generated in the crystal by the pa cking of the macrocycles are filled with water molecules.