THE X-RAY CRYSTAL-STRUCTURE OF THE DOUBLE-HEADED AMPHIPHILE (1S,2S)-1,2-BIS(D-GLUCONAMIDO)CYCLOHEXANE

If a mixture of diastereomeric and enantiomeric 1,2-diaminocyclohexanes is amidated with D-glucono-1,5-lactone, only one of the four diasteroeomeric amides, namely the title compound, crystallizes from the mixture. The same amide was also synthesized and crystallized from enantiomerically pure S,S-diamino-cyclohexane. The 1R,2R-diamide was also synthesized, but could not be crystallized. (1S,2S)-1,2-bis(D-gluconamido)cyclohexane, C18H34N2O12, M(r) = 470.47, orthorhombic P2(1)2(1)2(1), a = 4.877 (1), b = 18.962 (5), c = 23.432 (9) Angstrom, V = 2166.9 Angstrom(3), Z = 4, D-x = 1.422 g cm(-3), lambda (CuK alpha) = 1.5418 Angstrom, mu = 10.49 cm(-1), F(000)= 1008.0, T = 295K, final R = 0.057 and R(w) = 0.054 for 1808 reflections with F > 2 sigma(F). When compared to crystal structures of other gluconamides, the title compound exhibits regular differences in its gluconamide moieties. These differences are explained by an equilibrium between the tendency to form an extended hydrogen bonding net, the tendency of gluconamide chains to adopt an all-trans conformation and the restrictions imposed on the sugar chains by the topology. The hydrophobic parts of the molecule form parallel 'oil-tubes' in the crystal rather than hydrophobic sheets, a pattern never observed before.