THE CRYSTAL PACKING OF N-(N-OCTYL)-D-GULONAMIDE CONTAINING TAIL-TO-TAIL SHEETS COMPARED TO ITS GLUCONAMIDE DIASTEREOMER SHOWING HEAD-TO-TAIL ARRANGEMENT

N-Octylamides of diastereomeric gluconic and gulonic acids form molecular aggregates of extremely different curvature, namely helical micellar rods with a diameter of 4 nm and planar bilayers. In the crystal structure of the gulonamide compound, symmetric ''tail-to-tail'' bilayer sheets are observed, whereas the gluconamide derivative (whose crystal structure was determined previously) forms an unusual ''head-to-tail'' arrangement. These differences are unexpected because both diastereomers contain one pair each of syn- and anti-oriented hydroxyl groups in 1,3-positions of the extended aldonic acid chains. The experimental results are explained by the occurrence of hydrogen-bond patterns between hydroxyl groups, either within one crystal sheet or hydrophobic bilayer (gluconamide) or between the end groups of neighboring sheets (gulonamide).