Molecular and crystal structures of two 1,6-anhydro-β-maltotriose derivatives

Crystal structures of two 1,6-anhydro-β-maltotriose derivatives, 1,6-anhydro-β-maltotriose nonaacetate and 6″-bromo-6″-deoxy-1,6-anhydro-β-maltotriose octaacetate, have been determined. Both structures are isomorphous and belong to the orthorhombic system, space group of P212121, with cell dimensions of a = 15.659(3) Å, b = 20.587(6) Å, c = 13.023(2) Å and a = 15.402(7) Å, b = 19.737(8) Å, c = 13.481(5) Å, respectively. Each molecule has three α-(1 → 4)-linked glucose units, and two of them have a typical 4C1 chair conformation, while the glucose unit with the 1,6-anhydro bridge has a 1C4 chair-envelope intermediate conformation. In spite of introducing the 1,6-anhydro bridge and acetyl groups, the conformations of the glycosidic linkages in these molecules are almost the same as those of other α-(1 → 4)-linked oligosaccharides. Crystal structures are stabilized by hydrophobic interactions and by a weak intermolecular hydrogen bond of C-H ··· O.