The crystal structure of N-acetylneuraminic acid methyl ester monohydrate

Abstract

The crystal structure of the methyl ester of N-acetylneuraminic acid monohydrate has been determined from three-dimensional X-ray diffraction data. The crystals are orthorhombic, space group P212121, with unit-cell constants a=7.954+ 1, b= 11.675+4, c= 16.974+2 ~. The structure was solved using the tangent formula and refined by block-diagonal least-squares techniques to R=0.042. The three bulky substituent groups, the N-acetyl, the glycero and the methyl ester groups, are all equatorially bonded to the pyranose ring while the hydroxyl group at the anomeric carbon atom C(2) is in the axial position. An extensive system of seven interand one intramolecular hydrogen bonds holds the molecules quite rigidly in the crystal lattice, resulting in an average overall isotropic temperature factor coefficient of only 2.7 ,~2.