Synthesis and structural studies of anomeric 2,3,4,6-tetra-O-acetyl-5-thio-D-glucopyranosyl azides

Two methods are presented for the preparation of the alpha and beta anomers of 2,3,4,6-tetra-O-acetyl-5-thio-D-glucopyranosyl azide. These methods are comparable in yield, but the one that converts a glucopyranosyl bromide into the azide is preferable because of easier purification. After chromatographic separation, the alpha and beta anomers were analysed by NMR spectroscopy. The crystal and molecular structure of the beta anomer was determined by X-ray diffraction. It crystallises in space group P2(1) [a = 11.729(3), b = 7.305(3), c = 11.363(3)Angstrom, beta = 107.63(5)degrees, Z = 2]. The hexopyranose ring of the beta anomer assumes a C-4(1) conformation and the orientation of the azido group is compatible with the requirements of the exo-anomeric effect. This geometry is compared to that of other similar structures. (C) 1999 Elsevier Science Ltd. All rights reserved.