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 in to the azide is preferable because of easier purification. After chromatogr aphic separation, the alpha and beta anomers were analysed by NMR spectrosc opy. 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 h exopyranose ring of the beta anomer assumes a C-4(1) conformation and the o rientation of the azido group is compatible with the requirements of the ex o-anomeric effect. This geometry is compared to that of other similar struc tures. (C) 1999 Elsevier Science Ltd. All rights reserved.