Crystal structures of heptakis(2,6-di-O-tert-butyldimethylsilyl)cyclomaltoheptaose, heptakis(2-O-methyl-3,6-di-O-tert-butyldimethylsilyl)-cyclomaltoheptaose and heptakis(2-O-methyl)-cyclomaltoheptaose

Crystal structures of heptakis(2,6-di-O-tert-butyldimethylsilyl)cyclomaltoheptaose, heptakis(2-O-methyl-3,6-di-O-tert-butyldimethylsilyl)cyclomaltoheptaose and heptakis(2-O-methyl)cyclomaltoheptaose were determined from X-ray diffraction patterns obtained for single crystals of the title compounds grown from ethyl acetate and ethanol, respectively, as solvent. The crystal structures prove conclusively that quantitative migration of the tert-butyldimethylsilyl group from the 2-O- to the 3-O-position [D. Icheln, B. Gehrcke, Y. Piprek, P. Mischnick, W.A. Konig, M.A. Dessoy, A.F. Morel, Carbohydr. Res., 280 (1996) 237-250] was achieved during methylation of heptakis(2,6-di-O-tert-butyldimethylsily)cyclomaltoheptaose by iodomethane-sodium hydride. (C) 2000 Elsevier Science Ltd. All rights reserved.