CARBOHYDRATE RESEARCH zyxwvutsrqpo Carbohydrate Research 264 ( 1994) 135-140 Note High resolution solid state 13C NMR study of crystalline methyl D-xylopyranoside anomeric mixtures Michel Bardet, Marc Vincendon * zyxwvutsrqponmlkjihgfedcba CEA, Dipartement de Recherche Fondamentale SW la Mat&e Condensie/SESAM, Centre d’Etudes de Grenoble, F-38054 Grenoble, France Received 4 January 1994; accepted in final form 17 May 1994 Keywords: Methyl D-xylopyranosides; 13C solid state NMR; Anomeric crystalline mixture; Cocrystallization zyxwvutsrqp High resolution solid state 13C cross polarization with magic angle spinning NMR spec- troscopy ( 13C CP/ MAS NMR) can provide interesting and rapid indications concerning the isomeric composition of sugars in the solid state. This technique may be used as a screening tool, before undertaking a more complex X-ray diffraction single crystal structural study. Solid state 13C NMR is especially sensitive to the anomeric equilibrium which can result from the crystallization of solutions of reducing sugars. It is also well adapted to the observation of conformational changes. When two isomers crystallize simultaneously from their solutions, it is to be expected that the less soluble component will crystallize preferentially. Therefore, the existence of anomers of reducing sugars in the same unit cell is considered as unusual, 2-Acetamido-2- deoxy-D-glucose [ 11 and 6-deoxy-cr-L-sorbofuranose [ 21 have, however, been reported to present a cocrystallization of the two anomers with a small proportion of the p anomeric form. The cocrystallization of different isomers is more common in the case of reducing disaccharides, such as, for example, lactulose [ 3 ] and lactose [ 4,5] . A crystalline mixture of glycoside anomers has been reported in a 1: 1 ratio for n-octyl (;Y- and / 3-D-glucopyranoside [61. The solid state 13C NMR spectra of methyl cy- and / 3-D-xylopyranoside have already been published [ 71. The LY anomer crystallizes with two nonequivalent molecules per asymetric unit of the monoclinic cell and gives two signals for each type of carbon atom in the NMR spectrum of the solid. The p anomer crystallizes with only one molecule per asymetric unit, * Corresponding author. 000%6215/94/$07.00 0 1994 Elsevier Science B.V. All rights reserved SSDIOOOS-6215(94)00173-D