Pergamon Tetrahedron: Asymmetry 10 (1999) 2881–2889 Stereochemical analysis of D-glucopyranosyl-sulfoxides via a combined NMR, molecular modeling and X-ray crystallographic approach Peter H. Buist, a,* Behnaz Behrouzian, a Kenzie D. MacIsaac, a Stephanie Cassel, b Patrick Rollin, b Anne Imberty, c Catherine Gautier, c Serge Pérez c and Pierre Genix d a Ottawa-Carleton Chemistry Institute, Department of Chemistry, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada, K1S 5B6 b ICOA, Université d’Orléans, B.P. 6759, F-45067 Orléans, France c CERMAV-CNRS(affiliated with Joseph Fourier University), BP53, F-38041 Grenoble, Cedex 9, France d Rhône-Poulenc Agrochimie, 14/20 Rue Pierre Baizet, 69009 Lyon, France Received 2 June 1999; accepted 7 July 1999 Abstract (S)-α-Methoxyphenylacetic acid (MPAA) was used as an NMR shift reagent in combination with molecular modeling to predict the absolute configuration of a representative epimeric pair of glucopyranosyl sulfoxides. The correctness of this assignment was confirmed by X-ray crystallographic examination of one of the epimers, 3a1. The crystal structure of ethyl 2,3-di-O-acetyl-4,6-O-benzylidene-1-thio-β-D-glucopyranoside S-oxide mo- nohydrate 3a1 was solved by direct methods and was shown to bear the (R)-configuration at the sulfinyl center in accordance with our prediction. Furthermore, the conformation of 3a1 in the solid state was found to be remarkably similar to that predicted by molecular mechanics calculations. © 1999 Elsevier Science Ltd. All rights reserved. 1. Introduction The stereochemical analysis of chiral sulfoxides remains an important research objective. We have demonstrated that (S)-(+)-α-methoxy-phenylacetic acid (MPAA) 1 can be used as a chiral NMR shift reagent to determine the % ee and absolute configuration of a substantial number of acyclic sulfoxides. 1 a,b Others have extended these studies using related chiral aromatic acids. 2a,b We have also used MPAA in combination with molecular modeling techniques to correctly predict the stereochemistry of some thiosugar sulfoxides. 3 To date, our methodology has enjoyed a 100% success rate. Recently, the Rollin group has prepared a number of epimeric glucopyranosyl sulfoxides, 3a–f, which have important * Corresponding author: Tel: 613-520-2600, ext. 3643; fax: 613-520-3749; e-mail: p.buist@ccs.carleton.ca 0957-4166/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PII: S0957-4166(99)00294-3