Effect of Solvation on the Rotation of Hydroxymethyl Groups in

Barmak Mostofian , Jeremy C. Smith , Xiaolin Cheng. Interdisciplinary Sciences: .... Marie-Christine Brochier-Salon , Christophe Morin. Magnetic Reson...
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J. Am. Chem. Soc. 1998, 120, 10953-10963

10953

Effect of Solvation on the Rotation of Hydroxymethyl Groups in Carbohydrates Glen D. Rockwell and T. Bruce Grindley* Contribution from the Department of Chemistry, Dalhousie UniVersity, Halifax, NS B3H 4J3, Canada ReceiVed June 4, 1998. ReVised Manuscript ReceiVed August 25, 1998

Abstract: The solvent dependences of the populations of the hydroxymethyl rotamers of methyl 2,3,4,6-tetraO-[2H3]-R-D-glucopyranoside (2a) and methyl 2,3,4-tri-O-[2H3]-R-D-glucopyranoside (6) in 10 and 8 solvents, respectively, have been determined by analysis of 3JH5,H6R and 3JH5,H6S values and by consideration of evidence for hydrogen bonding through infrared spectroscopy and 3JH,OH values. The methods used to determine coupling constants in individual hydroxymethyl rotamers were reexamined, and an improved protocol was developed. When O-6 is methylated (2a), the populations of the hydroxymethyl rotamers are largely independent of solvent polarity at ratios of about 61:38:0 gg:gt:tg, except that a small population (