Acta Crystallographica Section B

Structural Science

Volume 57, Part 2 (April 2001)

research papers

Acta Cryst. (2001). B57, 213-220 [ doi:10.1107/S010876810001661X ]

Structures of furanosides: geometrical analysis of low-temperature X-ray and neutron crystal structures of five crystalline methyl pentofuranosides

A. Evdokimov, A. J. Gilboa, T. F. Koetzle, W. T. Klooster, A. J. Schultz, S. A. Mason, A. Albinati and F. Frolow

Abstract: Crystal structures of all five crystalline methyl D-pentofuranosides, methyl [alpha] -D-arabinofuranoside (1), methyl [beta] -D-arabinofuranoside (2), methyl [alpha] -D-lyxofuranoside (3), methyl [beta] -D-ribofuranoside (4) and methyl [alpha] -D-xylofuranoside (5) have been determined by means of cryogenic X-ray and neutron crystallography. The neutron diffraction experiments provide accurate, unbiased H-atom positions which are especially important because of the critical role of hydrogen bonding in these systems. This paper summarizes the geometrical and conformational parameters of the structures of all five crystalline methyl pentofuranosides, several of them reported here for the first time. The methyl pentofuranoside structures are compared with the structures of the five crystalline methyl hexopyranosides for which accurate X-ray and neutron structures have been determined. Unlike the methyl hexopyranosides, which crystallize exclusively in the C₁ chair conformation, the five crystalline methyl pentofuranosides represent a very wide range of ring conformations.

Keywords: pentofuranosides; low temperature; ring geometry.