Precision X-ray and neutron diffraction studies of methyl β-D-ribopyranoside, C₆H₁₂O₅

Abstract

The structure of methyl #D-ribopyranoside has been refined with three-dimensional X-ray and neutron diffractometer data. The crystals are orthorhombic, space group P2~2t2 t with four molecules in a cell of dimensions: a = 5.753 (5), b = 19.986 (5), c = 6.413 (5) ,~,. Full-matrix least-squares refinements have led to a conventional R factor of 0.040 for X-rays and 0.043 for neutrons. The X-ray and neutron results are in good agreement for tl~e heavy atoms. The neutron study provides the precise determination of positional and thermal parameters for the H atoms which is especially important as the structure has both intermolecular and intramolecular hydrogen bonding.

(1R*,2S*,4S*,5S*)-Cyclohexane-1,2,4,5-tetrol

“…Compound (1) can be conveniently prepared from 1,4-cyclohexadiene via a selective epoxidation-hydrolysis-osmylation strategy (McCasland et al, 1963) and is the only readily obtainable configurational isomer of 1,2,4,5-cyclohexanetetrol capable of existing in two energetically different conformational isomers, (1a) and (1b). While conformer (1a) has three of the four hydroxy groups equatorial and is capable of solely intermolecular O-HÁ Á ÁO hydrogen bonding, conformer (1b), with two syn-diaxial hydroxy groups, can be stabilized through an intramolecular O-HÁ Á ÁO hydrogen bond (Girling et al, 1974;Panagiotopoulos et al, 1974;James et al, 1978).…”

1,2-O-Isopropylidene-D-glucofuranose

“…4. The hydrogen bonding is unusual since it includes (James, Stevens & Moore, 1978) rrL-Sorbopyranose (Nordenson, Takagi & Jeffrey, 1979) a-L-Rhamnopyranose (Takagi & Jeffrey, 1978) Thermal ellipsoids are at 50% probability (Johnson, 1976).…”