CONFORMATIONS AND STRUCTURE STUDIES OF SUGAR LACTONES IN THE SOLID-STATE .2. THE MOLECULAR-STRUCTURE OF ALPHA-D-GLUCOSACCHARINO-GAMMA-LACTONE - 2-C-METHYL-D-RIBO-PENTONO-1,4-LACTONE

The crystal structure of 2-C-methyl-D-ribo-pentono-1,4-lactone (alpha- D-glucosaccharino-gamma-lactone, 1) has been determined by single-crys tal X-ray diffraction. The crystals are orthorhombic, space group P2(1 )2(1)2(1) with a = 7.7429(6), b = 8.3373(7), c = 11.3258(7) Angstrom, V = 731.1(2) Angstrom(3) (CuK alpha, lambda = 1.54184 Angstrom), mu = 10.82 cm(-1), D-c = 1.473 g cm(-3), and Z = 4. The structure was refin ed to R = 0.0307 and R(w) = 0.0424 for 876 observed reflections. Compo und 1 has the D-riba configuration, in agreement with an earlier deduc tion from chemical evidence. The lactone ring adopts the T-3(2) confor mation, with puckering parameters phi = 279.8(9)degrees and q = 0.32(5 ) Angstrom. The orientation of the methyl group about the C-2-C-3 bond is gauche-trans, with the C-6-C-2-C-3-O-3 and C-6-C-2-C-3-C-4 torsion angles being -81.3(2)degrees and 154.7(1)degrees, respectively. The m olecules are linked in the crystal in a two-dimensional intermolecular hydrogen bonding network that involves all hydroxyl groups as well as the carbonyl oxygen atom.