Conformations and structure studies of sugar lactones in the solid state. Part II. The molecular structure of α-d-glucosaccharino-γ-lactone: 2-C-methyl-d-ribo-pentono-1,4-lactone

The crystal structure of 2-C-methyl-d-ribo-pentono-1,4-lactone (α-d-glucosaccharino-γ-lactone, 1) has been determined by single-crystal X-ray diffraction. The crystals are orthorhombic, space group P212121 with a=7.7429(6), b=8.3373(7), c=11.3258(7) , V=731.1(2) 3 (CuKα, λ=1.54184 ); μ=10.82 cm−1, Dc=1.473 g cm−3, and Z=4. The structure was refined to R=0.0307 and Rw=0.0424 for 876 observed reflections. Compound 1 has the d-ribo configuration, in agreement with an earlier deduction from chemical evidence. The lactone ring adopts the 3T2 conformation, with puckering parameters φ=279.8(9)° and q=0.32(5) . 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)° and 154.7(1)°, respectively. The molecules 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.