The crystal structure of 5-O-acetyl-1,2:3,4-di-O-isopropylidene-α-D-glucoseptanose [P212121,
Z 8, a 14.329(5), b 22.075(5), c 10.012(5) �] has been determined by X-ray and neutron diffraction
analyses. For the neutron diffraction analysis, the acetate group and the
trans-O-isopropylidene group were
deuterated. Constrained refinement was used in the neutron diffraction analysis
to counter over parameterization in the block-diagonal least-squares
refinement. Final unweighted R-values were 0.038 [X-ray for 3070 reflections
with [Fo > 2.58σ (Fo)] and 0.061 [neutron for
1118 reflections with Fo > 4σ ([Fo)]The neutron
refinement revealed a disordering of the acetate methyl group in each of the
two independent molecules in the asymmetric unit. The septanose ring in each
molecule adopted the same twist-chair conformation but the dioxolan rings
assumed different twist and envelope conformations.