Cyclitols. Part XXXIV. X-Ray crystal and molecular structure of 1,2:5,6-Di-O-isopropylidene-3,4-di-O-tosyl-L-chiro-inostol, and its conformation in solution by nuclear magnetic resonance

The crystal structure of the title compound was determined from X-ray diffractometer data by direct methods and refined by least-squares techniques to R 0·047 for 1317 observed reflections. Crystals are tetragonal, space group P41212, a= 9·304 ± 0·005, c= 32·008 ± 0·017 A, Z= 4. The cyclohexane ring was found to be in a flattened skew conformation, with four substituents in axial orientation. By contrast, n.m.r. spectroscopy indicates that in solution the title compound adopts predominantly a distorted chair conformation. The conformations of six-membered rings fused to five-membered rings are discussed.