Xylose halogen derivatives

Luetzen, A, Koell, P, D-Xylose derived oxazolidin-2-ones as chiral auxiliaries in stereoselective acylations and halogenations. Tetrahedron Asymmetry, 8, 29-32, 1997. 

The anomeric effect also influences the conformational equilibria in pyranoses with an electronegative atom, usually oxygen or halogen, at C-1. For example, the equilibrium mixture of the P-pyranosyl chloride derived from xylose triacetate contains 98% of the conformer in which chlorine is axial. These two conformations are not interconverted by mutarotation but by chair-chair interconversion. The anomeric effect is sufficiently large so that all four substituents occupy axial positions in the more stable conformer. 

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