The role of lone pair interactions in the chemistry of the monosaccharides. Stereo-electronic effects in unsaturated monosaccharides

The X-ray crystallopraphic structural data for simple unsaturated monosaccharides do not support the participation of the electron density of a C2-C3 π bond in the modification of the geometry at the anomeric center, or the existence of a vinylogous anomeric effect in glycals. The delocalization phenomena (n-σ*, n-π* and π-σ*) are insignificant in the ground states of the simple sugars, and n-n repulsions are the dominant stereo-electronic effects in these molecules