Abstract
The X-ray crystal structures of the semicarbazide derivatives of
d-glucose,
d-galactose, and
d-xylose are described. All are glycopyranosyl derivatives in the solid state. The glucose semicarbazide crystallizes as a dihydrate. Two different conformations of the galactose semicarbazide are found, one having the
gg side-chain orientation unfavorable for monosaccharides having the
4
C
1-
d-
galacto configuration. In the two other known examples, this conformation is stabilized by an intramolecular hydrogen bond, but in the current structure, the hydrogen bonds involving the side chain are intermolecular. In these semicarbazides the NNCO torsional angle is approximately 180°, in contrast to the angles of 0.60 and 13.9° in the two solid-state conformations of 2-benzoyl-1-(α-
d-xylopyranosyl)hydrazine [Ernholt, B. V.; Thomsen, I. B.; Lohse, A.; Plesner, I. W.; Jensen, K. B.; Hazell, R. G.; Liang, X.; Jakobsen, A.; Bols, M.
Chem. Eur. J.
2000,
6, 278–287]. The water molecules and the carbonyl oxygen are heavily involved in H-bonding.
The structures
1–
3 have been determined by X-ray crystallography. Glucose derivative
1 is a dihydrate. Galactose derivative
2 crystallizes with two molecules in the asymmetric unit, one of which has the
gg side chain conformation. In all three structures, the carbonyl oxygen atom serves as a strong H-bond. It is likely to play a similar role in intermolecular interactions in macromolecular systems.