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(Refu le 4 d~cembre 1975, acceptd le 16 dOcembre 1975 e-D-Mannopyranose crystallizes in the orthorhombic space group P212121. Cell dimensions are a= 23.447 (8), b= 9-460 (2), c= 6.891 (1) A,. There are two molecules in the asymmetric unit. Intensity data for 1674 independent reflexions were collected with an automatic four-circle diffractometer and the three-dimensional structure obtained by direct methods was refined by least squares to R= 0-035. Both molecules are in the C1 chair conformation with normal bond lengths and angles, although there is a difference for the conformation around the C(5)-C(6) extracyclic bond. Molecules are associated in the crystal by an extensive network of hydrogen bonds.

The molecular structure of an anhydrous hydroxybisphosphonic acid was determined by X-ray diffraction techniques and compared to the corresponding hydrated crystalline form. The hydrogen bond network and intermolecular interactions show that the polar bisphosphonic group undergoes a rotation to accomodate a different distribution in the hydrophobic/polar zones observed in the crystal packing, while the rest of the amino side chain connected to the functional carbon atom has identical conformation.

The crystal structure of the non-reducing trisaccharide melezitose monohydrate, O-e-D-glucopyranosyl-(1-->-2)-O-fl-o-fructofuranosyl-(3-->-1)-e-D-glucopyranoside, has been determined by direct methods and refined by least-squares calculations to a final R of 0.032. The space group is P212121 with four formula units of CtsHa2Ox6. H20 per unit cell. The lattice parameters are a= 14.950 (8), b= 13-863 (6), c= 10.812 (4) ,~. The e-o-glucopyranoside units are in the Cx chair conformation with the same conformation (gg) around the Cs-C6 extracyclic bond. The fructofuranoside unit adopts the twist conformation 4Ta. The conformation of the 1 -+ 2 linkage in the sucrose moiety is compared with those of planteose, raffinose, L-kestose and sucrose. Molecules are associated in the crystal by an extensive network of hydrogen bonds: one bifurcated intramolecular hydrogen bond is found; the three ring oxygen atoms accept a hydrogen bond; the majority of the hydroxyl groups are both donor and acceptor.