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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.

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Crystals of N-acetylgalactosamine are monoclinic with unit-cell constants a=9.159 (4), b= 6.320 (2), c=9.208 (4) /~, ,8=107.88 (6) ° and space group P2~. The structure has been determined by direct methods and refined by least-squares calculations to a final R of 0.04. The main features of the molecular structure are the shortening of the anomeric bond in agreement with the observation on other saccharides, the electron delocalization of the amide group similar to that of N-acetylglucosamine and oligopeptides, and the existence of an intramolecular hydrogen bond.

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