CRYSTAL-STRUCTURES OF METHYL 6-O-ACYL-ALPHA-D-GALACTOPYRANOSIDES

The crystal structures of methyl 6-O-n-octanoyl-alpha-D-galactopyranos ide (1) and methyl 6-0-n-decanoyl-alpha-D-galactopyranoside (2) were i nvestigated by X-ray analysis. Anhydrous crystals obtained from methan ol solution by slow evaporation are monoclinic, and the space group is PT, with Z = 2. The cell dimensions are as follows, 1: a = 5.774(1), b = 8.013(1), c = 19.183(1) Angstrom, beta = 98.50(1)degrees; 2: a = 5 .762(1), b = 8.003(1), c = 21.227(2) Angstrom, beta = 93.93(1)degrees. The galactopyranoside ring is nearly in a C-4(1) chair conformation b ut slightly distorted to twist boat and the alkyl chain is in all-tran s conformation. In these crystals, molecules are arranged in a bilayer structure with interdigitated alkyl chains. The hydrogen bonding link ages between sugar moieties, which are found only between the layers, form an infinite chain through the crystal. 1 and 2 show higher meltin g points than those of corresponding beta-D-glucopyranosides. The resu lts indicate the important role of the sugar in the crystal.