Crystal structures of methyl [formula omitted

Abstract

The crystal structures of methyl 6-O- n-octanoyl-α- d-galactopyranoside ( 1) and methyl 6-O- n-decanoyl-α- d-galactopyranoside ( 2) were investigated by X-ray analysis. Anhydrous crystals obtained from methanol solution by slow evaporation are monoclinic, and the space group is P2 1 with Z = 2. The cell dimensions are as follows, 1: a = 5.774(1), b = 8.013(1), c = 19.183(1) A ̊ , β = 98.50(1)°; 2: a = 5.762(1), b = 8.003(1), c = 21.227(2) A ̊ , β = 93.93(1)° . The galactopyranoside ring is nearly in a 4C 1 chair conformation but slightly distorted to twist boat and the alkyl chain is in all- trans conformation. In these crystals, molecules are arranged in a bilayer structure with interdigitated alkyl chains. The hydrogen bonding linkages between sugar moieties, which are found only between the layers, form an infinite chain through the crystal. 1 and 2 show higher melting points than those of corresponding β- d-glucopyranosides. The results indicate the important role of the sugar in the crystal.