BILAYER STRUCTURE OF GLYCOLIPID CRYSTALS - THERMAL-STABILITY OF THE CRYSTAL AND STATE OF THE ALKYL CHAIN

Citation
Y. Abe et al., BILAYER STRUCTURE OF GLYCOLIPID CRYSTALS - THERMAL-STABILITY OF THE CRYSTAL AND STATE OF THE ALKYL CHAIN, Perkin transactions. 2, (1), 1998, pp. 177-186
Citations number
25
Categorie Soggetti
Chemistry Physical","Chemistry Inorganic & Nuclear
Journal title
ISSN journal
03009580
Issue
1
Year of publication
1998
Pages
177 - 186
Database
ISI
SICI code
0300-9580(1998):1<177:BSOGC->2.0.ZU;2-T
Abstract
The role of alkyl chains in the stabilization of a bilayer structure o f glycolipids in the crystalline state has been studied for a series o f methyl 6-O-acyl-beta-D-glucopyranosides and methyl 6-O-acyl-alpha-D- galactopyranosides. Thermal properties and crystal structures of these glycolipids with an odd number of alkyl carbon atoms in the acyl moie ty have been investigated by thermal analysis and X-ray methods. The m elting temperatures of methyl 6-O-acyl-beta-D-glucopyranosides, which are lower than those of the corresponding methyl 6-O-acyl-alpha-D-gala ctopyranosides, decrease with increasing number of alkyl carbon atoms from one to seven, but increase for longer alkyl chains. The alpha-gal actosides show only a monotonic decrease in melting temperature with i ncreasing alkyl chain length. In the crystals, the molecules form a bi layer structure with interdigitated alkyl chains, The arrangement of s ugar moieties in the crystals differs between the beta-glucosides and the alpha-galactosides, but they are almost the same among sugar deriv atives with various alkyl chain lengths. The packing of the acetyl moi ety in a crystal of methyl 6-O-alpha-D-galactoside is different from t hat of the other alpha-galactoside derivatives with longer alkyl chain s, The carbonyl oxygen atom causes steric hindrance with adjacent alky l chains, and such unfavorable intermolecular contact explains the rel atively low thermal stability of the crystal, On the other hand, the c ontribution of the beta-glucoside to thermal stability is ascribed to the well-ordered packing of the long alkyl chain moiety.