Effect of the C-2 hydroxyl group on the mesomorphism of alkyl glycosides: synthesis and thermotropic behavior of alkyl 2-deoxy-D-arabino-hexopyranosides.
A homologous series of alkyl 2-deoxy-alpha-d-arabino-hexopyranosides and alkyl 2-deoxy-beta-d-arabino-hexopyranosides were synthesized, upon glycosylation of 1-alkanols (from C8 to C18 alkanols) with ethyl 2-deoxy-3,4,6-tri-O-acetyl-1-thio-d-arabino-hexopyranoside, followed by a deprotection. The thermotropic behavior of these new types of alkyl glycosides was investigated. It was observed that the beta-anomers of these alkyl glycosides, bearing nonyl to tetradecyl alkyl chain are mesomorphic, exhibiting monotropic smectic A phase. In contrast, the alpha-anomers are all non-mesomorphic. An effort to identify the liquid crystalline behavior of binary mixtures of the alpha- and beta-anomers was undertaken and it was found that mixtures containing equimolar amounts of the anomers exhibited mesomorphic behavior. A fine balance of the hydrophilic and hydrophobic components within the molecule is also found to be important for the alkyl 2-deoxy glycosides to form the mesophase.
Singh
Madan Kumar
MK
Department of Organic Chemistry, Indian Institute of Science, Bangalore 560 012, India.
Jayaraman
Narayanaswamy
N
Rao
D S Shankar
DS
Prasad
S Krishna
SK
D001089:Arabinose / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D006027:Glycosides / Q000138:chemical synthesis* / Q000737:chemistry*; D006878:Hydroxides / Q000737:chemistry*; D008853:Microscopy; D013237:Stereoisomerism; D013696:Temperature; D013816:Thermodynamics; D044366:Transition Temperature
D006027:Glycosides; D006878:Hydroxides; C031356:hydroxide ion; D001089:Arabinose