Synthesis of amphiphilic phenylazophenyl glycosides and a study of their liquid crystal properties

Abstract

Several 4-(4'-N,N-didodecylaminophenylazo)phenyl 1,2-trans glycosides 5a-e with various carbohydrate heads (beta-D-gluco, beta-D-galacto, beta-lacto, beta-D-xylo, and alpha-D-manno) have been synthesized. The key step was the formation of phenyldiazonium tetrafluoroborates 2a-e from the per-O-acetylated 4-aminophenyl glycosides 1a-e. These salts were condensed with N,N-didodecylaniline under phase transfer conditions and the per-O-acetylated 4-(4'-N,N-didodecylaminophenylazo)phenyl 1,2-trans glycosides 4a-e were fully de-O-acetylated by the Zemplén method. The self-organizing liquid crystal properties of the compounds were investigated by a variety of techniques, including polarized light microscopy, differential scanning calorimetry, and X-ray diffraction. All but one of the materials exhibited smectic A, lamellar phases. Remarkably, the glucose derivative exhibited a rectangular disordered columnar phase. This result has implications with respect to the induced curvature created by the recognition processes of the glucose headgroup relative to the other sugar moieties and to the prevalence of various glycolipids in cell membranes