Thermotropic and lyotropic properties of long chain alkyl glycopyranosides (original) (raw)
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Chemistry and Physics of Lipids, 2010
A homologous series of alkyl 6-deoxy--d-glucopyranoside amphiphiles was prepared, in an effort to identify the role of hydroxyl group in the mesomorphic behavior of alkyl glycosides. Synthesis was performed by a chlorination of the sugar moiety in alkyl -d-glucopyranosides with methylsulfonyl chloride in DMF, followed by a metal mediated dehalogenation to secure alkyl 6-deoxy--d-glucopyranosides, wherein the alkyl chain length varied from C 9 to C 16 . The mesomorphic behavior of these 6-deoxy alkyl glycosides was assessed using polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction method. Whereas the lower homologues exhibited a monotropic SmA phase till sub-ambient temperatures, the higher homologues formed a plastic phase. A partial interdigitized bilayer structure of SmA phase is inferred from experimental d-spacing and computationally derived lengths of the molecules. The results were compared with those of normal alkyl glucopyranosides, retained with hydroxyl groups at C-2-C-6 carbons, and alkyl 2-deoxy-glucopyranosides, devoid of a hydroxyl group at C-2 and the comparison showed important differences in the mesomorphic behavior.
Preparation of alkyl α- and β-d-glucopyranosides, thermotropic properties and X-ray analysis
Carbohydrate Research, 1998
Monohydrates of heptyl to decyl a-D-glucopyranosides as obtained from product mixtures of the Fischer glucosylation were crystallized from water at the Krafft point. The results of the single-crystal X-ray analysis of anhydrous a anomers and their monohydrates provide for a better understanding of crystal formation and stability of their hydrates. The preparation of alkyl b-D-glucopyranosides -without concomitant formation of a anomers as by-products-has been described. The thermotropic properties have been investigated for the a compounds and their monohydrates, and for the b-D-glucopyranosides.
Journal of Chemistry
Focusing on green chemistry protocols, a series of carbohydrate derivatives (5a–l) have been synthesized by Fischer glycosylation of α-D-glucose, D-xylose, and α-maltose with several nonpolar phenolic ester aglycones (3a–d) derived from menthol by employing solid-supported Si-H+ as the catalyst. In order to study the extent of mesomorphism in target molecules, the thermotropic behaviour has been studied by using the thermoanalytic DSC/TGA technique and polarized optical microscope. Phase transitions in the DSC thermograms of 5a–l with two endothermic melting point peaks and various exothermic crystalline transitions exhibits the existence of mesophases. However, optical photomicrographs revealed that the new glycopyranosides formed smectic A phases. Moreover, all the compounds (3a–d and 5a–l) were confirmed by FTIR and 1H NMR.
[Synthesis of aminoethyl glycosides of the carbohydrate chains of glycolipids Gb3, Gb4 i Gb5]
Bioorganicheskaia khimiia
4-O-Glycosylation of 2-azidoethyl 2,3,6-tri-O-benzoyl-4-O-(2,3,6-tri-O-benzoyl-beta-D-galactopyranosyl)-beta- D-glucopyranoside with ethyl 2,3,4,6-tetra-O-benzyl- and ethyl 3-O-acetyl-2,4,6-tri-O-benzyl-1-thio-alpha-D-galactopyranoside in the presence of methyl trifluoromethanesulfonate led to trisaccharide 2-azidoethyl (2,3,4,6-tetra-O-benzyl-alpha-D-galactopyranosyl)-(1-->4)- (2,3,6-tri-O-benzoyl-beta-D-galactopyranosyl)-(1-->4)2,3,6-tri-O- benzoyl-beta-D-glucopyranoside and its 3"-O-acetylated analogue, 2-azidoethyl (3-O-acetyl-2,4,6-tri-O-benzyl- alpha-D-galactopyranosyl)-(1-->4)-(2,3,6-tri-O-benzoyl-beta-D- galactopyranosyl)-(1-->4)-2,3,6-tri-O-benzoyl-beta-D-glucopyranoside, in yields of 85 and 83%, respectively. Deacetylation of the latter compound and subsequent glycosylation with 4-trichloroacetamidophenyl 3,4,6-tri-O-acetyl-2-deoxy-1-thio-2-trichloroacetamido-beta-D- galactopyranoside and 4-trichloroacetamidophenyl 4,6-di-O-acetyl-2-deoxy-3-O-(2,3,4,6-tetr...
Phase Behaviour of Nature-Like Branched-Chain Glycosides
Glycolipids are remarkable biomolecule which become primary constituents of bio-membranes and may form various biologically relevance phases. Due to their diverse functions in nature, investigation on their self-assembly have obtained great attention from the fundamental point of view as well as for technological aspects. The glycolipid materials are highly in demand but, natural products such as monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) found in plant membrane are difficult to extract and purify in large quantity. Therefore, synthetic substitutes are preferred such as those of glycolipids, since these are cheap renewable resources, highly biodegradable, environmental friendly materials and have diverse biological activity. In this study, a branched-chain glycolipids based on Guerbet alcohol have been synthesized namely 2-hexyldexyl-α-D-mannopyranoside. The neat compound was measured with optical polarizing microscopy (OPM) and differential scanning calorimetry (DSC) whereas their lyotropic phase behaviour was investigated by contact penetration technique. α-Man-OC 10 C 6 formed inverse hexagonal phase in dry form whereas in water, it gave inverse bicontinuous cubic phase. The presence of non-lamellar phases implies greater potential for the material (α-Man-OC 10 C 6 ) to be used in several applications such as drug-carrier systems and membrane protein crystallization.
Crystal structures and thermotropic properties of alkyl a- d-glucopyranosides and their hydrates
Carbohyd Res, 1999
Thermotropic properties and crystal structures of alkyl α-d-glucopyranosides and their hydrates were estimated by X-ray, DSC and thermogravimetric measurements (TGA). Monohydrates rapidly lose their crystal water several degrees below the melting point of the anhydrous glucopyranosides. The melting points of the monohydrates measured in DSC pressure cells (chain length longer than seven) are lower, and the clearing points higher than those of the anhydrous glucosides. Layer distances of smectic and crystalline phases of anhydrous compounds were established. Melting points, densities and layer distances of the crystalline anhydrous glucopyranosides display strong even–odd effects. The strong decrease of these effects in the case of the monohydrates can be elucidated by the results of X-ray crystal structure analysis.
Crystal structures and thermotropic properties of alkyl α-d-glucopyranosides and their hydrates
Carbohydrate Research, 1999
Thermotropic properties and crystal structures of alkyl a-D-glucopyranosides and their hydrates were estimated by X-ray, DSC and thermogravimetric measurements (TGA). Monohydrates rapidly lose their crystal water several degrees below the melting point of the anhydrous glucopyranosides. The melting points of the monohydrates measured in DSC pressure cells (chain length longer than seven) are lower, and the clearing points higher than those of the anhydrous glucosides. Layer distances of smectic and crystalline phases of anhydrous compounds were established. Melting points, densities and layer distances of the crystalline anhydrous glucopyranosides display strong even -odd effects. The strong decrease of these effects in the case of the monohydrates can be elucidated by the results of X-ray crystal structure analysis.
Synthesis of Branched-Chain Alkyl Glucosides and Their Liquid Crystal Behaviour
Although glycolipids exist in nature, they can also be synthesized either chemically or enzymatically. Due to their role in the nervous system and biomembranes, natural glycolipids are extensively studied by researchers, especially biochemists, but their liquid crystal state is not well understood. In this paper, starting from glucose and a series of branched-chain alcohols, novel alkyl glycosides have been synthesized. These compounds have been structurally elucidated using standard spectroscopic techniques like hydrogen (1 H) NMR, carbon-13 (13 C) NMR, and infra-red-(IR) and also using high resolution mass spectrometry (HRMS). Their thermotropic liquid crystalline properties were investigated using polarizing microscopy and differential scanning calorimetry. It was found that the shorter carbon chain analogues gave the smectic A phase while the longer ones gave only the columnar phase. The results were compared with those of the straight chain counterparts.
The Chemistry of Isopropenyl Glycopyranosides. Transglycosylations and Other Reactions
The Journal of Organic Chemistry, 1996
Various anomerically pure isopropenyl R-and -glycopyranosides have been synthesized and shown to undergo synthetically useful transglycosylation reactions with a variety of primary and secondary carbohydrate alcohols. Although stable when stored, isopropenyl glycosides are readily activated as glycosyl donors by a variety of electrophiles, including N-iodosuccinimide/triflic acid, trimethylsilyl triflate, and triflic anhydride. Under conditions that retard formation of the glycosyl cation, the reactivity of isopropenyl glycosides is diverted away from transglycosylation and toward electrophilic addition across the vinyl ether double bond.
Carbohydrate Research, 1989
The n-alkyl 1-thio-aD -glucopyranosides (n-propyl to n-dodecyl) were prepared by treating 1,2,3,4,6-penta-O-acetyl-/3-D-glucopyranose with an alkanethiol in the presence of boron trifluoride etherate followed by deacetylation. The npropyl and n-butyl derivatives are not thermotropic, the n-pentyl derivative is monotropic, and the compounds with n-hexyl and longer alkyl chains are enantiotropic, the largest liquid crystalline range being from ±100-175° for the n-undecyl derivative. The transition point data are typical for smectic behavior, and X-ray data and texture observations are indicative of a smectic A d phase .