Paul Godé

Novel Glycolipids Based on Cyclodextrins

Novel amphiphilic cyclodextrins have been prepared by grafting a phospholipid on a modified cyclodextrin through a spacing arm to combine the selectivity in size of cyclodextrins and the transport properties of phospholipids. Synthesis and full characterization by NMR and mass spectrometry have been performed. The aggregation process in water has been characterized by light scattering, DSC and 31P NMR. This compound appears to assemble into large objects and displays a very low CMC. The detergent properties of the phospholipidyl-cyclodextrins have been evaluated.

Substitution effects on the liquid crystalline properties of D,L-xylitol amphiphiles

In this article we describe the self-assembling properties of alkyl substituted xylitols in relation to both thermotropic and lyotropic liquid crystalline mesophases. Three series of substituted xylitols were prepared where aliphatic chains of varying length were attached to a xylitol moiety via ether, thioether and ester linking groups. The thermotropic properties were investigated by thermal polarized light microscopy and differential scanning calorimetry, and evaluated as a function of chain length and linking group. The lyotropic phase behaviour was investigated via the addition of water to each material at room temperature. The efficiency for forming thermotropic phases was found to be reversed for the lyotropic phases in respect of the three series, i.e. as a function of the linking unit.

The dependence of mesomorphic behaviour on the extent of hydrogen-bonding in sugar derived polyols

The thermotropic liquid crystalline properties of a variety of chiral and racemic dodecyloxy substituted polyols derived from carbohydrates were investigated as a function of the number of hydroxyl groups associated with the polyol unit. It was found that all of the materials exhibited smectic A* phases, and that the clearing points increased monotonically with the number of hydroxyl groups. The linear increase was found to be independent of stereochemical structure and the degree of optical purity. A model suggesting that the smectic A* phase has an internal microphase separated structure can be used to account for these observations.

Synthesis of Monoesters as Surfactants and Drugs from D-Glucose

Abstract We have synthesized a series of monoesters from D-glucose corresponding to the structures 3-O-acyl, 6-O-acyl-1,2-O-isopropylidene-α-D-glucofuranose and 3-O-acyl-D-glucose, following the sequence of reactions : D-glucose → diacetone glucose → acylation → partial or total deprotection. These compounds were prepared as either potential non-ionic surfactants (fatty acid esters and perfluoroalkylated ester) or antitumour drugs (n-butyric esters). Results concerning surface activity, toxicity and antitumour effects are reported. A novel method for obtaining partially deprotected 6-O-acyl esters from their corresponding 3-O-acyl isomers is reported. Deprotection conditions have been studied and a higher selectivity in partial deprotection has been achieved. We have given particular attention to the choice of solvents and reagents in order not to limit the extent to which the products might be applied.

An homologous series of 6-O-n-alkyl-alpha-D-galactopyranoses: synthesis and thermotropic mesomorphic properties

An homologous series of 6- O - n -alkyl- alpha -D-galactopyranoses has been prepared. The length of the terminal chains has been varied systematically and the effect on the liquid crystal transition temperatures studied. Most homologues of the series exhibit enantiotropic smectic A* phases. X-ray analysis indicates a lamellar structure for the smectic A* phase with hydrogen-bonded carbohydrate cores at the layer centre, either with no interdigitation of the tilted terminal alkyl chains but with a high degree of chain melting, or with some degree of chain intercalation. The 6- O - n -alkyl- alpha -D-galactopyranoses possess clearing points at higher temperatures than those of the corresponding n -alkyl alpha -D-galactopyranosides. The introduction of a higher degree of hydrogen bonding by the replacement of the oxygen atom in the ether linkage between the chain and the carbohydrate ring by an amide linkage leads to higher transition temperatures. The dependence of the liquid crystalline behaviour on the po...

Spacer arm influence on glucidoamphiphile compound properties

Abstract We prepared glucidoamphiphile derivatives from d -glucose, d -galactose and xylitol, in which the glucidic moiety and the hydrophobic alkyl chain are separated by spacer arm E (E=glyceryl, (OEt) 2 -α-polypropyleneglycyl and butyloxy). Their amphiphile characteristics are compared to those of the corresponding analogs 3- O -alkyl- d -glucopyranoses, 6- O -alkyl- d -galactopyranoses and 1- O -alkyl- d , l -xylitols. We discussed the spacer arm influence on hydrophobic lipophilic balance (HLB), critical micellar concentration (CMC), water solubility ( S w ) and phase transition temperatures of thermotropic and lyotropic mesophases.

Liquid crystalline derivatives of galactose and galactitol: dependence of thermotropic mesomorphism on carbohydrate form

An almost complete homologous series of the acyclic, open-chain 6- O - n -alkyl-D-galactitols has been prepared. Most homologues in this series exhibit an enantiotropic smectic A* phase. The liquid crystal transition temperatures of these open-chain carbohydrates are compared with those of the corresponding homologues in the cyclic form, i.e., with those of the 6- O - n alkyl-alpha-D-galactopyranoses. In general the carbohydrates in the open-chain form exhibit higher clearing points than those of the analogous cyclic pyranoses. However, the melting point of the galactitols is generally significantly lower than that of the corresponding galactopyranoses. This leads to a much wider temperature range of the smectic A* phase for the carbohydrates in the pyranose form. The lowest clearing point was found for related galactoses in the furanose form. Alternation was found for the clearing point of the 6-O-n alkyl-alpha-D-galactopyranoses and the 6- O - n -alkyl-D-galactitols. Powder X-ray diffraction studies ind...

The Effect of Molecular Shape and Microphase Segregation on the Formation of Liquid Crystal Phases in Poly-Ols

Abstract In this article we examine the effect of molecular shape on the formation of thermotropic phases of alkyl-substituted poly-ols. The relationship between the cross-sectional area of the hydrophilic head group with respect to the that of the hydrophilic tails determines the type of mesophase formed. The results obtained are similar to those found for the formation of lyotropic phases.

Synthesis and amphiphilic properties of glycosyl-1,4-benzodiazepin-2,5-diones.

Glycosyl-1,4-benzodiazepin-2,5-diones were prepared by coupling polyhydroxylated groups at N-1 of the corresponding benzodiazepine. The groups include 1-deoxy-D,L-xylit-1-yl, 6-deoxy-D-glucopyranos-6-yl, and 6-deoxy-3-OR-D-glucopyranos-6-yl (R = n-CnH(2n +1); n = 8, 12, and 16). The structural variations of the sugar group allowed comparison of such amphiphilic data as water solubility (Sw), critical micelle concentration (CMC), and corresponding surface tension (gamma) values. At 25 degrees C, unsubstituted benzodiazepines have Sw values from 0.9 to 4.2 10(-3) mol L(-1), whereas xylit-1-yl and 6-deoxy-D-glucopyranos-6-yl derivatives are, respectively, 7.4-25 and 58-204 times more soluble. Also, compounds with R = n-C8H17 are more soluble than corresponding benzodiazepines (1.4-5.8 times) and give micelles with CMC from 2.7 to 5.6 10(-3) mol L(-1) and corresponding gamma from 29 to 37 mN m(-1). In contrast, compounds with R = n-C12H25 and n-C16H33 are not soluble enough to reach the critical micelle concentration.

Synthesis of Enantiomerically Pure Alkylated d‐Erythritols and d‐Threitols from d‐Xylose—Structural Influences on Their Mesophasic Behavior

1‐O‐Alkyl and 2‐O‐alkyl‐d‐threitol enantiomers were derived from 5‐O‐alkyl and 5‐O‐benzyl‐1,2‐O‐isopropylidene‐α‐d‐xylofuranoses. The analogous erythrtol derivatives were also obtained from the same precursors via analogous d‐ribose monoacetals. Mesophasic behavior studies of these alditols and their alkylated d‐ribose and d‐xylose precursor, showed that the relative orientation of alkyl and OH groups appeared to be the main structural factor affecting the thermotropic and lyotropic phase transition temperatures.