Hélène G. Bazin

Enzyme Catalyzed Regioselective Synthesis of Sucrose Fatty Acid Ester Surfactants

Abstract A commercial subtilisin preparation was used in pyridine to catalyze the regioselective conversion of sucrose and fatty acid vinyl esters into the 1′-O-acyl sucrose derivatives. The 1′-O-laury sucrose, 1′-O-myristyl sucrose and 1′-O-stearyl sucrose were obtained as the major products of these reactions. The 1′,6-di-O-acyl sucrose derivatives were also obtained as minor products. The critical micellar concentration (CMC) of each of these sucrose monoesters was determined.

SYNTHESIS OF SUCROSE-BASED SURFACTANTS THROUGH REGIOSELECTIVE SULFONATION OF ACYLSUCROSE AND THE NUCLEOPHILIC OPENING OF A SUCROSE CYCLIC SULFATE

Synthesis of a new class of anionic and amphoteric sucrose-based surfactants is described. Direct sulfonation of 6-O-acylsucrose using the pyridine‐sulfur trioxide complex led to a mixture of the regioisomeric monosulfates, 6-O-acyl-4 0 ‐O-sulfosucrose and 6-O-acyl-1 0 -O-sulfosucrose, while sulfonation of 1 0 -O-acylsucrose aAorded a mixture of 1 0 -O-acyl-6 0 -O-sulfosucrose and 1 0 -O-acyl-6O-sulfosucrose. The ratio of regioisomers ranged from 4.7:1.0 to 7.5:1.0, depending on reaction time and the size of the fatty acyl chain. The regiospecific synthesis of 6-O-acyl-4-O-sulfosucrose derivatives was accomplished by nucleophilic substitution of the sucrose 4,6-cyclic sulfate using various fatty acids. The amphoteric 6-alkylamino-6-deoxy-4-O-sulfosucrose surfactants were also synthesized by nucleophilic substitution of the sucrose cyclic sulfate by diAerent fatty amines. All the newly synthesized sucrose-based surfactants displayed excellent surface-active properties. # 1998 Elsevier Science Ltd. All rights reserved

The ‘Ethereal’ nature of TLR4 agonism and antagonism in the AGP class of lipid A mimetics

To overcome the chemical and metabolic instability of the secondary fatty acyl residues in the AGP class of lipid A mimetics, the secondary ether lipid analogs of the potent TLR4 agonist CRX-527 (2) and TLR4 antagonist CRX-526 (3) were synthesized and evaluated along with their ester counterparts for agonist/antagonist activity in both in vitro and in vivo models. Like CRX-527, the secondary ether lipid 4 showed potent agonist activity in both murine and human models. Ether lipid 5, on the other hand, showed potent TLR4 antagonist activity similar to CRX-526 in human cell assays, but did not display any antagonist activity in murine models and, in fact, was weakly agonistic. Glycolipids 2, 4, and 5 were synthesized via a new highly convergent method utilizing a common advanced intermediate strategy. A new method for preparing (R)-3-alkyloxytetradecanoic acids, a key component of ether lipids 4 and 5, is also described.

Conformational study of synthetic Δ4-uronate monosaccharides and glycosaminoglycan-derived disaccharides

Sixteen delta 4-uronate monosaccharides were chemically synthesized. Their carboxy group was protected as a methyl or benzyl ester, the anomeric hydroxyl group as a benzyl glycoside and the 2 and 3 hydroxyl groups were protected with different substitution patterns as both ester and ether derivatives. Disaccharides containing delta 4-uronates were prepared from heparin layses. Their carboxy group was unprotected or protected as a benzyl ester and the two hydroxyls in the uronate moiety were free, as O-sulfo derivates or acylated. The conformation of these unsaturated uronate monosaccharide and disaccharide residues was studied using 1H NMR by examining interproton vicinal coupling constants. The delta 4-uronate residue adopted either the 2H1 or the 1H2 conformations. The equilibrium between these two conformers was shown to be controlled by substitution pattern.

Regio and stereoselective conversion of Δ4-uronic acids to l-Ido- and d-glucopyranosiduronic acids

Abstract Synthesis of l -ido- and d -glucopyranosiduronic acids was performed starting from protected Δ 4 -uronic acids 3a-f . Bromination of the C-4,5 double bond provided the trans-diaxial bromohydrin derivatives 6a-d , which were converted to the corresponding epoxides 7a-d in high yields. Direct reduction of these epoxides using borane-tetrahydrofuran complex afforded the d -glucopyranosiduronic acids 9b-d , while Lewis acid rearrangment through the C-4 keto intermediate 10b-d afforded the l -idopyranosiduronic acids 11b-d .

Evaluation of novel synthetic TLR7/8 agonists as vaccine adjuvants

Small-molecule adjuvants that boost and direct adaptive immunity provide a powerful means to increase the effectiveness of vaccines. Through rational design several novel imidazoquinoline and oxoadenine TLR7/8 agonists, each with unique molecular modifications, were synthesized and assessed for their ability to augment adaptive immunity. All agonists bound human TLR7 and TLR8 and induced maturation of both human mDCs and pDCs. All agonists prompted production of type I interferon and/or proinflammatory cytokines, albeit with varying potencies. In most in vitro assays, the oxoadenine class of agonists proved more potent than the imidazoquinolines. Therefore, an optimized oxoadenine TLR7/8 agonist that demonstrated maximal activity in the in vitro assays was further assessed in a vaccine study with the CRM197 antigen in a porcine model. Antigen-specific antibody production was greatly enhanced in a dose dependent manner, with antibody titers increased 800-fold compared to titers from pigs vaccinated with the non-adjuvanted vaccine. Moreover, pigs vaccinated with antigen containing the highest dose of adjuvant promoted a 13-fold increase in the percentage of antigen-specific CD3(+)/CD8(+) T cells over pigs vaccinated with antigen alone. Together this work demonstrates the promise of these novel TLR7/8 agonists as effective human vaccine adjuvants.

Structural requirements for TLR7-selective signaling by 9-(4-piperidinylalkyl)-8-oxoadenine derivatives.

We report the synthesis and biological evaluation of a new series of 8-oxoadenines substituted at the 9-position with a 4-piperidinylalkyl moiety. In vitro evaluation of the piperidinyl-substituted oxoadenines 3a-g in human TLR7- or TLR8-transfected HEK293 cells and in human PBMCs indicated that TLR7/8 selectivity/potency and cytokine induction can be modulated by varying the length of the alkyl linker. Oxoadenine 3f containing a 5-carbon linker was found to be the most potent TLR7 agonist and IFNα inducer in the series whereas 3b possessing a 1-carbon linker was the most potent TLR8 agonist.

Hydrolysis of Cyanoethylated Carbohydrates: Synthesis of New Carboxylic Derivatives of Sucrose, d-Glucose and d-Fructose

Abstract Synthesis of new cyanoethylated compounds and carboxylic acids derived from sucrose, methyl D-glucopyranoside, methyl D-fructopyranoside and methyl D-fructofuranoside are described. Basic hydrolysis of these cyanoethylated compounds to the corresponding amides and carboxylates and acidic alcoholysis to the corresponding methyl esters are discussed.

Characterization of TRIF Selectivity in the AGP Class of Lipid A Mimetics: Role of Secondary Lipid Chains

TLR4 agonists that favor TRIF-dependent signaling and the induction of type 1 interferons may have potential as vaccine adjuvants with reduced toxicity. CRX-547 (4), a member of the aminoalkyl glucosaminide 4-phosphate (AGP) class of lipid A mimetics possessing three (R)-3-decanoyloxytetradecanoyl groups and d-relative configuration in the aglycon, selectively reduces MyD88-dependent signaling resulting in TRIF-selective signaling, whereas the corresponding secondary ether lipid 6a containing (R)-3-decyloxytetradecanoyl groups does not. In order to determine which secondary acyl groups are important for the reduction in MyD88-dependent signaling activity of 4, the six possible ester/ether hybrid derivatives of 4 and 6a were synthesized and evaluated for their ability to induce NF-κB in a HEK293 cell reporter assay. An (R)-3-decanoyloxytetradecanoyl group on the 3-position of the d-glucosamine unit was found to be indispensable for maintaining low NF-κB activity irrespective of the substitutions (decyl or decanoyl) on the other two secondary positions. These results suggest that the carbonyl group of the 3-secondary lipid chain may impede homodimerization and/or conformational changes in the TLR4-MD2 complex necessary for MyD88 binding and pro-inflammatory cytokine induction.

Properties of Carbohydrates

The physical, chemical, and biological properties of carbohydrates depend on their primary structures and, less frequently, on their higher-order structures. While monosaccharides are comprised of a single saccharide unit, oligosaccharides are less clearly defined and may consist of from 2-10 glycosidically linked monosaccharide units. Because of the high level of conformational flexibility associated with monosaccharides and oligosaccharides, these molecules typically do not form stable secondary or higher order structures when dissolved in a solvent. Thus, the physical, chemical, and biological properties of monosaccharides and oligosaccharides are mainly attributable to their primary structures.