Combinatorial synthesis of amino acid- and peptide-carbohydrate conjugates on solid phase

Polygalacturonic acid hydrogel with short-chain hyaluronate cross-linker to prevent postoperative adhesion

The purpose of this study was to develop a poly(galacturonic acid) (PGA)-based hydrogel using a short-chain hyaluronate (sHA) cross-linker for medical applications. PGA was grafted with adipic acid dihydrazide (ADH) to yield PGA–ADH, an amine-containing PGA derivative. This PGA–ADH formed a water-insoluble hydrogel by reacting with 1,1′-carbonyldiimidazole (CDI)–grafted sHA (sHA–CDI) in aqueous solution. The sHA–cross-linked PGA hydrogel has a water content of about 94%–97% and compressive modulus of 10.7–26.9 kPa. The in vitro data indicated that the sHA–cross-linked PGA hydrogel is degradable and noncytotoxic, thus suitable for biomedical applications. Animal implant studies showed that the sHA–cross-linked PGA hydrogel membrane exhibited antiadhesion potency, significantly higher than that found in untreated rats and has great potential for future clinical applications.

Carbohydrates as scaffolds in drug discovery

Drug discovery has long suffered from the difficulty of having to place pharmacophoric groups in just the right spatial arrangement to elicit the desired biological response. Although some molecule classes have been discovered that seem to be privileged structures for at least some drug-receptor interactions, there remains the challenge to design and synthesize molecules with high specific affinity to pharmacologically important targets. With their high density of stereochemical information and their relative rigidity, carbohydrates provide excellent platforms upon which to display a number of substituents in a sterically defined way, hence offering the opportunity to harness their unique features for the drug-discovery process. This review highlights the progress that has been made in the development of carbohydrate scaffolds for drug discovery.

A novel heterobifunctional linker for facile access to bioconjugates

A convenient synthesis of a novel heterobifunctional linker molecule is described. The linker contains a thiol-reactive nitropyridyl disulfide group (Npys) and an aldehyde-reactive aminooxy group with a propensity to form disulfide and oxime linkages. The utility of the linker molecule to cross-link different biomolecules has been demonstrated by employing it in the efficient preparation of a peptide-oligonucleotide conjugate. The linker reported herein could be a useful tool for cross-coupling of different but appropriately functionalised biomolecules.

Synthesis of Somatostatin Mimetics Based on the 1-Deoxymannojirimycin Scaffold

A novel synthesis of somatostatin mimetics based on the 1-deoxymannojirimycin (DMJ) scaffold has been developed. This involved development of a route suitable for the strategic grafting of pharmacophoric tryptophan and lysine side chains to the nitrogen atom of the piperidine ring and to the primary hydroxyl group of DMJ, respectively. The novel peptidomimetics were found to bind with higher affinity to sst4 receptors than to sst5 receptors.

Synthesis of Structurally Defined Scaffolds for Bivalent Ligand Display Based on Glucuronic Acid Anilides. The Degree of Tertiary Amide Isomerism and Folding Depends on the Configuration of a Glycosyl Azide

[structures: see text] Syntheses and structural analyses of bivalent carbohydrates based on anilides of glucuronic acid are described. Secondary anilides predominantly adopted the Z-anti structure; there is also evidence for population of the Z-syn isomer. Bivalent tertiary anilides displayed two signal sets in their NMR spectra, consistent with the presence of (i) a major isomer where both amides have E configurations (EE) and (ii) a minor isomer where one amide is E and the other Z (EZ). Qualitative NOE/ROE spectroscopic studies in solution support the proposal that the anti conformation is preferred for E amides. The crystal structure of one bivalent tertiary anilide showed E-anti and E-syn structural isomers; intramolecular carbohydrate-carbohydrate stacking was observed and mediated by carbonyl-pyranose, azide-azide, and pyranose-aromatic interactions. The EE to EZ isomer ratio, or the degree of folding, for tertiary amides, was greatest for a bivalent compound containing two alpha-glycosyl azide groups; this was enhanced in water, suggesting that hydrophobic interactions are partially but not wholly responsible. Computational methods predicted azide-aromatic (N...H-C interaction) and azide-azide interactions for folded isomers. The close contact of the azide and aromatic protons (N...H-C interaction) was observed upon examination of the close packing in the crystal structure of a related monomer. It is proposed that the alpha-azide group is more optimally aligned, compared to the beta-azide, to facilitate interaction and minimize the surface area of the hydrophobic groups exposed to water, and this leads to the increased folding. The alkylation of bivalent secondary anilides induces a switch from Z to E amide that alters the scaffold orientation. The synthesis of a bivalent mannoside, based on a secondary anilide scaffold, for investigation of mannose-binding receptor cross-linking and lattice formation is described.

Synthesis and Structural Analysis of the Anilides of Glucuronic Acid and Orientation of the Groups on the Carbohydrate Scaffolding

[structures: see text] The synthesis of anilides derived from glucuronic acid is described. Secondary anilides had a Z configuration in the solid state and showed intramolecular and intermolecular hydrogen bonding. However, on the basis of NMR and IR studies, there was generally no evidence for the same hydrogen bonding in solution. Tertiary anilides showed a strong preference for the E configuration on the basis of NOE studies and molecular mechanics calculations. The alkylation of the secondary anilides induces a configurational switch that alters the orientation of the aromatic group with respect to the pyranose, which has relevance for presentation or orientation of pharmacophoric groups on carbohydrate scaffolds.