Carbohydrates as Multifunctional Chiral Scaffolds in Combinatorial Synthesis

Development of carbohydrate-based scaffolds for restricted presentation of recognition groups. Extension to divalent ligands and implications for the structure of dimerized receptors

The solution structure of glycosyl amides has been studied by using NMR. A strong preference is displayed by tertiary aromatic glycosyl amides for E-anti structures in contrast with secondary aromatic glycosyl amides where Z-anti structures predominate. The structural diversity displayed by these classes of molecules would seem to be important as the directional properties of the aromatic ring, or groups attached to the aromatic ring, would be determined by choosing to have either a secondary or tertiary amide at the anomeric center and could be considered when designing bioactive molecules with carbohydrate scaffolds. The structural analysis was also carried out for related divalent secondary and tertiary glycosyl amides and these compounds display preferences similar to that of the monovalent compounds. The constrained divalent compounds have potential for promoting formation of clusters that will have restricted structure and thus have potential for novel studies of mechanisms of action of multivalent ligands. Possible applications of such compounds would be as scaffolds for the design and synthesis of ligands that will facilitate protein-protein or other receptor-receptor interactions. The affinity of restricted divalent (or higher order) ligands, designed to bind to proteins that recognize carbohydrates which would facilitate clustering and concomitantly promote protein-protein interactions, may be significantly higher than monovalent counterparts or multivalent ligands without these properties. This may be useful as a new approach in the development of therapeutics based on carbohydrates.

3-Azido-3-deoxy-glycopyranoside derivatives as scaffolds for the synthesis of carbohydrate-based universal pharmacophore mapping libraries

The regiospecific syntheses of six monosaccharide scaffolds, 1-6, containing a carboxylic acid, an azido and a free hydroxyl group were accomplished through the utilization of a key intermediate, namely, methyl 3-azido-3-deoxy-beta-D-glucopyranoside (10). Scaffold 2 was also used in generating combinatorial libraries using solid-phase methodologies.

D-glucose as a multivalent chiral scaffold for combinatorial chemistry

Due to their high density of functional groups and their availability in a variety of diastereomeric forms, monosaccharides are considered attractive scaffolds for combinatorial chemistry that allow the attachment and defined spatial alignment of up to five different pharmacophoric groups. For their application in combinatorial syntheses on solid phase, a set of selectively removable hydroxy protecting groups in combination with a cleavable anchor is required. Herein, we report on the construction and use of a versatile multivalent glucose building block for parallel synthesis on the solid phase.

Synthesis of alpha-glucuronic acid and amide derivatives in the presence of a participating 2-acyl protecting group

[reaction: see text] Participating acyl groups located at C-2 in glucosyl and related donors generally promote formation of 1,2-trans-glycosides. Reactions of some glucuronic acid donors with TMSN(3)/SnCl(4) or ROH/SnCl(4) gave only the 1,2-cis-glycoside. The stereoselectivity is consistent with participation of the C-6 group. The methodology was used for the synthesis of a Kdn2en mimetic with the alpha-configuration.

Design, synthesis and biological activity of carbohydrate-containing peptidomimetics as new ligands for the human tachykinin NK-2 receptor

Enantiopure cycloadducts between glycals and alkyl or aryl heterodienes were selected as small, rigid, nonpeptide molecules able to superimpose to the structure of the cyclopeptide tachykinin NK-2 antagonist 1. The presence of three aromatic groups in the pyranose ring resulted essential for NK-2 affinity, while an increase in activity was shown by the corresponding sulfoxides.

Structure-based design and synthesis of HIV-1 protease inhibitors employing beta-D-mannopyranoside scaffolds

A preliminary account on the structure-based design, synthesis and evaluation of peptidomimetic inhibitors of HIV-1 protease containing beta-D-mannopyranoside scaffolds is given. The compounds prepared had IC(50) values in the micromolar range. The results provide a platform for the development of more potent carbohydrate-based inhibitors of HIV-1 and other aspartic proteases.

Combinatorial carbohydrate chemistry

The application of combinatorial chemistry to the synthesis of carbohydrate-based compound collections has received increased attention in recent years. New strategies for the solution-phase synthesis of oligosaccharide libraries have been reported, and the use of monosaccharides as scaffolds in the generation of combinatorial libraries has been described. Novel approaches to the assembly of carbohydrate-based antibiotics, such as aminoglycoside analogs and vancomycin derivatives, have also been disclosed.

A pentaerythritol-based molecular scaffold for solid-phase combinatorial chemistry

A convergent synthesis has been developed for the preparation of solid-phase bound construct 1, consisting of an orthogonally protected trifunctional core structure that is attached to TentaGel via a photocleavable linker. [structure: see text]

Combinatorial chemistry toward understanding the function(s) of carbohydrates and carbohydrate conjugates

Combinatorial chemistry has contributed significantly to understanding the structure-function relationships of biologically important molecules such as proteins and nucleic acids. However, carbohydrates and carbohydrate conjugates, which have been identified as key modulators of several biological functions have not enjoyed the same measure of success. The complexity and synthetic challenges of carbohydrate conjugates have resulted in a number of conceptual approaches to rapidly access sufficient quantities of these biomolecules. This article summarizes these combinatorial approaches and also highlights fully automated library synthesis of artificial glycopeptides with the goals of understanding their biological roles.