Bicyclic carbohydrate-derived scaffolds for combinatorial libraries

Linearization of carbohydrate derived polycyclic frameworks

We report an easy access to carbohydrate derived diverse tricyclic skeletons which could be beneficial for exploring polyfunctionalized chiral alicycles.

Discovery and design of carbohydrate-based therapeutics

IMPORTANCE OF THE FIELD

Till now, the importance of carbohydrates has been underscored, if compared with the two other major classes of biopolymers such as oligonucleotides and proteins. Recent advances in glycobiology and glycochemistry have imparted a strong interest in the study of this enormous family of biomolecules. Carbohydrates have been shown to be implicated in recognition processes, such as cell-cell adhesion, cell-extracellular matrix adhesion and cell-intruder recognition phenomena. In addition, carbohydrates are recognized as differentiation markers and as antigenic determinants. Due to their relevant biological role, carbohydrates are promising candidates for drug design and disease treatment. However, the growing number of human disorders known as congenital disorders of glycosylation that are being identified as resulting from abnormalities in glycan structures and protein glycosylation strongly indicates that a fast development of glycobiology, glycochemistry and glycomedicine is highly desirable.

AREAS COVERED IN THIS REVIEW

The topics give an overview of different approaches that have been used to date for the design of carbohydrate-based therapeutics; this includes the use of native synthetic carbohydrates, the use of carbohydrate mimics designed on the basis of their native counterpart, the use of carbohydrates as scaffolds and finally the design of glyco-fused therapeutics, one of the most recent approaches. The review covers mainly literature that has appeared since 2000, except for a few papers cited for historical reasons.

WHAT THE READER WILL GAIN

The reader will gain an overview of the current strategies applied to the design of carbohydrate-based therapeutics; in particular, the advantages/disadvantages of different approaches are highlighted. The topic is presented in a general, basic manner and will hopefully be a useful resource for all readers who are not familiar with it. In addition, in order to stress the potentialities of carbohydrates, several examples of carbohydrate-based marketed therapeutics are given.

TAKE HOME MESSAGE

Carbohydrates are a rich class of natural compounds, possessing an intriguing and still not fully understood biological role. This richness offers several strategies for the design of carbohydrate-based therapeutics.

Carbohydrate mimetics and scaffolds: sweet spots in medicinal chemistry

Several glycoprocessing enzymes and glycoreceptors have been recognized as important targets for therapeutic intervention. This concept has inspired the development of important classes of therapeutics, such as anti-influenza drugs inhibiting influenza virus neuraminidase, anti-inflammatory drugs targeting lectin-sialyl-Lewis X interaction and glycosidase inhibitors against HIV, Gaucher’s disease, hepatitis and cancer. These therapeutics are mainly carbohydrate mimics in which proper modifications permit stronger interactions with the target protein, higher stability, better pharmacokinetic properties and easier synthesis. Furthermore, the conformational rigidity and polyfunctionality of carbohydrates stimulate their use as scaffolds for the generation of libraries by combinatorial decoration with different pharmacophores. This mini-review will present examples of how to exploit carbohydrates mimics and scaffolds in drug research.

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 Method of Orthogonal Oligosaccharide Synthesis Leading to a Combinatorial Library Based on Stationary Solid-Phase Reaction

A new, efficient synthesis of oligosaccharides, which involves solid-phase reactions without mixing in combination with an orthogonal-glycosylation strategy, is described. Despite a great deal of biological interest, the combinatorial chemistry of oligosaccharides is an extremely difficult subject. The problems include 1) lengthy synthetic protocols required for the synthesis and 2) the variety of glycosylation conditions necessary for individual reactions. These issues were addressed and solved by using the orthogonal-coupling protocol and the application of a temperature gradient to provide appropriate conditions for individual reactions. Furthermore, we succeeded in carrying out solid-phase reactions with neither mechanical mixing nor flow. In this report, the synthesis of a series of trisaccharides, namely, alpha/beta-L-Fuc-(1-->6)-alpha/beta-D-Gal-(1-->2/3/4/6)-alpha/beta-D-Glc-octyl, is reported to demonstrate the eligibility of the synthetic method in combinatorial chemistry.