The synthesis of pennogenin 3-O-β-D-glucopyranosyl-(1 → 3)-[α-L-rhamnopyranosyl-(1 → 2)]-β-D-glucopyranoside

Pennogenin 3-O-β-D-glucopyranosyl-(1 → 3)-[α-L-rhamnopyranosyl-(1 → 2)]-β-D-glucopyranoside, a monodesmosidic saponin isolated from Paris polyphylla Smith var. yunnanensis with promised antitumor activities, was firstly synthesized from glucoside thiol via nine steps and with 27% overall yield.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update for the period 2005-2006

This review is the fourth update of the original review, published in 1999, on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2006. The review covers fundamental studies, fragmentation of carbohydrate ions, method developments, and applications of the technique to the analysis of different types of carbohydrate. Specific compound classes that are covered include carbohydrate polymers from plants, N- and O-linked glycans from glycoproteins, glycated proteins, glycolipids from bacteria, glycosides, and various other natural products. There is a short section on the use of MALDI-TOF mass spectrometry for the study of enzymes involved in glycan processing, a section on industrial processes, particularly the development of biopharmaceuticals and a section on the use of MALDI-MS to monitor products of chemical synthesis of carbohydrates. Large carbohydrate-protein complexes and glycodendrimers are highlighted in this final section.

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.

Synthesis of Sulfated Galactocerebrosides from an Orthogonal β-D-Galactosylceramide Scaffold for the Study of CD1–Antigen Interactions

CD1a protein binds sulfatide (3-O-sulfo-beta-D-galactosylceramide) to form an antigen complex that interacts with T cell receptors and activates T cells. To assess the role of the position of the sulfate in T cell activation, the synthesis of three beta-D-galactosylceramides, variously bearing a sulfate at position 2, 4, or 6 of galactose, has been planned and carried out. The compounds were synthesized by an orthogonal sulfation strategy from a common beta-D-galactosylceramide scaffold, which was in turn obtained through an efficient glycosylation reaction between a fully orthogonally protected galactosyl imidate and 3-O-benzoylazidosphingosine. Immunological evaluation of the three sulfated compounds in CD1a-mediated T cell activation, in comparison with natural sulfatide, provided evidence of the influence of the sulfate position in the recognition event between the antigen, the CD1 protein and the T cell receptor.

Bicyclic carbohydrate-derived scaffolds for combinatorial libraries

A bicyclic scaffold derived from the natural monosaccharide d-glucose, and possessing several diversity sites, was linked to various resins through the primary (C-6) hydroxyl and decorated on the solid phase: the hydroxyl group at C-4 was functionalized as ester, ether, and carbamate, the amino group in the second cycle (C-3' position) was functionalized as amide, sulfonamide, and ureido- and thioureido-derivatives. The compounds synthesized on the solid phase were tested for their antiproliferative activity on tumor cell lines.

A Tuneable Method forN-Debenzylation of Benzylamino Alcohols

[reactions: see text] N-Iodosuccinimide provides a mild, convenient, and tuneable reagent for the selective mono- or didebenzylation in representative, multifunctionalized carbohydrate and amino acid derived N-dibenzylamines with neighboring O-functionality.

Synthesis of beta-D-glucose oligosaccharides from Phytophthora parasitica

The glucohexaose, beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->3)-beta-D-Glcp-(1-->3)-beta-D-Glcp-(1-->6)]-beta-D-Glcp-(1-->3)-D-Glcp, was synthesized as its allyl glycoside via 3+3 strategy. The trisaccharide donor, 2,3,4,6-tetra-O-benzoyl-beta-D-glucopyranosyl-(1-->3)-2,4,6-tri-O-acetyl-beta-D-glucopyranosyl-(1-->3)-2,4,6-tri-O-acetyl-alpha-D-glucopyranosyl trichloroacetimidate (11), was obtained by 3-selective coupling of isopropyl 4,6-O-benzylidene-1-thio-beta-D-glucopyranoside (2) with 2,3,4,6-tetra-O-benzoyl-beta-D-glucopyranosyl-(1-->3)-2-O-acetyl-4,6-O-benzylidene-alpha-D-glucopyranosyl trichloroacetimidate (6), followed by hydrolysis, acetylation, dethiolation, and trichloroacetimidation. Meanwhile, the trisaccharide acceptor, allyl 2,3,4,6-tetra-O-benzoyl-beta-D-glucopyranosyl-(1-->3)-2-O-acetyl-beta-D-glucopyranosyl-(1-->3)-4,6-di-O-acetyl-2-O-benzoyl-alpha-D-glucopyranoside (14), was prepared by coupling of allyl 4,6-di-O-acetyl-2-O-benzoyl-alpha-D-glucopyranoside (12) with 6, followed by debenzylidenation. Condensation of 14 with 11, followed by deacylation, gave the target hexaoside. A beta-(1-->3)-linked tetrasaccharide 29 was also synthesized with methyl 2-O-benzoyl-4,6-O-benzylidene-beta-D-glucopyranosyl-(1-->3)-2,4,6-tri-O-acetyl-beta-D-glucopyranoside (25) as the acceptor and acylated beta-(1-->3)-linked disaccharide 21 as the donor.