A facile total synthesis of ganglioside GD2

Immunotherapy for cancer: synthetic carbohydrate-based vaccines

Aberrant glycosylation of glycoproteins and glycolipids of cancer cells, which correlates with poor survival rates, is being exploited for the development of immunotherapies for cancer. In particular, advances in the knowledge of cooperation between the innate and adaptive system combined with the implementation of efficient synthetic methods for assembly of oligosaccharides and glycopeptides is providing avenues for the rationale design of vaccine candidates. In this respect, fully synthetic vaccine candidates show great promise because they incorporate only those elements requires for relevant immune responses, and hence do not suffer from immune suppression observed with classical carbohydrate-protein conjugate vaccines. Such vaccines are chemically well-defined and it is to be expected that they can be produced in a reproducible fashion. In this feature article, recent advances in the development of fully synthetic sub-unit carbohydrate-based cancer vaccines will be discussed.

Recent trends in the synthesis of O-glycosides of 2-amino-2-deoxysugars

The discovery of new methods for stereoselective glycoside synthesis and convergent oligosaccharide assembly has been critical for the area of glycosciences. At the heart of this account is the discussion of the approaches for stereoselective synthesis of glycosides of 2-amino-2-deoxysugars that have emerged during the past two decades. The introductory part provides general background information and describes the key features and challenges for the synthesis of this class of compounds. Subsequently, major approaches to the synthesis of 2-amino-2-deoxyglycosides are categorized and discussed. Each subsection elaborates on the introduction (or protection) of the amino functionality, synthesis of glycosyl donors by introduction of a suitable leaving group, and glycosidation. Wherever applicable, the deprotection of a temporary amino group substituent and the conversion onto the natural acetamido functionality is described. The conclusions part evaluates the current standing in the field and provides a perspective for future developments.

A facile synthesis of the GalNAcβ1→4Gal target sequence of respiratory pathogens

The carbohydrate sequence, GalNAcbeta1-->4Gal, is the target for the adhesion of several respiratory pathogens. The sequence was prepared in an optimized synthesis in forms that allow conjugation to scaffolds or surfaces.

Synthesis of 7-O-(2-deoxy-2-sulfamido-alpha-D-glucopyranosyl)-4-methylcoumarin sodium salt: a fluorogenic substrate for sulfamidase

The title compound, useful for testing the efficacy of heparin sulfamidase, was synthesized in good yield starting from 2-azido-2-deoxy-3,4,6-tri-O-acetyl-D-glucopyranosyl fluoride, reducing the azido group efficiently with SnCl(2)-PhSH-Et(3)N reagent and finally crystallizing the N-sulfated product from methanol after deacetylation.

A synthetic approach to the c-series gangliosides containing sialyl-alpha(2-->8)sialyl-alpha(2-->8)sialic acid: synthesis of ganglioside GT4, alpha(2-->6) GT4 and GT3

Trimeric sialic acid [Neu5Ac alpha(2-->8)Neu5Ac alpha(2-->8)Neu5Ac, 1] residue-containing gangliosides, GT4, alpha(2-->6)GT4 and GT3, have been synthesized for the first time. Methyl [phenyl] 5-acetamido-8-O-[5-acetamido-8-O-(5-acetamido-4, 7, 8, 9-tetra-O-acetyl-3, 5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosylono-1", 9'-lactone)-4,7-di-O-acetyl-3,5-dideoxy-D- glycero-alpha-D-galacto-2-nonulopyranosylono-1',9-lactone]-4,7-di- O-acetyl -3,5-dideoxy-2-thio-D- glycero-D-galacto-2-nonulopyranosid]onate (3) was prepared from 1, via lactonization, methyl esterification of the carboxyl group at the reducting end, O-acetylation and conversion of the anomeric acetoxy group into a phenylthio group. Iodonium-promoted glycosylation of 3 with 2-(trimethylsilyl)ethyl 2,6-di-O-benzyl-beta-D-galactopyranoside (5), 2-(trimethylsilyl)ethyl 3-O-benzyl-beta-D-galactopyranoside (6), 2-(trimethylsilyl)ethyl 2-O-benzoyl-3-O-benzyl-beta-D-galactopyranoside (9), and 2-(trimethylsilyl)ethyl 2, 3-di-O-benzyl-beta-D-galactopyranoside (11) gave the corresponding tetrasaccharides (13-15, 17) having the (Neu5Ac)3-Gal structure. The peracylated oligosaccharides 18 and 24 derived from 13 and 17, and the previously reported lactose derivative 29 were converted into the alpha-trichloroacetimidates 20, 26 and 31, and coupled with (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol (21) to afford the corresponding beta-glycosides 22, 27 and 32. These protected azidosphingosine derivatives were each transformed into the target gangliosides GT4, alpha(2-->6)GT4 and GT3 via selective reduction of the azido group, subsequent coupling with octadecanoic acid, O-deacylation and saponification of the methyl ester and lactone groups.