Synthesis of hyaluronic-acid-related oligosaccharides and analogues, as their 4-methoxyphenyl glycosides, having N-acetyl-beta-D-glucosamine at the reducing end.

To contribute to the possibilities to study the ability of oligosaccharide fragments of hyaluronic acid to induce angiogenesis, several hyaluronic-acid-related oligosaccharides and their 6-O-sulfated analogues were synthesised as their 4-methoxyphenyl glycosides having 2-acetamido-2-deoxy-D-glucopyranose at the reducing end. In all syntheses described, the D-glucopyranosyluronic acid residue was obtained by oxidation at C-6 of a corresponding D-glucopyranosyl residue after construction of the oligosaccharide backbone, using pyridinium dichromate and acetic anhydride.

Preparation of spacer-containing di-, tri-, and tetrasaccharide fragments of the circulating anodic antigen of Schistosoma mansoni for diagnostic purposes.

The chemical synthesis of beta-D-GlcpA-(1-->3)-beta-D-GalpNAc-(1-->O)CH2CH = CH2, beta-D-Galp-NAc-(1-->6)-[beta-D-GlcpA-(1-->3)]-beta-D-GalpNAc-(1-- >O)CH2CH = CH2, and beta-D-GlcpA-(1-->3)-beta-D-GalpNAc-(1-->6)-[beta-D-GlcpA-(1 -->3)] -beta-D-GalpNAc-(1-->O)CH2CH = CH2 is described. These oligosaccharides represent fragments of th circulating anodic antigen, secreted by the parasite Schistosoma mansoni in the circulatory system of the host. The applied synthesis strategy includes the preparation of a non-oxidised backbone oligosaccharide, with a levulinoyl group at O-6 of the beta-D-glucose residue. After the selective removal of the levulinoyl group, the obtained hydroxyl functions were converted into carboxyl groups, using pyridinium dichromate and acetic anhydride in dichloromethane, to afford the desired glucuronic-acid-containing oligosaccharides. Subsequently, the allyl glycosides have been elongated with cysteamine to give the corresponding amine-spacer-containing oligosaccharides.

Synthesis of hyaluronic acid-related di-, tri-, and tetra-saccharides having an N-acetylglucosamine residue at the reducing end.

The synthesis is reported of 4-methoxyphenyl O-(beta-D-glucopyranosyluronic acid)-(1-->3)-2-acetamido-2-deoxy-beta-D-glucopyranoside (1), 4-methoxyphenyl O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-(1-->4)-O-(beta-D- glucopyranosyluronic acid)-(1-->3)-2-acetamido-2-deoxy-beta-D-glucopyranoside (5), and 4-methoxyphenyl O-(beta-D-glucopyranosyluronic acid)-(1-->3)-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-(1-->4)-O-(b eta-D- glucopyranosyluronic acid)-(1-->3)-2-acetamido-2-deoxy-beta-D-glucopyranoside (10), which are structural elements of the extracellular polysaccharide hyaluronic acid. 6-O-Levulinoyl-2,3,4-tri-O-p-toluoyl-alpha-D-glucopyranosyl trichloroacetimidate (3) was condensed with 4-methoxyphenyl 2-deoxy-4,6-O-isopropylidene-2-phthalimido-beta-D-glucopyranoside (4). De-isopropylidenation and acetylation of the obtained disaccharide derivative yielded 4-methoxyphenyl O-(6-O-levulinoyl-2,3,4-tri-O-p-toluoyl-beta-D-glucopyranosyl)-(1-->3)-4 ,6-di-O - acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranoside, and subsequent delevulinoylation, oxidation, complete deprotection, and N-acetylation gave 1. Coupling of 4-O-allyloxycarbonyl-6-O-levulinoyl-2,3-di-O-p-toluoyl-alpha-D-glu copyranosyl trichloroacetamidiate with 4 followed by de-isopropylidenation, acetylation, and deallyloxycarbonylation of the obtained disaccharide derivative gave 8. Condensation of 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl trichloroacetimidate with 8 afforded trisaccharide derivative 4-methoxyphenyl O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-(1--> 4)-O-(6 - O-levulinoyl-2,3-di-O-p-toluoyl-beta-D-glucopyranosyl)-(1-->3)-4,6-di-O- acetyl- 2-deoxy-2-phthalimido-beta-D-glucopyranoside, and subsequent delevulinoylation, oxidation, complete deprotection, and N-acetylation gave 5. 3-O-Allyloxycarbonyl-2-deoxy-4,6-O-isopropylidene-2-phthalimido-be ta-D- glucopyranosyl trichloroacetimidate was coupled with disaccharide acceptor 8, and deallyloxycarbonylation of the obtained trisaccharide derivative yielded 12. Condensation of 3 with 12 followed by de-isopropylidenation and acetylation of the obtained tetrasaccharide derivative gave 4-methoxyphenyl O-(6-O-levulinoyl-2,3,4-tri-O-p-toluoyl-beta-D-glucopyranosyl)-(1-->3)-O -(4,6- di-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-(1-->4)-O-(6-O- levulinoyl-2,3-di-O-p-toluoyl-beta-D-glucopyranosyl)-(1-->3)-4,6-di-O-ac etyl-2- deoxy-2-phthalimido-beta-D-glucopyranoside, and delevulinoylation, oxidation, complete deprotection, and N-acetylation yielded 10.

Synthesis of two phosphate-containing "heptasaccharide" fragments of the capsular polysaccharides of Streptococcus pneumoniae types 6A and 6B.

The "heptasaccharides" O-alpha-D-galactopyranosyl-(1----3)- O-alpha-D-glucopyranosyl-(1----3)-alpha, beta-L-rhamnopyranose 2''-[O-alpha-D-galactopyranosyl-(1----3)-O-alpha-D-glucopyranosyl- (1----3)-O-alpha-L-rhamnopyranosyl-(1----3)-D-ribit-5-yl sodium phosphate] (25) and O-alpha-D-galactopyranosyl- (1----3)-O-alpha-D-glucopyranosyl-(1----3)-alpha, beta-L-rhamnopyranose 2''-[O-alpha-D-galactopyranosyl-(1----3)-O-alpha-D-glucopyranosyl- (1----3)-O-alpha-L-rhamnopyranosyl-(1----4)-D-ribit-5-yl sodium phosphate] (27), which are structural elements of the capsular polysaccharides of Streptococcus pneumoniae types 6A and 6B ([----2)- -alpha-D-Galp-(1----3)-alpha-D-Glcp-(1----3)-alpha-L-Rhap- (1----X)-D-RibOH-(5-P----]n; 6A X = 3, 6B X = 4), respectively, have been synthesized. 2,4-Di-O-acetyl- 3-O-[2,4,6-tri-O-acetyl-3-O-(2,3,4,6-tetra-O-acetyl-alpha-D- galactopyranosyl)-alpha-D-glucopyranosyl]-alpha-L-rhamnopyranosyl trichloroacetimidate (13) was coupled with 5-O-allyloxycarbonyl-1,2,4-tri-O- benzyl-D-ribitol (10), using trimethylsilyl triflate as a promotor (----14), and deallyloxycarbonylation (----15) and conversion into the corresponding triethylammonium phosphonate then gave 16. Condensation of 16 with 4-methoxybenzyl 2,4-di-O-benzyl-3-O-[2,4,6-tri-O-benzyl-3-O-(3,4,6-tri-O-benzyl-alpha-D- galactopyranosyl)-alpha-D-glucopyranosyl]- alpha-L-rhamnopyranoside (22) followed by oxidation and deprotection afforded 25. 5-O-Allyl-1-O-allyloxycarbonyl-2,3-di-O-benzyl-D-ribitol (12) was coupled with 13, using trimethylsilyl triflate as a promoter, the resulting tetrasaccharide-alditol derivative 17 was deallyloxycarbonylated (----18), acetylated (----19), and deallylated (----20), and the product was converted into the triethylammonium phosphonate derivative 21. Condensation of 21 with 22 followed by oxidation and deprotection afforded 27.

Synthesis of structural elements of the capsular polysaccharides of Streptococcus pneumoniae types 6A and 6B.

O-alpha-d-Glucopyranosyl-(1----3)-alpha, beta-L-rhamnopyranose (15), O-alpha-D-galactopyranosyl-(1----3)-O-alpha-D-glucopyranosyl-(1----3)-al pha, beta-L-rhamnopyranose (17), O-alpha-D-galactopyranosyl-(1----3)-O-alpha-D-glucopyranosyl-(1----3)- O-alpha-L-rhamnopyranosyl-(1----3)-D-ribitol (23), and O-alpha-D-galactopyranosyl-(1----3)-O-alpha-D-glucopyranosyl-(1----3)- O-alpha-L-rhamnopyranosyl-(1----4)-D-ribitol (27), which are structural elements of the capsular polysaccharides of Streptococcus pneumoniae types 6A and 6B ([----2)-alpha-D-Galp-(1----3)-alpha-D-Glcp-(1----3)-alpha-L-Rhap- (1----X)- D-Rib-ol-(5-P----]n; 6A X = 3, 6B X = 4), have been synthesised. Ethyl 3-O-allyl-2,4,6-tri-O-benzyl-1-thio-beta-D-glucopyranoside (3) was coupled with benzyl 2,4-di-O-benzyl-alpha-L-rhamnopyranoside (4), and subsequent deallylation (----14) and debenzylation gave 15. Condensation of 14 with ethyl 2,3,4,6-tetra-O-benzyl-1-thio-beta-D-galactopyranoside (2) followed by debenzylation gave 17. Acetylation of 17 followed by removal of AcO-1, conversion into the imidate, coupling with 1,2,4,5-tetra-O-benzyl-D-ribitol (11), deacetylation, and debenzylation gave 23. Coupling of the imidate with 1-O-allyloxycarbonyl-2,3,5-tri-O-benzyl-D-ribitol (12) followed by deallyloxycarbonylation, deacetylation, and debenzylation yielded 27.

Synthesis of a selectively protected trisaccharide building block of the capsular polysaccharide of Streptococcus pneumoniae types 6A and 6B.

4-Methoxybenzyl 2,4-di-O-benzyl-3-O-[2,4,6-tri-O-benzyl-3-O-(3,4,6-tri-O-benzyl-alpha-D- galactopyranosyl)-alpha-D-glucopyranosyl]-alpha-L-rhamnopyranoside (22), a building block for the alpha-D-Galp-(1----3)-alpha-D-Glcp-(1----3)-alpha-L-Rhap fragment of the capsular polysaccharides of Streptococcus pneumoniae types 6A and 6B [----2)-alpha-D-Galp-(1----3)-alpha-D-Glcp-(1----3)-alpha-L-Rhap-( 1----X)-D- RibOH-(5-P----]n (6A, X = 3; 6B, X = 4) has been synthesised. Ethyl 3-O-allyl-2,4,6-tri-O-benzyl-1-thio-beta-D-glucopyranoside was coupled with 4-methoxybenzyl 2,4-di-O-benzyl-alpha-L-rhamnopyranoside in ether, using methyl triflate as promoter. The resulting alpha-D-Glcp-(1----3)-alpha-L-Rhap derivative was deallylated with KOBut in N,N-dimethylformamide followed by 0.1M HCl in 9:1 acetone-water. The product was coupled with 3,4,6-tri-O-acetyl-2-O-allyl-alpha,beta-D-galactopyranosyl trichloroacetimidate in ether, using trimethylsilyl triflate, to yield 19. Deacetylation, benzylation, and deallylation then gave 22.