Expeditious Synthesis of a Tetrasaccharide Repeating Unit of the O-Antigen of Escherichia coli O163

Abstract

The synthesis of the tetrasaccharide repeating unit of the O-antigen of Escherichia coli O163 as its p-methoxyphenyl (PMP) glycoside was achieved followed by sequential glycosylation strategy through thioglycoside activation using sulfuric acid immobilized on silica (H 2 SO 4 -silica) in conjunction with N-iodosuccinimide as a Brønsted acid catalyst. The application of one-pot reaction conditions for two glycosylations and in situ PMB-group removal reduced the number of reaction steps significantly. The L-QuipNAc building block was obtained from known carbohydrate L-rhamnose precursors. The stereoselective outcomes of all glycosylation reactions were found to be very good. A late-stage TEMPO-mediated oxidation was performed for the formation of required uronic acid moiety. An analogue of the target tetrasaccharide was also prepared by using one-pot glycosylation approach. Such synthetic oligosaccharides could later be effectively conjugated with an appropriate protein to furnish glycoconjugate derivatives for their use in immunochemical studies.

N-Aryl iminochromenes inhibit cyclooxygenase enzymesviaπ–π stacking interactions and present a novel class of anti-inflammatory drugs

“…Twenty-two NAIs (1–22) previously synthesized via a cross-coupling strategy 26 were used in this study ( Fig. 1 ).…”

“… 23–25 Further, the structure–activity relationship (SAR) of 2 H -chromene at various positions, including C-3, C-6, and C-7, have been studied. 24 Markedly, via a cross-coupling strategy, our group has successfully synthesized twenty-two N -aryl iminochromenes (NAIs), 26 which belong to a class of novel 2 H -chromene ring-containing molecules with different N -arylimino substituents vicinal to the oxygen ( Fig. 1 ).…”

Facile synthesis of tetrasaccharide fragments of bioactive Asterosaponins novaeguinosides I and II from starfish Culcita novaeguineae

“…With all the required building blocks in hand, p-methoxyphenyl 2,4,6-tri-O-benzyl-α -D-glucopyranoside (3) was glycosylated with thioglycoside derivative 4 in the presence of N-iodosuccinimide (NIS) in conjunction with sulfuric acid immobilized on silica (H2SO4-silica) [34][35][36][37][38][39] to afford the disaccharide 14 in 85% yield. The use of H2SO4-silica instead of TfOH or TMSOTf as the acid source for the Niodosuccinimide promoted activation of thioglycoside is particularly beneficial since it is a solid and can be weighed easily.…”

“…Iodonium ion promoted stereoselective glycosylation of compound 15 with thioglycoside donor 5 in the presence of N-iodosuccinimide (NIS) in conjunction with sulfuric acid immobilized on silica (H2SO4-silica) [34][35][36][37][38][39] to furnish β-(1→2)-linked trisaccharide 16 in 80% yield, which was transformed to trisaccharide derivative 17 under a one-pot deacetylation-benzylation 30 reaction condition in 79% yield. Then the benzylidene acetal was removed from compound 17 using silica supported sulfuric acid (H2SO4-SiO2) 41 followed by selective tosylation of the primary hydroxyl group using tosyl chloride in the presence of DMAP in pyridine.…”

α/β-Stereo- and diastereoselective glycosylation with n-pentenyl glycoside donors, promoted by N-iodosuccinimide and catalyzed by chiral Brønsted acid

“…[3][4][5][6][7][8][9][10] Sulfuric acid immobilized on silica as BA in combination with N-iodosuccinimide (NIS) was utilized to activate a thioglycoside for the synthesis of tetrasaccharide fragments. [11][12][13] Furthermore, attempts at achieving α/β-stereoselectivity in glycosylation were made with chiral BAs (CBAs)activation. This involved the use of a tetrazole-amino acid ionic liquid, 9 chiral binaphthol (BINOL) phosphoric acids, [14][15][16] and peptides bearing carboxylic acid groups in combination with an MgBr 2 Lewis acid.…”