Triflic acid-mediated synthesis of thioglycosides

Abstract

Examples include all common hexoses, aminosugars, sialic acids, and disaccharides.

Syntheses of Salmonella Paratyphi A Associated Oligosaccharide Antigens and Development towards Anti‐Paratyphoid Fever Vaccines

“…5 Hz, H-1 C ), 4.44 (d, J = 7.5 Hz, H-1 D )i n 1 HNMR and at d 101.6 (C-1 D ), 82.1 (C-1 C )i ni ts 13 CNMR spectrum.T he assignment of signals to rings Cand Dwas made based on the typical chemical shift values of anomeric carbons of similar disaccharide thioglycosides. [37,38] From the anomeric carbon, the HÀCc orrelations in 2D HMQC spectrum helped to assign the anomeric Changing the parameters such as temperature, promoter and reactions olvents did not improve the yield of a-paratosylated product 18.…”

“…NMR signals for 17 were observed at δ 5.26 (d, J= 1.5 Hz, H‐1 C ), 4.44 (d, J= 7.5 Hz, H‐1 D ) in 1 H NMR and at δ 101.6 (C‐1 D ), 82.1 (C‐1 C ) in its 13 C NMR spectrum. The assignment of signals to rings C and D was made based on the typical chemical shift values of anomeric carbons of similar disaccharide thioglycosides [37, 38] . From the anomeric carbon, the H−C correlations in 2D HMQC spectrum helped to assign the anomeric 1 Hs.…”

SnCl4-catalyzed solvent-free acetolysis of 2,7-anhydrosialic acid derivatives

“…Next, acetolysis of 2,7-anhydro derivative 6 was examined with SnCl 4 as catalyst under neat conditions, which provided the expected β-ring-opened product 12 in a moderate yield ( Table 1, It is known that anomeric acetates can be transformed smoothly into thioglycoside [15,16,35] and sialyl halide [38,39] donors when treated with a thiol in the presence of triflic acid, BF 3 ⋅OEt 2 , and HCl, respectively.…”

“…NMR also showed no correlation with position C-2, but exhibited a correlation separated by three bonds with the quaternary carbon atom of the acetyl group in position O-7 (Figure 3). The anomeric configuration of the acetolysis products was identified by the coupling constant for the correlation C-1-C-2-C-3-H-3 ax ( = 1.6-2.2 Hz, see Supporting Information File 1) and indicated the β-anomer [12][13][14][15][16]. Moreover, the similar chemical shifts of positions H-3 eq and H-3 ax in the 1 H NMR spectra of α-sialosides 6, 21, and 25 became much more different for the ring-opening products 12, 22, and 26, again representative of the β-configuration.…”

“…The most common glycosidic linkages of Neu5Ac in glycoconjugates are α(2→3) and α(2→6) to galactose, α(2→8) and α(2→9) in polysialic acids [2,3], fucosyl and galactosyl α(1→4) to Neu5Ac, and intramolecularly C-7-to-C-2-linked (via oxygen), forming 2,7-anhydro-Neu5Ac [4][5][6]. Owing to the substantial role of sialic acids in biological systems, numerous synthetic methods have been described in the literature [7][8][9][10][11][12][13][14][15][16]. 2,7-Anhydro-Neu5Ac is the main prebiotic, which is utilized as a sole carbon source for human gut commensal anaerobic bacterium and plays a key biological role in body fluids and secretion [17][18][19].…”