Silver zeolite - effective catalyst for the regio-stereoselective formation of the Neu5Acα2→6 glycosyl linkage - synthesis of several sialosaccharides

Synthesis of oligosaccharides of 2-amino-2-deoxy sugars

“…124 Selective /3-(l-»-6) glycosylation of HO-4, HO-6 free diol containing acceptors were successfully achieved by several groups. 63,123,125,126 Some important examples will be discussed in the following sections. The oxazoline glycosylation procedure was extremely suitable for such syntheses, which involved the simultaneous creation of a d-(l"*6) linkage and the amide function, which resulted from the direct opening of the oxazoline ring.…”

“…Similar yields were obtained for the syntheses of higher oligosaccharides containing the same d-(l-*-6) disaccharide units under the same conditions (excess of the glycopyranosyl donor 3). [146][147][148][149][150] d-(l-*-6) regioselective glycosylation reactions were also achieved with glycosyl acceptors containing diols located at either HO-3 and HO-654 or HO-4 and HO-6144,151-153 in moderate yields (less than 50%).…”

Metallic Clusters and Color Changes in Silver-Exchanged Zeolites: 109Ag Solid State NMR and Optical Studies

“…Silver mordenites are active and selective in the epoxidation of ethylene . Silver-exchanged faujasites are reported to be effective catalysts for the exclusive synthesis of sialosaccharides containing specific glycosyl linkage . The functional properties of silver-exchanged zeolites are strongly influenced by the position and local dynamics of silver cations.…”

“…6 Silver-exchanged faujasites are reported to be effective catalysts for the exclusive synthesis of sialosaccharides containing specific glycosyl linkage. 7 The functional properties of silver-exchanged zeolites are strongly influenced by the position and local dynamics of silver cations. Solid-state nuclear magnetic resonance (NMR) spectroscopy is an excellent tool for probing molecular dynamics and environments of metal cations in zeolites.…”

The Chemistry of Sialic Acid

“…Other promoters, including ZnBr 2 [85], silver triflate [86], silver zeolite [87], I 2 / 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) [88], diisopropylethylamine [89], and the phase-transfer catalyst BnNEt 3 Cl [90], have also been applied for the sialylation of 2-chloro derivatives of Neu5Ac. It has also been shown that glycosylation of aliphatic alcohols can be effectively performed in the absence of added promoter both for free acid and for the corresponding methyl ester [91].…”