Glycosyl carbonate

Synthesis of C-Nucleosides in which the Glycosylic Carbon Atom is Attached to Two Carbon Atoms... 

This Section is concerned with the synthesis of C-nucleosides having the Type A arrangement of atoms attached to the glycosylic carbon atom, and covers the synthesis of pseudouridine (1), show-... 

Combination of Cp2HfCl2 and AgC104 in the ratio 1 2 catalyzes the decarboxylation of glycosyl carbonates, thereby giving rise to glycosides (Eq. 3). The stereochemical outcome is solvent-dependent—a-selectivity is obtained in Et20, yS-selectivity in CH2CI2 [13]. 

Among the different glycosyl carbonates and related derivatives summarized in Table 4.13, anomeric aryloxycarbonyl derivatives 234 were used in thermal glycosylation reactions to give... 

SCHEME 4.47 Synthesis of avermectin Bla using glycosyl carbonate donors. 

Mukaiyama, T, Miyazaki, K, Uchiro, H, Highly stereoselective synthesis of 1,2-tranr-glycosides using p-chlorobenzylated glycosyl carbonate as glycosyl donor, Chem. Lett., 635-636, 1998. 

The relative yields of various carbon species in these chars are shown in Table VI. These data indicate that the glycosylic carbon disappears on heating up to 400 °C. At this temperature the char contains 69% aromatic and 27% paraffinic carbons which change to 88% and 12%, respectively, at 500 °C. 

Glycosylation with Glycosyl Carbonates and Related Donors. 551... 

Roesy experiment (Table 5) allowed differentiation between hypotheses I and II showing spatial correlations between anomeric protons and protons linked to glycosylated carbons. 

K13. Kondo, T., Murakami, K., Ohthuka, Y., Tsuji, M., Gasa, S., Tanaguchi, N., and Kawakami, Y., Estimation and characterization of glycosylated carbonic anhydrase I in erythrocytes from patients with diabetes mellitus. Clin. Chim. Acta 166, 227-236 (1987). 

Further research into the types of substrates available for transition metal mediated C-glycosidations demonstrated the utility of glycosyl carbonates. As shown in Scheme 4.3.5, Engelbrecht, et al.,22 effected the formation of glycosyl carbonates on reaction of anhydrosugars with isobutyl chloroformate and pyridine. Under these conditions, the a glycosyl carbonate was isolated in 75% yield. Subsequent treatment with diethyl malonate in the... 

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