Mannosyl pyridyl sulfones

Coupling of the mannosyl pyridyl sulfone 37 with aldehydes 36a and 36b in the presence of Smij was remarkably efficient leading to only one diastereomer 38a and 38b in each case, as shown in Figure 23 That indeed no epimerization of the aldehyde had occurred under the reaction conditions was confirmed by comparing the coupling product with that obtained from the same C-glycosyl donor and the aldehyde earlier prepared by Jung and Choe (Fig. 17). ... 

We have noted exceptional behavior of this type with anomeric pyridyl sulfone 46 and similar mannosyl and galactosyl sulfones (Fig. 27). ... 

The benzyl-protected mannosyl a-trichloroacetimidate has been used for the gly-cosylation of 2-mercaptopyridine (Scheme 50) [207], but the stereoselectivity was low. The P-glycoside was separated and oxidized to Ae 2-pyridyl sulfone which was employed as glycosyl donor for the synthesis of C-glycosides. The corresponding azidogalactose and 7V-acetylgalactosamine derivatives have also been prepared [208],... 

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