ABSTRACT
Thioglycosides are widely used as a major class of glycosyl donors in oligosaccharide synthesis because they are usually stable under the various conditions used for chemically manipulating of hydroxy groups. Thioglycosides can be selectively activated with a variety of thiophilic reagents [1; see also Chap. 11]. In 1980, we introduced the concept of remote activation of an anomeric group in glycoside synthesis based on 0-unprotected 2-thiopyridyl glycosyl donors which, when treated by Hg(N03)2 in the presence of an excess of alcohol, afforded the desired glycosides in good yield, with good to moderate a-selectivities [2]. The method is applicable in the glycosylation of aglycones derived from complex antibiotics, as in the total syntheses of erythromycin [3] and avennectin B13 [4].
