Pentenyl Glycosides as Glycosyl Donors

A promoter of intermediate potency is iodonium di-vym-collidinc perchlorate (IDCP), which was successfully used for coupling reactive (armed) NPGs.62 A problem is that some IDCP-promoted reactions tend to stall, leaving substantial amounts of unreacted starting material, an effect probably caused by liberation of collidine during the course of the reaction. 

The concept of armed/disarmed glycosyl donors was subsequently extended by other groups to thioglycosides21 and selenoglycosides.64 A similar strategy has been used by Friesen and Danishefsky to achieve chemoselectivity in electrophilic addition to glycal double bonds.65 

the latter approach was clearly preferable and several NPG donors were coupled to 41 under these conditions in order to investigate trends in anomeric selectivity, as monitored by gel-phase 13C NMR spectroscopy (Table 5.1).66 As expected, neighboring-group active donors 44 and 45 produced solely the 

In contrast to Merrifield resin or TentaGel, this material reacts only on the surface swelling by the solvent and diffusion of reagents into the material is not required. 

TABLE 5.1 Stereoselectivity in Coupling Reaction of 41 to Some -Pentenyl Glycosides66 

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E. Glycosylation Methods Using n-Pentenyl Glycosides as Glycosyl Donors... 

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