Glycosyl armed

Transfer of the Armed-Disarmed Concept to Thioglycoside Glycosylation... 

A few years later, the same group extended this strategy in order to access metabolically stable C-glycosyl clusters containing long-arm spacers via a sequence of transition metal-catalyzed transformations (Scheme 11).93 In this context, crossmetathesis reactions of various C-glycosyl compounds with alkenes having available... 

Stereoselective Clycosylations of Glycosyl Iodides General methods for a-selective glycosylation of glycosyl iodides via in situ anomerization have been established [197]. Armed glycosyl iodides undergo the reaction in the presence of tetrabutylam-monium iodide (TBAI) and Hiinig s base (diisopropyl ethylamine DIPEA) with... 

Although glycosyl triflates have been demonstrated to be intermediates with a number of armed donors, and even with disarmed donors not capable of neighboring-group participation, such as the sulfonate esters, typical disarmed donors with esters in the 2-position function in the anticipated manner through anchimeric... 

The combination of dicyclopentadienylzirconium dichloride and silver perchlorate activates armed glycosyl sulfoxides in dichloromethane between -20 °C and room temperature, but only very simple acceptors were studied [335]. Other Lewis and Bronsted acids studied include the environmentally benign europium, lanthanum and ytterbium triflates [336], certain polyoxometallates [337], sulfated zirconia [338] and Nafion H [338]. 

Diol 159 was chosen as a model for probing regioselective glycosylation with armed and disarmed thioglycosides 160 and 163, and NPOE 108. The results obtained were not anticipated (Scheme 5.35b-d). 

Remarkably, armed glycosyl donor 160 preferred the secondary-OH of 159 (Scheme 5.37b). Disarmed donor 163 and NPO E108 both preferred the primary-0 H, but the NPOE furnished a single regioisomer 176 (Scheme 5.35c and d). 

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