Chemoselective glycosylation armed-disarmed

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... 

Ley and coworkers reported the one-pot synthesis of tetrasaccharide 176 by combining selective activation with reactivity-based armed-disarmed glycosylation [113]. As shown in Scheme 6.35, the first chemoselective coupling was achieved via selective activation of the fluoride donor 173 over the selenoglycoside acceptor 174. The resulting disaccharide intermediate was more armed than the bifunctional... 

Chiba, H, Funasaka, S, Kiyota, K, Mukaiyama, T, Catalytic and chemoselective glycosylation between armed and disarmed glycosyl p-trifluoromethylbenzylthio-p-trifluoromethylphenyl formimidates, Chem. Lett., 1A6-1A1, 2002. 

Armed-disarmed strategy for chemoselective glycosyl couplings... 

Additionally, the arming and disarming properties of the STaz glycosides were evaluated. It was demonstrated that activated (benzylated) STaz derivatives could be activated over electronically disarmed (partially acylated) STaz glycosyl acceptors in die presence of either AgOTf or Cu(OTf)2 78). For example, a classic armed-disarmed approach (79) allowed chemoselective activation of 54 over disarmed acceptor 61 in the presence of Cu(OTf)2to afford... 

The armed/disarmed chemoselectivity, although useful and serviceable, required further investigation to determine the limits of its effectiveness. From the earliest stages it had been evident that a disarmed donor was not inert, because it could be activated, probably under different conditions. Thus the disarmed partner, 10, on its own could serve as a glycosyl donor as will be exemplified in Scheme 6 [25]. However, this role was subjugated when it was forced to compete with the armed counterpart 9a in Scheme 3. 

Keywords Armed-disarmed strategy. Carbohydrates, Chemoselective activation. Expeditious S3mthesis, Glycoconjugates, Glycosylation, Oligosaccharides, Synthetic strategy... 

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