Fluorides, glycosyl donor

The preparation of glycosyl fluorides is described next. Aiming to have a convenient glycosyl donor convertible into 1,2-CM-furanosides, Mukaiyama and coworkers prepared 2,3,5-tri-O-benzyl-yS-D-ribofuranosyl fluoride (36y3) by treatment of a protected D-ribofuranose (35) with 2-fluoro-1 -meth-ylpyridinium tosylate (FMPTs) the total yield was raised by anomerizing the simultaneously produced a-1-fluoride (36a, 7, p 66, 72.f 24 Hz) to 36 (7, F 63.5 Hz, 72,F very small ) by treatment with BF3-OEt2. 

Trialkylsilane resin (PS-DES) 50 was incorporated for solid-phase glycosylation by anchoring a glycosyl donor via their corresponding thio-phenyl ether or 3-glucopyranosyl fluorides (Scheme 20) [59]. Disaccharides... 

Glycosylation Using Glycosyl Fluorides as Glycosyl Donors 36... 

Table 2.2 Synthesis of 1,2-c/s-glycosides by using glycosyl fluorides as glycosyl donors promoted by SnCI2-AgCI04 [6] or SnCI2-TrCI04 [7],...

Figure2.7 Two-stage activation procedure using glycosyl fluoride and thioglycoside as glycosyl donor.

Despite the high utility of glycosyl fluorides as stand-alone glycosyl donors, there has been only one example of a direct dehydrative glycosylation whereby hemiacetal activation proceeds through a glycosyl fluoride intermediate. Hirooka and Koto have detailed the use of diethylaminosulfur trifluoride (DAST) for dehydrative glycosylations with hemiacetal donors (Scheme 3.16) [160]. Treatment of a mixture of hemiacetal 1 and alcohol acceptor (R OH) with DAST 108 (2 equiv) at 0°C provides the... 

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