Boron Trifluoride-Catalyzed Rearrangement of 2-Aryloxytetrahydropyrans: A New Entry to C-Arylglycosidation

Synthesis of aryl sialosides using Mitsunobu conditions

“…The Mitsunobu reaction 7 has been widely used for the synthesis of aryl glycosides, [8][9][10][11][12][13][14][15][16][17] acyl glycosides, [16][17][18][19] alkyl glycosides, 16,20,21 and amino glycosides 16,22 by reacting hemiacetals of aldosugars, predominantly glucose, galactose, and mannose, with weakly acidic acceptors in the presence of diethyl azodicarboxylate (DEAD) and triphenylphosphine (Ph 3 P). A major advantage of this direct dehydrative coupling procedure is that activated glycosyl donors do not need to be isolated and all reaction steps-anomerization, activation, and glycosidic bond formation-occur in a single series of events.…”

Synthetic Uses of Phenols

“…Suzuki and coworkers showed that the initial aryl O-glycosidation followed by a rearrangement to the C-glycoside (Oto C-glycosyl rearrangement) provides convenient access to this C−C bond formation (equation 37) 141 Cp 2 HfCl 2 -AgClO 4 reagent giving the C-glycosidated phenol at the o-position. Kometani and coworkers reported the use of BF 3 žOEt 2 for this transformation 144 . The stereochemistry of the glycosyl center is dependent on the Lewis acid, and the stronger Lewis acid Cp 2 HfCl 2 -AgClO 4 gives the thermodynamically stable β-anomer from glucopyranosides.…”

Catalysis and deactivation of montmorillonite K10 in the aryl O-glycosylation of glycosyl trichloroacetoimidates

“…Most of the time, expensive reagents are required to activate the reaction, such as trimethylsilyl trifluoromethanesulfonate (TMSOTf) [5,6], silver trifluoromethanesulfonate (AgOTf) [7], and LiClO 4 [8], and even rigid conditions are needed as well. However, due to the different reactivity between phenols and ordinary alcohols, the conventional synthesis of aryl O-glycosides by phenol glycosylations generally needs a large excess of acid catalyst and substrates [9][10][11][12], and in order to prevent the production of aryl C-glycoside by O-C glycoside rearrangement, a low temperature reaction condition is occasionally required [13,14], which makes the O-glycosylation ineffectively. To find a suitable Lewis acid catalyst is essential for developing an efficient synthesis of aryl O-glycosides.…”