Perfluorophenylboronic acid-catalyzed direct α-stereoselective synthesis of 2-deoxygalactosides from deactivated peracetylated d-galactal

Abstract

Perfluorophenylboronic acid 1c catalyzes the direct stereoselective addition of alcohol nucleophiles to deactivated peracetylated d-galactal 2 to give 2-deoxygalactosides 4a–o, 6a–11a in 55–88% yield with complete α-selectivity.

Copper-Catalyzed Stereoselective Synthesis of 2-Deoxygalactosides

“…In addition, its synthetic potential was successfully demonstrated in gram-scale reaction and by a simple synthesis of oligosaccharides. It should be pointed out that the reaction may result from various processes: 25,26 Cu-alcohol-complexes that lower the pK a of the alcohol components is the most likely, but 'hidden acid catalysis' (i.e., hydrolysis/alcoholysis of the salt), acid impurities in the salt used, or bromine formation from CuBr 2 may also be operating. (1) TBAF/THF…”

Anion‐Bridged Dual Hydrogen Bond Enabled Concerted Addition of Phenol to Glycal

“…To date, three strategies have been employed to construct phenolic 2‐deoxyglycosides, which involve arylation of anomeric hydroxyl groups, [ 5 ] nucleophilic substitution of glycosyl donors containing leaving groups at anomeric center, [ 2 , 6 ] and direct addition of phenol to glycals. [ 7 ] (Figure 1B ). While the former two strategies were capable of producing the desired compounds, the major drawback of these strategies is the need to synthesize the glycosyl donor in multiple steps, which involves introducing and removing auxiliary functional groups such as halo and chalcogen atoms, making them time‐consuming and producing substantial reagent waste.…”

Stereoselective Synthesis of O-Glycosides with Borate Acceptors

“…10 Organoboronic acids were utilized by Judeh and co-workers to catalyze O-glycosylation with alcohols and phenols as acceptors and hemiacetals were obtained as side products (Scheme 1b). 11 Borate esters have been widely exploited in organic synthesis as starting materials, reagents, and catalysts, especially as coupling partners. 12 As shown in Scheme 1c, borate esters demonstrated high reactivity and reacted with four-membered heterocyclic rings directly to form new C−O and C−C bonds without the requirement of transition-metal catalysis, 13 but their application in glycosylation was quite rare.…”

“…Galan and McGarrigle reported an observation of mixed products 2-deoxy O -glycosides and 2,3-unsaturated O -glycosides, which was catalyzed by p -toluenesulfonic acid using alcohols as acceptors and glycal donors without a trans -fused cyclic 3,4- O -disiloxane protecting group (Scheme a) . Organoboronic acids were utilized by Judeh and co-workers to catalyze O -glycosylation with alcohols and phenols as acceptors and hemiacetals were obtained as side products (Scheme b) . Borate esters have been widely exploited in organic synthesis as starting materials, reagents, and catalysts, especially as coupling partners .…”