Gold(III)-Catalyzed Glycosylation using Phenylpropiolate Glycosides: Phenylpropiolic Acid, An Easily Separable and Reusable Leaving Group

Abstract

An efficient and operationally simple gold­(III)-catalyzed glycosylation protocol was developed using newly synthesized benchtop stable phenylpropiolate glycosyl (PPG) donors. Gold­(III)-catalyzed activation of PPGs proceeds well with various carbohydrate and noncarbohydrate-based glycosyl acceptors and leads to their corresponding O/N-glycosides in good to excellent yields with regeneration of reusable and easily separable phenylpropiolic acid. Differentially protected PPGs reacted well under the optimized reaction conditions. In particular, good anomeric selectivity was observed with mannosyl and rhamnosyl PPG donors. A preliminary mechanistic study reveals that the presence of a triple bond adjacent to the ester group is essential for activation, and PPG-based donor shows higher reactivity than analogous acetate and benzoate donors.

Monitoring of the Pre-Equilibrium Step in the Alkyne Hydration Reaction Catalyzed by Au(III) Complexes: A Computational Study Based on Experimental Evidences

“…In fact, the high reduction potential of Au(III) makes it very unstable in solution. Au(III) easily tends to reduce to Au(I) or Au(0) if electron-rich species are present in the reaction environment [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. On the other hand, the ligands that completely stabilize the charge of the metal generate a catalytically non-active complex [ 34 ].…”

Gold(I)-Catalyzed Glycosylation with Glycosyl Ynenoates as Donors

“…In the search of popular glycosylation methods, gold-catalyzed glycosylation with alkyne-containing glycosides as donors was widely investigated due to the unique catalytic mechanism . In 2008, Yu et al reported the gold­(I)-catalyzed glycosylation with glycosyl ortho -alkynylbenzoates as donors .…”

Additive‐Free Gold(III)‐Catalyzed Stereoselective Synthesis of 2‐Deoxyglycosides Using Phenylpropiolate Glycosides as Donors

“…[20] With these understanding and continuation of our own research interest on the development of as ustainable approach for the stereoselective glycoside bond formation, [21] we applied phenylpropiolate glycosides for the directa nd stereoselective synthesis of 2-deoxyglycopyranosides under the mild and additive-free catalytic system and ultimately regenerate the leaving group (Scheme 1e). [20] With these understanding and continuation of our own research interest on the development of as ustainable approach for the stereoselective glycoside bond formation, [21] we applied phenylpropiolate glycosides for the directa nd stereoselective synthesis of 2-deoxyglycopyranosides under the mild and additive-free catalytic system and ultimately regenerate the leaving group (Scheme 1e).…”

“…Very recently, we have introduced phenylpropiolate glycosides (PPGs) as glycosyl donors for making O‐glycosidic bonds . With these understanding and continuation of our own research interest on the development of a sustainable approach for the stereoselective glycoside bond formation, we applied phenylpropiolate glycosides for the direct and stereoselective synthesis of 2‐deoxyglycopyranosides under the mild and additive‐free catalytic system and ultimately regenerate the leaving group (Scheme e).…”