Cooperative Brønsted Acid-Type Organocatalysis for the Stereoselective Synthesis of Deoxyglycosides

Palo‐Nieto, Carlos; Sau, Abhijit; Williams, Ryan; Galan, M. Carmen

doi:10.1021/acs.joc.6b02498

Cited by 62 publications

(35 citation statements)

References 38 publications

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“…While the thiourea itself does not catalyse the glycosylation, it is critical in accelerating the reaction, improving the yields and α/β selectivities. This cooperativity effect was utilized by Galan et al in 2017, where the substrate scope of the glycal addition was expanded towards D -Glucal and L -Rhamnal derivatives when thiourea 4 was used in conjunction with an axial chiral BINOL based phosphoric acid catalyst 23 . Galan et al, Yoshida and Takao et al, as well as Schmidt et al contributed to thiourea catalyzed O and S -glycosylation of 2-nitroglycals 24 – 26 .…”

Section: Introductionmentioning

confidence: 99%

An ultra-low thiourea catalyzed strain-release glycosylation and a multicatalytic diversification strategy

Xu¹,

Loh²

2018

Nat Commun

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The utility of thiourea catalysis in selective glycosylation strategies has gained significant momentum lately due to its versatility in hydrogen bonding or anionic recognition activation modes. The use of these non-covalent interactions constitute a powerful means to construct glycosidic linkages as it mimics physiologically occurring glycosyltransferases. However, glycosyl donor activation through the currently employed catalysts is moderate such that, in general, catalyst loadings are rather high in these transformations. In addition, thiourea catalysis has not been well explored for the synthesis of furanosides. Herein, we demonstrate an ultra-low loadings stereoselective and stereospecific thiourea catalyzed strain-release furanosylation and pyranosylation strategy. Our ultra-low organocatalyzed furanosylation enables a multicatalytic strategy, which opens up a unique avenue towards rapid diversification of synthetic glycosides. In-situ NMR monitoring unravel insights into unknown reaction intermediates and initial rate kinetic studies reveal a plausible synergistic hydrogen bonding/Brønsted acid activation mode.

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Section: Introductionmentioning

confidence: 99%

An ultra-low thiourea catalyzed strain-release glycosylation and a multicatalytic diversification strategy

Xu¹,

Loh²

2018

Nat Commun

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“…The Schmidt group has successfully applied the synergistic catalysts (thiourea derivatives with phosphorus acids) for stereoselective O -glycoside bond formation [30]. Similarly, Galan et al reported a method for the preparation of 2-deoxyglycosides from glycals under the influence of cooperative catalysis (chiral phosphoric acids/thiourea derivatives) [31]. Encouraged by these reports and our own research interest in developing stereoselective glycosylation methods, we decided to focus our attention on the synthesis of glycosides via cooperative catalysis.…”

Section: Introductionmentioning

confidence: 99%

Electron-deficient pyridinium salts/thiourea cooperative catalyzed O-glycosylation via activation of O-glycosyl trichloroacetimidate donors

Shaw

Kumar

Thakur

2017

Beilstein J. Org. Chem.

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The glycosylation of O-glycosyl trichloroacetimidate donors using a synergistic catalytic system of electron-deficient pyridinium salts/aryl thiourea derivatives at room temperature is demonstrated. The acidity of the adduct formed by the 1,2-addition of alcohol to the electron-deficient pyridinium salt is increased in the presence of an aryl thiourea derivative as an hydrogen-bonding cocatalyst. This transformation occurs under mild reaction conditions with a wide range of O-glycosyl trichloroacetimidate donors and glycosyl acceptors to afford the corresponding O-glycosides in moderate to good yields with predictable selectivity. In addition, the optimized method is also utilized for the regioselective O-glycosylation by using a partially protected acceptor.

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“…We sought to establish whether the diphenylphosphoric acid generated as a stoichiometric by-product has any effect on the glycosylation reaction. In prior work by Schmidt and coworkers (6,(17)(18)(19), Fairbanks and coworkers (20), Toshima and coworkers (21), Nagorny and coworkers (22,23), Galan and coworkers (24), Bennett and coworkers (25), and others (26,27), phosphoric acids have been shown to be competent catalytic activators in glycosylation reactions involving different types of donors. However, in the model system, addition of exogenous diphenylphosphoric acid was shown to have no detectable effect on either reaction rate or α/β selectivity.…”

Section: Resultsmentioning

confidence: 96%

Catalytic activation of glycosyl phosphates for stereoselective coupling reactions

Levi

Rötheli

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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Glycosyl phosphates are shown to be activated to stereospecific nucleophilic substitution reactions by precisely tailored bis-thiourea catalysts. Enhanced reactivity and scope is observed with phosphate relative to chloride leaving groups. Stronger binding (Km) to the H-bond donor and enhanced reactivity of the complex (kcat) enables efficient catalysis with broad functional group compatibility under mild, neutral conditions.

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Cooperative Brønsted Acid-Type Organocatalysis for the Stereoselective Synthesis of Deoxyglycosides

Cited by 62 publications

References 38 publications

An ultra-low thiourea catalyzed strain-release glycosylation and a multicatalytic diversification strategy

An ultra-low thiourea catalyzed strain-release glycosylation and a multicatalytic diversification strategy

Electron-deficient pyridinium salts/thiourea cooperative catalyzed O-glycosylation via activation of O-glycosyl trichloroacetimidate donors

Catalytic activation of glycosyl phosphates for stereoselective coupling reactions

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