Cooperative Catalysis in Glycosidation Reactions with <i>O</i>‐Glycosyl Trichloroacetimidates as Glycosyl Donors

Geng, Yixing; Kumar, Amit; Faidallah, Hassan M.; Albar, Hassan Abdulkader; Mhkalid, Ibrahim A.; Schmidt, Richard R.

doi:10.1002/anie.201302158

Cited by 130 publications

(94 citation statements)

References 39 publications

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“…90 The same thiourea has also been employed as a catalyst for the selective addition of alcohols to glycals resulting in the formation of 2-deoxy-α-glycosides, although in this instance it is considered to function merely as a mild protic acid. 91–92 In related work chiral binol-derived phosphoric acid catalysts have been employed to promote cyclization of 1-(γ-hydroxypropyl)glycals and their homologs to spiroketals.…”

Section: Counterion and Additive Effectsmentioning

confidence: 99%

A propos of glycosyl cations and the mechanism of chemical glycosylation; the current state of the art

Bohé

Crich

2015

Carbohydrate Research

126

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An overview of recent advances in glycosylation with particular emphasis on mechanism is presented. The mounting evidence for both the existence of glycosyl oxocarbenium ions as fleeting intermediates in some reactions, and the crucial role of the associated in counter ion in others is discussed. The extremes of the SN1 and SN2 manifolds for the glycosylation reaction are bridged by a continuum of mechanisms in which it appears likely that most examples are located.

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Section: Counterion and Additive Effectsmentioning

confidence: 99%

A propos of glycosyl cations and the mechanism of chemical glycosylation; the current state of the art

Bohé

Crich

2015

Carbohydrate Research

126

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“…Despite the broad application of cooperative catalysis, it is still uncommonly employed in the area of carbohydrate chemistry, especially for glycosylation reactions, due to the prerequisite of having both catalysts being compatible under the reaction conditions. 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].…”

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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“…24 Although the original study reported 6-dEB production titers as high as 129 mg/L in shake flask fermentation experiments, we were unable to reproduce these yields under the same conditions, typically acquiring ~5 mg/L of isolated material. Furthermore, quantification of 6-dEB production by LC-MS prior to culture extraction revealed that the low isolated yields were not due to loss of material from downstream workup, isolation, and purification procedures.…”

Section: Resultsmentioning

confidence: 87%

Regiodivergent Glycosylations of 6-Deoxy-erythronolide B and Oleandomycin-Derived Macrolactones Enabled by Chiral Acid Catalysis

et al. 2017

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This work describes the first example of using chiral catalysts to control site-selectivity for the glycosylations of complex polyols such as 6-dEB and oleandomycin-derived macrolactones. The regiodivergent introduction of sugars at the C3, C5 and C11 positions of macrolactones was achieved by selecting appropriate chiral acids as catalysts or through introduction of stoichiometric boronic acid-based additives. The BINOL-based CPAs were used to catalyze highly selective glycosylations at the C5 positions of macrolactones (up to 99:1 rr) whereas the use of SPINOL-based CPAs resulted in selectivity switch and glycosylation of the C3 alcohol (up to 91:9 rr). Additionally, the C11 position of macrolactones was selectively functionalized through traceless protection of the C3/C5 diol with boronic acids prior to glycosylation. The investigation of the reaction mechanism for the CPA-controlled glycosylations revealed the involvement of covalently linked anomeric phosphates rather than oxocarbenium ion pair as the reactive intermediates.

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Cooperative Catalysis in Glycosidation Reactions with O‐Glycosyl Trichloroacetimidates as Glycosyl Donors

Cited by 130 publications

References 39 publications

A propos of glycosyl cations and the mechanism of chemical glycosylation; the current state of the art

A propos of glycosyl cations and the mechanism of chemical glycosylation; the current state of the art

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

Regiodivergent Glycosylations of 6-Deoxy-erythronolide B and Oleandomycin-Derived Macrolactones Enabled by Chiral Acid Catalysis

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