Direct Synthesis of Diastereomerically Pure Glycosyl Sulfonium Salts

Mydock, Laurel K.; Kamat, Medha N.; Demchenko, Alexei V.

doi:10.1021/ol2009818

Cited by 38 publications

(52 citation statements)

References 43 publications

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“…One of the most stable sulfonium ions among those mentioned above is the one prepared from the "superdisarmed" glycosyl donor 23 reported by Demchenko and co-workers (Fig. 6) (21). As can be seen, this sulfonium ion 24 satisfies the following three factors required to stabilize sulfonium ions.…”

Section: Stability and Reactivity Of Glycosyl Sulfonium Ionsmentioning

confidence: 77%

“…Demchenko and co-workers prepared the stable β-sulfonium ion 24 by the direct alkylation of β-ethyl-thioglycoside 23 using methyl triflate (MeOTf) as an alkylating reagent ( Fig. 4f) (21). Although this direct method enables us to access an isolable sulfonium ion 24 from a stable thioglycoside 23, the "superdisarmed" glycosyl donor, which has 2-O-benzyl, 3,4,6-tri-O-benzoyl protecting groups, is crucial.…”

Section: B Preparation Of Glycosyl Sulfonium Ionsmentioning

confidence: 99%

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Sulfonium Ions as Reactive Glycosylation Intermediates

Nokami

2012

TIGG

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Glycosyl sulfonium ions are positively charged organosulfur compounds having the positive charge on a sulfur atom that is covalently attached to the anomeric carbon. These species have received attention because of their potential as glycosylation intermediates. Recently, novel methods for the preparation of glycosyl sulfonium ions have been reported. The reactivity of glycosyl sulfonium ions can be controlled by changing the substituents on the sulfur atom and the protecting groups of the hydroxyl groups. Recent studies have also shown that glycosyl sulfonium ions are unique glycosylation intermediates that have modifiable reactivity.

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Section: Stability and Reactivity Of Glycosyl Sulfonium Ionsmentioning

confidence: 77%

Section: B Preparation Of Glycosyl Sulfonium Ionsmentioning

confidence: 99%

Sulfonium Ions as Reactive Glycosylation Intermediates

Nokami

2012

TIGG

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“…46 Besides the issue of coupling efficiency, the α-selectivity of some modulated glycosylation methods is inconsistent in different settings as exemplified by the thioether-modulated glycosylations. 41,42,49 The inconsistency implies that the selectivities of the modulated glycosylation methods are kinetic controlled, thus depends on multiple factors such as procedure, solvent system, temperature, etc. Modification of even one of these factors would change the reaction mechanism leading to erosion of reaction selectivity.…”

Section: Outlook and Conclusionmentioning

confidence: 99%

Modulating glycosylation with exogenous nucleophiles: an overview

et al. 2014

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“…Methanolysis of this compound was completed within 15 min to give only the α -glucoside without a need for a promoter. 7 …”

Section: Introductionmentioning

confidence: 99%

Mechanism of Glycosylation of Anomeric Sulfonium Ions

Fang

Huang

et al. 2016

J. Am. Chem. Soc.

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Anomeric sulfonium ions are attractive glycosyl donors for the stereoselective installation of 1,2-cis glycosides. Although these donors are receiving increasing attention, their mechanism of glycosylation remains controversial. We have investigated the reaction mechanism of glycosylation of a donor modified at C-2 with a (1S)-phenyl-2-(phenylsulfanyl)ethyl chiral auxiliary. Preactivation of this donor results in the formation of a bicyclic β-sulfonium ion that after addition of an alcohol undergoes 1,2-cis-glycosylation. To probe the importance of the thiophenyl moiety, analogs were prepared in which this moiety was replaced by an anisoyl or benzyl moiety. Furthermore, the auxiliaries were installed as S- and R-stereoisomers. It was found that the nature of the heteroatom and chirality of the auxiliary greatly influenced the anomeric outcome and only the one containing a thiophenyl moiety and having S-configuration gave consistently α-anomeric products. The sulfonium ions are sufficiently stable at a temperature at which glycosylations proceed indicating that they are viable glycosylation agents. Time-course NMR experiments with the latter donor showed that the initial rates of glycosylations increase with increases in acceptor concentration and the rate curves could be fitted to a second order rate equation. Collectively, these observations support a mechanism by which a sulfonium ion intermediate is formed as a trans-decalin ring system that can undergo glycosylation through a bimolecular mechanism. DFT calculations have provided further insight into the reaction path of glycosylation and indicate that initially a hydrogen-bonded complex is formed between sulfonium ion and acceptor that undergoes SN2-like glycosylation to give an α-anomeric product.

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Direct Synthesis of Diastereomerically Pure Glycosyl Sulfonium Salts

Cited by 38 publications

References 43 publications

Sulfonium Ions as Reactive Glycosylation Intermediates

Sulfonium Ions as Reactive Glycosylation Intermediates

Modulating glycosylation with exogenous nucleophiles: an overview

Mechanism of Glycosylation of Anomeric Sulfonium Ions

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