Revisiting Wittig Olefination and Aza-Wittig Reaction for Carbohydrate Transformations and Stereocontrol in Sugar Chemistry

Cachatra, Vasco; Rauter, Amélia P.

doi:10.2174/1385272819666140527230833

Cited by 6 publications

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“…In particular, synthesis of tri-and tetrasubstituted alkenes in a stereoselective manner is of tremendous interest due to their presence in a plethora of natural products of biological significance as well as in material chemistry (Figure ). − The classical CC bond forming reactions such as Wittig reaction and its variants, aldol condensation, Julia olefination, McMurry coupling, etc., which involve either 1,2- or 1,4-additions and more recent metal-catalyzed reactions, are useful for the construction of complex organic frameworks. − However, CC bond forming reactions involving 1,6-addition are considerably underexplored compared to 1,2- and 1,4-additions. This is primarily due to the fact that the conjugated dienes have less positive charge density at the δ-carbon compared to that at the β-carbon.…”

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confidence: 99%

Stereoselective Synthesis of Tri- and Tetrasubstituted Olefins via 1,6-Additions of Diazo Compounds and Their Precursors to p-Quinone Methides

2021

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Reactions of para-quinone methides (p-QMs) with α-diazo-β-ketosulfones and their corresponding esters as well as simple β-dicarbonyl compounds and β-ketosulfones have been carried out under basic conditions. While the reaction of diazosulfone with p-QMs afforded trisubstituted olefins via deacylative 1,6-addition and elimination, α-diazo-β-ketoesters and various active methylene compounds such as 1,3-dicarbonyls and β-ketosulfones afforded tetrasubstituted olefins via 1,6-addition and aerial oxidation. These simple, environmentally benign, and mechanistically diverse protocols provided the products in moderate to excellent yields and selectivities.

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Section: Introductionmentioning

confidence: 99%

Stereoselective Synthesis of Tri- and Tetrasubstituted Olefins via 1,6-Additions of Diazo Compounds and Their Precursors to p-Quinone Methides

2021

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“…α,β-Unsaturated esters are often easily accessed by the reaction of the resonance-stabilized [(alkoxycarbonyl)methylene]triphenylphosphoranes with carbonyl compounds, and the reagent is frequently used in sugar elongation and the synthesis of branched-chain sugars. 1 One of the major challenges encountered in keto sugar olefination is reaction stereocontrol. The direct and regioselective oxidation of position 2 may also be quite challenging, although the synthesis of a 2-ulose from a 3,4,6-tri-O-acetyl-protected sugar was successful with Ac 2 O/ DMSO 2 but with concomitant elimination of acetic acid to give an α,β-unsaturated carbonyl compound.…”

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Wittig Reaction: Domino Olefination and Stereoselectivity DFT Study. Synthesis of the Miharamycins’ Bicyclic Sugar Moiety

et al. 2015

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2-O-Acyl protected-d-ribo-3-uloses reacted with [(ethoxycarbonyl)methylene]triphenylphosphorane in acetonitrile to afford regio- and stereoselectively 2-(Z)-alkenes in 10-60 min under microwave irradiation. This domino reaction is proposed to proceed via tautomerization of 3-ulose to enol, acyl migration, tautomerization to the 3-O-acyl-2-ulose, and Wittig reaction. Alternatively, in chloroform, regioselective 3-olefination of 2-O-pivaloyl-3-uloses gave (E)-alkenes, key precursors for the miharamycins' bicyclic sugar moiety.

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“…Examples for Wittig reactions with unprotected carbohydrates are summarized in reference [13][14][15][16][17][18][19][20][21][22][23], for reviews in this field see [24][25][26], whereas examples for Horner olefination (even in aqueous reaction medium) will be found in reference [27,28]. The reactions were carried out mostly at higher temperature.…”

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Organocatalyzed Cascade Reaction in Carbohydrate Chemistry

Mahrwald

2015

SpringerBriefs in Molecular Science

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The extensive and extremely strong development of organocatalysis over the last years provided versatile methodologies for convenient utilization of the carbonyl function of unprotected carbohydrates in C-C-bond formation processes. These biomimetic amine-activated mechanisms enable multiple cascade-protocols for the synthesis of a large scope of carbohydrate derived compound classes. Several, only slightly different protocols have been developed for the application of 1.3-dicarbonyls in stereoselective chain-elongation of unprotected carbohydrates and the synthesis of highly functionalized C-glycosides of defined configuration. Furthermore, the latter class of compounds can also be accessed by the use of methyl ketones. So a high substrate scope is available for the installation of desired functionalities in C-glycosides. By a one-pot, operationally simple cascade reaction of isocyanides with unprotected aldoses and amino acids an access to a broad range of defined glycosylated pseudopeptides is given. The elaborated organocatalyzed cascade-reactions provide defined access to highly functionalized carbohydrate derivatives. Depending on the reaction conditions different origin to control the installation of configuration during the bond-formation process were observed. The demonstrated organocatalyzed cascade sequences indicate the great potential of unprotected carbohydrates in the synthesis of highly functionalized bio-mimetic structure motifs by operationally simple, one-pot protocols.Due to the great biological importance of carbon chain elongated carbohydrates, the synthesis of this structural diverse compound class has attracted high synthetic interest from the scientific community. Among the elongated carbohydrates, C-Glycosides have gained considerable importance over the last few decades, since they are configuratively stable under enzymatic conditions and less prone to cleavage at the anomeric carbon. As such they are appealing substrates for chemical biology and medicinal chemistry.

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Revisiting Wittig Olefination and Aza-Wittig Reaction for Carbohydrate Transformations and Stereocontrol in Sugar Chemistry

Cited by 6 publications

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Stereoselective Synthesis of Tri- and Tetrasubstituted Olefins via 1,6-Additions of Diazo Compounds and Their Precursors to p-Quinone Methides

Stereoselective Synthesis of Tri- and Tetrasubstituted Olefins via 1,6-Additions of Diazo Compounds and Their Precursors to p-Quinone Methides

Wittig Reaction: Domino Olefination and Stereoselectivity DFT Study. Synthesis of the Miharamycins’ Bicyclic Sugar Moiety

Organocatalyzed Cascade Reaction in Carbohydrate Chemistry

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