Préparation de dérivés de sucres acétyléniques terminaux et d'acides ynuroniques par réaction de Wittig. Note de laboratoire

Abstract

The method described for the preparation of terminal acetylenic sugars presents two advantages over earlier procedures: no new asymmetric center is created and the chain can be extended by one or more C-atoms. The method also allows preparation of ynuronic acids. The aldehydosugars derivatives 1-7 gave in good to excellent yields the corresponding gem-dibromoenoses 8-14 from which either the terminal acetylenic sugars derivatives 15-21 or the ynuronic acids 22-24 were easily prepared. A few examples of 1,3-dipolar cycloadditions (leading to 28-30) with these acetylenic sugar derivatives are also described.

Synthesis of 1,4‐Disubstituted 1,2,3‐Triazoles from Terminal Vinyl Sulfones in Ionic Liquid: A Metal‐Free Eliminative Azide‐Olefinic Cycloaddition Route to Triazolyl Carbohydrates and Triazole‐linked Bissaccharides

“…For example, sugar derived alkynes are normally prepared by reacting sugar aldehydes with the variation of Witting reactions followed by elimination by strong bases. [17] Recently employed Ohira-Bestmann reagent (dimethyl diazomethyl phosphonate), by far the most efficient strategy for one step conversion of aldehydes employed is "sufficiently expensive"; [18] this issue also needs to be taken into consideration while scaling up reactions for the synthesis of starting materials. Interestingly, a perusal of the literature reveals that for CuAAC based synthesis of 1,4-DT modified carbohydrates, azidosugars are most often reacted with non-sugar alkynes and alternatively the triazole ring is generated far away from the sugar ring by using propargylated sugars instead of sugar alkynes.…”

“…However, methods related to the synthesis of terminal alkynes from complex or polyfunctionalized molecules are more difficult to access. For example, sugar derived alkynes are normally prepared by reacting sugar aldehydes with the variation of Witting reactions followed by elimination by strong bases [17] . Recently employed Ohira‐Bestmann reagent (dimethyl diazomethyl phosphonate), by far the most efficient strategy for one step conversion of aldehydes employed is “sufficiently expensive”; [18] this issue also needs to be taken into consideration while scaling up reactions for the synthesis of starting materials.…”

Synthesis, structure and pyrolysis of stabilised phosphonium ylides containing saturated oxygen heterocycles

“…10 In this paper we describe the preparation and pyrolysis behaviour of a series of ylides containing tetrahydrofuran, tetrahydropyran and 2,2-dimethyl-1,3-dioxolane rings to check the compatibility of these ring systems common in carbohydrates with the conditions required for alkyne formation. There has been considerable interest in acetylenic carbohydrate derivatives, both in their own right, 11 and as intermediates in synthesis of modified nucleosides. 12,13 Alkyne-containing 2,2-dimethyl-1,3-dioxolanes have also found use in total synthesis.…”