Cross-metathesis reaction of α- and β-vinyl C-glycosides with alkenes

Abstract

SummaryCross-metathesis of α- and β-vinyl C-deoxyribosides and α-vinyl C-galactoside with various terminal alkenes under different conditions was studied. The cross-metathesis of the former proceeded with good yields of the corresponding products in ClCH2CH2Cl the latter required the presence of CuI in CH2Cl2 to achieve good yields of the products. A simple method for the preparation of α- and β-vinyl C-deoxyribosides was also developed. In addition, feasibility of deprotection and further transformations were briefly explored.

Intramolecular and Ferrier Rearrangement Strategy for the Construction of C1‐β‐d‐xylopyranosides: Synthesis, Mechanism and Biological Activity Study

“…Although lots of transitional metal‐catalyzed cross coupling including Heck, Suzuki, Stille and Negishi‐type reactions have been developed for the synthesis of C‐glycosides using glycals, the functional regioselectivity and α / β stereoselectivity at the anomeric carbon constitute are still one of the most challenging issues in carbohydrate chemistry . For example, Ernest's group utilized Pd 0 ‐mediated cyclo‐etherification of 1‐acetoxy‐2,3‐dideoxy‐oct‐2‐enitols to produce C‐vinyl α ‐ and β ‐glycopyranosides with high stereoselectivity using ( S , S ) or ( R , R )‐DACH ligands in 2014 (Scheme ), and then Martin's group produced epimeric mixture of C‐vinyl deoxyriboside by the Lindlar hydrogenation of the epimeric mixture of C‐ethynyl deoxyriboside . Liu's group reported a palladium‐catalyzed one‐pot Tsuji‐Trost type decarboxylative allylation/Wittig reaction to synthesize β ,( E )‐selective C‐vinyl glycosides with pyridyl group containing aldehydes and β ,( Z )‐selective C‐vinyl glycosides with nonpyridyl aldehydes in 2017, which had potential to be applied in synthesizing C‐vinyl glycosides in high efficiency with controlled diastereoselectivity …”

“…[8] Generally, C-glycosylation reactions can involve glycosyl electrophilic/cationic species, anionic species, radical species, or transition-metal complexes. [12] Liu's group reported a palladium-catalyzed one-pot Tsuji-Trost type decarboxylative allylation/Wittig reaction to synthesize b,(E)-selective C-vinyl glycosides with pyridyl group containing aldehydes and b,(Z)selective C-vinyl glycosides with nonpyridyl aldehydes in 2017, which had potential to be applied in synthesizing C-vinyl glycosides in high efficiency with controlled diastereoselectivity. [9] Although lots of transitional metal-catalyzed cross coupling including Heck, Suzuki, Stille and Negishi-type reactions have been developed for the synthesis of C-glycosides using glycals, the functional regioselectivity and a/b stereoselectivity at the anomeric carbon constitute are still one of the most challenging issues in carbohydrate chemistry.…”

“…[10] For example, Ernest's group utilized Pd 0mediated cyclo-etherification of 1-acetoxy-2,3-dideoxy-oct-2-enitols to produce C-vinyl a-and bglycopyranosides with high stereoselectivity using (S,S) or (R,R)-DACH ligands in 2014 (Scheme 1), [11] and then Martin's group produced epimeric mixture of C-vinyl deoxyriboside by the Lindlar hydrogenation of the epimeric mixture of C-ethynyl deoxyriboside. [12] Liu's group reported a palladium-catalyzed one-pot Tsuji-Trost type decarboxylative allylation/Wittig reaction to synthesize b,(E)-selective C-vinyl glycosides with pyridyl group containing aldehydes and b,(Z)selective C-vinyl glycosides with nonpyridyl aldehydes in 2017, which had potential to be applied in synthesizing C-vinyl glycosides in high efficiency with controlled diastereoselectivity. [13] For facial construction of synthetically valuable complex C-glycosides, the intramolecular rearrangements including Claisen rearrangement, Ramberg-Bä cklund rearrangement, and 1,2-Wittig rearrangement have become powerful tools for the C-glycosylations.…”

“…This positive result promoted us to further search more appropriate catalyst to improve the efficiency of the reaction, and then the gold (I) complex and silver (I) salts could catalyze the reaction in comparative yields (entries 8-10). To our surprise, we found that the combined catalytic system exhibited superior to the single catalyst (entries [11][12][13][14]. Therefore, Ph 3 PAuCl and AgSbF 6 system was selected as the best catalyst for the high yield of 58% yields, and further optimization of solvent contributed to improve the yield of 3 a in 75% yields ( Table 1, entries [14][15][16][17][18][19][20].…”

C‐Glycosyl Styrene Type Compounds by Pd‐Catalyzed Cross‐Coupling Reactions of Anhydro‐Aldose Tosylhydrazones with Benzyl Bromides

“…In other syntheses the construction of the C=C bond in styrenes F are realized in one step: dehydration reaction of O ‐perbenzylated or O ‐peracetylated 1‐phenyl‐2‐(β‐ d ‐glucopyranosyl)ethanol H , prepared from free aldoses in three‐step reactions or the Julia olefination of the O ‐perbenzylated β‐ C ‐glucopyranosyl aldehyde I resulted in C ‐glycopyranosyl styrenes F . Another possibility is the formation of the C=C bond in a cross‐metathesis reaction between a vinyl α‐ C ‐ d ‐galactopyranoside J with alkenes in the presence of Hoveyda‐Grubbs II catalyst and CuI …”