Reaction of 2,3-unsaturated aryl glycosides with lewis acids : a convenient entry to C-aryl glycosides
TL;DR: In this article, a facile synthesis of 2,3-unsaturated aryl glycosides by BF 3.Et 2 O mediated O to C transformation was reported.
About: This article is published in Tetrahedron Letters.The article was published on 1992-05-19. It has received 22 citations till now. The article focuses on the topics: Aryl & Lewis acids and bases.
Citations
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TL;DR: The aryl C-glycoside structure is, among the plenty of biologically active natural products, one of the distinct motifs embedded, and the synthetic strategies and tactics employed in the total synthesis of this class of natural products.
Abstract: The aryl C-glycoside structure is, among the plenty of biologically active natural products, one of the distinct motifs embedded. Because of the potential bioactivity as well as the synthetic challenges, these structures have attracted considerable interest, and extensive research toward the total synthesis has been performed. This Review focuses on the synthetic strategies and tactics employed in the total synthesis of this class of natural products. The Introduction describes the historical background, structural features, and synthetic problems associated with aryl C-glycoside natural products. Next the Review summarizes the methods for constructing the aryl C-glycoside bonds. Completed total syntheses—and, in some cases, selected examples of incomplete syntheses—of natural aryl C-glycosides are also summarized. Finally described are the strategies for constructing polycyclic structures, which were utilized in the total syntheses.
173 citations
TL;DR: Glycals (or usually their O-substituted derivatives) are readily converted into 2,3-unsaturated glycosyl compounds with O-, C-, N-, S- or otherwise linked substituents at the anomeric position as discussed by the authors.
Abstract: Glycals (or usually their O-substituted derivatives) are readily converted into 2,3-unsaturated glycosyl compounds with O-, C-, N-, S- or otherwise linked substituents at the anomeric position. These products have been found to be useful for a range of synthetic purposes. In particular, the C-glycosidic compounds have served as readily available starting materials for the preparation of useful non-carbohydrate compounds. While these allylic rearrangement processes are usually conducted under the influence of Lewis acid catalysts, adaptations that involve activation of the allylic substituents of the starting glycals as leaving groups under neutral conditions have been developed. General features of the reactions are described as well as applications in synthesis and extensions of the basic processes.
146 citations
TL;DR: This perspective analyzes the various methods used for the activation and [1, 3] rearrangement of vinyl ethers with an emphasis on mechanism and applications to stereoselective synthesis.
Abstract: The relay of stereochemistry of a breaking C–O bond into a forming C–C bond is well-known in the context of [3, 3] sigmatropic shifts; however, this useful strategy is less well-known in other types of molecular rearrangements. Though the first successful example of a [1, 3] O-to-C rearrangement was reported more than 100 years ago, this class of reactions has received less attention than its [3, 3] counterpart. This perspective analyzes the various methods used for the activation and [1, 3] rearrangement of vinyl ethers with an emphasis on mechanism and applications to stereoselective synthesis. We also highlight our own contributions to this area.
70 citations
TL;DR: In this paper, aryl and allyl C-glycosidation methods using unprotected sugars as glycosyl donors have been developed, which are versatile synthetic intermediates for the syntheses of optically active natural products.
Abstract: Practical and highly stereoselective aryl and allyl C-glycosidation methods using unprotected sugars as glycosyl donors have been developed. Aryl C-glycosidations of several unprotected 2-deoxy sugars with phenol and naphthol derivatives by the combined use of trimethylsilyl trifluoromethanesulfonate (TMSOTf)−AgClO4 or TMSOTf exclusively gave the corresponding unprotected o-hydroxyaryl β-C-glycosides which appear in many biologically attractive aryl C-glycoside antibiotics as the key subunit. On the other hand, allyl C-glycosidations of several unprotected glycals with allyltrimethylsilane by TMSOTf afforded the corresponding unprotected and 2,3-unsaturated allyl α-C-glycosides in high yields which are versatile synthetic intermediates for the syntheses of optically active natural products.
51 citations
TL;DR: Montmorillonite K10 was found to catalyze, under microwave irradiation, rapid O-glycosidation of 3,4,6-tri-O-acetyl-d-galactal to afford exclusively the alkyl and aryl 2,3-dideoxy-dthreo-hex-2-enopyranosides with very high α-selectivity as mentioned in this paper.
46 citations
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TL;DR: In this article, a model study was carried out on three types of 2-deoxy-glycosyl acetates including amino sugar derivative, Cp 2 HfCl 2 -AgClO 4, SnCl 4, BF 3 ·OEt 2 is described.
82 citations
TL;DR: In this paper, a stereo-controlled formation of C-aryl β-d -olivoside linkage is achieved by the reaction of naphthol or anthrol derivatives with d -livosyl fluoride, the reaction is efficiently promoted by Cp 2 HfCl 2 AgClO 4 and the bond formation occurs selectively at the ortho position of the phenolic hydroxyl.
62 citations
60 citations
TL;DR: In this article, achiral precursors up to five new centers of chirality are generated in a three-step procedure, which are readily transformed into C-aryl-β-glucopyranosides and into methyl α-methoxyacrylate.
40 citations
TL;DR: In this article, a guideline to the correct assignment of the anomeric congiguration of 2,3-unsaturated C -glucopyranosides is suggested, which violates the Hudson isorotation rule.
29 citations