Microwave-induced, Montmorillonite K10-catalyzed Ferrier rearrangement of tri-O-acetyl-d-galactal: mild, eco-friendly, rapid glycosidation with allylic rearrangement
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.
Abstract: 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-d-threo-hex-2-enopyranosides with very high α-selectivity and without the formation of the 2-deoxy-d-lyxo-hexopyranosides. Under these conditions, 3,4,6-tri-O-acetyl-d-glucal as usual also underwent the Ferrier rearrangement.
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TL;DR: Perchloric acid supported on silica gel acts as an excellent reagent system in converting glucals into 2,3-unsaturated-O-glucosides in good to excellent yields in short reaction time with good alpha selectivity.
Abstract: Perchloric acid supported on silica gel acts as an excellent reagent system in converting glucals into 2,3-unsaturated-O-glucosides in good to excellent yields in short reaction time with good a selectivity. Primary, secondary, and allylic alcohols, phenols, and thiols react with 3,4,6-tri-O-acetyl glucal with equal ease. In addition to this, a chiral furan diol is obtained from unprotected D-glucal or D-galactal in good yields.
109 citations
TL;DR: A review of recent developments in the use of promoters for the Ferrier rearrangement of O-, N-, C- and S-nucleophiles with glycals can be found in this paper.
Abstract: Glycals (1,2-unsaturated, cyclic carbohydrate derivatives) readily undergo (catalyzed) substitution reactions at C-1 accompanied by allylic rearrangement. This reaction, currently named Ferrier rearrangement, or the Ferrier I reaction, has established itself as a useful synthetic tool for carbohydrate transformations. By means of this reaction, glycals can be converted into highly useful 2,3-unsaturated glycosides. This review summarizes recent developments in the use of promoters for the Ferrier rearrangement of O-, N-, C- and S-nucleophiles with glycals.
96 citations
TL;DR: This Review will focus on the key developments towards chemical O‐glycosylations in the current century, including synthesis of novel glycosyl donors and acceptors and their unique activation for successful glycosidic bonds.
Abstract: The development of glycobiology relies on the sources of particular oligosaccharides in their purest forms. As the isolation of the oligosaccharide structures from natural sources is not a reliable option for providing samples with homogeneity, chemical means become pertinent. The growing demand for diverse oligosaccharide structures has prompted the advancement of chemical strategies to stitch sugar molecules with precise stereo- and regioselectivity through the formation of glycosidic bonds. This Review will focus on the key developments towards chemical O-glycosylations in the current century. Synthesis of novel glycosyl donors and acceptors and their unique activation for successful glycosylation are discussed. This Review concludes with a summary of recent developments and comments on future prospects.
69 citations
TL;DR: In this paper, a novel glycal-based O-glycosylation reaction, in which the substrates are not only peracetyl glycals but also perbenzyl glucals to afford the corresponding 2,3-unsaturated-O-glucosides via Ferrier rearrangement, was developed.
Abstract: We have developed a novel glycal-based O-glycosylation reaction, in which the substrates are not only peracetyl glycals but also perbenzyl glucals to afford the corresponding 2,3-unsaturated-O-glycosides via Ferrier rearrangement. The reaction of the perbenzyl glucal with various alcohols catalyzed by ferric sulfate hydrate (Fe2(SO4)3·xH2O) was successfully carried out to give 2,3-unsaturated d-O-glucosides with exclusive α-selectivity and no formation of addition products 2-deoxy hexopyranosides was observed. It is the first report on peralkyl glycal efficiently undergoing Ferrier rearrangement instead of addition of alcohols catalyzed by Lewis acids. Fe2(SO4)3·xH2O is an effective, convenient, and environmentally benign heterogeneous catalyst. It has low catalytic loading and recyclable without significant loss of activity.
66 citations
TL;DR: In this article, the application of clay catalyssts in ORGANIC SYNTHESIS is discussed. And a review of the application can be found in the Appendix.
Abstract: (2008). APPLICATION OF CLAY CATALYSTS IN ORGANIC SYNTHESIS. A REVIEW. Organic Preparations and Procedures International: Vol. 40, No. 1, pp. 1-65.
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References
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941 citations
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12 Oct 1994
TL;DR: This chapter discusses the history and applications of the Anomeric Effect in Organic Synthesis, and some of the applications can be found in the literature on endoelectronic effects of the anomeric effect.
Abstract: Historical Aspects and Definitions Origin and Consequences of the Anomeric Effect Theoretical Studies of the Anomeric Effect Stereoelectronic Effects Associated with the Anomeric Effect Endo and Exo Anomeric Interactions The Enthalpic Anomeric Effect Second- and Lower-Row Anomeric Interactions The Reverse Anomeric Effect The Kinetic Anomeric Effect Applications of the Anomeric Effect in Organic Synthesis
236 citations
TL;DR: Tri-O-acetyl-D-glucal undergoes complete reaction with alcohols in benzene solution in the presence of boron trifluoride to give 4,6-di-OðOðAðEðDÞÞ −2,3-dideoxy-α-DÒÞ−EðE Þ−hex-hex-2-enopyranosyl as discussed by the authors, which can be used to prepare the known crystalline ethyl αglucoside easily and in greatly improved
Abstract: Tri-O-acetyl-D-glucal undergoes complete reaction with alcohols in benzene solution in the presence of boron trifluoride to give 4,6-di-O-acetyl-2,3-dideoxy-D-erythro-hex-2-enopyranosides. The α-anomers predominate (ca. 90%), and the method can be used to prepare the known crystalline ethyl α-glucoside easily and in greatly improved yield. Other alkyl glycosides have been prepared similarly, and the procedure has afforded means of obtaining the cholesteryl analogue and the disaccharide derivative 6-O-(4,6-di-O-acetyl-2,3-dideoxy-α-D-erythro-hex-2-enopyranosyl)-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose. Tri-O-acetyl-D-glucal again gave the 2,3-unsaturated glycosides on treatment with acetals in the presence of boron trifluoride; no evidence was obtained for the formation of branched-chain products produced by additions to the double bond.
175 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.
141 citations