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Journal ArticleDOI

A new ferrier system: 2-C-acetoxymethylglycals. A covenient entry to 2-C-methylene glycosides

01 Jan 1993-Journal of The Chemical Society, Chemical Communications (The Royal Society of Chemistry)-Iss: 18, pp 1394-1395
Abstract: Syntheis of tri-O-benzyl-2-C-acetoxymethylglycals and subsequent Ferrier rearangement to give 2-C-methylene glycosides is described.

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Topics: Ferrier rearrangement (73%), Glycal (54%), Aldose (50%)
Citations
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Journal ArticleDOI
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.

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96 citations


Journal ArticleDOI
TL;DR: An efficient approach for the synthesis of a variety of C-aryl and spiro-C-aryl glycosides is described, which relies on a sequential enyne metathesis to generate the 1,3-diene moiety and Diels-Alder reaction with different dienophiles followed by aromatisation.

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Abstract: An efficient approach for the synthesis of a variety of C-aryl and spiro-C-aryl glycosides is described. This diversity-oriented strategy employed here relies on a sequential enyne metathesis to generate the 1,3-diene moiety and Diels–Alder reaction with different dienophiles followed by aromatisation. Whereas cross-enyne metathesis with ethylene gas is used to install the 1,3-diene moiety at the anomeric centre for the synthesis of C-aryl glycosides, an intramolecular enyne metathesis on the sugar enyne is performed to generate the 1,3-diene moiety for the synthesis of spiro-C-aryl glycosides. Efforts to extend this strategy to the synthesis of the core structure of natural C-aryl glycoside gilvocarcin are also described. A combination of both C-aryl and spiro-C-aryl glycosides in the same moiety to combine the features thereof has also been accomplished. A tandem enyne metathesis/Diels–Alder reaction/aromatisation has also been attempted to directly access the C-aryl glycosides in one pot albeit in low yield.

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52 citations


Journal ArticleDOI
Russell J. Hewitt1, Joanne E. Harvey1Institutions (1)
TL;DR: The conversion of cyclopropane-fused carbohydrates into oxepines is an attractive method for accessing diverse members of the septanoside family of carbohydrate mimetics, and 2-Bromooxepines are obtained through silver(I)-promoted thermal ring expansion of a d-glucal-derived gem-dihalocyclopropanated sugar.

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Abstract: The conversion of cyclopropane-fused carbohydrates into oxepines is an attractive method for accessing diverse members of the septanoside family of carbohydrate mimetics. 2-Bromooxepines are obtained through silver(I)-promoted thermal ring expansion of a d-glucal-derived gem-dihalocyclopropanated sugar. In contrast, cyclopropane ring cleavage under basic conditions leads to 2-C-branched pyranosides, not the 2-bromooxepine structures assigned in an earlier report.

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45 citations


Journal ArticleDOI
Abstract: Naturally occurring carbohydrates and their derivatives have been useful during the last few decades as “chiral pool” constituents in the enantioselective synthesis of biologically active natural and non-natural products. The ready availability of a wide range of carbohydrates in nature and their multichiral architecture, coupled with their well defined stereochemistry, make them attractive starting materials in organic synthesis. The synthesis of key intermediates by incorporation of suitable functional groups onto carbohydrates, which can then be further exploited, has always been a challenging task. In this context, 2-C-formyl glycals, a new class of carbohydrates incorporating an α,β-unsaturated carbonyl system, have recently emerged as potential synthons for numerous organic transformations. Four different syntheses of 2-C-formyl glycals have been reported so far. However, the importance of 2-C-formyl glycals has become well established after our development of a more general, one-step synthesis, employing the well known Vilsmeier−Haack reaction. Synthetic transformations of these 2-C-formyl glycals have resulted in a variety of new compounds of significant synthetic and biological interest. 2-C-Formyl glycals have been shown to be ideal substrates for chemo-, regio- and stereoselective glycosidation, nucleophilic addition/substitution and cycloaddition reactions. The reported syntheses and applications of these important “chiral intermediates” are presented. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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41 citations


Reference EntryDOI
Robert J. Ferrier1, Oleg A. Zubkov1Institutions (1)
15 Apr 2004-Organic Reactions
TL;DR: Various elimination procedures conducted on appropriate pyranoid and furanoid carbohydrate derivatives, especially on O-protected glycosyl halides afford cyclic vinyl ethers which Fischer (inappropriately) named glycals, form the major part of this chapter.

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Abstract: Various elimination procedures conducted on appropriate pyranoid and furanoid carbohydrate derivatives, especially on O-protected glycosyl halides afford cyclic vinyl ethers which Fischer (inappropriately) named glycals. These are used extensively in general organic synthesis and for the preparation of non-carbohydrate natural products as well as biologically important complex carbohydrates and glycoconjugates. The best known member, tri-O-acetyl-D-glucal, is normally made from tetra-O-acetyl-alpha-D-glucopyranosyl bromide, is commercially available, and is used very frequently in this chapter to represent the family in examples of the reactions under discussion. Because of the pronounced region- and stereoselectivities with which their addition reactions can be conducted, glycal derivatives are of major importance in synthesis. They also, however, take part in rearrangement processes that, likewise, have proved useful for synthesis. The principal one involves nucleophilic substitution of the allylic group with allylic rearrangement and results in products having double bonds in the 2, 3 positions and new substituents at the anomeric centers. By far the simplest and most commonly used way to this conversion involves the removal of the allylic substituent of the glycal and the generation of highly resonance-stabilized oxocarbenium ion intermediate. This may then react with nucleophiles at the anomeric center to give products as mixtures of diastereomers. Many examples and variations of this theme are described and form the major part of this chapter, but other ways are also considered Almost no formal mechanistic studies have been carried out on the reactions in this chapter. Categorization of mechanism required for the treatment of this topic has been done on the basis of conditions used, product identification and largely, chemical intuition. Keywords: glycals; transformation; oxocarbenium ions; regioselectivity; diasterioselectivity; nucleophilic substitutions; homoallylic center; addition-elimination reactions; palladium; leaving groups; electrocyclic reactions; unsaturated compounds; free sugars; glycosyl peroxides; glycosyl caroxylates; S-glycosides; glycosyl halides; glycosyl azides; glycosyl phosphonates; glycosyl hydrides; furanoid glycols; intramolecular applications; reverse reaction; reaction variations; scope; limitations; configuration; experimental procedures; other methods

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35 citations


References
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Journal ArticleDOI
TL;DR: DMDC as well as 2'-deoxy-2'-methylidene-5-fluorocytidine (19a) showed potent antileukemic activity against murine L 1210 cells in culture and in vivo antitumor activity of DMDC against L1210 was also described.

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Abstract: A new type of antineoplastic nucleoside, 2'-deoxy-2'-methylidenecytidine (DMDC) has been synthesized from the corresponding 2'-keto pyrimidine nucleosides 3 and 8 by the Wittig reaction. During the course of the reaction, we found that an intermediate betaine could pick a proton from the excess triphenylphosphonium bromide to form the 2'-phosphonium salts 5 and 10, which could be further converted into the 2'-deoxy-2'-methylidene nucleosides 4 and 9 by treatment with sodium hydride. Various 5-substituted DMDC derivatives 19a-e,h and their uracil congeners 16a-h were also synthesized from the corresponding 5-substituted uridines 12a-f,h. Among them, DMDC as well as 2'-deoxy-2'-methylidene-5-fluorocytidine (19a) showed potent antileukemic activity against murine L1210 cells in culture. The activity of DMDC and 19a toward various human tumor cells in culture compared with 1-beta-D-arabinofuranosylcytosine and 5-fluorouracil was also examined. In vivo antitumor activity of DMDC against L1210 was also described.

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85 citations


Journal ArticleDOI
Abstract: 3,4,6-Tri- O -acetyl- d -galactal, on treatment in 1,2-dichloroethane with alcohols and stannic chloride as catalyst, readily undergoes allylic rearrangement-substitution, forming alkyl 4,6-di- O -acetyl-2,3-dideoxy-α- d - threo -hex-2-enopyranosides in yields of 43-92%. Alkyl 3,4,6-tri- O -acetyl-2-deoxy-αβ- d - lyxo -hexopyranosides are formed as side-products in yields of 2-14 %. Stannic chloride-catalysis is also useful in allylic rearrangement of 3,4,6-tri- O -acetyl-1,5-anhydro-2-deoxy- d - arabino - hex-l-enitol (3,4,6-tri- O -acetyl- d -glucal) which, with methanol or ethanol, affords the corresponding alkyl 4,6-di- O -acetyl-2,3-dideoxy-α- d - erythro -hex-2-enopyranosides in yields of 83 and 94%.

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73 citations


Journal ArticleDOI
Abstract: Reaction of nitrosyl chloride with acetylated glycals affords, with a high degree of stereospecificity, dimeric acetylated 1,2-cis-2-deoxy-2-nitroso-α-D-aldopyranosyl chlorides. Reaction of acetylated glycals with dinitrogen tetroxide, depending on the reaction conditions, can give either acetylated 2-deoxy-2-nitroso-α-D-aldopyranosyl nitrates as dimers or acetylated 2-nitroglycals. The mechanisms of these reactions are discussed.

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52 citations


Journal ArticleDOI
TL;DR: A short and straightforward route has been accomplished for the synthesis of C-2-formyl glycals by a Vilsmeier-Haack reaction of glycals.

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Abstract: A short and straightforward route has been accomplished for the synthesis of C-2-formyl glycals by a Vilsmeier-Haack reaction of glycals.

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51 citations