Showing papers on "Glycal published in 1995"
70 citations
49 citations
49 citations
TL;DR: In this paper, a transformation involving a 6-aryl "exo" glycal is used to prepare the target structures from carbohydrate starting materials, which is called exo-exo transformation.
30 citations
TL;DR: In this paper, the glycal 5 is converted to intermediates which undergo, under mild conditions, thermal aza-Claisen rearrangements, leading to the amides 7 and 8 and the 2 pyrimidone 9, all potential precursors to 2′,3′-dideoxynucleosides.
21 citations
TL;DR: In this paper, the pyrazolo[1, 5a]-1, 3, 5-triazine aglycon system has been prepared by palladium-mediated coupling of 8-iodopyrazolo and the furanoid glycal 1, 4-anhydro-2-deoxy-3-O[(1, 1 dimethylethyl)diphenylsilyl]-D-erythro-pent-1-enitol.
Abstract: C-Nucleosides of the pyrazolo[1, 5-a]-1, 3, 5-triazine aglycon system have been prepared by palladium-mediated coupling of 8-iodopyrazolo[1, 5-a]-1, 3, 5-triazines. 4-(N, N-Diisobutyloxycarbonyl)amino-8-iodopyrazolo[1, 5-a]-1, 3, 5-triazine and the furanoid glycal 1, 4-anhydro-2-deoxy-3-O[(1, 1 dimethylethyl)diphenylsilyl]-D-erythro-pent-1-enitol coupled in the presence of catalytic palladium(0) to yield, after desilylation of the intermediate silyl enol ether, a C-glycoside analog of adenosine.
21 citations
TL;DR: Glycosyl phenyl sulfone obtained in 4 steps from isosaccharino-lactone was converted into a 2′-C-acetoxymethylfuranoid glycal with SmI 2 -HMPA as mentioned in this paper.
18 citations
TL;DR: In this article, the reductive elimination of the benzoylated β-D-fructopyranosyl and α-L-sorbopyranoyl bromides 10 and 23 was examined in order to determine suitable conditions for effecting the elimination from the exo- as well as the endo-positions.
Abstract: The reductive elimination of the benzoylated β-D-fructopyranosyl and α-L-sorbopyranosyl bromides 10 and 23 has been examined in order to determine suitable conditions for effecting the elimination from the exo- as well as the endo-positions. Exposure of 10 and 23 to Zn/HOAc or Zn/N-methylimidazole gave the tribenzoates of exo-D-fructal (1) and exo-L-sorbal (25), in yields of 79 and 80%, respectively; minor products (ca, 10% each) were the corresponding endo-D-fructal (6) and endo-L-sorbal esters (26). For the reductive elimination to occur primarily from the endo-position, enhancement of the leaving group capacity of the respective ring acyloxy group was required, and materialized via the 3-O-mesyl analogues of fructosyl bromide 10, which smoothly reacted with Zn/HOAc to give the endo-D-fructal esters 20 and 21; their yields, over the five steps from diacetone-fructose, were in the 50% range. Accordingly, the methodology for generating ketose-derived glycal esters in exo- or endo-version, is now available. Some ensuing reactions of the exo-glycals have been exploited, that is, their ozonolysis to the respective pyranoid pentonolactones, and their hydrogenation to 1,5-anhydro-6-deoxy-hexitols.
18 citations
TL;DR: By adaption of an intramolecular radical cyclisation protocol to the furanoid glycal derivative 3 derived from D-mannose, synthesis of the crucial bicyclo[3.3.0] octane system 6 is reported in this article.
Abstract: By adaption of an intramolecular radical cyclisation protocol to the furanoid glycal derivative 3 derived from D-mannose, synthesis of the crucial bicyclo[3.3.0]octane system 6 is reported. A sequence of reactions on this key synthon 6, leading to the formal synthesis of (−)-canadensolide (1) is described.
14 citations
TL;DR: The [2,3]-Wittig rearrangement of trimethylsilylpropargyl ethers of furanoid glyals derived from D-mannose and L-gulonic γ-lactone affords cis 2,5-disubstituted dihydrofurans with predominant erythro selectivity as discussed by the authors.
14 citations
TL;DR: In this article, a novel chemoenzymatic method for the preparation of glucal 4 in high yield is presented, which helps to gain further insight into the mechanism of the well-documented hypervalent iodine-promoted allylic oxidation of cyclic enol ethers.
Abstract: The reaction of 3,4-bis(O-tert-butyldimethylsilyl)-6-O-tosyl-D-glucal 4 with the Koser reagent [PhI(OH)OTs] unexpectedly afforded tetrahydrofurfural 6 as well as 2,3-anhydropyranose 7 as major products. This unprecedented, stereoselective transformation helps to gain further insight into the mechanism of the well-documented hypervalent iodine-promoted allylic oxidation of cyclic enol ethers. A novel chemoenzymatic method for the preparation of glucal 4 in high yield is presented.
TL;DR: Hydrolysis of the glycal with hydrochloric acid led to 4-(5-hydroxymethylfuran-2-yl)imidazole, which contains both hydrophilic and hydrophobic aromatic heterocycles.
Abstract: Reaction of ribofuranosyl chlorides with 2 eq of 5-lithio-imidazole afforded 1-(5-imidazolyl)ribofuranoid glycals in good yields. Hydrolysis of the glycal (3) with hydrochloric acid led to 4-(5-hydroxymethylfuran-2-yl)imidazole (7), which contains both hydrophilic and hydrophobic aromatic heterocycles.
TL;DR: Fusion of the glycal 3 and purines/pyrimidines without acid catalyst provides anomeric mixtures of the 2′,3′-unsaturated pentopyranosyl nucleosides 4, which have been worked out to furnish the 3′-hydroxymethyl analogues, e.g. 5.
Abstract: Fusion of the glycal 3 and purines/pyrimidines without acid catalyst provides anomeric mixtures of the 2′,3′-unsaturated pentopyranosyl nucleosides 4, which have been worked out to furnish the 3′-hydroxymethyl analogues, e.g. 5.
Patent•
04 Apr 1995
TL;DR: An enzymatic process for the preparation of galactosyl β 1,3 glycal disaccharides such as Gal beta 1, 3Glucal, an intermediate useful in Lea preparation and an inhibitor of beta -galactosidase was disclosed in this paper.
Abstract: An enzymatic process is disclosed for the preparation of galactosyl beta 1,3glycal disaccharides such as Gal beta 1,3Glucal, an intermediate useful in Lea preparation and an inhibitor of beta -galactosidase. The process utilizes beta -galactosidase, an enzyme usually used for bond breaking, to form a bond between a galactoside and a glucal such as glycal, a 6-O-C1-C6 acylglucal or 6-O-C1-C6 acetylgalactal.
TL;DR: In this paper, the glycal 5 is converted to intermediates which undergo, under mild conditions, thermal aza-Claisen rearrangements, leading to the amides 7 and 8 and the 2 pyrimidone 9, all potential precursors to 2′,3′-dideoxynucleosides.
Abstract: The glycal 5 is converted to intermediates which undergo, under mild conditions, thermal aza-Claisen rearrangements, leading to the amides 7 and 8 and the 2-pyrimidone 9 , all potential precursors to 2′,3′-dideoxynucleosides.
TL;DR: The [2,3]-Wittig rearrangement of trimethylsilylpropargyl ethers of furanoid glyals derived from D-mannose and L-gulonic γ-lactone affords cis 2,5-disubstituted dihydrofurans with predominant erythro selectivity.
Abstract: The [2,3]-Wittig rearrangement of trimethylsilylpropargyl ethers of furanoid glycals derived from D-mannose and L-gulonic γ-lactone affords cis 2,5-disubstituted dihydrofurans with predominant erythro selectivity. Under the same conditions, [1,2]-Wittig rearrangement is observed with a glycal derived from D-ribonic γ-lactone.
TL;DR: In this article, reaction of ribofuranosyl chlorides with 2 eq of 5-lithio-imidazole afforded 1-(5-IMidazolyl)ribofuranoid glycals in good yields.
Abstract: Reaction of ribofuranosyl chlorides with 2 eq of 5-lithio-imidazole afforded 1-(5-imidazolyl)ribofuranoid glycals in good yields. Hydrolysis of the glycal (3) with hydrochloric acid led to 4-(5-hydroxymethylfuran-2-yl)imidazole (7), which contains both hydrophilic and hydrophobic aromatic heterocycles.
TL;DR: In this paper, a transformation involving a 6-aryl "exo" glycal is used to prepare the target structures from carbohydrate starting materials, which is called exo-exo transformation.
Abstract: A transformation involving a 6-aryl “exo” glycal is used to prepare the target structures from carbohydrate starting materials.
TL;DR: Glycals are converted to the corresponding epoxides in high yields by a diastereoselective one-step epoxidation using the m -chloroperoxybenzoic acid-KF complex in anhydrous dichloromethane as mentioned in this paper.
Abstract: Glycals are converted to the corresponding epoxides in high yields by a diastereoselective one-step epoxidation using the m -chloroperoxybenzoic acid-KF complex in anhydrous dichloromethane.