Topic
Glycal
About: Glycal is a research topic. Over the lifetime, 897 publications have been published within this topic receiving 17422 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: The first application of perfluorinated solvent in the stereoselective formation of O-/S-glycosidic linkages that occurs via a Ferrier rearrangement of acetylated glycals is described.
Abstract: Described herein is the first application of perfluorinated solvent in the stereoselective formation of O-/S-glycosidic linkages that occurs via a Ferrier rearrangement of acetylated glycals. In this system, the weak interactions between perfluoro-n-hexane and substrates could augment the reactivity and stereocontrol. The initiation of transformation requires only an extremely low loading of resin-H+ and the mild conditions enable the accommodation of a broad spectrum of glycal donors and acceptors. The ‘green’ feature of this chemistry is demonstrated by low toxicity and easy recovery of the medium, as well as operational simplicity in product isolation.
TL;DR: A literature survey on the synthesis of C-2-formyl-glycals can be found in this article , which further highlights the importance of these molecules for many medicinal, supramolecular, biological, organic as well as material chemistry-based molecules.
Abstract: Since last couple of decades, C-2-formyl glycals have sustained interest in carbohydrate chemistry as they afford valuable chiral building blocks for many biological / pharmaceutical / industrial based important molecules. Basically, C-2-formyl glycals are a class of carbohydrates incorporating an α,β-unsaturated aldehyde. Therefore in many organic reactions, the C-2-formyl-glycals molecule could therefore serve as an α,β-unsaturated aldehyde core. In this review, we have compiled a literature survey on the synthesis of C-2-formyl-glycals and further their importance for the synthesis of many medicinal, supramolecular, biological, organic as well as material chemistry-based molecules.
TL;DR: The O -benzyl derivatives of 1,5-anhydro-2-deoxy-d - arabino -hex-1-enitol (d -glucal, 1,7 and 9) showed the same reactivity as the protected glycals by action of the TTN-NaBH 4 reagent in MeOH, resulting selectively in the ring contracted compounds at the glycal moiety as discussed by the authors.
Abstract: The O -benzyl derivatives of 1,5-anhydro-2-deoxy- d - arabino -hex-1-enitol ( d -glucal, 1 ), 1,5-anhydro-2,6-dideoxy- l - arabino -hex-1-enitol ( l -rhamnal, 7 ), and 1,5-anhydro-2-deoxy- d - lyxo -hex-1-enitol ( d -galactal, 9 ), underwent stereoselectively a ring contraction by treatment with thallium(III) nitrate (TTN) in MeOH, giving respectively the dimethylacetal derivatives of 3,4,6-tri- O -benzyl-2,5-anhydro- d -mannose, 3,4-di- O -benzyl-6-deoxy-2,5-anhydro- l -mannose ( 8 ) and 3,4,6-tri- O -benzyl-2,5-anhydro- d -talose ( 10 ). Conversely, the protected glycals 1 , 7 and 9 , underwent the ring opening reaction by action of the TTN–NaBH 4 reagent in MeOH, providing the enantiomerically pure methyl enol-ethers 3,4,6-tri- O -benzyl-2-deoxy-1- O -methyl- d - arabino -hex-1-enitol, 3,4-di- O -benzyl-2,6-dideoxy-1- O -methyl- l - arabino -hex-1-enitol and 3,4,6-tri- O -benzyl-2-deoxy-1- O -methyl- d - lyxo -hex-1-enitol. The perbenzylated glycosyl-glycals, such as 3,6-di- O -benzyl-4- O- (2,3,4,6-tetra- O -benzyl- β - d -glucopyranosyl)-1,5-anhydro-2-deoxy- d - arabino -hex-1-enitol (cellobial) ( 16 ), 3,6-di- O -benzyl-4- O- (2,3,4,6-tetra- O -benzyl- β - d -galactopyranosyl)-1,5-anhydro-2-deoxy- d - arabino -hex-1-enitol (lactal) ( 19 ) and 3,4-di- O -benzyl-6- O- (2,3,4,6-tetra- O -benzyl- α - d -galactopyranosyl)-1,5-anhydro-2-deoxy- d - arabino -hex-1-enitol (melibial) ( 22 ), showed the same reactivity as the corresponding glycals by reaction with TTN in MeOH, resulting selectively in the ring contracted compounds at the glycal moiety. The reaction with TTN–NaBH 4 in MeOH, carried out on 16 , 19 and 22 , led to the formation of the open chain derivatives at the glycal site.
Patent•
03 Dec 2008TL;DR: In this article, a method for the production of glycosamine analogues (I) from natural carbohydrates, i.e. 5- or 6-ring glycals, involves reacting the glycal with a nitroalkane to give a carbohydrate 2-C-N-analogue in which the nitrogen is in the form of a Nitro group and reducing this to (I).
Abstract: A method for the production of glycosamine analogues (I) from natural carbohydrates , i.e. 5- or 6-ring glycals, involves (a) reacting the glycal with a nitroalkane to give a carbohydrate 2-C-N-analogue in which the nitrogen is in the form of a nitro group and (b) reducing this to (I).
TL;DR: In this paper, the susceptibility of glycal-derived carbinols to acid-catalyzed ring expansion is described, and the composite reaction profiles reveal for the first time the fundamental importance of exothermicity and substitution in these spiro glycosidation reactions.
Abstract: The susceptibility of glycal-derived carbinols to acid-catalyzed ring expansion is described. In the systems prepared from cyclopentanone, Ferrier ionization precedes the pinacol-like Wagner−Meerwein shift, thermodynamic control operates, and high stereoselectivity is seen if a C(6) substituent is present. In contrast, the adducts to cyclobutanone exhibit release of ring strain under kinetically controlled conditions and intercept the oxonium species reversibly formed via direct proton transfer. The results show that the substituents positioned on the glycal ring have a pronounced influence on whether a chair-like or twist-boat transition state geometry is adopted primarily. The composite reaction profiles reveal for the first time the fundamental importance of exothermicity and of substitution in these spiro glycosidation reactions. Since optical activity is preserved in all instances, the utility of this chemistry for the synthesis of bis-C,C-glycosides and more complex oxacyclics appears promising.