Showing papers on "Aldose published in 2008"

Selective fractionation of carbohydrate complex mixtures by supercritical extraction with CO2 and different co-solvents

Abstract: Nowadays consumers hold high standards for the foods they consume and they also demand for products that can provide added healthful benefits; two of these products with an observed prebiotic activity, tagatose and lactulose, are the core of our study. These two carbohydrates are ketoses and have important biological activities, such as the stimulation of the growth of beneficial microorganisms in the colon. They are currently produced by alkaline isomerization of the corresponding aldose, followed by several purification steps to remove carbohydrate by-products and the unreacted aldose (around 30%). In this work, the possibility of using supercritical fluid extraction (SFE) technology to fractionate complex carbohydrate mixtures is analyzed. The study is based on previous results obtained for the fractionation of solid binary carbohydrate mixtures such as lactulose–lactose and tagatose–galactose. The appropriate selection of the co-solvent employed, together with the most suitable extraction conditions (including temperature, pressure and co-solvent flow rate) allows the selective extraction of the prebiotic ketose with high selectivity and recovery. The fractionation by SFE of a complex commercial carbohydrate mixture, containing around 74 wt.% of lactulose and 24 wt.% of different aldose carbohydrates, was carried out at the optimal extraction conditions attained in the study of binary mixtures. The selective extraction of the ketosugar lactulose was also observed in this case, obtaining an extract with 81 wt.% lactulose and around 67% yield.

Metal-Free One-Pot Oxidative Amidation of Aldoses with Functionalized Amines

Abstract: Metal-free one-pot oxidative amidation of aldoses with functionalized amines using iodine provides a rapid access to functionalized aldonamides. The main advantage of this approach relies on the fact that aldehyde oxidation and C-N bond formation are performed in a single synthetic operation.

Three-component reaction of aldose sugars, aryl amines, and 1,3-diones: a novel synthesis of annulated pyrroles.

Abstract: Aldose sugars undergo smooth coupling with enamines, generated in situ from aryl amines and 1,3-diketones, in the presence of 10 mol % of InCl3 in water at 80 degrees C to furnish annulated pyrrole derivatives in relatively good to high yields. The use of InCl3, in combination with water, makes this procedure quite simple, more convenient, and environmentally friendly.

Synthesis of acyclo C-Nucleosides of H1-antihistaminic 4-substituted [1,2,4]triazolo[4,3-a]quinazolin-5(4H)-ones

Abstract: Two series of aldose N-(3-substituted-4-oxo-3,4-dihydroquinazolin-2-yl)hydrazones were prepared by the reaction of each of the aldoses with the appropriate 2-hydrazino-3-substituted-quinazolin-4(3H)-ones. Oxidative cyclisation of these aldose hydrazones with ferric chloride in ethanol yielded the title acyclo C-nucleosides.