Synthesis of 3″- and 4″-deoxy-Lewisx trisaccharides: A useful tool for study of carbohydrate-carbohydrate interaction

Synthesis of 3″-deoxy and 4″-deoxy Lewis^x trisaccharides is described. Phenyl 2,3,6-tri-O-benzoyl-4-deoxy-1-thio-β-d-xylo-hexopyranoside was condensed with a diol of glucosamine to give regio- and stereo-selectively a disaccharide. Stereoselective fucosylation of this disaccharide provided a protected deoxy Lewis^x trisaccharide which was deprotected to give the 4″-deoxy Lewis^x trisaccharide. Application of the similar synthetic sequence provided the 3″-deoxy Lewis^x trisaccharide.     

Simple,rapid, and clean condensation of sulfonamide and maleic anhydride derivatives: Synthesis of novel 1H- Pyrrole-2,5-diones under heterogeneous conditions

H₆P₂W₁₈O₆₂ is used as an efficient catalyst for the synthesis of novel N-substituted sulfonyl maleimides (1H-Pyrrole-2,5-diones) via the condensation of sulfonamide and maleic anhydride derivatives. The Dawson heteropolyacid was used with a catalytic amount of 2 mmol% in acetonitrile at reflux. The reuse of H₆P₂W₁₈O₆₂ as heterogeneous catalyst several times without decrease in their activity, short reaction times, easy isolation of desired products with good to excellent yields shows the advantages of this novel methodology.     

An efficient green synthesis of new benzothiazoles containing sulfonamide or cyclic imide moieties

An efficient and convenient protocol for the one-pot synthesis of new benzothiazoles bearing sulfonamide or cyclic imide moieties using Cesium salt of Wells-Dawson heteropolyacid (Cs₅HP₂W₁₈O₆₂) as solid catalyst and water as solvent under ultrasound irradiation was reported. The reaction speed was remarkably catalyzed with the aid of ultrasound irradiation. Moreover, this approach prepares multiple other benefits such as operational ease, higher yields, and energy performance.     

Practical one-pot,two-step protocol for the ultrasound-assisted synthesis of new mono- and bis-pyrrolidine-2,5-diones containing sulfonamide moiety

A simple and efficient preparation of novel series of mono- and bis-pyrrolidine-2,5-diones containing sulfonamide moiety was described. The strategy involved sequential one-pot sulfonylation-nucleophilic substitution procedure and was found effective under ultrasound activation and used for the first time. This approach allows the synthesis of products in good to excellent yields in short reaction time.     

Weak calcium-mediated interactions between Lewis X-related trisaccharides studied by NMR measurements of residual dipolar couplings

The Lewis X (LeX) determinant, a trisaccharide with the carbohydrate sequence Galbeta(1-->4)[Fucalpha(1-->3)]GlcNAcbeta, is believed to be responsible for Ca2+-mediated cell-cell interactions. In partly oriented phases composed of mixtures of penta(ethyleneglycol)monododecyl ether HO(CH2CH2O)5C12H25 and n-hexanol in the presence of Ca2+ ions, the variation of the residual dipolar couplings 1DCH of various CiHi vectors in LeX as a function of the concentration of the trisaccharide demonstrates the existence of very weak LeX-Ca2+-LeX complexes in solution. Synthetic 3-, 4-, and 6-deoxy-LeX variants were also shown to form complexes in the presence of calcium ions, despite the replacement of one of their hydroxyl groups by hydrogen atoms. This is the first direct observation in solution of a calcium-mediated interaction between LeX molecules.