Design and synthesis of new carbohydrate-lithocholic acid conjugates linked via 1,2,3-triazole rings

In this work, we report the synthesis of a novel carbohydrate-lithocholic acid conjugate linked through of 1,2,3-triazole rings and its derivatives in good to excellent yields. The conjugate was synthesized via copper-catalyzed azide?alkyne cycloaddition (CuAAC) from methyl 4,6-O-benzylidene-2,3-di-O-propargyl-α-d-glucopyranoside and methyl 3-azidolithocholate. The structures of all new compounds were properly characterized by infrared (IR), high-resolution mass spectroscopy (HRMS) and one- and two-dimensional nuclear magnetic resonance (NMR).     

In Vitro Screening of Bioactive Compounds in some Gluten-Free Plants

Electrophoretic, antioxidant, and FTIR profiles of some varieties of amaranth, quinoa, and buckwheat seeds and their by products were compared. Water extracts of these products were evaluated by the Folin–Ciocalteau method in order to determine total phenolic content. The antioxidant activities were determined by 2,2′-azobis-2-methyl-propanimidamide, ferric-reducing/antioxidant power, and cupric reducing antioxidant capacity radical scavenging assays. FTIR spectra showed the secondary structure of pseudocereals in the ranges of amides I, II, and III shifts. Results of evaluated methods could be used to control several products (seeds, flours, extracts, flakes, roasting) with high phenolic content and antioxidant activity suitable for supplementation in food applications.

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A computer simulation study of the segregation of amphiphiles in binary immiscible matrices: short asymmetric copolymers in short homopolymers

The bulk and interfacial properties of ternary mixtures with asymmetric amphiphiles (A2B8) in A2 and B2 matrices and in A2 and B10 matrices are investigated by the dissipative particle dynamics type of molecular-dynamics simulations. The monomer concentrations of A2B8(phiA2B8) studied are below the critical micelle concentration (phiA2B8(cmc)) for the formation of micelles in the presence of an adsorbed amphiphilic monolayer at the interface. Macrophase separation from the mixed phase to the segregated state with A-rich and B-rich coexisting phases and the segregation of A2B8 at the interface are thermodynamically gradual but are accompanied by a pronounced stretching and orientation of the constituent chains. The segregation of A2B8 at the interface broadens the interfacial region and reduces the interfacial tension. The chain conformation of the asymmetric amphiphilic molecules and the interfacial properties are dominated by the majority block in the amphiphilic chain and dependent on the composition of the matrix in contact with the majority block. In the A2 and B2 matrices, the B8 blocks in A2B8 chains at the interface resemble a wet brush swollen by short B2 chains. Swelling is responsible for the pronounced stretching and orienting of the amphiphilic chains and the reduced interfacial amphiphile enrichment. At the same interfacial amphiphile excess, however, swollen amphiphiles are more efficient in reducing the interfacial tension than nonswollen amphiphiles.     

Intramolecular hydrogen bonding (P=O--H) stabilizes the chair conformation of six-membered ring phosphates

[reaction: see text] Six-membered cyclic phosphates (2-phenoxy-2-oxo-1,3,2-dioxaphosphorinanes) bearing an internal protected or unprotected hydroxyl group were designed, synthesized, and studied by NMR and computational methods. Selective opening of O-isopropylidene-protected 1,2-diols at the primary site was achieved with either triethylsilane or trimethylallylsilane in the presence of BF3.OEt2. Applied to 5,6-O-isopropylidenepentofuranosides, this reaction gave rise to the formation of the corresponding 1,3-diol precursors for the six-membered ring phosphates containing an O-isopropyl or O-1,1-dimethyl-3-butenyl functional group at C-6. The O-1,1-dimethyl-3-butenyl protecting group was efficiently removed after the phosphorylation with BF3.OEt2, and the six-membered cyclic phosphates containing free hydroxyl groups were obtained. A cyclic phosphate with a free hydroxyl group oriented cis to the phosphoryl group shows a vicinal coupling constant 3J(HP) that is in accordance with the chair conformation. This is due to the formation of a seven-membered intramolecular hydrogen-bonded ring structure that stabilizes the chair conformation. Thus, the strong tendency of the phenoxy group to be in an axial position is diminished by the internal hydrogen bonding interaction. Computational studies provided strong support for the experimental observation.     

Cobalt(II) and nickel(II) complexes of N(4′) substituted 3- and 4-acetylpyridine thiosemicarbazones

Co^II and Ni^II complexes of N(4)-methyl and N(4)-ethyl thiosemicarbazones derived from 3- and 4-acetylpyridine have been prepared and characterized by microanalyses, magnetic susceptibility and molar conductivity measurements and by their electronic, i.r. and n.m.r. (in the case of Ni^II complexes) spectra.     

A Short Synthesis of Astemizole

The synthesis of astemizole 6, a potent H₁-antihistaminic agent, was achieved in 20% overall yield. Compound 6 was obtained in high purity and on a multigram scale starting from 2-hydroxybenzimidazole.     

Phase equilibrium and charge fractionation in polyelectrolyte solutions

A new type of phase separation in the polyelectrolyte solutions consisting of several types of charged macromolecules differing in their degree of ionization is presented. Via a general thermodynamic consideration we show that even a small difference in the degree of ionization of otherwise equivalent high‐molecular components results in their spatial separation occurring upon decreasing the temperature much earlier than precipitation of any of the pure components from the solution. Some implications of charge fractionation are discussed, including the separation of DNA (or RNA) strands interacting with different proteins and the appearance of heterogeneities in polyelectrolyte solutions of partially charged hydrophobic chains with polydispersed charge distributions such as sodium polystyrene sulfonate. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3003–3009, 2007