Solid phase synthesis of mandelic acid-derived thioethers by α-keto carbocation trapping

Resin-bound α-keto mesylates were cleaved under acidic conditions (TFA/CH₂Cl₂) in the presence of a variety of aryl or alkyl thiols to give the corresponding thioethers. Access to the target compounds via standard nucleophilic displacement proved to be much less efficient. The stereochemical outcome of the reaction suggested formation of a highly reactive α-keto carbocation trapped in situ by the thiol acting as a scavenger.     

Optimized synthesis of tetrahydroisoquinoline-hydantoins

Several methods have been developed and compared for the solution synthesis of tetrahydroisoquinoline-hydantoin (Tic-hydantoin) derivatives. Starting materials were Tic-OH and amines readily available from commercial sources. The best yields were observed when the imidazolidine-2,4-dione ring was synthesized in two steps: (1) reaction of Tic-OH with the appropriate amine and (2) cyclization with 1,1′-carbonyldiimidazole.     

Improved Syntheses of 2-Bromonicotinaldehyde and Acid

Synthetically useful 2-bromonicotinaldehyde and 2-bromonicotinic acid can be conveniently prepared in high yield from the directed ortho metalation of 2-bromopyridine.     

Vapor-liquid critical-point properties of a symmetric binary fluid mixture

We propose a microscopic approach for investigating the behavior of a symmetric binary fluid mixture in the vicinity of the vapor-liquid critical point. The problem can be reduced to calculating the partition function of a 3D Ising model in an external field. For a square-well symmetric binary mixture, we express the parameters of the critical point as functions of the microscopic parameter r measuring the relative strength of interactions between the particles of dissimilar and similar species. The calculations are performed at intermediate (λ=1.5) and moderately long (λ=2) intermolecular potential ranges. The obtained results agree well with the results of computer simulations. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 124, No. 2, pp. 339–352, August, 2000.     

Bis(2-sulfanylethyl)amino native peptide ligation

The reaction of a peptide featuring a bis(2-sulfanylethyl)amino (SEA) group on its C-terminus with a cysteinyl peptide in water at pH 7 and 37 °C leads to the chemoselective and regioselective formation of a native peptide bond. This method called SEA ligation enriches the native peptide ligation repertoire available to the peptide chemist. Preparation of an innovative solid support which allows the straightforward synthesis of peptide SEA fragments using standard Fmoc/tert-butyl solid phase peptide synthesis procedures is also described.     

Facile synthesis and characterization of functionalized, monocrystalline rutile TiO2 nanorods

Functionalized, monocrystalline rutile TiO2 nanorods were prepared from TiCl4 in aqueous solution under acidic conditions in the presence of dopamine, followed by aging and hydrothermal treatment at 150 degrees C. The surface-bound organic ligand controls the morphology as well as the crystallinity and the phase selection of TiO2. The presence of monocrystalline rutile TiO2 was confirmed by X-ray powder diffraction and HRTEM investigations. The as-prepared nanorods are soluble in water at pH <3. The surface functionalization was analyzed by IR and 1H NMR, confirming the presence of dopamine on the surface. The surface amine groups can be tailored further with functional molecules such as dyes. Confocal laser scanning microscopy (CLSM) was used to characterize the binding of the fluorescent dye 4-chloro-7-nitrobenzofurazan (NBD) to the functionalized surface of the TiO2 nanorods.     

Fluidics of a nanogap

We have determined the filling properties of nanogaps with chemically heterogeneous walls. The quantitative criteria we present allow the prediction of the liquid loading of the nanostructure. They can easily be applied in combination with contact-angle measurements on planar substrates of the nanogap materials. We present an application of the theory to a recently developed nanogap biosensor. Chemical force microscopy (CFM) is employed to characterize the initial silanol properties of the gap. The functionality of the complex surface chemistry of the biosensor is demonstrated by the observation of functionalized nanoparticles in the gap with its resulting characteristic current-voltage relationship.