Rapid oligosaccharide synthesis using a fluorous protective group

The Bfp-OH, a novel fluorous protecting reagent, was able to be easily prepared. The Bfp group was readily introduced to a carbohydrate, removed in high yield, and recyclable after cleavage. The use of the Bfp group made it possible to synthesize a pentasaccharide by minimal column chromatography purification. Each synthetic intermediate was able to be easily purified only by simple fluorous-organic solvent extraction and monitored by TLC, NMR, and MS.     

Synthesis of peptides and oligosaccharides by using a recyclable fluorous tag

A hexakis(fluorous chain)-type alcohol was used in the synthesis of oligosaccharides and peptides through connection with a linker suitable for the particular type of target compound. After the preparation of the desired compound, the fluorous alcohol was easily recovered in good yields under basic conditions. It appears that the fluorous alcohol can be recovered, recycled, and reused.     

Post-oxidative conversion of thiol residue to sulfonic acid in the binding sites of molecularly imprinted polymers: disulfide based covalent molecular imprinting for basic compounds

An imprinted polymer using a disulfide derivative as a template was treated with NaBH4 to yield the polymer with thiol groups in the binding sites. The thiol groups were then oxidized with H2O2/AcOH to yield the molecularly imprinted polymer with sulfo groups in the binding sites. This site conversion can provide amine-imprinted polymers, in which amine is retained to the imprinted polymer by the strong electrostatic interaction between the amino group and the sulfo group in the binding sites.     

An application of silaned glass beads to the preconcentration and spectrophotometric determination of traces of phosphorus with molybdate

Silaned glass beads are applied to the preconcentration and spectrophotometric determination of phosphorus as the phosphomolybdenum blue complex. Traces of phosphorus in water are collected as a phosphomolybdenum blue complex on a column of the beads. The phosphomolybdenum blue is eluted with N,N-dimethylformamide and the absorbance of the eluate continuously monitored at 700 nm. The height of the very sharp peak obtained is proportional to the amount of phosphorus present and 0.1-0.5 mug of phosphorus in a 10-ml sample can be determined reproducibly. Interference from arsenate is eliminated by addition of a reducing agent. High concentrations of silica cause a small positive error. This method is applicable to the analysis of river water and sea-water samples.     

A novel method for preparation of 2-(methyl- or phehnylthio)alkanoic esters

Ethyl 2-acetylalkanoate gave ethyl 2-(methyl- or phenylthio)alkanoate in high yield on treatment wiht CH₃SSO₂CH₃, PhSSO₂Ph, or PhSSPh in the presence of small excess of EtONa in EtOH. Application of the present method to synthesis of pellitorine and the queen substance is also described.     

Computer simulation for the cooligomerization system

In order to clarify the kinetic features of the styrene (A)–methyl methacrylate (B)–CCl₄(S) cooligomerization system, a computer simulation was carried out. The experimental data on the degree of polymerization and the deviation of the cooligomer composition from the statistical steady-state composition were comparatively well explained by calculations based on the kinetic equations derived from the assumed reaction scheme and the values of the velocity coefficients, although the values of the four velocity coefficients in the initiation step and the velocity coefficient of the termination by the coupling of two solvent radicals were estimated. The results of the calculation of the rate of each component reaction show that the following two reactions are the most important in the initiation and in the transfer and termination steps when the [S]/([A] + [B]) ratio is large: where, A, A*, and P are styrene, polystyryl radical, and the cooligomer, respectively. Moreover, it was concluded that the deviation of the cooligomer composition from the statistical steady-state composition was caused by these two reactions.     

Protective effects of small amounts of bis(2-ethylhexyl)sulfosuccinate on the helical structures of human and bovine serum albumins in their thermal denaturations

The protective effect of an anionic double-tailed surfactant, sodium bis(2-ethylhexyl)sulfosuccinate (AOT), on the structures of human serum albumin (HSA) and bovine serum albumin (BSA) in their thermal denaturations was examined by means of circular dichroism measurements. The structural changes of these albumins were reversible in the thermal denaturation below 50 degrees C, but became partially irreversible above this temperature. The effect was observed in the thermal denaturation above 50 degrees C. Although the helicity of HSA decreased from 66% to 44% at 65 degrees C in the absence of the surfactant, the decrement of it was restrained in the coexistence of AOT of extremely low concentrations. When the HSA concentration was 10 muM, the maximal protective effect appeared at 0.15 mM AOT. In the coexistence of the surfactant of this concentration, the helicity was maintained at 58% at 65 degrees C, increasing to the original value upon cooling to 25 degrees C. Beyond 0.15 mM AOT, the helicity sharply decreased until 3 mM AOT. A particular AOT concentration required to induce the maximal protective effect ([AOT]REQ) was examined at different HSA concentrations. [AOT]REQ shifted to higher values with an increase of the protein concentration. From the protein concentration dependences of [AOT]REQ, the maximal protection was estimated to require 8.0 and 5.0 AOT ions per a molecule of HSA and BSA, respectively. The AOT concentration, where the protective effect was observed, was too low to form its micelle-like aggregate. Then the protein structures might be stabilized by a cross-linking of surfactant monomers bound to specific sites. These specific sites might exist between a group of nonpolar residues and a positively charged residue located on several sets of amphiphilic helical rods in the proteins. Such a unique function of the double-tailed ionic surfactant is first presented by its characteristic nature as an amphiphilic material.     

Reductive metabolism of nitro-p-phenylenediamine by rat liver

Reductive metabolism of the hair dye constituent, nitro-p-phenylenediamine (2-nitro-1,4-diaminobenzene, NPDA), and its acetylated metabolite, NPDA N4-acetate, was investigated with rat liver subcellular fractions, microsomes and cytosol. Under anaerobic conditions, these compounds were reduced to their corresponding amines by these fractions. The microsomal nitro-reducing activity was retarded completely by air and strongly by carbon monoxide. Reduced nicotinamide adenine dinucleotide phosphate (NADPH) functioned more effectively than reduced nicotinamide adenine dinucleotide (NADH) as an electron donor in the microsomal reduction of the nitro compounds, and flavin mononucleotide (FMN) gave rise to a marked enhancement in the microsomal activity, especially when added to an anaerobic incubation mixture containing both NADH and NADPH. The cytosolic nitro-reducing activity was attributed to xanthine oxidase, aldehyde oxidase and other unknown enzyme(s), based on the results of cofactor requirements and inhibition experiments.