Thermolysis of [1,2,4]triazolo[1,5-a]pyrimidine n-ylides

5,7-Dimethyl[1,2,4]triazolo[1,5-a]pyrimidinio-3-phenacylide ($\text{3}$) generated by the reaction of an iminium salt ($\text{2}$) with 1 eq. of triethylamine, underwent a new thermal ring cleavage of the triazole moiety to give the pyrimidine derivative. However reaction of $\text{2}$ with 2 eq. of triethylamine afforded the 2-iminooxazoline derivative. The iminooxazoline reacted with nucleophiles such as alcohols or amines to give imidazoles.     

Chemical structure of poly(trisubstituted vinylsilane) produced by γ irradiation

The chemical structure of polymers produced by the γ irradiation of monovinylsilanes was studied. γ-ray addition polymerization of monovinylsilanes such as trialkylvinylsilane was very slow, and only the liquid oligomers were formed from them by large radiation dose. The presence of silethylene or silmethylene linkage was ascertained in these polymers by infrared absorption spectroscopy and ¹H-NMR measurement, even when no Si? H bond existed in the monomers. The polymers were supposed to be produced by addition polymerization with intervening silalkylene linkage.     

Macromolecular helicity induction in a cationic polyacetylene assisted by an anionic polyisocyanide with helicity memory in water: replication of macromolecular helicity

We report the first example of the replication of macromolecular helicity. An optically active helical and anionic polyelectrolyte, the sodium salt of poly(4-carboxyphenyl isocyanide), was found to serve as the template for further helicity induction in a different polyelectrolyte with opposite charges in water, resulting in interpolymer helical assemblies with controlled helicity. The effects of the pH and salt concentration on the helicity induction were investigated.     

Synthesis, isolation via self-assembly, and single-molecule observation of a [60]fullerene-end-capped isotactic poly(methyl methacrylate)

We report the preparation and single-molecule observation of a high molecular weight C60-end-capped, stereoregular poly(methyl methacrylate) (PMMA-C60) with a precisely controlled structure. The highly isotactic PMMA-C60 (mm = 98%) with a narrow molecular weight distribution was synthesized by the stereospecific anionic living polymerization of tert-butyl methacrylate followed by end-capping with C60, hydrolysis of the pendant esters, and methylation with CH3I. Although the functionality of the C60 (fC60) of the as-prepared isotactic PMMA was imperfect (ca. 40%), the completely C60-end-capped PMMA (fC60 approximately 100%) was successfully isolated through self-assembly of the PMMA-C60 in a polar solvent by size exclusion chromatography. Furthermore, the individual PMMA chains together with the covalently bonded terminal C60 molecules were clearly visualized by atomic force microscopy, which definitely showed the structure of the isolated PMMA-C60.     

Novel immobilized zinc(II) affinity chromatography for phosphopeptides and phosphorylated proteins

Immobilized metal ion affinity chromatography (IMAC) is now a widely accepted technique for the separation of natural or artificial products that is beginning to find industrial applications. Here, we introduce a novel procedure for the separation of phosphopeptides and phosphorylated proteins by immobilized zinc(II) affinity chromatography. The phosphate-binding site of the affinity gel is an alkoxide-bridged dinuclear zinc(II) complex, the 1,3-bis[bis(pyridin-2-ylmethyl)amino]propan-2-olato dizinc(II) complex (Phos-tag), which is linked to a highly cross-linked 4% (w/v) agarose. The affinity gel (Phos-tag agarose) was prepared by the quantitative reaction of N-hydroxysuccinimide-activated Sepharose and a Phos-tag derivative having a 2-aminoethylcarbamoyl group in dry CH3CN. Phosphopeptides were retrieved in a quantitative and highly selective manner by a spin column method using Phos-tag agarose at room temperature. Furthermore, in this study, we demonstrate a simple, rapid, and reusable affinity column chromatography for the separation of phosphorylated proteins such as ovalbumin, alpha(s1)-casein, and beta-casein at physiological pH.     

Differential scanning coulometric titrometry: Application to the system CoNiO at 1000°C

A novel technique involving solid state coulometric titration using stabilized zirconia electrolytes is presented. The method is termed differential scanning coulometric titrometry (DSCT). It is useful for the phase equilibrium studies of multicomponent oxide systems. In the DSCT, two independent and isostructural galvanic cells are used. One is a sample cell in which a sample is charged, while the other is a reference cell without a sample. Under the condition that oxygen activities in both cells are equal to each other, coulometric titration is carried out continuously in both cells. The difference between the titration currents provided to both cells corresponds to the amount of oxygen which is allowed to react with a sample per unit time. If the difference is recorded with respect to the oxygen activity, it starts to deviate from a base line when the sample starts to be oxidized or reduced. This method was successfully applied to the system CoNiO at 1000°C. The phase diagram of the system and related thermodynamic data were obtained.     

Low-spin state structure of [Fe(chloroethyltetrazole)6](BF4)2 obtained from synchrotron powder diffraction data

The complex [Fe(teec)6](BF4)2 (teec = chloroethyltetrazole) shows a two-step complete spin-crossover transition in the temperature range 300-90 K. Time-resolved synchrotron powder diffraction experiments have been carried out in this temperature range, and crystal structure models have been obtained from the powder patterns by using the parallel tempering technique. Of these models, the low-spin state structure at 90 K has been refined completely with Rietveld refinement. Its structural characteristics are discussed in relation to the high-spin state model and other spin-crossover compounds. The complex shows a remarkable anisotropic unit-cell parameter contraction that is dependent on the applied cooling rate. In addition, the possible important implications for the interpretation of spin-crossover behavior in terms of structural changes are discussed.     

Conformational aspects of germacrene B are the germacrenes resolvable ?

Molecular mechanics calculations revealed that germacrene B has two comparably stable conformations. The lowest barrier (δH^Δ) to ring inversion of the most stable conformer to its mirror imageg is estimated to be 23 Kcal/mol.     

Macromolecular helicity induction on a poly(phenylacetylene) with C2-symmetric chiral [60]fullerene-bisadducts

Three chiral N-methylfulleropyrrolidine bisadducts were prepared, isolated, and completely resolved into each enantiomer using a chiral HPLC column, which were then converted to the corresponding optically active, cationic C(60)-bisadducts to investigate if they could act as a macromolecular helicity inducer in a poly(phenylacetylene) bearing an anionic monoethyl phosphonate pendant (poly-1) in aqueous solution. Upon complexation with the chiral C(60)-bisadducts, only the trans-3 bisadduct exhibited the characteristic induced circular dichroism (ICD) in the UV-visible region of the polymer backbone in dimethyl sulfoxide-water mixtures due to the predominantly one-handed helix formation of poly-1, while the trans-2 and cis-3 bisadducts induced almost no apparent CD in the same region. These results indicate that the helicity induction on poly-1 is highly sensitive to the structure and geometry of the cationic C(60)-bisadducts with a different distance between the separated charges.     

Chiral stimuli-responsive gels: helicity induction in poly(phenylacetylene) gels bearing a carboxyl group with chiral amines

Poly(phenylacetylene) gels (gel-1-H and gel-2-H) bearing a carboxy pendant were synthesized either by the copolymerization of (4-carboxyphenyl)acetylene (gel-1-H) with a bis(phenylacetylene) derivative as the cross-linking reagent using a rhodium complex ([Rh(cod)(2)]BF(4): cod = 1,5-cyclooctadiene) as the catalyst or by the cross-linking of poly[(4-carboxyphenyl)acetylene] with diamines (gel-2-H). The obtained gels were found to swell in DMSO and exhibited an induced circular dichroism (ICD) in the long absorption region of the main chain in the presence of optically active amines. These results indicate that a predominantly one-handed helix can be induced in the polymer network of the gels through chiral acid-base interactions. The swelling properties and the Cotton effect intensities of the gels depend on the cross-linking ratio and the chiral amines. Gel-1-Na and gel-2-Na prepared from gel-1-H and gel-2-H, respectively, also significantly swelled in water and showed ICDs characteristic of chiral amino alcohols and free amino acids in water.