Synthesis and properties of calixarene analogs incorporating a thiophene unit in the macrocyclic ring

Calixarene analogs containing a thiophene unit in the macrocyclic ring were prepared by a stepwise method. The macrocycles adopt a cone‐like form as the preferred conformation in solution. The induced chemical shift change, nOe experiment, and ¹H relaxation time (T₁) measurement supported the fact that the macrocycle forms a complex with the N‐methylpyridinium salt. In contrast, O‐tetramethylated macrocycles and linear phenol‐formaldehyde tetramer, could not efficiently include the N‐methylpyridinium salt.     

A general synthesis of s-triazolo[1,5-x] diazines

Treatment of 2-aminopyrimidime, a 4-aminopyrimidine, aminopyrazine, and 3-aminopyridazines with O-mesilylenesulfonylhydroxylamine gave the corresponding N-aminodiazinium salts in high yields. These salts could be transformed into s-triazolo[1, 5-a] pyrimidines, s-triazolo[1, 5-a]-pyrazines, s-triazolo[1, 5-c]pyrimidines, and s-triazolo[1, 5-b]pyridazines hy treatment with acylating agents.     

Photo‐Cross‐Linked Small‐Molecule Microarrays as Chemical Genomic Tools for Dissecting Protein–Ligand Interactions

We have developed a unique photo‐cross‐linking approach for immobilizing a variety of small molecules in a functional‐group‐independent manner. Our approach depends on the reactivity of the carbene species generated from trifluoromethylaryldiazirine upon UV irradiation. It was demonstrated in model experiments that the photogenerated carbenes were able to react with every small molecule tested, and they produced multiple conjugates in most cases. It was also found in on‐array immobilization experiments that various small molecules were immobilized, and the immobilized small molecules retained their ability to interact with their binding proteins. With this approach, photo‐cross‐linked microarrays of about 2000 natural products and drugs were constructed. This photo‐cross‐linked microarray format was found to be useful not merely for ligand screening but also to study the structure–activity relationship, that is, the relationship between the structural motif (or pharmacophore) found in small molecules and its binding affinity toward a protein, by taking advantage of the nonselective nature of the photo‐cross‐linking process.     

1,3-Dipolar cycloaddition reaction of benzodiazinium and naphthyridinium N-imines with acetylenic esters

1,3-Dipolar cycloaddition of N-imines derived from mono-N-amino salts of phthalazines, 2-phenylquinoxaline, 1,5- and 1,8-naphthyridines with dimethyl acetylenedicarboxylate: and methyl propiolate resulted in the formation of new tricyclic: heterocyclic ring systems with bridgehead nitrogen.     

Sulfilimines in organic syntheses: new entries into tetrahydro-1,2-benzothiazepine and 1,2-benzisothiazole systems

Novel ring transformations of thiochroman-4-ones and benzo[b]thiophen3(2H)-ones to tetrahydro-1,2-benzothiazepin-5-ones and 1,2-benzisothiazoles via sulfilimine intermediates are described.     

Incorporation of selenium into selenoprotein P and extracellular glutathione peroxidase: HPLC-ICPMS data with enriched selenite

The metabolic turnover of selenoprotein P (Sel P) and extracellular glutathione peroxidase (eGPx) in plasma was examined by HPLC-ICPMS, with the use of enriched Se, [82Se]selenite. [82Se]selenite was injected intravenously into rats at a dose of 25 micrograms 82Se kg-1 body weight, and the concentrations of labeled 82Se and naturally occurring 77Se in the serum, liver and kidneys were determined in samples obtained 1, 3, 6, 9, 12, 18 and 24 h after the injection. The distributions of both exogenous (labeled) 82Se and endogenous (naturally occurring) 77Se in serum, and supernatant fractions of the liver and kidneys were determined on a gel filtration column by HPLC-ICPMS. This dose was shown not to affect the constitutive levels of cellular GPx (cGPx), eGPx and Sel P. The labeled Se in Sel P increased soon after the injection, peaked at 6-9 h and then decreased, whereas that in eGPx continued increasing after 6 h post-injection and then throughout the remaining observation period in the bloodstream. These observations demonstrated the rapid and efficient incorporation of Se into Sel P in the liver and excretion into the plasma followed by the slow and steady incorporation of Se into eGPx in the kidneys and excretion into the plasma, with a minimal response of cGPx to selenite injection.     

57Fe-Mössbauer study of electrically conducting barium iron vanadate glass after heat treatment

Local structure and thermal durability of semiconducting xBaO·(90?? x)V₂O₅ · 10Fe₂O₃ glasses (x = 20, 30 and 40), NTA glass ^TM, before and after isothermal annealing were investigated by ⁵⁷Fe-Mössbauer spectroscopy and differential thermal analysis (DTA). An identical isomer shift ( $\mathit{\delta}$ ) of 0.39 ± 0.01 mm s^???1 and a systematic increase in the quadrupole splitting (Δ) were observed from 0.70 ± 0.02 to 0.80 ± 0.02 mm s^???1 with an increasing BaO content, showing an increase in the local distortion of Fe^IIIO₄ tetrahedra. From the slope of the straight line in the T _g–Δ plot of NTA glass ^TM, it proved that Fe^III plays a role of network former. Large Debye temperature (Θ _D) values of 1000 and 486 K were respectively obtained for 20BaO · 70V₂O₅ · 10Fe₂O₃ glass before and after isothermal annealing at 400°C for 60 min, respectively. This result also suggests that Fe^III atoms constitute the glass network composed of tetrahedral FeO₄, tetrahedral VO₄ and pyramidal VO₅ units. The electric conductivity of 20BaO · 70V₂O₅ · 10Fe₂O₃ glass increased from 1.6 × 10^???5 to 5.8 × 10^???2 S cm^???1 after isothermal annealing at 450°C for 2,000 min. These results suggest that the drastic increase in the electric conductivity caused by heat treatment is closely related to the structural relaxation of the glass network structure.     

Thiazolo [3,2-b]-s-triazole

2-Formamidothiazole and O-mesitylenesulfonylhydroxylamine readily gave 3-umino-2-form-amidothiazolium mesitylenesulfonate that with polyphosphoric acid gave thiazolo [3,2-b]-s-triazole. triazole. In its nmr spectrum, a long-range coupling of 1.4 Hz between H-2 and H-6 is observed.     

Studies in organic mass spectrometry. III. Adenosine 8-Cyclonucleosides

The mass spectra of purine 8-cyclonucleosides have been determined and compared with those of purine nucleosides. The mass spectra of the former are characterized not only by the presence of an intense molecular ion but also by the presence of the peaks corresponding to 8-oxy (or 8-thio) adenine and its protonated form due to a double and triple hydrogen transfer.     

Distribution and metabolism of selenohomolanthionine labeled with a stable isotope

The distribution and metabolism of selenohomolanthionine (4,4′-selenobis[2-aminobutanoic acid], SeHLan), a newly identified selenoamino acid in selenized Japanese pungent radish, were evaluated by administering ⁷⁷Se-labeled SeHLan at a dose of 25 μg/kg body weight in rats. Exogenous ⁷⁷Se of SeHLan was preferably distributed to the kidneys and remained in the intact form for up to 6 h after dosing. The accumulation in the kidneys is one of the specific characteristics of SeHLan, differing from other selenoamino acids, such as selenomethionine and Se-methylselenocysteine, which preferably accumulate in the pancreas. The intact form of SeHLan was detected in the serum and kidney supernatant but not in the urine, suggesting that the amount of exogenous Se that was distributed to the kidneys was within metabolic capacity. Indeed, the exogenous Se was converted into two urinary metabolites, Se-methylseleno-N-acetyl-galactosamine and trimethylselenonium. Exogenous Se was also detected in several selenoproteins, including selenoprotein P and extracellular glutathione peroxidase. SeHLan is expected to be a potential supplemental source of Se because its distribution differs from that of selenomethionine and Se-methylselenocysteine.