Curve-structured phenalenyl chemistry: synthesis, electronic structure, and bowl-inversion barrier of a phenalenyl-fused corannulene anion

We have demonstrated the features of curve-structured phenalenyl chemistry, for the first time. A phenalenyl-fused corannulene anion has been designed by the annelation of a six-memberd ring across peri-positions of corannulene and generated as a stable species in a degassed solution. The 1H and 13C NMR spectra have shown the highly symmetrical structure and high-field shifts of protons and carbons at the asterisked positions in the chemical structure, indicating the occurrence of large negative charge densities at these positions. These results well agree with the HOMO picture and the electrostatic potential surface, demonstrating the phenalenyl anion-type electronic structure is retained in the curved-surface pi-system. The calculated bowl-inversion barrier of the anion (11.3 kcal/mol) is larger than that of corannulene (9.2 kcal/mol) because of peri-annelation of the corannulene skeleton. The calculations of the barriers of the neutral radical (12.6 kcal/mol), radical dianion (8.1 kcal/mol), and trianion (5.4 kcal/mol) of the phenalenyl-fused corannulene have exhibited a stepwise flattening of the curvature with increase in negative charge. Therefore, we have revealed that the bowl-inversion barrier of the anion is governed by the setoff of the peri-annelation and negative charge effects.     

Fluorophotometric determination of hydrogen peroxide and other reactive oxygen species with fluorescein hydrazide (FH) and its crystal structure

Methods for the fluorophotometric determination of hydrogen peroxide (H(2)O(2)) and other reactive oxygen species (ROS) were proposed by using the fluorescence reaction between H(2)O(2) or other ROS and fluorescein hydrazide (FH). In the determination of H(2)O(2), the calibration curve exhibited linearity over the H(2)O(2) concentration range of 2.1-460 ng ml(-1) at an emission wavelength of 527 nm with an excitation of 460 nm and with the relative standard deviations (n=6) of 4.06%, 1.78%, and 2.21% for 3.1 ng ml(-1), 30.8 ng ml(-1), and for 308 ng ml(-1) of H(2)O(2), respectively. The detection limit for H(2)O(2) was 0.7 ng ml(-1) due to three blank determinations (rho=3). The calibration curves for ROS-related compounds were also constructed under the optimum conditions. This method was successfully applied in the assay of H(2)O(2) in human urine. In addition, we performed the characterization of FH, and interesting information was obtained with regard to the relationship between the chemical structure and fluorescence.     

Isomerization of cyclooctatetraene oxide in the reaction with organometallic reagents : Possible involvement of homotropylium cation intermediate

The reaction of cyclooctatetraene oxide (1) with several organometallic reagents and metal salts were investigated with reference to skeletal change of the ring. LAH causes ring cleavage to yield octa-2,4,6-trienal along with the formation of cycloocta-3,5-dienol. Ethylmagnesium bromide and triethylaluminum afford ethyl(cyclohepta-2,4,6-trienyl)methanol in good yields, but the addition of HMPA in the Grignard reaction results in reduction of the reactivity and formation of the isomerized cyclic trienone. A similar medium effect by HMPA or solvent is found in the reaction of 1 with ethyllithium which affords 5-ethylcycloocta-2,6-dienone (70·2%) in ether, and also in the metal salts (MgBr₂, LiBr, and LiClO₄) induced isomerization giving cycloheptatrienylcarboxyaldehydes and phenylacetaldehyde. The diverse nature of the products in the reactions is accounted for by the formation of homotropylium cation intermediates.     

Water-insoluble condensed tannins content of young persimmon fruits-derived crude fibre relates to its bile acid-binding ability

In this study, we prepared crude fibre samples from young fruits of 10 persimmon (Diospyros kaki) cultivars and from young fruits of Japanese pear (Pyrus pyrifolia var. culta) and peach (Prunus persica) and compared their bile acid-binding abilities in?vitro. All crude fibre samples from young fruits of persimmon were able to bind to cholic acid in a 4?mM cholic acid solution, but crude fibre samples from young fruits of Japanese pear and peach did not show bile acid-binding ability. The bile acid-binding ability was strongly correlated with the water-insoluble condensed tannins content in crude fibre samples (r?=?0.909, p?相似文献   

Copolycondensations of bisphenols with aggregates of isophthalic acid and terephthalic acid activated by tosyl chloride/dimethylformamide/pyridine in different manners

A mixture of isophthalic acid (IPA) and terephthalic acid (TPA) was activated by a tosyl chloride/dimethylformamide/pyridine (Py) condensing agent in two steps via the treatment of a mixture of the initially activated IPA/TPA with additional TPA followed by the activation of TPA with the agent. The resulting mixture showed a solubility in Py different from that obtained by the activation of them all at once; the difference might be due to different structures of the aggregates of the activated IPA and TPA at the same composition of the diacids. The structures of the aggregates were evaluated on the basis of melting points and the IR spectra of a mixture of dimethyl esters of IPA and TPA produced by the quenching of the reaction mixtures with methanol. The mixture obtained by two‐step activation showed lower melting points and spectral changes due to enhanced associations of the esters with respect to the mixture prepared by the activation of them all at once. The aggregates were also examined in terms of the distributions of IPA and TPA in thermotropic copolyesters prepared from methylhydroquinone and chlorohydroquinone by their transition temperatures and ¹³C NMR. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3884–3892, 2001     

Facially Dispersed Polyhydride Cu9 and Cu16 Clusters Comprising Apex‐Truncated Supertetrahedral and Square‐Face‐Capped Cuboctahedral Copper Frameworks

By using a linear tetraphosphine, meso‐bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm), nona‐ and hexadecanuclear copper hydride clusters, [Cu₉H₇(μ‐dpmppm)₃]X₂ (X=Cl ( 1 a ), Br ( 1 b ), I ( 1 c ), PF₆ ( 1 d )) and [Cu₁₆H₁₄(μ‐dpmppm)₄]X₂ (X₂=I₂ ( 2 c ), (4/3) PF₆?(2/3) OH ( 2 d )) were synthesized and characterized. They form copper‐hydride cages of apex‐truncated supertetrahedral {Cu₉H₇}²⁺ and square‐face‐capped cuboctahedral {Cu₁₆H₁₄}²⁺ structures. The hydride positions were estimated by DFT calculations to be facially dispersed around the copper frameworks. A kinetically controlled synthesis gave an unsymmetrical Cu₈H₆ cluster, [Cu₈H₆(μ‐dpmppm)₃]²⁺ ( 3 ), which readily reacted with CO₂ to afford linear Cu₄ complexes with formate bridges, leading to an unprecedented hydrogenation of CO₂ into formate catalyzed by {Cu₄(μ‐dpmppm)₂} platform. The results demonstrate that new motifs of copper hydride clusters could be established by the tetraphosphine ligands, and the structures influence their reactivity.     

Simultaneous analysis of cardiac glycosides in blood and urine by thermoresponsive LC-MS-MS

A new thermoresponsive polymer separation column was applied to simultaneous analysis of four cardiac glycosides (CGs) being widely used for the treatment of arrhythmias and heart failure in human blood and urine. This column is composed of an N-isopropylacrylamide polymer, the surface of which undergoes a reversible alteration from hydrophilic to hydrophobic by changing temperature. The chromatographic separation and retention times can be easily be controlled by adjusting the column temperature. As the column temperature was changed from 50 to 10 °C over 8 min, five CGs, including deslanoside, digoxin, methyldigoxin, digitoxin, and digitoxigenin (internal standard) were better resolved. Using these LC conditions, we analyzed four CGs in human whole blood and urine simultaneously by liquid chromatography-tandem mass spectrometry (LC-MS-MS). Validation data as functions of recovery rates, linearity, accuracy, and precision were carefully tested; all were generally satisfactory. The detection limits for the four CGs in both matrices were 0.2–0.3 ng/mL. The method was applied to analysis of methyldigoxin and its main metabolite digoxin in whole blood and urine samples obtained from a deceased person in actual autopsy case. To our knowledge, this is the first report describing an LC-MS-MS method using a thermoresponsive column for analysis of drug(s). The inclusion of the thermoresponsive column in an LC-MS-MS technique seems to extend the possibility for simultaneous analysis of compounds of different properties, such as hydrophobic precursors and their hydrophilic metabolites in biological samples within limited analysis times.     

Overlapping chemical and genetic diversity in Ligularia lamarum and Ligularia subspicata. Isolation of ten new eremophilanes and a new seco-bakkane compound

Root chemicals and DNA sequences were analyzed for Ligularialamarum samples collected in Yunnan and Sichuan Provinces of China and the relationship between the plant and Ligulariasubspicata, its taxonomically closest species, was examined. Both species produce furanoeremophilanes and eremophilan-8-one derivatives as the major components. Eleven new compounds, including a new seco-bakkane compound, were isolated. The two species were found to harbor overlapping intra-specific diversities with respect to the chemicals and the DNA sequences.