Application of chemical reaction mechanistic domains to an ecotoxicity QSAR model,the KAshinhou Tool for Ecotoxicity (KATE)

The validity of chemical reaction mechanistic domains defined by skin sensitisation in the Quantitative Structure–Activity Relationship (QSAR) ecotoxicity system, KAshinhou Tools for Ecotoxicity (KATE), March 2009 version, has been assessed and an external validation of the current KATE system carried out. In the case of the fish end-point, the group of chemicals with substructures reactive to skin sensitisation always exhibited higher root mean square errors (RMSEs) than chemicals without reactive substructures under identical C- or log?P-judgements in KATE. However, in the case of the Daphnia end-point this was not so, and the group of chemicals with reactive substructures did not always have higher RMSEs: the Schiff base mechanism did not function as a high error detector. In addition to the RMSE findings, the presence of outliers suggested that the KATE classification rules needs to be reconsidered, particularly for the amine group. Examination of the dependency of the organism on the toxic action of chemicals in fish and Daphnia revealed that some of the reactive substructures could be applied to the improvement of the KATE system. It was concluded that the reaction mechanistic domains of toxic action for skin sensitisation could provide useful complementary information in predicting acute aquatic ecotoxicity, especially at the fish end-point.     

Electroreductive intramolecular coupling of phthalimides with aromatic aldehydes: application to the synthesis of lennoxamine

The electroreductive intramolecular coupling of phthalimides with aromatic aldehydes in the presence of chlorotrimethylsilane and triethylamine led to five-, six-, and seven-membered cyclized products (58-84%). The electroreductive cyclization was applied to the total synthesis of lennoxamine.     

Concentration of239, 240Pu in human bone

Some results of the plutonium determination for bone ash samples collected in Japan are presented. Mean^239,240Pu concentration in the adult vertebra was 0.53 pCi/kg of ash during the period 1978 through 1983. The data are roughly in coincidence with estimated plutonium concentrations in the trabecular bone from reported air plutonium concentrations using the ICRP model and metabolic data, and weight of bone in Reference Japanese Man.     

Stationary and time-resolved spectra of 2,2′:5′,2″-terthiophene

By analyzing the stationary absorption spectrum of 2,2′:5′,2″-terthiophene in dichloromethane at room temperature, the zero–zero S₁←S₀ transition energy is determined. Time-resolved fluorescence measurements show that the S₁→S₀ radiative relaxation in various solvents decays exponentially with a common time constant of 170±10 ps. The fluorescence anisotropy of 2,2′:5′,2″-terthiophene in dichloromethane is also studied and the transient dichroism is interpreted in terms of the revolution of a hydrodynamic prolate ellipsoid with the emission dipole aligned parallel to the long molecular axis.     

Synthesis of optically active alicyclic polyimides from a chiral,nonracemic dianhydride

Optically active alicyclic polyimides were prepared for the first time from (?)‐[1S*,5R*,6S*]‐3‐oxabicyclo[3.2.1]octane‐2,4‐dione‐6‐spiro‐3′‐(tetrahydrofuran‐ 2′,5′‐dione) [(?)‐DAn] via polycondensation with diamines and subsequent chemical or thermal imidization. The dianhydride (?)‐DAn was synthesized by an asymmetric Diels–Alder reaction of a chiral itaconic acid derivative as a key step. Colorless or slightly yellow flexible films were obtained for the (?)‐DAn‐derived polyimides {PI[(?)‐DAn]s}. PI[(?)‐DAn]s showed good solubility toward dipolar aprotic solvents and pyridine. For 1,4‐dioxane and chloroform, the optically active polyimides showed slightly better solubility than the corresponding polyimides prepared from rac‐DAn [PI(rac‐DAn)s]. PI[(?)‐DAn]s showed glass‐transition temperatures of 267–268 °C and 10% weight‐loss temperatures of 416–424 °C in nitrogen. These values were almost identical to those of PI(rac‐DAn)s. The circular dichroism spectra of PI[(?)‐DAn]s showed exciton coupling patterns indicating that to some extent these polyimides had a higher order structure in solution. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4038–4044, 2002     

Enol-to-keto tautomerism of peptide groups

Density functional based simulations, performed on polyglycine containing an enol peptide group [-C(OH)N-] which is a structural isomer of a keto form [-CONH-], show that in the enol-to-keto tautomeric reaction, the enol peptide group is less stable than the keto form, and that the enol-to-keto tautomerism is characterized by a cis/trans isomerization of the C-N peptide bond. The rate-limiting step in the cis/trans isomerization is a hydrogen migration from O to N atoms in the peptide group with a transition state consisting of a four-membered ring in the cis configuration. An analysis of the cis/trans isomerization pathway shows that the mechanisms for the cis/trans isomerization are essentially different between the enol and keto forms.     

The effect of aluminium compounds in the copolymerization of ethylene / α-olefins

Two types of copolymerizations were found with the catalyst system Cp₂ZrCl₂/MAO. One was a less exothermic reaction, and another was a more exothermic one. The former provided a polymer with a single composition distribution because of a single cationic active site. The latter provided a polymer with a bimodal composition distribution, indicating the existence of two active sites. The two active sites were investigated through the comparison of MAO systems and alkylaluminium / borate systems. We speculated that the two active sites were the normal cationic site and the active site where the interaction between a cationic metallocene and an aluminium compound was strong.