Rhenium-catalyzed insertion of aldehyde into a C-H bond: synthesis of isobenzofuran derivatives

A rhenium complex, [ReBr(CO)3(thf)]2, catalyzed reactions of aromatic ketimines with aldehydes to give isobenzofuran derivatives in good to excellent yields. In contrast to ruthenium and rhodium catalysts, aldehydes, which are polar unsaturated molecules, inserted into the C-H bond after activation by the rhenium complex.     

Evaluation of CH3-DTPA-Gd (NMS60) as a new MR contrast agent: early phase II study in brain tumors and dual dynamic contrast-enhanced imaging

PURPOSE: A newly developed contrast material, CH3-DTPA-Gd (NMS60), a trimer containing 3 Gd(3+) atoms per molecule, has been shown to offer greater enhancement and longer vascular retention than gadopentetate dimeglumine (Gd-DTPA) in animals. We report on our early phase II study on NMS60 in brain tumor patients together with supplementary investigations. METHODS AND MATERIALS: The longitudinal relaxation rate (R(1)=1/T(1)) and the transverse relaxation rate (R(2)*=1/T(2)*) of NMS60 and Gd-DTPA were determined at 20 degrees C in water at 1.5 T. An NMS60 dose of 0.1 or 0.2 mmol (Gd)/kg was randomly assigned and administered to 10 patients (five women, five men; mean age: 49 years) with brain tumors. Safety and contrast-enhancing ability of NMS60 were evaluated. Dual dynamic contrast-enhanced T(1) and R(2)* studies (DUCE imaging) were also carried out in two patients. RESULTS: Regarding the relaxivity per Gd, R(1) and R(2)* of NMS60 were 9.5 and 11.0 (mmol/L x s)(-1), respectively, compared to 4.8 and 7.2 (mmol/L x s)(-1) for Gd-DTPA. Although a transient slight increase of alanine aminotransferase was observed in one case, no other adverse reactions were observed after administration of NMS60. Contrast enhancement by NMS60 was excellent at both concentrations, and when tumor detectability was assessed with a five-point scale, the diagnostic usefulness was 4 or higher in all cases. In DUCE imaging, NMS60 appeared to show high signal intensity, when compared with the data obtained separately for Gd-DTPA. CONCLUSION: NMS60 had a high contrasting effect and little toxicity, and is expected to be clinically useful.     

Aerobic oxidation of thiols to disulfides catalyzed by trichlorooxyvanadium

Thiols were converted into disulfide by the aerobic oxidation catalyzed by trichlorooxyvanadium in the presence of molecular sieves 3A.     

Enantioselective Synthesis of 1,2-Benzothiazine 1-Imines via RuII/Chiral Carboxylic Acid-Catalyzed C−H Alkylation/Cyclization

Sulfondiimines are diaza-analogues of sulfones with a chiral sulfur center. Compared to sulfones and sulfoximines, their synthesis and transformations have so far been studied to a lesser extent. Here, we report the enantioselective synthesis of 1,2-benzothiazine 1-imines, i.e., cyclic sulfondiimine derivatives from sulfondiimines and sulfoxonium ylides via C−H alkylation/cyclization reactions. The combination of [Ru(p-cymene)Cl₂]₂ and a newly developed chiral spiro carboxylic acid is key to achieving high enantioselectivity.     

Discovery of New Cytotoxic Aplaminone Derivatives from the Sea Hare Aplysia kurodai and Elucidation of Their Accumulation from Local Sea Algae through the Food Chain

The shell-less herbivorous marine mollusk (sea hare) Aplysia kurodai is known to contain a variety of bioactive substances. While these compounds have been thought to originate from sea algae or their associated microbes, most of their origin and acquisition pathways are still unclear. Six new cytotoxic aplaminone derivatives, bromodopamine-terpenoid hybrid molecules, were isolated from A. kurodai. Among them, isoaplaminone had a reverse prenyl group at the C15 aliphatic chain, which is a rare structural feature from the viewpoint of terpenoid biosynthesis. Investigation for chemical components in A. kurodai and the sea algae collected at several different locations revealed that two major aplaminones were contained in the Laurencia complex species at specific sites. Our chemical and ecological studies provide new insights into the origin of marine alkaloid toxins and their dynamism through the food chain.     

Optimal harvesting policy of an inland fishery resource under incomplete information

A new mathematical model for finding the optimal harvesting policy of an inland fishery resource under incomplete information is proposed in this paper. The model is based on a stochastic control formalism in a regime‐switching environment. The incompleteness of information is due to uncertainties involved in the body growth rate of the fishery resource: a key biological parameter. Finding the most cost‐effective harvesting policy of the fishery resource ultimately reduces to solving a terminal and boundary value problem of a Hamilton‐Jacobi‐Bellman equation: a nonlinear and degenerate parabolic partial differential equation. A simple finite difference scheme for solving the equation is then presented, which turns out to be convergent and generates numerical solutions that comply with certain theoretical upper and lower bounds. The model is finally applied to the management of Plecoglossus altivelis, a major inland fishery resource in Japan. The regime switching in this case is due to the temporal dynamics of benthic algae, the main food of the fish. Model parameter values are identified from field measurement results in 2017. Our computational results clearly show the dependence of the optimal harvesting policy on the river environmental and biological conditions. The proposed model would serve as a mathematical tool for fishery resource management under uncertainties.     

Copper-Catalyzed Oxidative Benzylic C(sp3)−H Cyclization for the Synthesis of β-Lactams

β-Lactams are important structural motifs because of their ubiquity in natural products and pharmaceuticals. We report herein a Cu-catalyzed intramolecular oxidative C(sp³)−H amidation for the synthesis of β-lactams using tBuOOtBu. This method is based on Kharasch–Sosnovsky amidation and does not require prefunctionalization of C(sp³)−H bonds or the installation of a directing group, thereby allowing for the straightforward synthesis of β-lactams. Our intramolecular functionalization protocol can be extended to diverse benzylic C(sp³)−H bonds and shows excellent functional-group tolerance.     

Success or Failure of Chiral Crystallization of Similar Heterocyclic Compounds

Single crystals of two achiral and planar heterocyclic compounds, C₉H₈H₃O(CA1) and C₈H₅NO₂ (CA4), recrystallized from ethanol, were characterized by single crystal X-ray analysis, respectively, and chiral crystallization was observed only for CA1 as P2₁2₁2₁ (# 19), whereas it was not observed for CA4 P2₁/c (# 14). In CA1, as a monohydrate, the hydrogen bonds were pronounced around the water of crystallization (O4), and the planar cyclic sites were arranged in parallel to slightly tilted positions. On the other hand, an anhydride CA4 formed a dimer by hydrogen bonds between adjacent molecules in the crystal, which were aggregated by van der Waals forces and placed in parallel planar cyclic sites.     

Synthesis,crystal structure,and FET characteristics of thieno[2,3-b]thiophene-based bent-thienoacenes

Two novel bent-shaped thienoacenes, naphtho[2,3-b]naphtho[2′,3′:4,5]thieno[3,2-d]thiophene (bent-DNTT) and anthra[2,3-b]anthra[2′,3′:4,5]thieno[3,2-d]thiophene (bent-DATT) were synthesized from thieno[2,3-b]thiophene and their corresponding aromatic anhydrides by three steps: Friedel–Crafts acylation, acid-promoted cyclization, and reductive aromatization. The structural curvature improved the solubility of these thienoacenes in organic solvents. The bent-DNTT based FET device was fabricated by the spin-coating method. The device exhibited p-type characteristics with a mobility of 5.1 × 10^?5 cm² V^?1 s^?1. Its thin-film structure was fully characterized as an edge-on orientation with large intermolecular orbital coupling.     

Optimisation of pre-treatment and ionisation for GC/MS analysis for the determination of chlorinated PAHs in atmospheric particulate samples

Chlorinated polycyclic aromatic hydrocarbons (ClPAHs) have been discovered to represent ubiquitous environmental pollutants in the last decade. In the present study, sample pre-treatment and ionisation conditions associated with the gas chromatography/mass spectrometry (GC/MS) analysis of ClPAHs were evaluated. The optimal pre-treatment of ambient air particulate samples was achieved using fractionation over silica gel with 10% dichloromethane in n-hexane as the eluent. The optimised condition of GC/MS with electron impact ionisation permitted analysis of all target ClPAHs. Not all target ClPAHs were detected using GC/MS with negative chemical ionisation, although this technique exhibited greater sensitivity for several of the compounds compared to electron impact ionisation. The analytical method was applied to the survey of ClPAHs in atmospheric particulate matter obtained close to an industrial site and in a standard sample of tunnel dust. Fourteen and eighteen species of ClPAHs were detected in the industrial air samples and tunnel dust, respectively, confirming the capability of the method. The compositions of ClPAHs were significantly different between air samples and tunnel dust. It suggests that alternative emission sources rather than vehicle exhaust could play a significant role in the air.