Bifunctional Catalysts Based on m‐Phenylene‐Bridged Porphyrin Dimer and Trimer Platforms: Synthesis of Cyclic Carbonates from Carbon Dioxide and Epoxides

Highly active bifunctional diporphyrin and triporphyrin catalysts were synthesized through Stille coupling reactions. As compared with a porphyrin monomer, both exhibited improved catalytic activities for the reaction of CO₂ with epoxides to form cyclic carbonates, because of the multiple catalytic sites which cooperatively activate the epoxide. Catalytic activities were carefully investigated by controlling temperature, reaction time, and catalyst loading, and very high turnover number and turnover frequency were obtained: 220 000 and 46 000 h^?1, respectively, for the magnesium catalyst, and 310 000 and 40 000 h^?1, respectively, for the zinc catalyst. Results obtained with a zinc/free‐base hybrid diporphyrin catalyst demonstrated that the Br^? ions on the adjacent porphyrin moiety also function as nucleophiles.     

Spatiotemporal laser inactivation of inositol 1,4,5-trisphosphate receptors using synthetic small-molecule probes

A malachite green-conjugated inositol 1,4,5-trisphosphate (MGIP(3)) induces specific inactivation of IP(3) receptor (IP(3)R) in tissue samples upon laser irradiation. To verify potential usefulness of the method for studies of cellular Ca(2+) signaling, we conducted laser inactivation at the single-cell level and show that IP(3)R was inactivated with extremely high spatiotemporal resolution. In the presence of MGIP(3), the Ca(2+) release function of IP(3)R in single B lymphoma cells decayed exponentially with increasing duration of laser irradiation with a time constant of 3.4 s. Moreover, by confining laser irradiation to a spatially distinct region of differentiated PC12 cells, subcellular inactivation of IP(3)R was attained, as revealed by a loss of local Ca(2+) signal. Such real-time inactivation of IP(3)R only within a subcellular region may provide a powerful method for investigating spatiotemporal dynamics of Ca(2+) signaling.     

Frequency dependence of intermolecular proton spin-lattice relaxation rate and pair-diffusion constant in neat acetonitrile -d2

Frequency dependence of intermolecular proton spin-lattice relaxation rate [(1/T₁)inter(ω)] in neat acetonitrile-d₂ was studied. From (1/T₁)inter(ω) pair-diffusion constants were determined to be 0.281 × 10^?5 and 0.237 × 10^?5 cm² s^?1 at 22 and ?32.6°C, respectively. These values differ greatly from the self-diffusion constants.     

Total synthesis and biological evaluation of verticipyrone and analogues

[reaction: see text] Total synthesis of verticipyrone, a novel NADH-fumarate reductase inhibitor, has been accomplished by a convergent approach using novel "Reverse Julia olefination" method. During total synthetic studies, we also prepared and evaluated several synthetic verticipyrone analogues, some of which exhibited more potent antiparasitic activity than the natural verticipyrone.     

The reaction of selenoaldehydes with 2-methoxyfuran using their generation by retro Diels-Alder reaction

Selenoaldehydes, regenerated by thermal retro Diels-Alder reaction of anthracene cycloadducts under neutral conditions, reacted with 2-methoxyfuran to give methyl penta-2,4-dienoates along with the deposition of elemental selenium. In a similar reaction with 2-methoxyfuran using thioaldehyde, thiirane compound was isolated. This suggests the formation of selenirane intermediates in the above reaction.     

Selective synthesis of lower olefins by catalytic conversion of methanol

C₂C₄ olefins were synthesized from methanol on modified ZSM-34 type zeolite catalyst at 400°C. Methanol vapor of 12 vol.% was converted completely under flow conditions at 800 h^–1 space velocity, and in molar selectivity 42.9% C₂H₄, 33.4% C₃H₆, and 3.3% C₄H₈ were produced.

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C₂C₄ ZSM-34 400°C. 12 .%-, 800 h–1 : C₂H₄-42,9%, C₃H₆-33,4% C₄H₈-3,3%.

     

Convergent and enantioselective total synthesis of (−)-nalanthalide, a potential Kv1.3 blocking immunosuppressant

The first total synthesis of (−)-nalanthalide (1), a novel blocker of the voltage-gated potassium channel Kv1.3 from a microorganism, was accomplished in a convergent manner by utilizing coupling reaction of the trans-decalin 5 with 3-lithio-γ-pyrone 4. The key intermediate 5 was efficiently prepared from the known trans-decalone 7 through a [2,3]-Wittig rearrangement of the stannylmethyl ether 6 to install the stereogenic center at C9 and the exo-methylene function at C8.     

Facile Synthesis of Azahelicenes and Diaza[8]circulenes through the Intramolecular Scholl Reaction

Carbazole-based aza[7]helicenes and hetero[9]helicenes were successfully obtained via the intramolecular Scholl reaction of 3,6-bis(biphenyl-2-yl)carbazole congeners, while the reaction of 3,6-bis(naphthylphenyl)-appended carbazole gave a triple helicene via an unexpected simultaneous double aryl rearrangement. DFT calculations suggested that the rearrangement proceeded via an arenium cation intermediate. In addition, the reaction of methoxy-appended substrate gave an azahepta[8]circulene via the concurrent C−C bond formation. These helical dyes showed circularly polarized luminescence. The azahepta[8]circulene was further transformed into deeply saddle-distorted dibenzodiaza[8]circulenes as the first example of its solution-based synthesis and unambiguous structural determination.