1,4‐Diiodobenzene with –COO–TEMPO (TEMPO = 2,2,6,6‐tetramethylpiperidine‐1‐oxyl‐4‐yl) substituents at 2,5‐positions: synthesis and use as a monomer for new π‐conjugated polymers having nitroxyl radicals in side chains

The reaction of 2,5‐diiodo‐1,4‐benzenedicarbonyl chloride, C₆H₂I₂(COCl)₂‐p, with 4‐hydroxy‐2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO‐ol) gave I–Ph(COO–TEMPO)₂–I, Monomer‐1. Pd‐catalyzed polycondensation of Monomer‐1 with Me₃Sn‐Th‐SnMe₃ (2,5‐bis(trimethylstannyl)thiophene) and Bu₃Sn–CH = CH–SnBu₃ (1,2‐bis‐(tributylstannyl)ethylene) gave the corresponding π‐conjugated polymers, Polymer‐1 and Polymer‐2, respectively. Monomer‐1 was converted to a diethynyl compound, H–C ≡ C–Ph(COO–TEMPO)₂–C ≡ C–H (Monomer‐1'), and Pd‐catalyzed polycondensation between Monomer‐1 and Monomer‐1' gave a π‐conjugated poly(arylene ethynylene) type polymer, Polymer‐3. According to the expansion of the π‐conjugation system by the polymerization, the UV–vis peaks of Monomer‐1 (λ_max = 323 nm) and Monomer‐1' (327 nm) are shifted to longer wavelengths (λ_max = 365 nm, 385 nm, and 396 nm for Polymer‐1, Polymer‐2, and Polymer‐3, respectively). Polymer‐1–Polymer‐3 showed ESR signals at about g = 2.01 with reasonable intensities. They are electrochemically active and showed a peak current anodic (oxidation) peak at about 0.9 V versus Ag/AgCl, which is reasonable for TEMPO polymers. Copyright © 2013 John Wiley & Sons, Ltd.     

A novel one-pot synthesis of carbazole-1,4-quinones through Pd-catalyzed cyclocarbonylation,desilylation and oxidation processes from 3-iodo-2-propenylindoles

A novel one-pot synthesis of carbazole-1,4-quinone by consecutive Pd-catalyzed cyclocarbonylation, desilylation, and oxidation reactions is described. We propose a possible mechanism of the cyclocarbonylation reaction between 3-iodo-2-propenylindole and CO (1 atm) in the presence of a tributyl(vinyl)tin and Pd-catalyst and the resulting acylpalladium species was directly coupled with a terminal alkene to produce the carbazole-1,4-quinone. To our knowledge, this is the first example of this type of reaction. A new formal total synthesis of a carbazole-1,4-quinone alkaloid, murrayaquinone A was established using this reaction.     

SEM observation of the live morphology of human red blood cells under high vacuum conditions using a novel RTIL

In this study, we succeed in visualizing a ‘living’ morphology of red blood cells (RBCs) by a rapid and simple scanning electron microscope (SEM) pretreatment using a hydrophilic room temperature ionic liquid (RTIL) with asymmetrical structure. The conventional pretreatment induces size shrinkage of the cells, and the diameter observed in an SEM (less than 6 µm) was smaller than that in an optical microscope (8 µm). Though RBCs are well‐known to be easily deformed with the environmental conditions, the cells did not show the deformation when they were pretreated with our RTILs. Since the chemical structure of our RTIL resembles a ‘choline’, which is a typical bioactive material, and has biocompatibilities, they may make it avoid from the deformation of RBCs. In fact, only immersing RBCs, our novel RTIL can provide a clear SEM image without size shrinkage and deformation. Interestingly, the obtained SEM image shows 8 µm in the diameter, almost same size as that in optical microscope. Therefore, this method is expected for novel SEM pretreatment for various biological samples observation as ‘living’ matter. Copyright © 2014 John Wiley & Sons, Ltd.     

On $$A_1^2$$ A 1 2 restrictions of Weyl arrangements

Journal of Algebraic Combinatorics - Let $$\mathcal {A}$$ be a Weyl arrangement in an $$\ell $$ -dimensional Euclidean space. The freeness of restrictions of $$\mathcal {A}$$ was first settled by a...     

Second-Order Term of Cover Time for Planar Simple Random Walk

Journal of Theoretical Probability - We consider the cover time for a simple random walk on the two-dimensional discrete torus of side length n. Dembo et al. (Ann Math 160:433–464, 2004)...     

<Emphasis Type="Italic">C</Emphasis><Subscript>2</Subscript>-Cofiniteness of the 2-Cycle Permutation Orbifold Models of Minimal Virasoro Vertex Operator Algebras

In this article, we give a sufficient and necessary condition for the C ₂-cofiniteness of \({\widetilde{V} = (V\otimes V)^\sigma}\) for a C ₂-cofinite vertex operator algebra V and the 2-cycle permutation σ of \({V\otimes V}\) . As an application, we show that the 2-cycle permutation orbifold model of the simple Virasoro vertex operator algebra L(c, 0) of minimal central charge c is C ₂-cofinite.     

Orbifold equivalence and the sign problem at finite baryon density

We point out that SO(2N(c)) gauge theory with N(f) fundamental Dirac fermions does not have a sign problem at finite baryon number chemical potential μ(B). One can thus use lattice Monte Carlo simulations to study this theory at finite density. The absence of a sign problem in the SO(2N(c)) theory is particularly interesting because a wide class of observables in the SO(2N(c)) theory coincide with observables in QCD in the large N(c) limit, as we show using the technique of large N(c) orbifold equivalence. We argue that the orbifold equivalence between the two theories continues to hold at finite μ(B) provided one adds appropriate deformation terms to the SO(2N(c)) theory. This opens up the prospect of learning about QCD at finite μ(B) using lattice studies of the SO(2N(c)) theory.     

Synthesis of a base-stabilized silanone-coordinated complex by oxygenation of a (silyl)(silylene)tungsten complex

Base-stabilized silanone complex Cp*(OC)(2)W(SiMe(3)){O═SiMes(2)(DMAP)} (2) was synthesized by the reaction of (silyl)(silylene)tungsten complex Cp*(OC)(2)W(SiMe(3))(═SiMes(2)) (1) with 1 equiv of pyridine-N-oxide (PNO) in the presence of 4-(dimethylamino)pyridine (DMAP). Further oxygenation of 2 with 3 equiv of PNO at 80 °C resulted in the formation of a W-O-Si-O-Si framework to give disiloxanoxy complex Cp*(O)(2)W{OSiMes(2)(OSiMe(3))} (3). Complex 3 was also obtained by the direct reaction of complex 1 with 4 equiv of PNO at 80 °C.     

Fabrication and electrochemical instrumentation of redox‐active nanofiber mat for polyaniline incorporated with poly(imide sulfonate)

In this study, we demonstrate the fabrication of an electrochemically active nanofiber mat that is a composite of high‐performance poly(imide sulfonate) (PIS) and polyaniline (PANI). First, a nonconductive nanofiber mat comprising nanofibers having diameters of ca. 300 nm was fabricated by the electrospinning of ionomeric PIS in N,N‐dimethylformamide (DMF). Then, the nanofibers were modified using PANI, which was synthesized by the oxidative polymerization of aniline, yielding an electrochemically active nanofiber mat having a diameter of ca. 350 nm. It was confirmed that PANI was successfully incorporated onto the PIS nanofiber mats by X‐ray photoelectron spectroscopy. Subsequently, we conducted electrochemical measurements of the PANI‐modified nanofiber mats using a tailor‐made attachment in which the working electrode gently comes in contact with the nanofiber mat surface. This attachment was observed to be widely useful in the cyclic voltammetry measurements related to redox‐active nanofibers. These observations are expected to contribute to the advancements in application development of the electrochemically active nanofiber mats.     

Biosynthesis of Biscognienyne B Involving a Cytochrome P450‐Dependent Alkynylation

The alkyne is a biologically significant moiety found in many natural products and a versatile functional group widely used in modern chemistry. Recent studies have revealed the biosynthesis of acetylenic bonds in fatty acids and amino acids. However, the molecular basis for the alkynyl moiety in acetylenic prenyl chains occurring in a number of meroterpenoids remains obscure. Here, we identify the biosynthetic gene cluster and characterize the biosynthetic pathway of an acetylenic meroterpenoid biscognienyne B based on heterologous expression, feeding experiments, and in vitro assay. This work shows that the alkyne moiety is constructed by an unprecedented cytochrome P450 enzyme BisI, which shows promiscuous activity towards C5 and C15 prenyl chains. This finding provides an opportunity for discovery of new compounds, featuring acetylenic prenyl chains, through genome mining, and it also expands the enzyme inventory for de novo biosynthesis of alkynes.