Nucleophilic Aromatic Substitution Reactions of meso‐Bromosubporphyrin: Synthesis of a Thiopyrane‐Fused Subporphyrin

meso‐Bromosubporphyrin undergoes nucleophilic aromatic substitution (S_NAr) reactions with arylamines, diarylamines, phenols, ethanol, thiophenols, and n‐butanethiol in the presence of suitable bases to provide the corresponding substitution products. The S_NAr reactions also proceed well with pyrrole, indole, and carbazole to provide substitution products in moderate to good yields. Finally, the S_NAr reaction with 2‐bromothiophenol and subsequent intramolecular peripheral arylation reaction affords a thiopyrane‐fused subporphyrin.     

Tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene: A Potential Tetraradicaloid Hydrocarbon

A tetramesityl derivative of hitherto unknown tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene (TCPTP), which is a potential tetraradicaloid hydrocarbon, was synthesized. Theoretical calculations based on spin‐flip time‐dependent density functional theory predict that the closed‐shell D_2h form of TCPTP is more stable than the open‐shell D_4h form with its slightly tetraradical character. The tetramesityl derivative (Mes)₄‐TCPTP exhibits remarkable antiaromaticity as a result of the peripheral 20‐π‐electron circuit, which causes an absorption maximum at a long wavelength and a small HOMO–LUMO gap. In solution, (Mes)₄‐TCPTP most likely adopts rapidly equilibrating D_2h structures that interconvert via the D_4h transition state. X‐ray crystallographic analysis showed (Mes)₄‐TCPTP as an approximate D_2h structure.     

meso‐Hydroxysubporphyrins: A Cyclic Trimeric Assembly and a Stable meso‐Oxy Radical

Treatment of meso‐chlorosubporphyrin with potassium hydroxide in DMSO followed by aqueous work up and recrystallization gave a cyclic trimer consisting of meso‐hydroxysubporphyrin units linked between the central boron atoms and meso‐hydroxy groups. Solutions of this trimer are nonfluorescent, but become fluorescent when exposed to acid or base, since hydrolytic cleavage of the axial B? O bonds generates the meso‐hydroxysubporphyrin monomer or its oxyanion. Ring cleavage of the trimer was also effected by reaction with phenylmagnesium bromide to produce meso‐hydroxy‐B‐phenyl subporphyrin, which can be quantitatively oxidized with PbO₂ to furnish a subporphyrin meso‐oxy radical as a remarkably stable species as a result of spin delocalization over almost the entire molecule.     

Chirality induction in binuclear phthalocyanine tweezers

A novel binuclear phthalocyanine tweezers, in which two zinc-phthalocyanine rings are linked to an optically active binaphthyl group through triazolyl linkages, was self-cyclized through triazolyl-to-zinc coordination bonds. An axially chiral S-binaphthyl group induced planar chirality in a slipped-cofacial stack of phthalocyanine moieties, and therefore displayed fluorescence with a good quantum yield (Φ_F = 0.23) and circularly polarized luminescence with a moderate intensity of dissymmetry factor (g_lum = −4 × 10⁻⁴) in the near-infrared wavelength region.     

Amidine-bearing lipoplex targeting to hepatocyte cells

A lipoplex （i.e., pDNA#1/lipid complex and transfection reagent for pDNA delivery） containing galactosylceramide （GalCer） and an amidine-bearing lipid （TRX） was examined whether the bound pDNA was specifically ingested by hepatocyte via asialoglycoprotein receptor （ASGPR） and then expressed protein. Gel electrophoresis and small-angle X-ray scattering （SAXS） confirmed that the TRX-GalCer liposome#2 complexed with pDNA and the resultant lipoplex took a hexagonally packed inverted cylinder structure when the GalCer composition was less than 20 wt.% of the total lipid. When the lipoplex carrying pGL3 （luciferase-cording pDNA） was administrated to HepG2, the luciferase activity was increased with increasing the GalCer composition until it reached 3 wt.% and then decreased upon further addition of GalCer. When we added galactose itself as a competitor, the luciferase activity was decreased, while glucose did not show such decrease, suggesting that HepG2 ingested the lipoplex via ASGPR-mediated endocytosis. This paper indicated that the hexagonally packed inverted cylinder structures of lipoplex may not always provide excellent transfection and presented a possibility that the TRX lipoplex#3 can obtain a cellulartargeting ability through the receptors for oligosaccharide.     

Direct chlorination of alcohols with chlorodimethylsilane catalyzed by a gallium trichloride/tartrate system under neutral conditions

The reaction of secondary alcohols 1 with chlorodimethylsilane (HSiMe(2)Cl) proceeded in the presence of a catalytic amount of GaCl(3)/diethyl tartrate to give the corresponding organic chlorides 3. In the catalytic cycle, the reaction of diethyl tartrate 4a with HSiMe(2)Cl 2 gives the chlorosilyl ether 5 with generation of H(2). Alcohol-exchange between the formed chlorosilyl ether 5 and the substrate alcohol 1 affords alkoxychlorosilane 6, which reacts with catalytic GaCl(3) to give the chlorinated product 3. The moderate Lewis acidity of GaCl(3) facilitates chlorination. Strong Lewis acids did not give product due to excessive affinity for the oxy-functionalities. Although tertiary alcohols were chlorinated by this system even in the absence of diethyl tartrate, certain alcohols that are less likely to give carbocationic species were effectively chlorinated using the GaCl(3)/diethyl tartrate system.     

Potential energy landscape of bis(fluorosulfonyl)amide

The conformational landscape of the bis(fluorosulfonyl)amide, [FSI]-, anion was analyzed using data obtained from Raman spectroscopy, molecular dynamics (MD), and ab initio studies. The plotting of three-dimensional potential energy surfaces and the corresponding MD simulation conformer-population histograms show the existence of two stable isomers, C2 (trans) and C1 (cis) conformers, and confirm the nature of the anion as a flexible molecule capable of interconversion between conformers in the liquid state. In ionic liquids, the two [FSI]- conformers coexist in equilibrium, a result confirmed by the Raman data. The implications of the conformational behavior of the ion [FSI]- are discussed in terms of the solvation properties of the corresponding ionic liquids.     

Growth process and molecular packing of a self-assembled lipid nanotube: phase-contrast transmission electron microscopy and XRD analyses

Phase-contrast transmission electron microscopy (PC-TEM) and quick freezing method have been combined to study the initial growing process of a self-assembled lipid nanotube in water. The PC-TEM enabled us to detect thin lamellar edge structure and the very fast growth of the newborn edge to a thin tube with high contrast. The thin tube acts as a core structure for further growth into thick complete lipid nanotube. The initially formed nanotube structure is denoted as a "core tube". The core tube has uniform wall structure that consists of five lamellar layers and the inner and outer diameters of the core tube are 130 and 180 nm, respectively. The evaluated lamellar spacing of 4.6 nm is well compatible with that measured by X-ray diffraction. We also discussed the molecular packing of the nanotube from the pitch angle determined by the PC-TEM images, X-ray diffraction pattern in wide-angle region, and IR spectroscopy. The subcell structure of the nanotube is assigned to an orthorhombic type. The twisting angle between the neighboring lipid molecules is determined as ca. 0.26 degrees for the first time; it is a crucial parameter for the formation of a lipid nanotube in chiral packing but has not been elucidated before.     

Sulfur standard solution for use in the determination of low sulfur concentration in liquid fuels

A sulfur reference solution at the 1 mg kg⁻¹ level, NMIJ CRM 4215-a, has been issued by the National Metrology Institute of Japan at the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). The intended use of this CRM is for the calibration of standards used in the determination of sulfur in liquid fuels. The certified value of this CRM was determined using the gravimetric blending method. Thiophene and toluene were chosen as the high purity sulfur compound and the dilution solvent, respectively. Measurements of the trace sulfur in the solvent were performed using the total sulfur analyzer with an enrichment system; the standard addition method was employed. When trace sulfur in the solvent was evaluated, the signal which appears with no sample injection was subtracted as the background.     

Arraying heterotypic single cells on photoactivatable cell-culturing substrates

This article describes a photochemical method for the site-selective assembly of heterotypic cells on a glass substrate modified with a silane coupling agent having a caged functional group. Silane coupling agents having a carboxyl (COOH), amino (NH 2), hydroxyl (OH), or thiol (SH) group protected by a photocleavable 2-nitrobenzyl group were synthesized to modify the surfaces of glass coverslips. The caged substrates were first coated by the adsorption of a blocking agent, bovine serum albumin (BSA), to make the entire surface non-cell-adhesive and then irradiated at 365 nm under a standard fluorescence microscope. The photocleavage reaction on the surface was followed by contact angle measurements and X-ray photoelectron spectroscopy. When COS7, NIH3T3, and HEK293 cells were seeded onto these substrates in a serum-free medium, the cells adhered selectively and efficiently to the irradiated regions on the caged NH 2 substrate, whereas the other caged COOH, SH, and OH substrates were nonphotoactivatable for cell adhesion. Qualitative and quantitative analysis of BSA adsorbed to the uncaged substrates revealed that this highly efficient photoactivation on the caged NH 2 substrate arose because of the following reasons: (i) upon photoactivation, BSA adsorbed in advance on the 2-nitrobenzyl groups was readsorbed onto the uncaged functional groups and (ii) BSA readsorbed onto the NH 2 groups became unable to passivate the surface against cell adhesion whereas BSA on the other groups still had normal passivating activity. It was also demonstrated that heterotypic single COS7, NIH3T3, and HEK293 cells were positioned at any desired arrangement on the caged NH 2 substrate by repeating the UV irradiation at optimized array spot sizes and cell seeding in optimized cell concentrations. The present method will be particularly useful in studying the dynamic processes of cell-cell interactions at a single-cell level.