DNA alkylation by pyrrole-imidazole seco-CBI conjugates with an indole linker: sequence-specific DNA alkylation with 10-base-pair recognition through heterodimer formation

The sequence-specific DNA alkylation by conjugates 4 and 5, which consist of N-methylpyrrole (Py)-N-methylimidazole (Im) polyamides and 1-(chloromethyl)-5-hydroxy-1,2-dihydro-3H-benz[e]indole (seco-CBI) linked with an indole linker, was investigated in the absence or presence of partner Py-Im polyamide 6. High-resolution denaturing polyacrylamide gel electrophoresis revealed that conjugate 4 alkylates DNA at the sequences 5'-(A/T)GCCTA-3' through hairpin formation, and alkylates 5'-GGAAAGAAAA-3' through an extended binding mode. However, in the presence of partner Py-Im polyamide 6, conjugate 4 alkylates DNA at a completely different sequence, 5'-AGGTTGTCCA-3'. Alkylation of 4 in the presence of 6 was effectively inhibited by a competitor 7. Surface plasmon resonance (SPR) results indicated that conjugate 4 does not bind to 5'-AGGTTGTCCA-3', whereas 6 binds tightly to this sequence. The results suggest that alkylation proceeds through heterodimer formation, indicating that this is a general way to expand the recognition sequence for DNA alkylation by Py-Im seco-CBI conjugates.     

Notable effect of an electron-withdrawing group at C3 on the selective formation of alkylidenecyclobutanes in the thermal denitrogenation of 4-spirocyclopropane-1-pyrazolines. Nonstatistical dynamics effects in the denitrogenation reactions

A detailed study of the thermal denitrogenation of 3-carbomethoxy-substituted 4-spirocyclopropane-1-pyrazolines 6 was conducted. Alkylidenecyclobutane derivatives 7 were selectively formed in a stereospecific manner. Unrestricted density functional calculations for a 1-pyrazoline 10a indicated that the concerted cleavage of two C-N bonds is the energetically favored process for the denitrogenation reaction to give the 2-spirocyclopropyl 1,3-diyl, followed by a conrotatory ring-closure process, which was calculated to be the energy minimum pathway, to afford a spiropentane derivative. The calculated energy minimum pathway is largely inconsistent with the experimental results observed for the denitrogenation of 6 and 10a. The contradiction between the experimental and standard computational results was solved by considering nonstatistical dynamics effects in the concerted denitrogenation reactions. Although the energy minimum pathway from the transition states of the concerted denitrogenation of the 3-carboalkoxy-substituted 1-pyrazolines involves generation of the corresponding 1,3-diradicals, many trajectory calculations using the Bohn-Oppenheimer molecular dynamics model from the transition state for the concerted denitrogenation led directly to the formation of alkylidenecyclobutanes at the UB3LYP/6-31G(d) level of theory.     

Unusual catalytic effect of the two-dimensional molecular space with regular triphenylphosphine groups

A novel organic-inorganic hybrid 2D molecular space with regular triphenylphosphine groups (triphenylphosphineamidephenylsilica, PPh(3)APhS) was successfully synthesized through grafting triphenylphosphine groups in the 2D structure of layered aminophenylsilica dodecyl sulfate (APhTMS-DS), which was developed in our previous research, with regular ammonium groups. The 2D structures were kept after the grafting reaction of triphenylphosphine groups in PPh(3)APhS. The catalytic potentials of 2D molecular space with regular triphenylphosphine groups were investigated. An unusual catalytic effect was found in a carbon-phosphorus ylide reaction. The PPh(3)-catalyzed reaction of modified allylic compounds, including bromides and chlorides with tropone yielded a [3 + 6] annulation product. However, an unusual [8 + 3] cycloadduct was obtained in the reaction of modified allylic compounds, including bromides and chlorides with tropone catalyzed by PPh(3)APhS. Otherwise, the stable catalytic intermediate was successfully separated, and the reaction activity of the catalytic intermediate was confirmed in the reaction of modified allylic compounds with tropone catalyzed by PPh(3)APhS. This research is the first successful example of directly influencing catalytic reaction processes and product structures by utilizing the chemical and geometrical limits of 2D molecular spaces with regular catalyst molecules and affords a novel method for controlling catalytic reaction processes and catalyst design.     

A rational design for the directed helicity change of polyacetylene using dynamic rotaxane mobility by means of through-space chirality transfer

Directed helicity control of a polyacetylene dynamic helix was achieved by hybridization with a rotaxane skeleton placed on the side chain. Rotaxane-tethering phenylacetylene monomers were synthesized in good yields by the ester end-capping of pseudorotaxanes that consisted of optically active crown ethers and sec-ammonium salts with an ethynyl benzoic acid. The monomers were polymerized with [{RhCl(nbd)}(2)] (nbd=norbornadiene) to give the corresponding polyacetylenes in high yields. Polymers with optically active wheel components that are far from the main chain show no Cotton effect, thereby indicating the formation of racemic helices. Our proposal that N-acylative neutralization of the sec-ammonium moieties of the side-chain rotaxane moieties enables asymmetric induction of a one-handed helix as the wheel components approach the main chain is strongly supported by observation of the Cotton effect around the main-chain absorption region. A polyacetylene with a side-chain rotaxane that has a shorter axle component shows a Cotton effect despite the ammonium structure of the side-chain rotaxane moiety, thereby suggesting the importance of proximity between the wheel and the main chain for the formation of a one-handed helix. Through-space chirality induction in the present systems proved to be as powerful as through-bond chirality induction for formation of a one-handed helix, as demonstrated in an experiment using non-rotaxane-based polyacetylene that had an optically active binaphthyl group. The present protocol for controlling the helical structure of polyacetylene therefore provides the basis for the rational design of one-handed helical polyacetylenes.     

Two new cytotoxic phenylallylflavanones from Mexican propolis

Two new phenylallylflavanones, (2R,3R)-6-[1-(4'-hydroxy-3'-methoxyphenyl)prop-2-en-1-yl]pinobanksin (1) and (2R,3R)-6-[1-(4'-hydroxy-3'-methoxyphenyl)prop-2-en-1-yl]pinobanksin 3-acetate (2) were isolated from a methanolic extract of Mexican propolis. Their structures were elucidated with spectroscopic analysis. Both compounds (1, 2) exhibited preferential cytotoxic activity against PANC-1 human pancreatic cancer cells in a nutrient-deprived medium with the concentration at which 50% cells died preferentially in NDM (PC??) values of 17.9 μM and 9.1 μM, respectively.     

A G-octamer scaffold via self-assembly of a guanosine-based Au(I) isonitrile complex for Au(I)-Au(I) interaction

A guanosine-based Au(I) isonitrile complex was demonstrated to serve as the reliable scaffold via self-assembly, wherein the quartet and octamer were formed in the absence and presence of a potassium ion, respectively, exhibiting a switchable emission based on Au(I)-Au(I) interaction.     

Thiourea-tagged poly(octadecyl acrylate) gels as fluoride and acetate responsive polymer gels through selective complexation

Fluoride and acetate-responsive polymer gels were prepared by incorporation of p-nitrophenylthiourea into poly(octadecyl acrylate) gels, and the colours and volumes were changed selectively in the presence of these ions by complexation in THF.     

Microscopic evidence of a metallic state in the one‐pot organic conductor ammonium tetrathiapentalene carboxylate

¹H NMR (nuclear magnetic resonance) and high‐field ESR (electron spin resonance) measurements were carried out for self‐doped organic conductors in the ammonium tetrathiapentalene carboxylate (TTPCOO)₂[(NH₄¹⁺)_1–x(NH₃⁰)_x ] system. While the pristine TTPCOOH molecule is closed‐shell, self‐doped carriers are generated by substitution of the carboxyl proton by (NH₃⁰) and (NH₄¹⁺), which can be regarded as a charge reservoir. The π‐extended system TTPCOO has a uniaxial g ‐tensor, indicating a 2D isotropic structure such as a herring‐bone‐like or parallel cross donor arrangement. The NMR‐relaxation rate indicated the Korringa relation in the temperature dependence, and the ESR linewidth followed the Elliot mechanism. Both of these observations provide supporting evidence for a stable metallic state. In this paper, we introduce self‐doped organic conductors as a branch of materials design, and emphasize that advanced magnetic resonance measurements are powerful tools for developing functional materials. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Preparation and Properties of Aliphatic Polybenzoxazoles from 4,4′-Diamino-3,3′-Dihydroxybiphenyl and Aliphatic Dicarboxylic Acid Chlorides by the Silylation Method

Abstract

A series of aliphatic polybenzoxazoles of high molecular weights was prepared in three steps by the low-temperature solution polycondensation of tetrakis(trimethylsilyl)-substituted 4,4′-diamino-3,3′-dihydroxy-biphenyl with aliphatic diacid chlorides with 7 to 12 methylene units yielding trimethylsilyl-substituted poly(o-hydroxysamide) precursor polymers, which were subjected to desilylation with methanol giving the poly(o-hydroxyamide)s, followed by thermal cyclodehydration. The aliphatic polybenzoxazoles had melting points in the 172 to 246 °C range with glass transition temperatures of 55-97°C. They were stable in the melt state up to 400 °C in nitrogen. These polybenzoxazoles and the corresponding bisbenzoxazole model compounds exhibited no liquid crystallinity.