Theoretical study on the phenyl torsional potentials of trans-diphenyldiphosphene

The phenyl torsional potentials of trans-diphenyldiphosphene ( trans-phosphobenzene; t-DPP), which is an analogue of trans-azobenzene ( t-AZB), have been examined by means of ab initio complete active space self-consistent field (CASSCF) calculations. Though the electronic structures of t-DPP are similar to those of t-AZB, the phenyl torsional potentials are different from each other. In S 0, the potential energy curve of t-DPP has double minima at nonplanar conformations with C 2 and C i symmetries, while that of t-AZB has only minimum at a planar conformation with C 2 h . In S 1, the phenyl torsion of t-AZB is impeded from a planar geometry more than that in S 0. On the other hand, the phenyl torsion of t-DPP is promoted so that the phenyl groups are perpendicularly twisted against the PP double bond around the Franck-Condon region. Comments on the experimental findings of realistic diphosphenes protected by bulky substituents are also made.     

Two new monodesmosidic triterpene saponins from Gypsophila oldhamiana

Two new monodesmosidic triterpene saponins were isolated from the roots of Gypsophila oldhamiana (Caryophyllaceae). Their structures were elucidated on the basis of spectral data to be quillaic acid, alpha-L-arabinopyranosyl-(1-->4)-alpha-L-arabinopyranosyl-(1-->3)-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-fucopyranosyl ester (1), and vaccaric acid, beta-D-glucopyranosyl-(1-->3)-[beta-D-xylopyranosyl-(1-->4)]-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-fucopyranosyl ester (2). Compound 1 showed a significant enhancement of granulocyte phagocytosis in vitro.     

Counterion, temperature, and time modulation of nanometric chiral ribbons from gemini-tartrate amphiphiles

Amphiphile supramolecular assemblies result from the cooperative effects of multiple weak interactions between a large number of subcomponents. As a result, prediction of and control over the morphologies of such assemblies remains difficult to achieve. Here, we described the fine-tuning of the shape, size, and morphology transitions of twisted and helical membranes formed by non-chiral dicationic n-2-n gemini amphiphiles complexed with chiral tartrate anions. We have reported that such systems express the chirality of the tartrate components at a supramolecular level and that the mechanism of the chiral induction by counterions involves specific anion cation recognition and the induction of conformationally labile chirality in the cations. Here, we demonstrate that the morphologies and dimensions of twisted and helical ribbons, as well as tubules, can be controlled and that interconversion between these structures can be induced upon modifying temperature, upon introducing small amounts of additives, or slightly modifying molecular structure. Specifically, electron microscopy, IR spectroscopy, and small-angle X-ray scattering show that (i) varying the hydrophobic chain length or adding gemini having bromide counterions (1%) or the opposite enantiomer (10%) leads to an increase of the diameter of membrane tubules from 33 to 48.5 nm; (ii) further addition (1.5%) of gemini bromide or a slight increase in temperature induces a transition from tubules to twisted ribbons; (iii) the twist pitch of the ribbons can be continuously tuned by varying enantiomeric excess; and (iv) it was also observed that the morphologies of these ribbons much evolve with time. Such unprecedented observations over easy tuning of the chiral supramolecular structures are clearly related to the original feature that the induction of chirality is solely due the counterions, which are much more mobile than the amphiphiles.     

Acid catalyzed ring contractions in endo-2,8-trimethylene-cis-bicyclo[3.3.0]octyl cations to methylperhydrotriquinacenes. One of the methyl ext

Sulfuric acid catalyzed ring contractions with extrusion of a methyl group were examined for alcohol and olefin derivatives (28–31) of endo-2,8-trimethylene-cis-bicyclo[3.3.0]octane (11), which was one of the two possible progenitors, among altogether 69 isomers, for methylperhydrotriquinacenes (6, 7 and 12), the only methyltricyclodecane intermediates found so far, in the tricycloundecane rearrangement. Only minor amounts (1.6–2.0%) of methylperhydrotriquinacenes were formed from these reactants 28–31, and the results support the earlier theoretical conclusion that the methyl extrusions were in general energetically quite unfavorable processes owing to the formation of primary carbinyl cations at the expense of more stable secondary bridge or tertiary bridgehead ones. Reaction pathways for these precursors 28–31 were discussed with reference to those of perhydrotriquinacene 2-carbinyl cations (33a's), which corresponded to some of the ring contraction product cations from 28–31.     

Synthesis of N-azolylindoles by copper-catalyzed C-H/N-H coupling-annulation sequence of o-alkynylanilines

A wide range of o-alkynylanilines undergo a copper-catalyzed direct C-H/N-H coupling with azoles followed by benzannulation to form the corresponding N-azolylindoles in good yields. The domino reaction proceeds effectively with molecular oxygen as the sole oxidant and provides a new dehydrogenative access to the titled compounds of interest in pharmaceutical and material sciences.     

Aggregation behaviors of gemini nucleotide at the air-water interface and in solutions induced by adenine-uracil interaction

Cationic gemini surfactants having nucleotides as counterions (called nucleo-gemini hereafter) were synthesized and their aggregation behavior at air-water surfaces as well as in bulk solutions were studied. Fluid solutions of these nucleo-gemini surfactants show transitions to hydrogels upon addition of complementary nucleoside bases or other nucleo-gemini surfactants having complementary bases as counterions. The FTIR-ATR measurements show that the carboxylate groups of uridine form hydrogen bonds with the amine groups of adenosine. The aggregation behavior was also confirmed at the air-water interface by Brewster angle microscopy as well as surface pressure measurements; the monolayer of a gemini nucleotide was observed to undergo a transition to multilayers when nucleosides with complementary bases were added into the subphase. Isotherm curves of surface pressure monitored in parallel show a decrease in molecular area upon addition of such nucleosides.     

Redox-switching of intramolecular magnetic interaction through π-conjugation mode change of 1,2-bis(4-dianisylamino)-1,2-bis(3-N-oxylamino)-substituted tetraarylethylene

To develop the redox-switching system of intramolecular magnetic interaction, 1,2-bis[3-(N-tert-butyl-N-oxylamino)phenyl]-1,2-bis[4-{N,N-bis(4-methoxyphenyl)amino}phenyl]ethylene, tetraarylethylene with two nitroxide radical groups at the meta-position, was synthesized, and characterized by the electrochemical method and ESR spectroscopy. Cyclic voltammetry showed the tetraarylethylene core has the lower oxidation potential than the substituted nitroxide radical moiety. ESR spectroscopy in frozen solution revealed that the neutral form shows the fine-structured spectrum characteristic of the spin triplet species, while the dicationic form shows the anisotropic hyperfine-structured spectrum characteristic of the randomly-oriented nitroxide radical, indicating the drastic change of intramolecular magnetic interaction.     

Vinyl Polymerization by Metal Complexes. VII

Abstract

The photopolymerization of vinyl monomers by metal salt-saccharide system was investigated in various solvents. The rate of polymerization in the presence of a iron(III) salt in aqueous media was remarkably accelerated by the addition of saccharides. The acceleration caused by a series of saccharides was found to be in the following order: glucose > fructose > lactose maltose. α-Methyl-d-glucoside and sucrose exhibited very little effect. The overall activation energy for the photopolymerization of acrylonitrile in the presence of glucose was found to be 2.7 kcal/mole, about half of the value obtained in the absence of glucose.     

Corrigendum to “Constraints on operator ordering from third quantization” [Ann. Phys. 365 (2016) 54–65]

In our previous paper Ohkuwa et al. (2016) corrigendum was found in Eqs. (3.4) and (3.6). However, conclusions of our previous paper are not changed.