Tailoring of ionic supramolecular assemblies based on ammonium carboxylates toward liquid‐crystalline micellar cubic mesophases

Ionic liquid crystals based on ionic complexation of tris(2‐aminoethyl)amine (1) with 3,4,5‐tris(7,7,8,8,9,9,10,10,11,11,12,12,12‐tridecafluorododecyloxy)benzoic acid (2) and with 3,4,5‐tris(2‐octyldodecyloxy)benzoic acid (3) were investigated. The ionic complex with the partially fluorinated alkyl chains (1·2) exhibited a morphological transition from a hexagonal columnar mesophase to a Pm3n micellar cubic phase upon increasing the molar ratio of 2 to 1. For the complex with the branched alkyl chains (1·3) a micellar cubic mesophase was exclusively generated at appropriate composite ratios. The generation of the micellar cubic mesophases is attributed to the introduction of the laterally expanded volume of the alkyl chains compared with the corresponding normal dodecyl chains. Their thermal stabilities were most enhanced at a specific molar ratio of 1:5 for 1·2 and 1:4 for 1·3. This result corresponds to the most suitable chain volume for the stable micellar cubic mesophase.     

Role of Re Species and Acid Cocatalyst on Ir‐ReOx/SiO2 in the C–O Hydrogenolysis of Biomass‐Derived Substrates

The catalytic performance of ReO_x‐modified Ir metal catalyst in the hydrogenolysis of C–O bonds is strongly dependent on the choice of solvent. The acidic property of the Re species becomes obvious in the alkane solvent, and the hydrogenolysis reaction proceeds mainly by acid‐catalyzed dehydration and the subsequent metal‐catalyzed hydrogenation. The acidic property of the Re species is weakened in water; however, the hydrogenolysis reaction proceeds in water via a direct mechanism involving S_N2‐like attack of a hydride species at the interface between Ir and ReO_x on the adsorbed Re alkoxide species. This mechanism enabled the selective dissociation of the C–O bond neighboring the CH₂OH group.     

Controlled Dynamic Helicity of a Folded Macrocycle Based on a Bisterephthalamide with a Twofold Z‐Shaped Structure

Dynamic helicity in a folded macrocycle and control of the helical preference are described. We designed macrocycle 1 with a dual mode of folding through the integration of two flexible units that are arranged twice to form a cyclic structure. As a folding unit, we used a terephthalamide skeleton and a Z‐shaped hydrocarbon: the former acted as a control unit to induce a preference of a particular sense of dynamic helicity and the latter was just a spacer. A terephthalamide unit provided a binding site for capturing a ditopic hydrogen‐bonding guest when it adopted helically folded syn forms (M/P). Thus, only the terephthalamide unit controlled the helical sense of dynamic helicity in a folded macrocycle through the supramolecular transmission of chirality upon complexation with a chiral ditopic guest. In addition, chirality on a host could also contribute to the control of the helical preference in a folded macrocycle, which led to exceptionally enhanced chiroptical signals.     

Swinging and tumbling of fluid vesicles in shear flow

The dynamics of fluid vesicles in simple shear flow is studied using mesoscale simulations of dynamically triangulated surfaces, as well as a theoretical approach based on two variables: a shape parameter and the inclination angle, which has no adjustable parameters. We show that, between the well-known tank-treading and tumbling states, a new "swinging" state can appear. We predict the dynamic phase diagram as a function of the shear rate, the viscosities of the membrane and the internal fluid, and the reduced vesicle volume. Our results agree well with recent experiments.     

Development of variable‐magnification X‐ray Bragg optics

A novel X‐ray Bragg optics is proposed for variable‐magnification of an X‐ray beam. This X‐ray Bragg optics is composed of two magnifiers in a crossed arrangement, and the magnification factor, M, is controlled through the azimuth angle of each magnifier. The basic properties of the X‐ray optics such as the magnification factor, image transformation matrix and intrinsic acceptance angle are described based on the dynamical theory of X‐ray diffraction. The feasibility of the variable‐magnification X‐ray Bragg optics was verified at the vertical‐wiggler beamline BL‐14B of the Photon Factory. For X‐ray Bragg magnifiers, Si(220) crystals with an asymmetric angle of 14° were used. The magnification factor was calculated to be tunable between 0.1 and 10.0 at a wavelength of 0.112 nm. At various magnification factors (M≥ 1.0), X‐ray images of a nylon mesh were observed with an air‐cooled X‐ray CCD camera. Image deformation caused by the optics could be corrected by using a 2 × 2 transformation matrix and bilinear interpolation method. Not only absorption‐contrast but also edge‐contrast due to Fresnel diffraction was observed in the magnified images.     

Non‐Heme Dioxygenase Catalyzes Atypical Oxidations of 6,7‐Bicyclic Systems To Form the 6,6‐Quinolone Core of Viridicatin‐Type Fungal Alkaloids

The 6,6‐quinolone scaffold of the viridicatin‐type of fungal alkaloids are found in various quinolone alkaloids which often exhibit useful biological activities. Thus, it is of interest to identify viridicatin‐forming enzymes and understand how such alkaloids are biosynthesized. Here an Aspergillal gene cluster responsible for the biosynthesis of 4′‐methoxyviridicatin was identified. Detailed in vitro studies led to the discovery of the dioxygenase AsqJ which performs two distinct oxidations: first desaturation to form a double bond and then monooxygenation of the double bond to install an epoxide. Interestingly, the epoxidation promotes non‐enzymatic rearrangement of the 6,7‐bicyclic core of 4′‐methoxycyclopenin into the 6,6‐quinolone viridicatin scaffold to yield 4′‐methoxyviridicatin. The finding provides new insight into the biosynthesis of the viridicatin scaffold and suggests dioxygenase as a potential tool for 6,6‐quinolone synthesis by epoxidation of benzodiazepinediones.     

Intramolecular Benzyne–Phenolate [4+2] Cycloadditions

An intramolecular benzyne–phenolate [4+2] cycloaddition is reported. Benzyne precursors, having vicinal halogen‐sulfonate functionalities, linked with a phenol(ate) by various tether groups undergo efficient intramolecular [4+2] cycloaddition by treatment with either Ph₃MgLi or nBuLi for halogen–metal exchange to form various benzobarrelenes.     

Formation of 3-Hydroxyalkyl Carbamates from Carbon Dioxide,Amines and Oxetanes

The reactions of carbon dioxide, primary or secondary aliphatic amines and oxetanes at a CO₂ pressure of 40 atm at 100–120°C without any catalysts afforded new monocarbamates of 1,3-propanediols, with concomitant formation of amino alcohols from oxetanes and amines.