Total Synthesis of the 7,10‐Epimer of the Proposed Structure of Amphidinolide N,Part II: Synthesis of C17–C29 Subunit and Completion of the Synthesis

The total synthesis of 7,10‐epimer of the proposed structure of amphidinolide N was accomplished. The requisite chiral C17–C29 subunit was assembled stereoselectively via Keck allylation, Shi epoxidation, diastereoselective 1,3‐reduction, and a later oxidative synthesis of the THF framework. The C1–C13 and C17–C29 subunits were successfully coupled using a Enders RAMP “linchpin” as the C14–C16 three carbon unit, thereby controlling the chirality at C14 and C16. The labile allyl epoxy moiety was successfully constructed by Grieco–Nishizawa olefination at a final stage of the synthesis.     

Aryl-β-C-glucosidation using glucal boronate: application to the synthesis of tri-O-methylnorbergenin

Novel aryl-β-C-glucosidation method using glucal boronate was developed. This protocol can offer several advantages including use of non-toxic, easily handling glucal boronate as a crystalline solid and storable at room temperature for several months. Tri-O-methylnorbergenin (8,10-di-O-methylbergenin), an anti-HIV active bergenin derivative, was concisely synthesized by application of the aryl-β-C-glucosidation method.     

Nonbonded P···P and P···Se Interactions in Naphthalene 1,8-Positions: Role of Lone-Pair Orbitals

The lone pair-lone pair repulsion plays an important role in the nonbonded P;;;P interaction in naphthalene 1,8-positions. The conformations around P and Se in 8-(PhSe)-1-(Ph 2 P=O)C 10 H 6 are determined by the attractive O;;;Se--C 3c-4e type interaction. The P;;;Se interaction in the 1,8-positions is also discussed.     

Grafting of Polymers Having Pendant Peroxycarbonate Groups Onto Carbon Black and Postpolymerization of Vinyl Monomers

Abstract

Postpolymerization of vinyl monomers initiated by pendant peroxycarbonate groups of grafted polymer chains on carbon black (CB) was investigated. The grafting of polymers having pendant peroxycarbonate groups onto CB was achieved by the trapping of polymer radicals formed by the thermal decomposition of copolymers of t-butylperoxy-2-methacryloyloxyethyl-carbonate (HEPO) with vinyl monomers such as vinyl acetate (VAc), styrene (St) and methyl methacrylate (MMA). The copolymers having pendant peroxycarbonate groups were prepared by copolym-erization of HEPO with vinyl monomers using azo initiator under irradiation of UV light at room temperature. The amount of remaining pendant peroxycarbonate groups of the poly(VAc-co-HEPO)-grafted CB obtained from the reaction at 90°C was maximum and decreased above the temperature. Furthermore, the postpolymerization of vinyl monomers, such as St, MMA, and VAc was initiated in the presence of poly(VAc-co-HEPO)-grafted and poly(St-co-HEPO)-grafted CB and the corresponding polymers were postgrafted onto CB to give branched polymer-grafted CB. The percentage of poly(St)-postgrafting (proportion of post-grafted poly(St) to poly(MMA-co-HEPO)-grafted CB used) increased with increasing polymerization time, but became constant at 20% after 4 hours.     

pH-Responsive Phase Transition of Supramolecular Hydrogel Consisting of Glycosylated Amino Acetate and Carboxylic Acid Derivative

By addition of a carboxylated amino acetate (2) to a low-molecular-weight hydrogel (1) which has a unique thermally induced volume-phase transition character, a macroscopic pH-responsive feature is newly conferred on the supramolecular hydrogel. The direct observation of temperature-dependent behavior of the mixed hydrogel clearly showed that the thermally induced swelling-shrinkage type of the volume phase transition at pH 4 is shifted to the gel–sol transition at pH 7 by 10?mol% addition of 2 to the hydrogel 1. On the basis of the measurements by TEM, SEM, XRD and FT-IR, it is conceivable that incorporation of the anionic carboxylate of 2 slightly disturbs the packing of the hydrogen bond belt of the mixed hydrogel. Such a slight disturbance greatly leads to the sol–gel transition by elevating temperature, instead of the volume-phase transition. Introduction of dynamic characteristics to supramolecular systems in a macroscopic level may extend the potential of these materials in various fields.     

Probe Design for the Effective Fluorescence Imaging of Intracellular RNA

Over the past two decades, the spatiotemporal analysis of fluorescently labeled single RNA species has provided a broad insight into the synthesis, localization, degradation, and transport of RNA. To elucidate the dynamic behavior of functional RNAs in living cells, researchers throughout the world have proposed numerous fluorometric strategies for intracellular RNA imaging. Because, like most other biological molecules, RNA is intrinsically nonfluorescent, the development of methods for the labeling of RNAs of interest with fluorescent molecules is essential. Several artificial tag sequences have been attached onto the 3′ end of target RNAs and used as scaffolds for interacting with their fluorescent counterparts. In this Personal Account, we focus on the methods that have been developed to show how RNAs expressed in cells can be labeled and visualized by fluorescent proteins, small molecules, or nucleic acids. Each of these methods is designed to increase the sensitivity and specificity for imaging or to decrease the background fluorescence.     

Linear Multiselenium Interactions in Dicationic Oligomers of 1,5‐(Diselena)canes: Behavior of Semc σ(mcc‐nee) (6≤mc≤16) Elucidated with QTAIM Dual Functional Analysis

Invited for this month''s cover picture is the group of Dr. Satoko Hayashi at Faculty of Systems Engineering and Chemistry at Wakayama University. The cover picture shows the linear Se₁₆ σ(16c–30e) interactions, illustrated by the molecular graph type on the optimized structure of the dicationic octamer of 1,5‐(diselena)cane. HOMO‐1 of ψ₄₆₂ is drawn on the structure, which is located predominantly on the Se atoms. The optimized structure is stable, due to the nice engagement between the (CH₂)₃ moieties. The contour maps of ρ(r) are also drawn on the molecular C _s planes of the dicationic dimer and trimer to demonstrate clearly the existence of the interactions between Se atoms. Read the full text of their Full Paper at 10.1002/open.202100017.

“… To improve the causality of experimental results, we have proposed a new concept, called “Keisan‐sendo…” Find out more about the story behind the front cover research at 10.1002/open.202100017.     

Selective detection of polyaromatic hydrocarbons on diesel exhaust particles using sputtered neutral mass spectrometry

Aiming for the highly sensitive analysis of aromatic hydrocarbons in organic mixtures, selective ionization using an ultraviolet laser ionization technique was examined for the determination of sputtered neutral species on organic surfaces. The mass spectrum of a model mixture containing pyrene and n‐alkane showed that only pyrene was ionized and detected, whereas a mass spectrum without laser irradiation, i.e. in the case of secondary ion mass spectrometry, was dominated by many n‐alkane fragment peaks. This technique was applied for the detection of polyaromatic hydrocarbons adsorbed on diesel exhaust particles. Two kinds of polyaromatic hydrocarbons were clearly detected because many aliphatic fragment signals were suppressed by means of ultraviolet laser ionization. Copyright © 2013 John Wiley & Sons, Ltd.     

Electro-optic effect,propagation loss,and switching speed in polymers containing nano-sized droplets of liquid crystal

Polymers containing droplets of liquid crystal smaller than 100 nm, which have good transparency and easily form films, were prepared under various conditions to evaluate their potential as electro-optic materials for waveguide-type devices. By varying the liquid crystal concentration and the strength of the UV irradiation causing photo-induced phase separation of the droplets, we were able to control the droplet size and density. We have clarified how the birefringence generated in an applied electric field, switching speed, and optical loss of light propagating in the film depend on droplet size and density. Polymer materials having a large electro-optic effect (δn = 0.001 at 8 V μm^-1), low propagation loss (~2.5 dB cm^-1), and fast response time (~10 μs) have been developed.