Synthesis of Functionalized Medium‐Sized trans‐Cycloalkenes by 4π Electrocyclic Ring Opening/Alkylation Sequence

Development of a novel synthetic method for medium‐sized trans‐cycloalkenes (TCAs) is described. Functionalized TCAs are readily prepared from simple cycloalkanones in a few steps, namely, enol silyl ether formation, [2+2] cycloaddition, and domino 4π electrocyclic ring opening/alkylation (conjugate addition). The first example of central‐to‐planar chirality transfer from enantiomerically enriched cyclobutenes to TCAs is also described.     

Applications of phase plane analysis of a Liénard system to positive solutions of Schrödinger equations

This paper deals with semilinear elliptic equations in an exterior domain of with . Sufficient conditions are obtained for the equation to have a positive solution which decays at infinity. The main result is proved by means of a supersolution-subsolution method presented by Noussair and Swanson. By using phase plane analysis of a system of Liénard type, a suitable positive supersolution is found out. Asymptotic decay estimation on a solution of the Liénard system gains a positive subsolution. Examples are given to illustrate the main result.

     

Studies on lens-aldose-reductase inhibitor in medicinal plants. II. Active constituents of Monochasma savatierii Franch. et Maxim

The 70% acetone extract of Monochasma savatierii FRANCH. et MAXIM. showed very strong inhibition of rabbit lens aldose reductase (AR). From the active fraction, five iridoid glucosides along with the two phenolic glycosides, acteoside and dehydroacteoside, have been isolated. Among them, acteoside showed the highest activity, being about 2.5 times more potent than baicalein, a known natural inhibitor of AR (IC50 = 9.8 x 10(-7) M). Demethylmussaenoside and 7-O-acetyl-8-epi-loganic acid, which are iridoid glucosides, had weak inhibitory activity.     

Use of a Catalytic Chiral Leaving Group for Asymmetric Substitutions at sp3‐Hybridized Carbon Atoms: Kinetic Resolution of β‐Amino Alcohols by p‐Methoxybenzylation

A catalytic strategy was developed for asymmetric substitution reactions at sp³‐hybridized carbon atoms by using a chiral alkylating agent generated in situ from trichloroacetimidate and a chiral phosphoric acid. The resulting chiral p‐methoxybenzyl phosphate selectively reacts with β‐amino alcohols rather than those without a β‐NH functionality. The use of an electronically and sterically tuned chiral phosphoric acid enables the kinetic resolution of amino alcohols through p‐methoxybenzylation with good enantioselectivity.     

Use of functional microgels with vinyl groups to accelerate photopolymerization reaction

Three types of functional microgels with vinyl groups on their surface were prepared. For the first type, the counter anion from clorin was exchanged with β-methacryloylethyl sulfonic acid, styrene sulfonic acid or allyl sulfonic acid in a microgel with ammonium anions. For the second and third types, a quaternization with N,N-dimethylaminoethyl methacrylate of 3-chloro-2-hydroxypropyl methacrylate in the presence of microgel particles was prepared by emulsion copolymerization of styrene, chloromethylstyrene or N,N-dimethylamino-methylbenzene, and divinylbenzene. The resulting samples show good dispersibility in organic solvents without an emulsifier. A functional microgel-based photopolymer combined with an acrylate monomer and ultraviolet (UV) or visible (VIS) light-absorbing photoinitiators provides oleophilic images when exposed to UV or VIS light and developed in tap water. This photopolymer has a higher sensitivity than those of photopolymers based on microgels with an analogous composition but without vinyl groups. Photopolymers pepared by using functional microgels with a methacryloyl group exhibited a higher rate of polymerization (R_p) than that of photopolymers based on microgels without a vinyl group. The R_p of photopolymers prepared by using a functional microgel with either an allyl group or vinylphenyl group was nearly equal to that of photopolymers based on microgels with ammonium ions. Their high sensitivities are attributed to the rapid photopolymerization in the methacryloyl group. To determine how the photoreaction mechanism enhances sensitivity, the photoreaction products were investigated using a model photopolymerization system. It was found that the gelation reactions enhancing sensitivity are predominantly the polymerization and crosslinking ones when a microgel with the methacryloyl group is used, and the graft copolymerization with acrylate monomers when a microgel with either the allyl group or vinylphenyl group is used.     

Phase transformations in Li2WO4 at high pressure

The phase diagram of Li₂WO₄ has been determined at high pressure up to 160 kbars and a temperature of 800°C. Three new high-pressure phases have been found in the present study. Crystallographic data are given for Li₂WO₄ III and Li₂WO₄ IV by means of single crystal and powder X-ray analyses. Li₂WO₄ III is orthorhombic with the large unit cell containing 16 molecules and having the edges: a₀ = 10.12(4) Å, b₀ = 10.07(1) Å, c₀ = 11.68(6) Å. Li₂WO₄ IV has an orthorhombic unit cell with the parameters: a₀ = 4.96(7) Å, b₀ = 9.72(8) Å, c₀ = 5.93(8)Å and Z = 4. The total volume decrease is estimated to be 24.8% through the high pressure transformations in Li₂WO₄. No spinel-like structure could be found in the present study.