Unique Ring Research Articles

Study of Polyelectrolyte Complex Nanoparticles as Novel Templates for Biomimetic Mineralization

Needle-like water-soluble polyelectrolyte complex nanoparticles (PEC NPs), consisting of sodium carboxylmethyl cellulose (CMCNa) and poly(methacryloxyethyl trimethyl ammonium chloride) (PDMC), were studied as novel templates for biomimetic mineralization. Barium acetate and sodium sulfate solutions were added simultaneously into CMCNa/PDMC polyelectrolyte complex (PEC) solutions as BaSO4 precursors. Spherical BaSO4 crystals with unique annual ring cross section were synthesized in different concentrations of PEC solution. Energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis (TGA) showed that these crystals were composed of ca. 90–95 wt % BaSO4 and 5–10 wt % PEC NPs. Study of ionic strength effect on PEC mineralization revealed that the rigid needle-like structure of PEC is responsible for BaSO4 morphology. In addition, the mineralization differences between CMCNa and CMCNa/PDMC PEC are discussed.

Tetra-μ-benzoato-bis[(3,5-dimethylpyridine)copper(II)

In the centrosymmetric binuclear title compound, [Cu2(C7H5O2)4(C7H9N)2], the CuII atom is coordinated by four O atoms from benzoate anions and one N atom from a dimethyl­pyridine ligand. A paddle-wheel-like dimer is formed by two CuII ions and four benzoate anions with two 3,5-dimethyl­pyridine ligands at the axial position of the CuII ions. The dihedral angle between the two unique benzene rings is 84.26 (16)°. The dihedral angles between the pyridine ring and the benzene rings are 61.67 (15) and 34.27 (14)°. There is π–π stacking of inversion-related pyridine rings, with a centroid–centroid distance of 3.833 (2) Å.

Azulene-based conjugated polymers: unique seven-membered ring connectivity leading to stimuli-responsiveness

A novel family of stimuli-responsible polyazulenes connected through the seven-membered ring, in contrast to traditional five-membered connectivity, have been prepared by Yamamoto-, Sonogashira-, and Stille-coupling of 4,7-dibromoazulenes. Polymer absorption can be tuned by structural modification of the conjugated backbones with UV-vis and EPR studies indicating that the seven-membered ring connection of the azulene unit is effective for the generation and stabilization of azulenium cations. The degree of conjugation and the reversibility of optical properties upon protonation and deprotonation is sensitive to the steric environment of the seven-membered ring and can be tuned by both substitution and incorporation of linkers between the azulene units.

Self-rolled-up microtube ring resonators: a review of geometrical and resonant properties

Strain-induced self-rolled-up microtubes, a category of recently discovered tubular structure with ultrathin walls, have been demonstrated to be unique ring resonators. Recent development in their geometrical and resonant properties are reviewed.

Evaluation of spinosad for the oral treatment and control of flea infestations on dogs in Europe

The novel ectoparasiticide spinosad is a naturally occurring mixture of spinosyns A and D formed during a fermentation process. The spinosyns are tetracyclic macrolides with a unique ring system. Their...

Jadomycins Derived from the Assimilation and Incorporation of Norvaline and Norleucine

Streptomyces venezuelae ISP5230 is recognized for the production of chloramphenicol and the jadomycin family of natural products. The jadomycins are angucycline natural products containing a unique oxazolone ring incorporating an amino acid present in the minimal culture media. Substitution of different amino acids results in products of varying biological activity. Analysis of cultures of S. venezuelae ISP5230 incubated with l- and d-norvaline and l- and d-norleucine indicated that only the d-configured amino acids were incorporated into the natural products. Subsequently, jadomycin DNV and jadomycin DNL were isolated and characterized (titers 4 and 9 mg L(-1), respectively). The compounds were evaluated in the National Cancer Institute cell line cancer growth inhibition and cytotoxicity screens, for antimicrobial activity against selected Gram-positive and Gram-negative bacteria, and as DNA-cleavage agents in vitro.

Novel dye-doped cholesteric liquid crystal cone lasers with various birefringences and associated tunabilities of lasing feature and performance

This study is the first to investigate novel cone lasers and the tunabilities of their lasing feature and performance based on dye-doped cholesteric liquid crystal (DDCLC) films with various LC birefringences (Δn). A unique conically-symmetric lasing ring with a low energy threshold occurs at a specific nonzero oblique angle (θ(ring)). The low energy threshold is comparable to those for common lasing signals occurring simultaneously at the short- and long-wavelength edges (SWE and LWE) of the CLC reflection band (CLCRB) for 0°. The lasing ring is induced by the enhancement in the density of photonic state for the fluorescence with a wavelength of λ(ring) based on an edge-overlapping effect, in which λ(ring) is just located at an edge-overlapping spectral position of the SWE of the CLCRB for 0° and the LWE of the CLCRB for θ(ring). The lasing feature (i.e., the lasing wavelengths of the three lasing signals and the emitted angle of the lasing ring) are tuned by varying Δn. The simulated relationship of an oblique angle with Δn, in which the SWE of the CLCRB for that oblique angle just overlaps the LWE of the CLCRB for 0°, can be obtained by calculating the dispersion relation of a planar CLC structure with various values of Δn based on Berreman's 4 × 4 matrix approach. The result of the calculation is highly consistent with the experimental data for the dependence of θ(ring) on Δn. Furthermore, the dependence of lasing performance (energy threshold and relative slope efficiency) on Δn for the three lasing signals is also measured, which findings can be used to qualitatively identify positive interaction or competition among the three lasing signals.

A biomimetic synthesis of the skeleton of trigonoliimine C

On basis of biomimetic concepts, the skeleton of trigonoliimine C was readily achieved in five steps from N-phthaloyl tryptamine. This result suggested a useful synthetic strategy for trigonoliimine alkaloids with this unique ring system.

N1,N3-Bis(pyridin-3-ylmethyl)isophthalamide dihydrate

The complete organic molecule in the title dihydrate, C20H22N4O4, is generated by crystallographic twofold symmetry, with two C atoms lying on the rotation axis. The symmetry unique pyridine ring forms a dihedral angle of 83.16 (8)° with the central benzene ring. In the crystal, inter­molecular N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds connect the components into a two-dimensional network lying parallel to (101).

DESIREE: a unique cryogenic electrostatic storage ring for merged ion-beams studies

In this proceedings I will describe the design of a new storage device currently under construction at Stockholm University, Sweden. This device uses purely electrostatic focussing and deflection elements and allows ion beams of opposite charge to be confined under extreme high vacuum and cryogenic conditions in separate "rings" and then merged over a common straight section. This Double ElectroStatic Ion Ring ExpEriment (DESIREE) apparatus allows for studies of interactions between cations and anions at low and well-defined centre-of-mass energies. I discuss the design of the DESIREE facility, highlighting some of the technical advantages of using purely electrostatic over magnetic elements, as well as the issues that have arisen during its development and construction. Finally, the advantages of this design are a boon to fundamental experimental studies and I finish by discussing an example of such potential research.

A Metal‐Free Route to 2‐Aminooxazoles by Taking Advantage of the Unique Ring Opening of Benzoxazoles and Oxadiazoles with Secondary Amines

Toss an amine into the ring: A new metal-free protocol for the amination of oxazoles has been developed by using iodobenzene diacetate to couple various oxazoles with amines (see scheme). The reaction proceeds through a ring-opening and subsequent ring-closing pathway. The optimal conditions are very mild and the substrate scope is broad, producing a range of 2-aminooxazoles, an important pharmacophore with high bioactivity.

Integrally closed ideals in regular local rings of dimension two

Let I be an integrally closed m -primary ideal of a two-dimensional regular local ring ( R , m , k ) . By Zariski’s unique factorization theorem, the ideal I factors as I 1 s 1 ⋯ I h s h , where the s i are positive integers and the I i are distinct simple integrally closed ideals. For each integer i with 1 ≤ i ≤ h , let V i denote the unique Rees valuation ring associated with I i , and let v i denote the Rees valuation associated with V i . Assume that the field k is relatively algebraically closed in the residue field k ( v i ) of V i . Let J = ( a , b ) R be a reduction of I and let ( a b ) v i ¯ denote the image of a b in the residue field k ( v i ) of V i . We prove that [ k ( v i ) : k ( ( a b ) v i ¯ ) ] = s i . Assume that ( e , f ) R is a reduction of I i . We prove that there exists a minimal generating set { g e s i , g e s i − 1 f , … , g f s i , ξ s i + 1 , … , ξ r } for I , where g ∈ ∏ j ≠ i I j s j with g V i = ( ∏ j ≠ i I j s j ) V i and v i ( ξ p ) > v i ( I ) for p with s i + 1 ≤ p ≤ r . There exists Q i ∈ Min ( m R [ I t ] ) such that V i = R [ I t ] Q i ∩ Q ( R ) . We prove that the quotient ring R [ I t ] / Q i is normal Cohen–Macaulay with minimal multiplicity at its maximal homogeneous ideal with this multiplicity being s i . In particular, R [ I t ] / Q i is regular if and only if s i = 1 .

The double electrostatic ion ring experiment: A unique cryogenic electrostatic storage ring for merged ion-beams studies

We describe the design of a novel type of storage device currently under construction at Stockholm University, Sweden, using purely electrostatic focussing and deflection elements, in which ion beams of opposite charges are confined under extreme high vacuum cryogenic conditions in separate "rings" and merged over a common straight section. The construction of this double electrostatic ion ring experiment uniquely allows for studies of interactions between cations and anions at low and well-defined internal temperatures and centre-of-mass collision energies down to about 10 K and 10 meV, respectively. Position sensitive multi-hit detector systems have been extensively tested and proven to work in cryogenic environments and these will be used to measure correlations between reaction products in, for example, electron-transfer processes. The technical advantages of using purely electrostatic ion storage devices over magnetic ones are many, but the most relevant are: electrostatic elements which are more compact and easier to construct; remanent fields, hysteresis, and eddy-currents, which are of concern in magnetic devices, are no longer relevant; and electrical fields required to control the orbit of the ions are not only much easier to create and control than the corresponding magnetic fields, they also set no upper mass limit on the ions that can be stored. These technical differences are a boon to new areas of fundamental experimental research, not only in atomic and molecular physics but also in the boundaries of these fields with chemistry and biology. For examples, studies of interactions with internally cold molecular ions will be particular useful for applications in astrophysics, while studies of solvated ionic clusters will be of relevance to aeronomy and biology.

Eudistomidins H–K, new β-carboline alkaloids from the Okinawan marine tunicate Eudistoma glaucus

Four new β-carboline alkaloids, eudistomidins H-K (1-4), were isolated from an Okinawan marine tunicate Eudistoma glaucus and the structures of 1-4 were elucidated on the basis of spectroscopic data. Eudistomidins H (1) and I (2) were new β-carboline alkaloids possessing a unique fused-tetracyclic ring system consisting of a tetrahydro β-carboline ring and a hexahydropyrimidine ring. Eudistomidin J (3) showed relatively potent cytotoxicity against murine leukemia cells P388 and L1210, and human epidermoid carcinoma cells KB in vitro.

Discovery of a new type inhibitor of human glyoxalase I by myricetin-based 4-point pharmacophore

The human glyoxalase I (hGLO I), which is a rate-limiting enzyme in the pathway for detoxification of apoptosis-inducible methylglyoxal (MG), has been expected as an attractive target for the development of new anti-cancer drugs. We have previously identified a natural compound myricetin as a substrate transition-state (Zn(2+)-bound MG-glutathione (GSH) hemithioacetal) mimetic inhibitor of hGLO I. Here, we constructed a hGLO I/inhibitor 4-point pharmacophore based on the binding mode of myricetin to hGLO I. Using this pharmacophore, in silico screening of chemical library was performed by docking study. Consequently, a new type of compound, which has a unique benzothiazole ring with a carboxyl group, named TLSC702, was found to inhibit hGLO I more effectively than S-p-bromobenzylglutathione (BBG), a well-known GSH analog inhibitor. The computational simulation of the binding mode indicates the contribution of Zn(2+)-chelating carboxyl group of TLSC702 to the hGLO I inhibitory activity. This implies an important scaffold-hopping of myricetin to TLSC702. Thus, TLSC702 may be a valuable seed compound for the generation of a new lead of anti-cancer pharmaceuticals targeting hGLO I.

Machilusides A and B: Structurally Unprecedented Homocucurbitane Glycosides from the Stem Bark of Machilus yaoshansis

Two structurally novel homocucurbitane triterpenoid glycosides, machilusides A (1) and B (2), possessing an unprecedented C(36) skeleton with a D-fructose moiety incorporated into a cucurbitane nucleus forming unique cage-like tricyclic ring moieties, were isolated from the stem bark of Machilus yaoshansis. Their structures were determined by spectroscopic methods. Both compounds exhibited nonselective cytotoxic activities against several human cancer cell lines. The biosynthetic pathway of 1 and 2 was postulated.

ChemInform Abstract: Lyconadins C and F, New Lycopodium Alkaloids from Lycopodium complanatum.

Abstract New Lycopodium alkaloids, lyconadins C ( 1 ) and F ( 2 ), were isolated from the club moss Lycopodium complanatum . Lyconadin C ( 1 ) is a new C 16 N 2 -type Lycopodium alkaloid possessing unique fused-tetracyclic ring system consisting of a cycloheptene ring fused to a decahydroquinoline and pyridone rings. Lyconadin F ( 2 ) possesses a primary amide moiety in its molecular, which is the first example of Lycopodium alkaloids. Biogenetically, lyconadins C ( 1 ) and F ( 2 ) might be related to lyconadins A ( 4 ) and B ( 5 ). The structures and relative stereochemistry of 1 and 2 were elucidated on the basis of spectroscopic data. The absolute stereochemistry of 2 was elucidated by chemical correlations with lyconadin B ( 5 ) through hemiaminal form of lyconadin F ( 3 ).

Studies of cyclization reactions of linear cumulenes and heterocumulenes using the neutralization–reionization procedure and/or ab initio calculations

A number of linear cumulenes and heterocumulenes have been made by charge stripping of anions of known bond connectivity in the source of a mass spectrometer. Some of these reactive molecules have been identified in interstellar molecular clouds. The structures of these neutrals may be investigated by reionization to a decomposing positive ion [the neutralization-reionization technique ((-)NR(+))], and/or by ab initio calculations. Energized linear cumulenes and heterocumulenes may undergo cyclization to form stable cyclic isomers. To cite a selection of the examples described in this review: (i) four-atom systems CCCC and some heterocumulenes CCCX (X=B, N, Al, Si, P) involve the formation of stable four-membered ring rhombic (also called kite and fan) structures. One of the cyclic molecules, cyclo-C(3) Si, has been detected in interstellar molecular clouds, (ii) five-atom cumulene and heterocumulene systems are more complex. Linear CCCCC rearranges the carbon skeleton by forming a C substituted rhomboid system, CCCCO forms a three-membered cyclic isomer, while nitrogen containing five-atom cumulenes effect nitrile to isonitrile interconversion via three-centered cyclized intermediates, and (iii) CCCCCC and CCCCBO cyclize to give unique six-membered ring systems.

Cytotoxic Triterpenoid Constituents from Two Plants of the Family Meliaceae

For their interesting structures and significant biological activities, triterpenoids from plants of the family Meliaceae have been the research focus for several years. In our initial screening of the Meliaceae species, the extracts of Aglaia abbreviata C. Y. Wu and Aphanamixis grandifolia Bl exhibited some inhibitory activity against a panel of tumor cell lines. Phytochemical investigations on the two plants afforded six new dammarane-type triterpenoids, named aglaiabbreviatins A-F (1–6), along with twenty known triterpenoids from the stems of A. abbreviata, and twenty new tirucallane-type triterpenoids, named aphagranins A-T (7–26), along with ten known triterpenoids from the stem bark of A. grandifolia. Their structures were elucidated mainly by spectroscopic evidence. Of them, compound 9 has a maleimide ring in the side-chain; compound 19 incorporates a unique pyrrole ring, representing the first protolimonoid with such a moiety. All the new isolates were evaluated for their cytotoxicity against several tumor cell lines including multidrug resistant ones. Compounds 3–6, 11, 14–16 were found to have cytotoxicity to the tumor cell lines used, especially, compounds 6, 14, and16 showed the most potent activity.

Synthesis of enantiopure 2-carba-cyclic phosphatidic acid and effects of its chirality on biological functions

Cyclic phosphatidic acid (cPA) is a naturally occurring phospholipid mediator, which has a quite unique cyclic phosphate ring at sn-2 and sn-3 positions of the glycerol backbone. We have designed and chemically synthesized several metabolically stabilized derivatives of cPA. 2-Carba-cPA (2ccPA) is one of the synthesized compounds in which the phosphate oxygen was replaced with a methylene group at the sn-2 position, and it showed much more potent biological activities than natural cPA. Here, we developed a new method of 2ccPA enantiomeric synthesis. And we examined the effects of 2ccPA enantiomers on autotaxin (ATX) activity, cancer cell invasion and nociceptive reflex. As well as racemic-2ccPA, both enantiomers showed inhibitory effects on ATX activity, cancer cell invasion and nociceptive reflex. As their effects were not significantly different from each other, the chirality of 2ccPA may not be critical for these biological functions of 2ccPA.