Two Novel Monoterpene Alkaloid Dimers from Incarvillea arguta

Two novel monoterpene alkaloid dimers, named argutanes A and B ( 1 and 2 , resp.), together with the known alkaloid boschniakine ( 3 ), were isolated from the roots of Incarvillea arguta. The structures were elucidated on the basis of 1D‐ and 2D‐NMR, as well as HR‐ESI‐MS data.     

Synthesis and Electroconductive Properties of Radical Salts Derived from Tetrathiafulvalene Dimers

Palladium(II)- or copper(II)-catalyzed homo-coupling reaction of either trimethylstannyltetrathiafulvalene or tetrathiafulvalenylzinc chloride produces symmetrical bitetrathiafulvalenes (bi-TTFs) in good yields, whereas palladium(0)-catalyzed cross-coupling reaction of tetrathiafulvalenylzinc chloride with 4-iodotetrathiafulvalenes leads to the corresponding unsymmetrically substituted bi-TTFs in moderate-to-high yields. The X-ray analysis of bi-TTF derivatives showed planar structures, and the cyclic voltammetry suggested that bi-TTFs have good donor ability comparable to that of BEDT-TTF. The symmetrical bi-TTFs formed the corresponding CT-complexes and cation radical salts. These CT-complexes and radical salts were found to be metallic or semiconducting, reflecting the effect of stoichiometry control in the dimeric TTF system. The X-ray structures of two cation radical salts revealed a unique stacking, and the precise conducting path in BEDO-bi-TTF·ClO₄ was discussed on the basis of MO calculations.     

Facile Preparation of Polymeric Dimers from Amphiphilic Patchy Particles

A straightforward strategy for assembling polymeric dimers from amphiphilic nanoparticles is reported. Amphiphilic polymeric nanoparticles with a mixed‐shell of PEO/P2VN blocks and a flexible core of PAA blocks are fabricated by a non‐covalent crosslinking method. Uniform polymeric dimers are efficiently and simply obtained via hydrophobic interactions under optimized conditions in selective solvent. The steric hindrance generated by reorganization of hydrophilic polymer brushes during the interparticle association is critical for morphological selectivity in the assembly. General applicability offers the possibility to organize functional NPs into superstructures with well‐defined geometry and association numbers.     

A New Antifungal Cyclic Lipopeptide from Bacillus marinus B‐9987

A new cyclic lipopeptide, marihysin A ( 1 ), along with the three known cyclodipeptides cyclo(Ala‐Ile) ( 2 ), cyclo(Ala‐Leu) ( 3 ), and cyclo(Ala‐Tyr) ( 4 ), was isolated from the fermentation broth of the marine microorganism Bacillus marinus B‐9987 isolated from the tissues of rhizophere of Suaeda salsa in the intertidal zone of the Bohai Bay of P. R. China. Marihysin A ( 1 ) was established to be cyclo(Pro‐Gln‐Asn¹‐Ser‐Asn²‐Tyr‐Asn³‐β‐aminotetradecanoic acid) by spectroscopic analysis, and it exhibits broad‐spectrum but low activity against plant pathogens as determined by antifungal bioassay.     

Two Triterpenoid Dimers from Rubus pungens Camb var. oldhamii

In the course of our continuous chemical studies of Rubus species'-', we have isolatedtwo new triterpenoid dimers (l) and (2), in their methyl ester forms (la) and (2a), fromthe aerial parts of Rubus pungens Camb var. oldhamii.Compound la, amorphous powder, m.p. 231-233'C, [a]." 12.32 (c 0.35,CH,OH ), gave a positive coloration in the Liebermann-Burchard and Molish tests whichsuggests that la was a triterpenoid glycoside. The iR spectrum revealed the presence ofhydroxyl (3435 cm-] ), est…     

Packing Structures of Thiophene Dimers and Their Effects on Excitation Energies of Thiophene Dimers

IntroductionPi(π) conjugated polymers have received exten-sive experimental and theoretical attention because oftheir fascinating electronic and optical properties[1—3].Recently, many new experiment results[4—6]have re-vealed that the inter-chain inter…     

钨硅杂多阴离子二聚体的合成及表征

单氧桥双铁化合物L_5Fe—O—FeL_5已有报道.但有关含杂多阴离子的桥氧二聚体XM_(11)M′—O—M′XM_(11)的报道则甚少.本文合成了3种杂多阴离子二聚体(SiMW_(11))_2O(M=Fe~(Ⅲ),Cr~(Ⅲ),Al~(Ⅲ)),并用XPS、UV、IR及磁化率测定等手段对其性质进行了研究.     

New Antifungal Chromenyl Ketones and their Pentacyclic Dimers from Hypericum revolutum VAHL

Two new 2H-1-benzopyranyl ketones 1 and 2 and three new pyrano[3,2-c: 4,5,6-d′ e′]di[1]benzopyrandiyl diketones 3 , 4a / 4b , and 5 have been isolated from the leaves and twigs of Hypericum revolutum VAHL (Guttiferae). The structure of 3 (hyperevoline) was established by X-ray analysis as 1,1′-[1,13,13a,13b-tetrahydro-5,8,10-trihydroxy-2,2,6,9,13,13-hexamethyl-2H, 7aH-pyrano[3,2-c:4,5,6-d′e′]di[1]benzopyran-4, 11-diyl]bis[2-methyl-1-propanone]. The structures of the isolated compounds were established by spectroscopic (UV, IR, EI-MS, ¹H- and ¹³C-NMR) and chemical (acetylation and acidic dimerization) methods.     

Zebrafish and Flavonoids: Adjuvants against Obesity

Obesity is a pathological condition, defined as an excessive accumulation of fat, primarily caused by an energy imbalance. The storage of excess energy in the form of triglycerides within the adipocyte leads to lipotoxicity and promotes the phenotypic switch in the M1/M2 macrophage. These changes induce the development of a chronic state of low-grade inflammation, subsequently generating obesity-related complications, commonly known as metabolic syndromes. Over the past decade, obesity has been studied in many animal models. However, due to its competitive aspects and unique characteristics, the use of zebrafish has begun to gain traction in experimental obesity research. To counteract obesity and its related comorbidities, several natural substances have been studied. One of those natural substances reported to have substantial biological effects on obesity are flavonoids. This review summarizes the results of studies that examined the effects of flavonoids on obesity and related diseases and the emergence of zebrafish as a model of diet-induced obesity.     

四氢键二聚体和分子组装

介绍了最近几年新的四氢键有机二聚体研究的进展及其在分子自组装和分子聚 集体化学研究中的应用。     

Hydrogen-Bonded Dimers in Dipyrrinones and Acyldipyrrinones

Summary.  A crystal structure determination of the 9-acyl-dipyrrinone 9-butanoyl-2,3,7,8-tetramethyl-(10H)-dipyrrin-1-one indicates the presence of intermolecularly hydrogen-bonded dimers; however, in CHCl₃ solution the pigment is monomeric as determined by vapor pressure osmometry measurements. Lacking an alkyl group at C(8), the 9-acyl-dipyrrinone exhibits only a weak tendency to form dimers in CHCl₃ (K _A ∼ 60 M ⁻¹) as determined by analysis of variable temperature ¹H NMR data. In contrast, when the 9-acyl group is replaced by formyl or when the acyl group is fixed in a syn orientation to the pyrrole NH, the dipyrrinone is strongly prone to dimerization in CHCl₃. Received August 22, 2000. Accepted September 5, 2000     

Structure and Thermal Behaviour of Methylcyclopentadiene Dimers

The mixture of isomeric dimethyl-endo-tricyclo[5.2.1.0^2,6]deca-3,8-dienes ( A ) resulting from Diels-Alder reactions of 1-, 2-, and 5-methylcyclopenta-1,3-dienes ( i – iii , respectively) at 20° was shown by GLC analysis to consist of at least 10 components (Table 1). The structures of the six major isomers 1 – 6 , representing 96% of the total mixture, were established by ¹H- and ¹³C-NMR spectroscopy. Whereas on heating up to 110° the proportions of 1 , 2 , 4 , and 6 remain nearly unaffected (±2 %), the dimers 3 and 5 , formed in 22 % and 24 % yield, respectively, at 20°, isomerise above 70° reversibly via [3,3]-sigmatropic rearrangement and equilibrate at 110° to a ca. 10:1 ratio.     

Antiosteoporotic Tetrahydroxanthone Dimers from Aspergillus brunneoviolaceus FB-2 Residing in Human Gut

Main observation and conclusionA complex community of human-associated microorganisms plays diversely important roles in maintaining health,and the metabo-lite...     

Cyclophane-Type Chlorin Dimers from Dynamic Covalent Chemistry of 2,18-Porphyrinyl Dicyanomethyl Diradicals

2,18-Bis(dicyanomethyl)-substituted Ni^II porphyrin 8 and Zn^II porphyrin 11 were prepared and subjected to oxidation with PbO₂ in CH₂Cl₂ at 298 K to give cyclophane-type chlorin dimers ( 9 )₂ and ( 12 )₂ as a consequence of double recombination of biradicals 9 and 12 , respectively. Dimer ( 9 )₂ takes a syn-conformation of two distorted Ni^II chlorins but ( 12 )₂ takes an anti-conformation of relatively planar Zn^II chlorins. At 298 K, dimer ( 9 )₂ is stable and its ¹H NMR spectrum is sharp but becomes broad at high temperature, while the ¹H NMR spectrum of ( 12 )₂ is considerably broad even at 298 K but becomes sharper at low temperature. These results indicate that the chlorin dimers dissociate to radical species, but the activation barrier of the dissociation of ( 12 )₂ is much less than that of ( 9 )₂. The involvement of diradicals in dynamic covalent chemistry has been suggested by thermal scrambling of hetero dimer ( 16 )₂ to give homo dimers ( 9 )₂ and ( 15 )₂.     

Formation of Cyclobutane Thymine Dimers from UVA Photosensitization of Pyridopsoralen Monoadducted DNA

The present report provides evidence that thymine dimerization can be UVA photosensitized at a tetranucleotide, 5′-TATT-3′, by a 7-methyl-pyrido(3, 4-c)psoralen monoadduct in DNA. The efficiency of the photoprocess depends on the tetranucleotide flanking sequences. These results demonstrate that one DNA lesion can originate the contiguous formation of a second type of lesion and emphasize the sequence-specific response to interaction of drugs with DNA. Results are related to the sensitivity of DNA to 1, 10-phenanthroline-cuprous ion complex nucleolytic activity and discussed in terms of the major role of local deformability of DNA in interaction with ligands.     

含"单"及"双"吡唑啉基化合物的光致发光和电致发光的比较研究

对7种含"单"或"双"吡唑啉化合物在溶液和在固体器件[ITO/TPD/TPBI-2%EP/TPBI/Mg-Ag]中作为掺杂发光材料的电致发光特性进行了研究.结果表明,由吡唑啉化合物所构成的器件具有优良的电致发光特性.特别是在5-位处联有芳基的双吡唑啉化合物,由于它们具有良好的成膜能力和较高的玻璃化转变温度,因此所制得的器件有很好的稳定性.结果还表明,含双吡唑啉基化合物的荧光量子产率较含单吡唑啉基者为低.由它们所构成器件的电致发光能力也大体反映出相同的趋势.     

Two New Insecticidal Amide Dimers from Fruits of Piper nigrum Linn.

The methanolic extract of dried ground seeds of Piper nigrum Linn . afforded fourteen compounds, of which thirteen were amides, including two new isomeric insecticidal amides, pipsaeedine ( 1 ) and pipbinine ( 2 ), along with eleven known amides and piptaline; (this is the first report of isolation of these compounds from this plant). The structures of 1 and 2 have been elucidated as (E,E)‐1‐[(E)‐5‐(7‐{6‐[5‐(piperidin‐1‐yl)‐5‐oxopent‐3‐enyl]‐1,3‐benzodioxol‐4‐yl}‐1,3‐benzodioxol‐5‐yl)‐1‐oxopenta‐2,4‐dienyl]piperidine and (E,E)‐1‐[(E)‐5‐(4‐{6‐[5(piperidin‐1‐yl)‐5‐oxopent‐3‐enyl]‐1,3‐benzodioxol‐4‐yl}‐1,3‐benzodioxol‐5‐yl)‐1‐oxopenta‐2,4‐dienyl]piperidine, respectively, through extensive 1D‐ and 2D‐NMR spectral studies, while the known constituents have been identified through comparison of their spectral data with those reported in the literature. Compounds 1 and 2 exhibited toxicities of 45.0 and 40.0 ppm, respectively, against fourth instar larvae of Aedes aegypti Liston.