Internal reaction of secondary alkyltin(IV) compounds having thionium ion gave internal trans olefins with high yield and regio- and stereoselectivity via 1,5- or 1,6-transfer of a hydride β to the trialkylstannyl group. 相似文献
In order to develop novel and orally active phosphodiesterase (PDE) 4 inhibitors, random screening was performed using our chemical library to find YM-10335 possessing the 1,8-naphthyridin-2(1H)-one skeleton which is a completely different structure from rolipram. In this report, the syntheses and structure-activity relationships of the YM-10335 derivatives were described. Some compounds showed selective inhibitory activities for PDE 4 derived from human peripheral blood cells and no effect on the other PDE types (1, 2, 3, 5). The inhibition of the tumor necrosis factor-alpha (TNF-alpha) release in vitro and the carrageenan-induced pleurisy in rats were also described. 相似文献
Several 8-substituted cordycepins were prepared via LDA lithiation of 2′,5′-bis-O-(t-butyldimethylsilyl)-cordycepin and successive reactions of its C-8 lithiated species with various types of electrophiles. Wittig reaction of the 8-formyl derivative was also examined. 相似文献
The structures of enopeptins A and B, novel depsipeptide antibiotics with 1,3,5,7,9-decapentaene-1,10-dicarboxylic acid and 2-amino-3-hydroxycyclopent-2-enone in a side chain, were determined by chemical and spectroscopic means. 相似文献
The chelating behavior of a new resin prepared by polycondensation of N-(o-hydroxybenzyl) iminodiacetic acid (o-HDA) with phenol and formaldehyde, is compared with that of the monomer, with p-HDA resin and p-HDA monomer, and with Chelex-100. The order of chelate stability for the o-HDA resin is Cu(II) > Ni(II) > Zn(II) > Co(II). An unusually high stability of the o-HDA and o-HDA resin iron(III) chelates in acidic solution is attributed to the participation of the o-hydroxyl group in the coordination process. 相似文献
Rotational correlation times (τT) of the 5′-AMP molecule deduced from spin-lattice relaxation times (T1) of different protons in the molecule agree fairly well with each other in the temperature range of 3.5–74°C. The same is true with τT values deduced from 13CT1 values. These results indicate that the internal motions are slow as compared to the overall rotation of the 5′-AMP molecule. 相似文献
Infrared absorption due to the surface chemical bonds on microcrystalline silicon (μc-Si) was investigated with recycling procedures of thermal oxygenation accompanied with dehydrogenation and HF etching. SiH bonds were reformed on the surface of μc-Si by HF etching of oxygenated μc-Si. The mechanism of the SiH bond formation was proposed. It was suggested that formation of =SiH2, SiH2x or -SiH3 group depended on the kind of a crystalline plane. 相似文献
Star-shaped poly(1,2-phenylenevinylene)s 4-substituted with multiple pendant phenoxyls (2 and 3) were synthesized by polymerizing 2-bromo-4-(acetoxyphenyl)styrene in the presence of 1,3,5-triiodobenzene or 1,3,5-tris(3',5'-diiodophenyl)benzene as the core via a simple one-pot Heck reaction and subsequent hydrolysis, phenolate formation, and heterogeneous oxidation. ESR spectra indicated a delocalized spin distribution into the core parts of the star-shaped molecules. The polyradicals, 2 and 3, were in a high-spin state at low temperature, and the ferromagnetic behavior was enhanced for the polyradical with a higher molecular weight. Although an average S of 3 remained at 3/2 to 4/2, the polyradical 2 even with a spin concentration of 0.8 spin/unit revealed an average S of 7/2 to 8/2. The 1,3,5-benzene core acted as an effective magnetic coupler to align the spins of the pendant phenoxyls through the star-shaped pi-conjugated backbone. 相似文献
Treatment of cyclotrisilathiane (Me2SiS)3 with 3 equiv. of RLi (R = Me, But) in hexane-Et2O afforded the lithium silanethiolates LiSSiMe2R, and the tmeda adduct [(tmeda)LiSSiMe2But]2 1 (tmeda =N,N,N',N'-tetramethylethylenediamine) was isolated in the case of R = But. Reaction of Fe(CH3CN)2(CF3SO3)2, CoCl2, and [Cu(CH3CN)4](PF6) with 1 gave rise to the silanethiolato complexes M(SSiMe2But)2(tmeda)(M = Fe 2, Co 3), and [Cu(SSiMe2But)]4 4, respectively. Complexes (C5H5)2Ti(SSiMe2R)2(R = Me 5, But 6) and Ni(SSiMe2R)2(dppe)[R = Me 7, But 8; dppe = 1,2-bis(diphenylphosphino)ethane] were prepared from treatments of (C5H5)2TiCl2 and NiCl2(dppe) with the corresponding lithium silanethiolates. Complex 7 readily reacted with (C5H5)TiCl3 to produce the Ti-Ni heterobimetallic compound (C5H5)TiCl(mu-S)2Ni(dppe) 9, in which silicon-sulfur bond cleavage took place. Characterization of all compounds through spectroscopic techniques and elemental analyses are also described. X-Ray structural data for compounds 1 and 3-9 are reported. 相似文献
A unique pentaketide dimer structure of a novel fungal metabolite with antiangiogenic activity, designated as epoxyquinol A (1), was determined on the basis of NMR spectral data as well as the X-ray crystallographic analysis. 1 inhibits the endothelial migration induced by vascular endothelial growth factor (ED100 = 3 mug/mL). 相似文献