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1.
Self-aggregation of naturally occurring bacteriochlorophyll (BChl)-e in nonpolar organic solvents was investigated by visible absorption, fluorescence emission and circular dichroism spectra. Cultured brown-colored photosynthetic bacteria have several BChl-e as light-harvesting antenna pigments. Three major BChl-e homologs were separated from the extracts of the culture by reverse-phase high-performance liquid chromatography (HPLC) and characterized by 1H-NMR and fast-atom bombardment mass spectroscopy: 8-ethyl-12-ethyl ([E,E])-, 8-propyl-12-ethyl- and 8-isobutyl-12-ethyl-BChl-e farnesyl esters. All the homologs consisted of a mixture of the 3(1)-epimers, and epimerically pure BChl-e were also given by HPLC separation. All the separated BChl-e epimers, the epimeric mixtures and the homologous mixtures formed self-aggregates in 2% dichloromethane/hexane, giving visible absorption spectra similar to that of the whole cells, which showed two peaks (or shoulders) around 430-450 and 520 nm at the Soret region as well as a red-shifted Qy band relative to the monomeric. The spectral properties of the Soret band were basically unchanged among the epimers or epimeric/homologous mixtures. In contrast, the Qy band of aggregates of epimeric mixtures (except [E,E]) and homologous mixtures red-shifted and broadened compared with the epimerically pure. The red-shift and broadening of the Qy band are advantageous for efficient energy transfer from BChl-e aggregates to BChl-a in a baseplate in chlorosomes because their spectral overlap increases. 相似文献
2.
R Fujita K Watanabe T Yoshisuji C Kabuto H Matsuzaki H Hongo 《Chemical & pharmaceutical bulletin》2001,49(7):893-899
Diels-Alder cycloadditions of 2(1H)-quinolones having an electron-withdrawing group at the 3-position with alkyl- and silyloxy-1,3-butadienes (2a,b) were carried out to give phenanthridones richly functionalized regio- or stereoselectively under conditions of atmospheric and high pressure. Furthermore, regioselectivity and chemoselectivity of 3-substituted 2(1H)-quinolones to 2a, b were examined using MO calculation. 相似文献
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Vincadifformine (), eburcine () and 3-epieburcine () in racemic forms have been synthesized from 1,2-dehydroaspidospermidine () by introduction of methoxycarbonyl group to C(3)-position of aspidosperma skeleton. 相似文献
5.
New β-lactam antibiotics. Functionalisation of the cephem 3-position with sulfur or nitrogen bearing substituents The tosylate sulfoxides or mesylates derived from the 3-hydroxy-ceph-3-em esters 1a, b reacted with thiols to give 3-thioethers which were converted into the microbiologically active acids 7a, c, 8a, c 9c, and 13c by known procedures. The 3-methylsulfonyl-derivative 17c was prepared from 6b. The synthesis of the 3-acylamino-ceph-3-em-4-carboxylic acids 23c and 24c is reported. 相似文献
6.
The number of pigments in single light-harvesting complexes (chlorosomes) were calculated by imaging single chlorosomes in a frozen buffer at cryogenic temperature with a confocal laser fluorescence microscope and pigment extraction. Chlorosomes were isolated from two types of green photosynthetic bacteria Chlorobium (Chl.) tepidum and Chloroflexus (Cfl.) aurantiacus and were individually imaged in the frozen medium. Each fluorescence spot observed mainly came from a single chlorosome and was ascribable to self-aggregates of bacteriochlorophyll (BChl) c molecules as core parts of chlorosomes. A three-dimensional distribution of fluorescence of single chlorosomes was analyzed, and the number of chlorosomes in a volume of 54,000 microm(3) was counted directly. On the basis of the results, averaged numbers of the BChl c molecules contained in a single chlorosome of Chl. tepidum and Cfl. aurantiacus were determined to be 1.4 x 10(5) and 9.6 x 10(4), respectively. The present numbers are almost comparable to those estimated by other methods (Martinez-Planells et al., Photosynth. Res. 2002, 71, 83 and Monta?o et al., Biophys. J. 2003, 85, 2560). 相似文献
7.
R Fujita K Watanabe T Yoshisuji H Hongo H Matsuzaki 《Chemical & pharmaceutical bulletin》2001,49(7):900-904
Diels-Alder reactions of 1-methyl-2(1H)-quinolones having an electron-withdrawing group at the 4-position with isoprene, butadiene sulfone, and cyclohexadiene were performed to yield functionalized phenanthridones stereoselectively at atmospheric and at high pressure. Regioselectivity and stereochemistry of a methoxycarbonyl group were studied using the semi-empirical and ab initio MO methods, respectively. 相似文献
8.
R. Resmi S. R. Amrutha M. Jayakannan 《Journal of polymer science. Part A, Polymer chemistry》2009,47(10):2631-2646
A new series of symmetrically substituted bulky PPV‐copolymers based on poly(bis‐2,5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene) ( BEH‐PPV ) bearing tricyclodecane (TCD) pendants were synthesized to study the effect of chain aggregation in the π‐conjugated polymer backbone. The composition of the copolymers was varied up to 100 mol % and the structures of the copolymer were confirmed by NMR and FTIR. The molecular weights of the copolymers were obtained as Mw = 11,500–1,78,800 depending on the TCD‐incorporation in BEH‐PPV. The origin of the π‐aggregation was investigated using mixture of solvents (polar or nonpolar) or temperature as external stimuli. Absorption, photoluminescence, and time‐resolved fluorescence decay techniques were employed as tools to trace molecular aggregation in solution and solid state. The TCD‐substituted bulky copolymers showed almost twice the enhancement in photoluminescence compared with that of BEH‐PPV . Solvent‐induced aggregation studies of copolymers revealed the existence of strong molecular aggregation in BEH‐PPV compared with that of bulky copolymers. Variable temperature studies further evidence for the reversibility of molecular aggregation on heating/cooling cycles and showed isosbetic points with respect to free and aggregated polymer chains. Time‐resolved fluorescent studies confirmed the existence of free and aggregated π‐conjugated species with a life time of 0.1 to 1.0 ns. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2631–2646, 2009 相似文献
9.
Six arsenic-containing β-D -ribofuranosides, including the naturally occurring (2′R)-dimethyl[1-O-(2′,3′-dihydroxypropyl)-5-deoxy-β-D -ribofuranos-5-yl]arsine oxide, were prepared in multi-step reactions from D -ribose and tetramethyldiarsine. The synthetic procedure uses the early substitution of the hydroxy group with bromine at C5, subsequent attachment of a chiral three-carbon aglycone at C1, and final delivery of arsenic at C5. The synthesis provides a viable route for the preparation of multigram quantities of the natural product. 相似文献
10.
Several benzothiazolyl, imidazobenzothiazolyl, benzothienyl, benzothienopyrimidinyl and quinazolinyl 4,5-dihydro-3(2H)-pyridazinones were synthesized and examined for cardiotonic activity in anesthetized dogs after i.v. administration. Among them, 4-methylamino-7-(2,3,4,5-tetrahydro-5-methyl-3-oxo-6- pyridazinyl)quinazoline (36) showed potent and long-lasting inotropic activity (relative potency = 2.11, milrinone = 1). The activity of 36 was more potent than indolidan (2) (relative potency = 1.53) which is one of the most potent inotropic agents to date. 相似文献
11.
The complexation in aqueous solution of ligands of the type o-Py? (CH2)(n-1) S(CH2)mNH2 (n and m: 2 or 3) with NiII ions has been investigated. The thermodynamic functions ΔG, ΔH, and ΔS of the complex formation have been determined at 25°C in 0.5 M KNO3 solution by means of potentiometric and of direct calorimetric titrations. They revealed that all ligands, except o-Py? (CH2)2S(CH2)3NH2 for which no appreciable complexation with NiII could be stated, act as tridentates towards NiII. Information on the stereochemistry of the NiII complexes was obtained from the electronic spectra. The NiL2+ and NiL22+ complexes both have distorted octahedral structures. The NiL22+ species were also compared to the corresponding NiL2(NO3)2 compounds in the solid state. 相似文献
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Mónica Pérez Perrino 《European Polymer Journal》2010,46(7):1557-1562
A general synthetic approach is described that allows to obtain novel 1-vinyl-2-pyrrolidone (VP) derivatives with different kinds of functional groups in its 3-position in a one-pot reaction. The strategy used to achieve this goal is the reaction of the carboxamide anion of 1-vinyl-2-pyrrolidone with cyclic precursors of these functionalities. While the driving force for the reactions of three-membered rings is their high annular tension, it is shown here that larger heterocycles can be opened with good yield when additional electron-withdrawing groups are present in the ring. This leads to VP with longer spacer groups between the functionality and the future polymeric main chain. Furthermore, the high versatility of this procedure is demonstrated by the preparation, for the first time, of VP modified with amine or sulfonic functionalities that allow to prepare the corresponding aminated and sulfonated PVPs. 相似文献
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Y Nomoto H Takai T Hirata M Teranishi T Ohno K Kubo 《Chemical & pharmaceutical bulletin》1991,39(1):86-90
A series of 1-(6,7-dimethoxy-4-quinazolinyl)piperidines carrying various 5-membered heterocycles at the 4-position was synthesized and examined for cardiotonic activity in anesthesized dogs. The (4-oxo-2-thioxo-3-imidazolindinyl)amino derivatives showed the most potent inotropic activity. Marked loss of activity was observed in the 2,4-dihydro-3-thioxo-3H-1,2,4-triazolyl, the 2,4-dihydro-3-oxo-3H-pyrazolyl and the (2,3-dihydro-2-thioxo-3H-1,3,4-thiadiazol-5-yl)amino derivatives. The synthesis and structure-activity relationships are discussed. 相似文献
16.
K Hirota H Hosono Y Kitade Y Maki C K Chu R F Schinazi H Nakane K Ono 《Chemical & pharmaceutical bulletin》1990,38(9):2597-2601
17.
Large-basis-set calculations of near Hartree-Fock accuracy were performed on CO+(1σ-hole 2Σ+) and CO+)2σ-hole, 2Σ+); correlation energies for these systems and for CO were calculated using an atoms-in-molecule approach, relativistic energies and vibrational structure corrections were also considered. The results are: IP(CO, 1σ) = 542.4 (542.57) eV, IP(CO,2σ) = 297.0 (296.24) cV, Dc(CO, 1Σ+) = 10.8 (11.1) Ev, D3(CO+, 1σ, 2Σ+) = 11.9 eV, De(CO+, 2σ, 2Σ+) = 9.1 eV, where IP and De stand respectively for ionization potential and dissociation energy, and where the numbers in parentheses refer to the most recent experimental values. The electron transfers resulting from the ionization of inner-shell electrons are discussed. Finally a quantitative correlation is developed correlating absolute chemical shifts to charge densities. Agreement between the calculated values and those derived from the correlation is quite satisfactory. 相似文献
18.
Martine Tessier Ernest Marechal 《Journal of polymer science. Part A, Polymer chemistry》1989,27(2):539-553
Several di-, tri- or multiblock poly(isobutylene-b-amide-11)s are prepared by reaction of α-mono or α,ω-dianhydride oligoisobutylenes with α-mono or α,ω-diamino oligoamides, in o-dichorobenzene at 140°C. They are characterized mainly by 1H- and 13C-NMR spectroscopy and GPC, using the trifluoroacetylation technique. Their thermal differential chromatograms are reported and analyzed. 相似文献
19.
Zdzislaw Chilmonczyk Markus Egli Christoph Behringcr AndrS. Dreiding 《Helvetica chimica acta》1989,72(5):1095-1106
In-situ-generated phthalimidonitrene was added to five α, β-unsaturated esters containing a chiral secondary O-function at C(γ). The additions were fully suprafacial, inasmuch as the (E)-isomers 1 afforded only the trans-aziridines 2 and 3 (J(β, γ) = 4.8?5.1 Hz) and the (Z)-isomers 4 only the cis-aziridines 5 and 6 (8.2?8.5 Hz). The products 2 , 3 , 5 , and 6 where shown to possess the arabino-, xylo-, ribo-, and lyxo- configuration, respectively, by X-ray structure analysis of 2b , 2d , and 6a . The diastereoface selectivity of the nitrene additions, induced by the chiral substructure around C(γ), resulted in more 2 than 3 from 1 , but more 6 than 5 from 4 , which means that the preference of attack at the double bond switches from one side to the other depending on the C=C configuration. The preferences were higher at lower temperature. The aziridines 2a , 2d , and 3d exhibit 1H-NMR-visible isomerism at the ring N-atom; the major (78?95 %)invertomer A is always the one with the phthalimido group in trans-position to the (larger) substructure around C(γ). The other aziridines only show 1H-NMR signals of one invertomer, which – by steric reasoning - ought to be A ; this is confirmed by a 1H-NMR argument for 3a , 5a , 6a , 5c , and 6c . 相似文献
20.
William T. Monte William A. Kleschick Jon Bordner 《Journal of heterocyclic chemistry》1999,36(1):183-188
A highly effective method for the selective removal of chlorine from the 7-position of the 1,2,4-triazolo[1,5-α]pyrimidine ring in the presence of chlorine at the 5- or 6-positions is reported. The method involves treatment of the appropriate substrate with zinc-copper couple in the presence of acetic acid in methanol-tetrahydrofuran. The method enables the construction of a variety of substitution patterns in key intermediates for the 1,2,4-triazolo[1,5-α]pyrimidine sulfonanilide herbicides. 相似文献