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1.
Two new polyoxygenated steroidal glucosides ( and ) have been isolated from the defensive secretion of C. hyperici and their structures have been determined by spectroscopic and chemical methods. 相似文献
2.
Edmund R. Marinelli 《Tetrahedron letters》1982,23(27):2745-2748
N-methyl and N-tert-butoxycarbonylindole-2,3-quinodimethanes ( and ) have been generated and observed to undergo intermolecular cycloaddition reactions with dienophiles. 相似文献
3.
Dervilla M.X. Donnelly Joseph OReilly Judith Polonsky G.W. van Eijk 《Tetrahedron letters》1982,23(51):5451-5452
Fomajorin S and D, two new isocoumarins have been isolated from the sporophores and ageing cultures of Fomes annosus, and have been assigned structures and respectively on the basis of spectroscopic evidence of the natural products and their derivatives. 相似文献
4.
The chemistry of phenalenium systems XXXIII. The Dibenzo[de;thi]naphthacenyl dication and the dianon
The dibenzo[de;hi]naphthacenyl dication () and dianion () have been generated from a mixture of the corresponding precursor hydrocarbons. The pmr spectra of and indicated that the positive and the negative charges were found to be fully delocalized over the molecules, respectively, consistent with the C2v-symmetry structures. The pmr chemical shifts of correlate well with the Hückel charge densities. 相似文献
5.
Syntheses for pyrazolo[3,4-g]quinazolin-8(7H)-one () and its [3,4-h]-analog 11 have been developed involving elaboration of aminoindazolcarboxylic acids and from correspondingly substituted methylnitroindazols, and subsequent anellation of the pyrimidine ring by v. Niementowski cyclization. 相似文献
6.
Six 20,24-dimethylscalarane derivatives (, , , , , and ) have been isolated from the Neo Guinean sponge Carteriospongia foliascens. Compound is identical with a C27 tetracyclic terpene previously isolated from an Australian specimen of the same sponge. The five other derivatives are new and their structures have been established on the basis of their spectral data. The structure of was confirmed by single-crystal X-ray diffraction and that of by chemical correlation with . The configuration at C-4 for all these compounds has been determined through 13C NMR data. Evidence leading to reverse the configuration at this centre in previously reported C27 tetracyclic terpenes is discussed. An ecological function is suggested for these molecules. 相似文献
7.
Three different types of butanolide complexes with EtnAlCl3?n in the molar ratios and have been investigated by IR with 1M NMR spectroscopy. The butanolides form and complexes with ethylaluminium halides, but with triethylaluminium only complexes are formed. The complexes are intermediates in the cleavage of butanolides. 相似文献
8.
Subodh Bhatnagar Judith Polonsky Marc Vuilhorgne Thierry Prangé Claudine Pascard 《Tetrahedron letters》1982,23(49):5159-5162
Laurycolactone A and B are new quassinoids with a C18 basic skeleton isolated from the Vietnamese Simaroubaceae, Eurycoma longifolia Jack. The structure of Eurycomalactone, a C19 quassinoid isolated previously from the same plant, has been revised and shown to be . The structures have been established by spectral means and those of and confirmed by X-ray diffraction analysis. 相似文献
9.
Ronald D. Brown Peter D. Godfrey Donald C. McGilvery Jonathan G. Crofts 《Chemical physics letters》1981,84(3):437-439
Microwave—optical double resonance signals have been detected in a mass-selected ion-beam spectrometer for 12C16O+. With the optical excitation of fluorescence from the R1 () line of the (0,0) band of the A2Π ← X2∑ transition of 20350.6 cm?1, the microwave resonances occurred at 118101.8 ± 0.2 MHz and at 117694 ± 2 MHz corresponding to the N= 1, J = ← N = 0, J = and the N = 1, J = ← N = 0, J = transitions. 相似文献
10.
Two new triterpenoid acids, designated as plectranthoic acid A and plectranthoic acid B, have been isolated from P. rugosus and are characterised as (20-S)-3α-hydroxy-18α,19α--urs-12-en-30β-oic acid and (14-S)-3α-hydroxy-18α, 19α -urs-12-en-27α-oic acid. 相似文献
11.
The potential K-region metabolites, - and -5,6-dihydroxy-7-methyl-5,6-dihydrobenz[c]acridine, 5,6-epoxy-7-methyl-5,6-dihydrobenz[c]acridine and 5-hydroxy-7-methylbenz[c]acridine, of 7-methylbenz[c]acridine have been synthesised. 相似文献
12.
Motomasa Kobayashi Nobuyoshi Shimizu Isao Kitagawa Yoshimasa Kyogoku Nobuyuki Harada Hisashi Uda 《Tetrahedron letters》1985,26(32):3833-3836
The absolute stereostructures of two pentacyclic hydroquinones, halenaguinol () and halenaquinol sulfate () from the Okinawan marine sponge Xestospongia sapra, have been determined by means of theoretical calculation of CD spectra. 相似文献
13.
Bogdan M. Angelov 《Chemical physics letters》1974,27(4):496-498
Diffuse reflectance spectra of tris-(2-pyridineamidoximato) lanthanide(III) chlorides, [Ln(PAO)3] Cl3, Ln = Pr, Nd, Sm, Eu, Dy and Ho, in the visible region have been recorded for the first time. Shifts (100–150 cm?1) of their f ? f transitions have been observed towards lower wave numbers in relation to the lanthanide aquoions. These data have been used for evaluation of the nephelauxetic ratio β′ and the covalency parameters b. Sublevels with J = 0 and J = as well as hypersensitive bands, obeying the selection rules|ΔJ|?2,|ΔL|?2, have been considered. The results have been discussed in terms of weak covalent bonding between the lanthanide ion and the nitrogen atoms of the ligands. 相似文献
14.
We have measured the vacuum ultraviolet absorption spectra of CH3I in solid and in liquid krypton in the spectral region 2000–1450 Å. In both phases we have observed two Wannier series n(2E) and n(2E) up to n = 3. Information has been obtained concerning the features of the conduction band in a liquid rare gas. 相似文献
15.
David P. Rininger Norman V. Duffy Robert C. Weir Edward Gelerinter Jack Standord David L. Uhrich 《Chemical physics letters》1977,52(1):102-106
Tris-(4-morpholinecarbodithioato-S,S′) iron (III) (FeM) and its dichloromethane solvate, (FeM·CH2Cl2), have been prepared and their temperature-dependent Mössbauer and EPR spectra have been determined at temperatures between liquid nitrogen and ambient. The Mössbauer spectra of FeM·CH2Cl2 differ considerably from that of FeM and is interpreted in terms of a four-line spectrum at 77 K. The EPR spectra of the two complexes indicate that the lower spin state of FeM·CH2Cl2 populates much more rapidly in the temperature range studied (100–300 K) than does FeM. These results support the postulation of an S = ? S = spin-equilibrium for FeM and a corresponding S = ? S = equilibrium for FeM·CH2Cl2. 相似文献
16.
Translational diffusion and intrinsic viscosity in 96% H2SO4 have been investigated for 20 samples of the para-isomer of polyoxyphenylbenzoxazoleterephthalamide (PpOPhBT) and 17 samples of its meta-isomer (PmOPhBT). The Mark-Kuhn equations have been obtained. The equilibrium rigidity of macromolecules in solution, calculated by using the wormlike chain theory, was characterized for PpOPhBT by the length of the Kuhn segment , the number of monomer units in a segment s = 17 and the coefficient of hindrance to intramolecular rotation in the chain σ = 1.5. For PmOPhBT the corresponding values are: , s = 5.9 and σ = 1.6. Analysis of flexibility mechanisms was carried out for PpOPhBT and PmOPhBT chains in solution. 相似文献
17.
Two new tetrahydropyrans have been isolated from the sponge Haliclona sp. From chemical and spectroscopic evidence they are shown to be (1′, 2, 2″, 5, 6)-2-(1′-bromethyl)-2,5-dimethyl-6-(penta-2″,4″-dienyl)-tetrahydropyran and (1′, 2, 5, 6)-2-(1′-bromoethyl)-2,5-dimethyl-6-(pent-4″-enyl)-tetrahydropyran. 相似文献
18.
(+/-)-6,9α-Methanoprostaglandin I3, () and (+/-)-5,6-dihydro-6,9α-methano-6β-prostaglandin I3, () have been synthesized using a new method for the stereoselective introduction of the 15α-hydroxy group via a stereoselective electrophilic addition of phenyl-sulfenyl chloride to the enol ether () and () respectively. 相似文献
19.
The reactions (I) Hg2Cl2(s) + Br2(g) and (II) HgCl2(s) + HgBr2(s) have been investigated by an X-ray method. Both the reactions yield two forms of the mixed halide HgClBr, designated as α-HgClBr and β-HgClBr. The cell parameters of the two are as follows:α-HgClBr: , , , z = 4, ? = 5.91 g/cm3. The powder pattern and cell parameters are similar to that of HgCl2. Therefore it is probable that the chlorine atoms, in the linear halogenHghalogen molecules of HgCl2 structure have been replaced by bromines, and since the radius of the bromine atom is larger than that of chlorine, the lattice is larger in this case.β-HgClBr: , , , z = 4, ? = 5.40. These parameters are the same as those reported in the literature for β-Hg(ClBr)2, and its X-ray powder pattern is similar to HgCl2. Therefore this phase also has linear halogenHghalogen molecules but the distribution of Cl and Br atoms is perhaps random.Heating the products (I) and (II) up to the melting point increases the amount of α phase and decreases the β phase, whereas crystallization increases the β phase. DTA study has supported the X-ray findings. 相似文献
20.
Jean-Raymond Gavarri Claude Carel Dominique Weigel 《Journal of solid state chemistry》1979,29(1):81-95
The structure of wüstite Fe1?zO is studied by neutron diffraction on one polycrystalline sample under equilibrium conditions at high temperature. The mean isotrope temperature factor B is expressed as a sum of two parts, BTh and BSt, which vary linearly with a single parameter, respectively temperature and z. A classification is established for clusters () settled from m vacancies in octahedral sites and n FeIII ions in interstitial sites. Sixteen values have been experimentally determined for the vacancies to interstitials ratio . A constant value of ?, which is lower than 3, is observed. This result characterizes the short-range order. It eliminates several possibilities of clusters like those obeying the relation . Other clusters, namely () or (), might agree. The () and () clusters obtained from () clusters joined by an edge would be the more likely. An analysis of diffuse scattering eliminates the hypothesis of large domains with inverse spinel structure. The structural differences between the three varieties W1, W2 and W3 would not be found in a structural change of clusters. 相似文献