A series of 9,10-dihydro-9,10-(1,2-tropylio)anthracene tetrafluoroborates has been prepared. The intramolecular charge-transfer interactions in were confirmed by their UV spectra and pKR+ values. As a model compound 1,2,3,4-tetrahydro-1,4-(1,2-tropylio)naphthalene tetrafluoroborate ()_was also examined. 相似文献
Kinetic theory of early stages of coherent clustering and continuous ordering in ordered phase is developed using the concept of concentration waves on the assumption of mean field energy. Linear differential equations of atom diffusion in ordered phase are solved by diagonalizing the coefficient matrix of the equations. It is shown that at the early stages of the reaction the concentration (fluctuation) waves evolve exponentially with respect to time on the sublattices of the ordered phase.The theory is applied to the Fe-10.9 at. %Si alloy which exhibits a sequence of transitions on aging at 775K. It is proved that the first transition from the disordered to the B2 phase occurs purely due to the kinetic reason that the amplification factors of the fluctuation waves have a positive maximum value only at the superlattice point of the B2 structure in the first Brillouin zone of the disordered phase. The second transition, which is from the metastable B2 phase to the stable phase, i.e. the spinodally decomposed D03 phase, is also explained consistently by the present theory that the amplifications calculated in the B2 phase exhibit two positive maxima in the first Brillouin zone. The maximum at point represents the amplification factor of the D03 ordering-wave in the B2 phase, while the other close to the Brillouin zone center represents the amplification factor of the fluctuation wave of the spinodal decomposition. 相似文献
The leaves of a tropical plant, Mitragyna speciosa KORTH (Rubiaceae), have been traditionally used as a substitute for opium. Phytochemical studies of the constituents of the plant growing in Thailand and Malaysia have led to the isolation of several 9-methoxy-Corynanthe-type monoterpenoid indole alkaloids, including new natural products. The structures of the new compounds were elucidated by spectroscopic and/or synthetic methods. The potent opioid agonistic activities of mitragynine, the major constituent of this plant, and its analogues were found in in vitro and in vivo experiments and the mechanisms underlying the analgesic activity were clarified. The essential structural features of mitragynines, which differ from those of morphine and are responsible for the analgesic activity, were elucidated by pharmacological evaluation of the natural and synthetic derivatives. Among the mitragynine derivatives, 7-hydroxymitragynine, a minor constituent of M. speciosa, was found to exhibit potent antinociceptive activity in mice. 相似文献
A new oleanan-type triterpene and three new cincholic acid glycosides were isolated from Peruvian "Una de Gato" (Cat's claw, plant of origin: Uncaria tomentosa), a traditional herbal medicine in Peru. Their structures were determined by spectroscopic analysis. 相似文献
The irradiation of N-(4-substituted benzoyl)-α-dehydroarylalanine alkyl esters (1) in methanol containing triethylamine (TEA) was found to quantitatively give cis- and trans-4,5-dihydrooxazole derivatives (2), which were described as being formed via electron transfer from TEA to the excited-state (E)-1 followed by kinetically-controlled cyclization of the (E)-1-derived anion radical. A product composition analysis showed that the cis-2/trans-2 composition ratio is greatly varied depending on the stereoelectronic properties of the substituents, the polarity of protic solvents and the concentration of TEA. 相似文献
A new yohimbine-type indole alkaloid (1). was isolated from the stem bark of Mitragyna africanus (WILLD.) collected in Nigeria, along with known seven Corynanthe-type oxindole alkaloids, two secoiridoids, three lignans, and a quinovic acid derivative. Their structures were elucidated by spectroscopic analyses. 相似文献
Ten new alkaloids, lycoposerramines-F (1), -G (2), -H (3), -I (4), -J (5), -K (6), -L (7), -M (8), -N (9), and -O (10), having lycopodine-related structures, were isolated from the club moss Lycopodium serratum THUNB. and their structures were elucidated on the basis of spectroscopic analysis and/or chemical transformation. 相似文献
Recent large helical device experiments revealed that the transition from ion root to electron root occurred for the first time in neutral-beam-heated discharges, where no nonthermal electrons exist. The measured values of the radial electric field were found to be in qualitative agreement with those estimated by neoclassical theory. A clear reduction of ion thermal diffusivity was observed after the mode transition from ion root to electron root as predicted by neoclassical theory when the neoclassical ion loss is more dominant than the anomalous ion loss. 相似文献
It was observed that the vacuum magnetic island produced by an external error magnetic field in the large helical device shrank in the presence of plasma. This was evidenced by the disappearance of flat regions in the electron temperature profile obtained by Thomson scattering. This island behavior depended on the magnetic configuration in which the plasmas were produced. 相似文献