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91.
92.
Two new C18-norditerpenoid alkaloids from Aconitum delavayi 总被引:2,自引:0,他引:2
Shan Hao Jiang Hai Qing Wang Yi Ming Li Shuang Jun Lin Jun Jie Tan Da Yuan Zhu 《中国化学快报》2007,18(4):409-411
Further phytochemical investigation of the unique C18-norditerpenoid alkaloids from the roots of Aconitum delavayi Franch ledto the isolation of two new norditerpenoid alkaloids,delavaconitine F 1 and delavaconitine G 2.Their structures were determinedfrom spectroscopic evidence. 相似文献
93.
A new potentially multidentate hexaprotic ligand H(6)[TETA-(PO)(2)] has been prepared by reaction of ethylenediamine-N,N'-diacetic acid (EDDA), paraformaldehyde, and phosphinic acid; its coordination properties with three lanthanide ions (La(3+), Gd(3+), and Lu(3+)) have been explored. The structures of the complexes were studied in aqueous solution by potentiometric pH titrations and by (31)P NMR spectroscopy. Four acidity constants were determined potentiometrically in the range 2.5 < pH < 14. The four measured pK(a) values can be divided into two groups, and within each group the initial deprotonation was found to have little effect on the second. Variable temperature (31)P and (31)P[(1)H] EXSY NMR spectra showed that, for [Lu(TETA-(PO)(2))](3-), the two phosphorus atoms exist in different chemical environments and undergo an exchange process which is very fast on the NMR time scale at room temperature. This result is consistent with one of the phosphinate residues coordinating the metal ion and exchanging with a free analogue. In the case of [La(TETA-(PO)(2))](3-), only one temperature invariant signal is observed in (31)P NMR spectra; it corresponds to both phosphinate residues remaining uncoordinated to La(3+). The stability of [Ln(TETA-(PO)(2))](3-) has an order of La(3+) > Gd(3+) > Lu(3+). The coordination of one phosphinate residue to Lu(3+) brings the metal ion closer to the plane of four nitrogens and farther from the four carboxylate arms, resulting in [Lu(TETA-(PO)(2))](3-) having a lower stability than the corresponding La(3+) and Gd(3+) complexes. A pM-pH distribution diagram showed that introducing two phosphinate groups into TETA renders [Gd(TETA-(PO)(2))](3-) more stable than [Gd(TETA)](-). The selectivity factor of the ligand for Gd(3+) vs Ca(2+), Zn(2+), and Cu(2+) has been calculated, and the hydration number for [Dy(TETA-(PO)(2))](3-) has been measured by (17)O NMR spectroscopy to be zero. 相似文献
94.
Shuang Zhang 《K-Theory》1992,6(1):1-27
We first determine the homotopy classes of nontrivial projections in a purely infinite simpleC*-algebraA, in the associated multiplier algebraM(A) and the corona algebraM
A/A in terms ofK
*(A). Then we describe the generalized Fredholm indices as the group of homotopy classes of non-trivial projections ofA; consequently, we determine theK
*-groups of all hereditaryC*-subalgebras of certain corona algebras. Secondly, we consider a group structure of *-isomorphism classes of hereditaryC*-subalgebras of purely infinite simpleC*-algebras. In addition, we prove that ifA is aC*-algebra of real rank zero, then each unitary ofA, in caseA it unital, each unitary ofM(A) and ofM(A)/A, in caseA is nonunital but -unital, can be factored into a product of a unitary homotopic to the identity and a unitary matrix whose entries are all partial isometries (with respect to a decomposition of the identity).Partially supported by a grant from the National Science Foundation. 相似文献
95.
Propargylic alcohols are versatile precursors to many organic molecules including natural products and pharmaceutical compounds.[1] In our continuing interest in the development of practical methods for synthesis of ferrocene derivatives, we decided to investigate the efficiencies of ferrocenylacetylene addition to aromatic aldehydes under t-BuOKcatalyzed condition.[2] Interestingly, we found that the usually reliable coupling reaction between terminal alkyne of type 1 and aromatic aldehydes of type 2 does not furnish the expected propargylic alcohols, but that the isomeric aryl enones 3are found in high yield and very short reaction time (10~20 min). This provided a promising protocol for preparation of ferrocenyl chalcones in a practical, economical and mild sense compared with the traditional method. To the best of our knowledge, this unusual reaction was first observed for the addition of ferrocenylacetylene to aldehyde in a base-catalyzed manner (Eq. 1). 相似文献
96.
The attempted Baylis-Hillman reactions of sulfonyl aldimines or aryl aldehydes with 3-methylpenta-3,4-dien-2-one or 3-benzylpenta-3,4-dien-2-one gave the corresponding Baylis-Hillman adducts in moderate yields in DMSO under the catalysis of DBU or PMe3, respectively. Moderate diastereoselectivities were observed in the reaction of 3-benzylpenta-3,4-dien-2-one with N-arylmethylidene-1-naphthalenesulfonamides catalyzed by chiral catalyst cinchona alkaloid derivative TQO {4-(3-ethyl-4-oxa-1-azatricyclo[4.4.0.0^3,8]dec-5-yl)quinolin-6-ol}. 相似文献
97.
MEN Xiu-Qin WANG Jin-Xian SHI Xiao-Ning WANG Ke-Hu 《有机化学》2003,23(Z1):307-307
Carbon-carbon double bond-forming reactions have always been great importance in organic synthesis. Manymethods have been described for C =C bond formation. We[1] have reported the new method of C =C bond formation of nickel catalyzed organozinc with aromatic aldehydes in the presence of Me3SiC1. 相似文献
98.
1INTRODUCTIONIntheearly1970'sthreegroupsofinvestigatorsL,~,'foundthatlow-valenttita-nium,preparedbythereactionofstrongreducingagentswithtitaniumtrichlorideortitaniumtetrachlorideintetrahydrofuran,canabstractoxygenfromketonesoraldehydes,leadingtotheforma-tionofolefins.Theinterestinthereactioninducedbylow--valenttitaniumreagentsisincreasingandalargenumberoffunctionalgroupscanbereduceds4-6).Recent-ly,wefoundthatthetitlecompoundisObtainedbycy-cllzatlonreactionof(3--oxo-1,3-diphenyl)propyl-pro… 相似文献
99.
100.
Guo X Shuang S Wang X Dong C Pan J Aboul-Enein HY 《Biomedical chromatography : BMC》2004,18(8):559-563
The interaction of rutin and venoruton (troxerutin), with alpha-, beta- and gamma-cyclodextrin (CD), hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and methyl-beta-cyclodextrin (M-beta-CD) was investigated by reversed-phase thin layer chromatography on polyamide plates. A mobile phase consisted of NH(4)OH; NH(4)Cl buffer solution containing various CD concentrations (pH = 9.7, 20 degrees C) was used as mobile phase. The equilibrium constants (K(f)) and the retention factor (R(f)) were determined and used to study the inclusion process. The in fluence of CDs on the solubility of rutin and venoruton was characterized by R(M) values and the increasing hydrophilicity of drugs. The results show that the inclusion capacity of cyclodextrins follows the order HP-beta-CD > M-beta-CD > beta-CD > gamma-CD, and rutin is more easily included by the studied cyclodextrins than venoruton. In addition, the thermodynamic parameters (Delta H, Delta S) for the formation of complexes were obtained from the van't Hoff equation, displaying the enthalpy-entropy compensation effect. 相似文献