Studies on the chemical constituents of Chinese azalea——Ⅰ.The structure of rhodomollein-Ⅰ,a new toxic diterpenoid

Two unknown toxic diterpenoids,rhodomollein-I and rhodompllein-Ⅱ,and the known rhodojaponin-Ⅲ,have been isolated from Chinese azalea (Ericaceae,Rhododendron molle G.Don). rhodomollein-I,C_(20)H_(32)O_6,colorless thin needles,[a]D^(20)-6.65 (c 3.76×10^(-2),EtOH),m.p.241— 242.5℃.Its structure has been established as 1 through spectral analysis of ^(13)C NMR,~1H NMR, MS,IR and UV.Moreover,its stereostructure was unambiguously identified from the different threshold level line of ~1H—~1H NOESY.

Diterpenoids from Rabdosia nervosa

Six ent-kaurene type diterpenoids have been isolated from the leaves of Rabdosia nervosa. Among them, ganervosin A and B were new compounds, the structures of which were elucidated as 1 and 2 respectively by spectral and chemical methods. The other four were identified as odonicin (3), novelrabdosin (4), nodosin (5) and shikokianal acetate (6), Compounds 5 and 6 were for the first time isolated from this herb.

Linear free energy relationships between reaction rate constants and equilibrium constants of complex compounds——III. Kinetics and mechanisms of ternary complex formation between (5-X-1, 10-phenanthroline)copper(II) and threonine

The kinetics of ternary complex formation involving Cu(5-X-1, 10-phen) and threonine (CuAL, A=5-X-1, 10-phen; L=threonine or represented by O-N; X=NO_2, Cl, H, CH_3) has been studied by temperature-jump and stopped-flow methods. The formation rate constants, k_f(M^(-1).s^(-1)), for the complexation reaction, CuA + LCuAL, are as follows; X=NO_2, 8.68×10~8; X=Cl, 7.13×10~8; X=H, 6.12×10~8; X=CH_3, 5.42×10~8. The rate constants for zwitterion attack are nil within experimental error. It has been found that a linear free energy relationship exists between the stability(logK_(CuAL)^(CuA) of the complexes CuAL and log kf as follows: IogK_(CuAL)^(CuA)=0.13 + 0.83 logk_f, r=0.99. It suggested that the formation rate governed the stability of the ternary complexes. The rates of formation of the ternary complexes increased with decreasing electron-donating property of the substituents. A linear relationship was found to exist as expressed by the following equation: log(k_f^R/k_F^O) = 0.097σ, r=0.96. A mechanism involves a rapid equilibrium between CuA and L followed by a slow ring closure of L.

Dysoanthraquinone and 2-demethyldysoanthraquinone from Dysosma majoense

Two new anthraquinones,dysoanthraquinone and 2-demethyldysoanthraquinone,were separated from Dysosma majoense.Both compounds contain methylendioxy at 6—C,7—C.It is very interesting in terms of biogenetic pathway that they may have been transformed from aryltetralin lignans by means of oxidative cleavage followed by ring closure.

Study on synthesis of lanthanide chelates of (l)-α- trifluoromethyl-polyfluoroalkyl-β-diketone and their application as chiral shift reagents

The lanthanide chelates of(l)-2,2-dimethyl-6-trifluoromethyl-7-oxa-6,8,8,9,9,10, 10,10-octafluoro-3,5-decanedione,Ln[(l)-CF_3CF_2CF_2OCF(CF_3)COCHCOC(CH_3)_3]_3(l-3a,Ln=Eu; 3b, Ln=Pr), are useful as ~1H NMR shift reagents for direct determination of enantiomeric composition of enantiomorphous alcohols. ketones and amines. With these substrates. l-3a induces shift difference similar to that induced by Eu(facam)_3 and Eu(hfbc)_3. However, due to the higher solubility of the chelates l-3a and l-3b in nonpolar organic solvent such as CHCl_3, CCl_4 and only one ~1H signal from l-3a and l-3b is observed. their application as the new chiral shift reagents seems promising. The spectral nonequivalence is also observed for dimethylsulfoxide in the presence of l-3a.

The reaction of perfluoroalkanesulfinate——A novel method for the preparation ofperfluorocarboxylic acid and the coupling product perfluoroalkane

Oxidation of perfluoroalkanesulfinate usually resulted in the formation of the correspon-ding sulfonyl derivatives,thus reaction with hydrogen peroxide or halogen（Cl,Br,I）gavesulfonic acid or sulfonyl halides.However in comparison with alkanesulfinate the perfluo-ro analog was shown to be relatively inert toward oxidizing agents.

Studies on intramolecular 1,3-dipolar cycloaddition reactions——Ⅲ. The synthesis of a novel heterocyclic ring system by regiospecific cycloaddition

The syntheses of a number of C-aryl-N-3-butenyl nitrones [aryl ring=4-CH_3O-phenyl (1a), phenyl(1b), 4-Cl-phenyl(1e), 4-Br-phenyl(1d), 4-NO2-phenyl(1e), 2-furyl (1f), 2-thienyl (1g), 2-pyrryl(1h)] and their thermochemical reactions have been investigated. The thermocycloadditions of 1a-1h are regiospecific in forming a novel heterobicyclic ring system. Exo-aryl-1-aza-7-oxabicyclo- [2.2.1]heptane.

Application of carbene reactive intermediates in organic synthesis——Ⅲ.Reaction of difluorocarbene with trimethylsilyl enol ethers

The addition of difluorocarbene generated from phenyl(trifluoromethyl)mercury and anhydrous sodium iodide,with trimethylsilyl enol ethers derived from cyclohexanone,cycloheptanone, 3-pentanone and acetophenone was described.The corresponding 2,2-difluoro-1-trimethylsilyloxy- cyclopropanes were obtained in good yields.The thermal stability of these cyclopropyl derivatives was affected by the molecular strain and the nature of their substituents.Thus,1-trimethylsilyloxy- cyclopentene reacted with difluorocarbene to give only 2-fluoro-2-cyclohexen-1-one instead of the expected 1-trimethylsilyloxy-6,6-difluorobicyclo[3.1.0]hexane,and a mechanism for its formation was proposed.

Catalysts and thermodynamic coupling of chemical reactions

The condition of occurrence of the thermodynamic coupling of chemical reactions is analysed from kinetics. It is found that the thermodynamic coupling is impossible for those reactions which obey kinetically the mass action law. The thermodynamic coupling of chemical reactions is further analysed in the case with catalyst. It is found that the thermodynamic coupling which is impossible without catalyst may become possible by introducing proper catalyst into the system. This implies that the catalysts can change not only the rates of chemical reactions, but also the behaviors of thermodynamic coupling of chemical reactions, including the direction of some reactions. Such role of catalysts comes into play not by changing the total free energy of the system, but by changing the reaction mechanism.

The isolation and characterization of indole alkaloids from the fruits of Kopsia officinalis

Sixteen alkaloids have been isolated from the fruits of Kopsia officinalis Tsiang and P.T. Li(Apocynaceae), a plant commonly used in folk medicine for treating tonsillitis and rheumatism. Ten of them were identified as known alkaloids-eburnamenine(1), kopsanone(2), 5, 18-dioxokopsan (3), kopsinilam(4), kopsinine(5), pleiocarpine(6), kopsamine(7), N-carbomethoxy-12-methoxykop- sinaline(8), N-carbomethoxy-11, 12-dimethoxykopsinaline (9) and(+)-vincadifformine (13). The other three have now been proved to be new. They are N-carbomethoxy-11-hydroxy-12-methoxy- kopsinaline(10), N-carbomethoxy-11-methoxy-12-hydroxykopsinanne (11) and kopsamine N-oxide (12).

Mechanism of boron atomization in graphite furnace atomic absorption spectroscopy

The mechanism of the atomization of boron and the enhancement of sensitivity by matrix modifier Sr(NO_3)_2 in graphite furnace AAS were discussed.X-ray diffraction and thermodynamic calculation were applied to study the mechanism of boron atomization with and without matrix mo- difier Sr(NO_3)_2.The formation of boron atom is due to the sublimation of solid boron which derived from the reduction of B_2O_3 by carbon.The enhancement of boron signal in the presence of Sr(NO_3)_2 is due to the formation of SrB_6 before atomization,which decreased the volatization losses of B_2O_3 and retarded the formation of B_4C.

Vibrational spectroscopic study of rotational isomerism in O,O-dimethylphosphorodithioic acid

In this paper,the IR and Raman spectra of(CH_3O)_2P(S)SH have been studied at room temperature and at lower temperature.It is found that the P=S stretching vibrational band consists of four sub-bands,which shows that there are four rotational isomers for(CH_3O)_2P(S)SH.With the aid of computer we have separated the P=S bands and measured the relative intensities of each sub-band at different temperatures,so the relation of interconversion bween isomers was obtained. Moreover,there exists intermolecular hydrogen bond in this compound,which will impede the rotation of S-H about P-S bond.Therefore,the interconversion of isomers results only from the rotation of O-CH_3 about P-O bond.

Determination of the acid dissociation constants of N-carboxymethyl-N-(p-hydroxy phenyl carbamoylmethyl)-2,3-dihydroxy- 5-carbomethoxy benzylamine and the stability constants of its metal complexes

The acid dissociation constants of N-carboxymethyl-N-(p-hydroxy phenyl carbamoyl- methyl)-2,3-dihydroxy-5-carbomethoxy benzylamine(CHDCB) and the stability constants of its 1:1 complexes with alkaline earth, Cd(Ⅱ), Co(Ⅱ), Ni(Ⅱ), Cu(Ⅱ), Zn(Ⅱ), Fe(Ⅲ),Th(Ⅳ)and U(Ⅵ)ions have been determined at 25.0±0.1℃ and at an ionic strength of 0.1(KNO_3)by pH titration method. The probable coordination sites have also been discussed.

Coordination of neighboring C——H bond to transition metal center——III. Study on localized molecular orbitals of the binucleate ion [Fe_2(CH_3)(CO) (Ph_2pCH_2PPh_2)Cp_2]^+

A localized INDO method was used to calculate the ion [Fe_2 (CH_3) (CO) (Ph_2PCH_2PPh_2)- Cp_2]^+. Based on the analysis of the localized molecular orbitals (LMO), bond orders and contour maps, it was pointed out that the LMO no. 20 corresponds to the coordination of C(1)-H(I) σbond to Fe(2) atom. Non occurrence of metal-metal bond between Fe(1) and Fe(2) atoms was found and the covalence of irons was numerated, which coincides with the value in ref 17.

The EXAFS and IR characterization of Rh particles derived from NaY-zeolite entrapped Rh_6(CO)_(16)in CO and H_2 chemisorption

Metal clusters made of neighbouring metal centers with unique structures and stabilizedon a support may provide well-defined heterogeneous catalysts.The idea of constructingthese metal clusters in zeolite cages has been coined as synthesis by a “ship-in-bottle” technique.Here,we report on the structural characterization and chemisorption behavior of NaY zeolite

Crystal and molecular structure of(μ-p-CH_3C_6H_4C_2S) (μ-n-C_3H_7S)Fe_2(CO)_6CO_2(CO)_6

The crystal and molecular structure of the complex containing cobalt-carbon and iron- sulfur cluster cores,(μ-ρ-CH_3C_6H_4C_2S)(μ-n-C_3H_7S)Fe_2(CO)_6Co_2(CO)_6,has been determined by X-ray diffraction method.The crystals are triclinic,space group P,with a=9.139(2),b=9.610(1), c=17.183(2),α=84.36(1),β=89.45(1),γ=88.15(1)°,V=1501.0~3;Z=2,D_c=1.74 g/cm^3. R=0.072,Rw=0.081.The results of the structure determination show a cobalt-carbon cluster core formed through the reaction of(μ-ρ-CH_3C_6H_4C_2S)(μ-n-C_3H_7S)Fe_2(CO)_6 with Co_2(CO)_8.In the cobalt-carbon cluster core,the bond length of the original C≡C lengthened to 1.324 which is close to the typical value of carbon-carbon double bond.The groups connecting the carbons of the cluster core are in cis position and lie on the opposite side of cobalt atoms.In this complex,the conformation of-SC_3H_7 is e-type,while that of-SC_2C_6H_4CH_3 is a-type.

ESR study of the free radical intermediates formed during the electrolytic process——III. Electrooxidation of substituted anilines

Active free radicals formed by the electrooxidation of substituted anilines RC_6H_4NH_3 (R=H, p-Br, p-Cl, p-I, p-Me, p-COOH, p-MeCO, p-NO_2, m-CO_2H, and m-Cl) are trapped by spin trap 2-methyl-2-nitroso propane (MNP). A multiple ESR signal of the solution containing electrolytic aniline and MNP is identified with the spin adduct of MNP and radical cation 1 by theore- tical simulation of observed spectrum. Furthermore, ESR spectra of para- or meta-substituted anilines give a reasonable explanation about spin adducts of MNP and the cation 2 or 3 by the same method.

Synthesis and structure of ammonium tricupric(II)-octadecatungsto-diantimonate(III)

This paper reports the synthesis, properties and structure of (NH_4)_(12)[Cu_3(H_2O)_3(SbW_9O_33)_2]· 11H_2O. The compound was prepared by the depolymerization reaction of (NH4_)_(18)[(NH_4)Sb_9W21O_(86)]. nH_2O,which was proposed firstly as a method of preparing new heteropoly tungstoantimonate(Ⅲ). Its properties were characterized by IR, Raman, UV-VS spectra, TG-DTA thermal analysis, and X-ray single ctystal analysis. The crystal is orthorhombic, with space group D_(2h)^(16)-Pnma. The crystal data are: a=15.423(4), b=19.307(6), c=30.275(6), V=9015.0~3, Z=4, Dc=3.881 g/cm_3. The structure has been refined by full-matrix least squares method to a final R factor of 0.064 for 2652 reflections collected at room temperature. The heteropoly anion contains two a-B-SbW_9O_(33) subunits joined by three square-pyramidal CuO_4(OH_2).

Total synthesis of(-)-curdione

(-)-curdione,the antipode of the antitumor principle of Chinese herb Curcuma aromtica Salisb.was synthesized from(-)-carvone via oxy-Cope rearrangement.This result also confirmed the absolute configuration of natural(+)-curdione.