二水草酸锌脱水的热分解动力学研究

提出一种多升温速率-等温法确定机理函数g(α)的新方法;并用迭代的等转化率法求出较为可靠的活化能Ea;在Ea和g(α)的基础上计算出指前因子A.用该法对二水草酸锌（ZnC2O4•2H2O）脱水反应的热分解动力学三因子进行了求算,得出Ea为87.22 kJ•mol－1, A为4.2120×108～7.2328×108 s－1;以及随机成核和随后生长型机理函数Am（Avrami-Erofeer）,其积分形式g(α)=[－ln(1－α)] 1/m和微分形式f(α)=m(1－α)•[－ln(1－α)](1－1/m),调节因子m=1.85～2.00.     

Some Taxane Derivatives from the Heartwood of Taxus Mairei

Five Taxane derivatives were isolated from Taxus mairei. Their structures were determined by spectroscopic methods and their physical constants were identical with the literature values. These are Taxa-4(20), 11-diene-2α, 5α, 7β-tetrol-5α, 7β, 10β-triacetate-2α-α-methylbutyrate(I); Taxa-4(20), 11-diene-2α, 5α, 9α, 10β, 13β-pentol-2α, 9α, 10β, 13α-tetraacetate-5α-cinnamate(II);Taxa-4(20), 11-diene-5α, 7β, 9α, 10β, 13α-pentol-pentaacetate(III); 7β-acetate-O-taxinine A(IV), 1β-hydroxy-baccatin-I(V).     

Transformed steroids. 193. Synthesis of 16α,17α-isopropylidene derivatives of pregn-4-ene-9α,16α,17α,21-tetraol-3,20-dione and its 17α-thioanalog

A study was carried out on the pathways for the transformation of 16α,17α-epoxypregn-4-ene-9α,21-diol-3,20-dione to give 16α,17α-isopropylidene derivatives of pregn-4-ene-9α,16α,17α,21-tetraol-3,20-dione and its 17α-thioanalog. The key step in this pathway is thecis-cleavage of the 20-carboethoxyhydrazone of this epoxide by acetic and thioacetic acids and subsequent condensation of the products formed with acetone. This pathway is an efficient approach to the synthesis of the 16α,17α-dioxolane derivative and is equally efficient for preparation of the thioanalog, namely, 16α,17α-isopropylidenepregn-4-ene-9α,16α,21-triol-17α-thiol-3,20-dione, which has already been synthesized by an alternative method.     

含有羧基配体的蝎型钒氧配合物的合成、结构及其热分解动力学

设计合成了两种新型的以聚吡唑硼酸盐、氨基酸为配体的钒氧配合物VO[phCH2CH(NH2)COO][HB(pz)3](1)和VO(3,5-Me2pz)[HB(3,5-Me2pz)3](CH3COO)(2). 通过元素分析、红外光谱对配合物进行了表征, 并利用单晶X射线衍射技术解析了它们的结构. 非等温热分解动力学研究表明, 配合物1和2的热分解反应都是分两步进行的. 通过计算, 配合物1热分解的第一步反应的可能机理为成核与生长(n=1/4); 第二步反应的可能机理为化学反应. 其非等温动力学方程分别为, dα/dT=(A/β)e-E/RT(1/4)(1-α)[-ln(1-α)]-3 和dα/dT=(A/β)e-E/RT(1-α)2. 分解反应的表观活化能分别是223.52 和331.94 kJ·mol-1; 指前因子ln(A/s-1)分别是49.67 和57.50. 配合物2 热分解的第一步反应的可能机理为化学反应; 第二步反应的可能机理为成核与生长(n=1/2). 其非等温动力学方程分别为, dα/dT=(A/β)e-E/RT(1-α)2, 和dα/dT=(A/β)e-E/RT(1/2)(1-α)[-ln(1-α)]-1. 分解反应的表观活化能分别是300.56 和444.72 kJ·mol-1; 指前因子ln(A/s-1)分别是75.53 和92.50.     

Thermotropic liquid crystalline polymer. III. Synthesis and properties of poly(amide-azomethine-ester)

A series of novel dialdehydes as new monomers, 4,4′-diformyl-α,ω-diphencarbonylalkane, 4,4′-diformyl-3,3′-methoxy-α,ω-diphencarbonylalkane, and 4,4′-diformyl-3,3′-ethoxy-α,ω-diphencarbonylalkane, was prepared from aliphatic diacid chloride with p-hydroxybenzaldehyde, vanillin, and 3-ethoxy-4-hydroxybenzaldehyde, respectively. A series of poly(amide-azomethine-ester)s was prepared by condensation of 4,4′-diaminoanilide with 4,4′-diformyl-α,ω-α,ω-diphencarbonylalkane, 4,4′-diformyl-3,3′-methoxy-α,ω-diphencarbonylalkane, and 4,4′-diformyl-3,3′-ethoxy-α,ω-diphencarbonylalkane, respectively. Their thermotropic liquid crystalline properties were examined by DSC microscope observations. In most cases, the mesophase extends up to ca. 288–380°C, where thermal decomposition prevents further observation.     

Diethylhydrogensilyl cyclic diethylsilylene derivatives in gas chromatography/mass spectrometry of hydroxylated steroids. III-Fragmentations of 5β-pregnane-17,20,21-triol derivatives

A reaction of N,O-bis-(diethylhydrogensilyl) trifluoroacetamide with 5β-pregnane-17,20,21-triols afforded diethylhydrogensilyl (DEHS) cyclic diethylsilylene (DES) derivatives. 5β-Pregnane-3α,17α,20β,21-tetraol yielded the 3α,21-bis-DEHS-17α,20β-DES compound, whereas the structure of the major product from its 20α isomer was assigned as the 3α,17α-bis-DEHS-20α,21-DES derivative, which would undergo facile isomerization to the unstable 3α,21-bis-DEHS-17α,20α-DES structure under electron ionization. Fragmentations of these DEHS-DES compounds are discussed on the basis of isotope labelling experiments, linked scanning data, and accurate mass measurements.     

Synthesis of new enantiomerically pure β-amino alcohols of the pinane series

A series of new β-amino alcohols with pinane structure, (+)- and (?)-3α-amino-10β-pinan-4β-ols, 4β-amino-10β-pinan-3α-ol, and 4α-amino-10β-pinan-3α-ol have been synthesized with the goal of using them as organocatalysts in the aldol reaction of isatin with acetone.     

Base-catalyzed redox reactions of α-hydroxyalkylazaaromatic N-oxides

The (α-hydroxybenzyl)pyridine 1-oxides on heating with aqueous sodium hydroxide yielded the corresponding benzoylpyridines in redox reactions. When the phenyl groups of the foregoing compounds was replaced by hydrogen or methyl the redox reactions occurred less readily. A kinetic isotope effect of 3 was found for 4-(α-deuterio-α-hydroxybenzyl)pyridine 1-oxide on reaction with sodium hydroxide. The removal of the α-deuterio group is non-reversible. A mechanism consistent with these observations is given. 6-Acetoxyphenanthridine 5-oxide yielded with concentrated hydrochloric acid a redox product, 6-formylphenanthridine hydrochloride, whereas under the same conditions neither (α-hydroxybenzyl)pyridine 1-oxides nor 2-hydroxy-methylquinoline 1-oxide yielded a redox product.     

Preparation of poly-p-xylylenes by electrolysis

Poly-p-xylylenes were prepared by electrolytic reduction of α,α′-dihalo-p-xylenes at controlled cathode potentials (c.p.). Polymers and halides are formed at the cathode; at the anode the halide is oxidized to halogen. Poly-p-xylylene was prepared from α,α′-dichloro-p-xylene (c.p. ?1.2 v.) and α,α′-dibromo-p-xylene (c.p. ?1.2 v.); poly-p-2-chloroxylylene from α,α′,2-trichloro-p-xylene (c.p. ?1.4 v.) and α,α′-dibromo-2-chloro-p-xylene (c.p. ?1.2 v.); poly-α,α,α′,α′-tetrachloro-p-xylylene from α,α,α,α′,α′,α′-hexachloro-p-xylene (c.p. ?0.7 v.), and poly-α,α,α′,α′-tetrafluoro-p-xylylene from α,α′-dibromo-α,α,α′,α′-tetrafluoro-p-xylene (c.p. ?1.1 v.). The cathode potentials were measured and controlled with respect to a saturated calomel electrode. Current efficiencies up to 96% were observed. α,α,α′,α′-Tetrachloro-p-xylylene was identified as an intermediate in the reduction of α,α,α,α′,α′,α′-hexachloro-p-xylene. A general mechanism for these reactions is suggested and discussed. It involves elimination of halide by a two-electron charge transfer with formation of a xylyl anion, followed by an elimination of halide in α′-position yielding xylylenes which then polymerize.     

Constituents of Fruit Bodies of Tramete orientalis

A known sterol, 5α,6α-epoxy-5α-crgosta-8(14),22E-diene-3β,7α-diol ( 1 ), and two new sterols, 5α,6α-epoxy-3β,8β,14α-trihydroxy-5α-ergost-22E-en-7-one ( 2 ), (3α,5α),(8β,11β)-diepidioxy-ergost-22E-en-12-one ( 3 ), were isolated and characterized from dried fruit bodies of Trametes orientalis. Their structures were elucidated according to spectral methods.     

A short convergent synthesis of the side chains of brassinolide,cathasterone, and cryptolide

A new approach to steroidal derivatives of the campestane series, containing the 22α-hydroxy-, 22α,23α-dihydroxy-, and 22α-hydroxy-23-ketone moieties characteristic of brassinolide and its congeners, has been developed. The key step is the coupling of a steroidal C-22 aldehyde with an anion derived from a specially synthesized thioacetal-containing chiral synthon. The cathasterone and cryptolide side chains are prepared by reductive or hydrolytic thioketal removal, respectively. The brassinolide side chain is obtained by DIBAL-H reduction of the TBS-protected 22α-hydroxy-23-ketone.     

New chiral phase-transfer catalysts possessing a 6,6′-bridged ring on the biphenyl unit: application to the synthesis of α,α-dialkyl-α-amino acids

A new chiral phase-transfer catalyst possessing a 6,6′-bridged ring on the biphenyl unit has been developed for the practical synthesis of α,α-dialkyl-α-amino acids. This catalyst shows very high activity for the asymmetric alkylation of an alanine derivative to give α,α-dialkyl-α-amino acid derivatives with high enantioselectivities.     

Synthesis of α‐Nitro‐α‐diazocarbonyl Derivatives and Their Applications in the Cyclopropanation of Alkenes and in O?H Insertion Reactions

A facile and highly efficient method for the preparation of α‐nitro‐α‐diazocarbonyl derivatives by a diazo‐transfer reaction involving (trifluoromethyl)sulfonyl azide has been developed. These substrates undergo a rhodium‐catalyzed cyclopropanation reaction with a variety of alkenes. A systematic study of the reaction indicated that the diastereoselectivity of the cyclopropanation could be effectively controlled through the modification of the steric bulk of the diazo reagent. A novel O? H insertion reaction of the metal? carbene complex derived from the α‐nitro‐α‐diazocarbonyl reagent afforded the corresponding novel α‐nitro‐α‐alkoxy carbonyl derivatives.     

云南美登木内生真菌Phomopsis sp. Lz42的化学成分

从云南美登木内生真菌Phomopsis species Lz42的琼脂平板发酵物中分离得到2个倍半萜和5个麦角甾醇类化合物(1~7), 其中化合物1和2为新化合物. 应用波谱技术确定其结构为4-Deacetyl-10-oxo-dihydrobotrydial(1)和麦角甾-6,22-二烯-5α,8α-环二氧-3-甲酸酯(2).     

Canataxpropellane, a novel taxane with a unique polycyclic carbon skeleton (tricyclotaxane) from the needles of Taxus canadensis

A novel taxane with an unprecedented 5/5/4/6/6/6-membered hexacyclic skeleton containing [3.3.2]propellane was isolated from the needles of the Canadian yew, Taxus canadensis. The structure was established as 2α,10β-diacetoxy-5α,9α,20α-trihydroxy-3α,11α;4α,12α;14α,20-tricyclotaxan-13-one (1), which exists as two conformational isomers on the basis of spectroscopic analysis. This compound would be biogenetically derived from a normal 6/8/6-taxane by the intramolecular aldol reaction and [2+2] cycloaddition.     

Synthesis of functionalized 2,3-dihydroisoxazoles by domino reactions in water and unexpected ring-opening reactions of 2,3-dihydroisoxazoles

α,α-Dicyanoolefins react with hydroxylamine to afford 2,3-dihydroisoxazoles (2,3-dihydroisoxazoles can be easily isolated by filtration) in excellent yields under mild and environmentally benign conditions. A one-pot reaction in tandem with an unexpected ring-opening of 2,3-dihydroisoxazoles has been developed as well.     

Studies on asterosaponins—V : A novel steroid conjugate, 5α-pregn-9(11)-ene-3β,6α-diol-20-one-3-sulfate,from a starfish saponin,asterosaponin A

A new crystalline steroid conjugate was obtained by partial acid hydrolysis of asterosaponin A, a steroidal saponin from the starfish, Asterias amurensis. The structure of the conjugate was established as 5α-pregn-9(11)-ene-3β,6α-diol-20-one-3-sulfate (2) on the basis of elemental analysis, IR and PMR spectra measurement and chemical reaction. Solvolysis of compound 2 yielded 5α-pregn-9(11)-ene-3β,6α-diol-20-one. Oxidation with chromium trioxide-pyridine complex followed by solvolysis afforded a new steroid, 5α-pregn-9(11)-ene-3β-ol-6,20-dione, whose structure was deduced by the measurement of ORD curve and PMR spectra. Thus, the location of carbohydrate moiety in asterosaponin A has been assigned to 6α-hydroxy group of the steroid conjugate.     

Asymmetric synthesis of α,α-difluoro-β-amino phosphonic acids using sulfinimines

Addition of diethyl lithiodifluoromethylphosphonate to enantiopure sulfinimines afforded the corresponding N-sulfinyl α,α-difluoro-β-amino phosphonates with good diastereoselectivity. A two-step deprotection involving treatment of diastereomerically pure N-sulfinyl α,α-difluoro-β-amino phosphonates with trifluoroacetic acid in EtOH followed by refluxing with 10 N HCl afforded enantiopure α,α-difluoro-β-amino phosphonic acids.     

Nuclephilic ring opening of epoxides promoted by multi-site phase-transfer catalyst:An efficient and eco-friendly route to synthesis of β-hydroxythiocyanate

A highly effective and mild protocol for ring opening of epoxides with NH4SCN in the presence of catalytic amount of a multisite phase-transfer catalyst,α,α′,α″-N-hexakis(triethylammoniummethylene chloride)-melamine,is developed.A variety ofβ-hydroxy thiocyanates as important intermediates in agricultural and pharmaceutical chemistry were obtained in high yields with excellent regioselectivity and in short reaction times.     

Chemical Constituents of a Formosan Soft Coral Sinularia sp.

A new marine sterol 7β-hydroperoxy-24-methylenecholesterol ( 1 ) along with five known compounds sarcophytol A ( 2 ), (Z)-N-[2-(4-hydroxyphenyl)ethyl]-3-methyldodec-2-enamide ( 3 ), 5α,7αH-eduesm-11(13)en-4α-ol ( 4 ), 24-methylenecholesterol ( 5 ) and 1β-hydroxy-α-cyperone ( 6 ) have been isolated from a Formosan soft coral Sinularia sp. The structures of the above compounds were determined by spectral analyses. Cytotoxicity of compounds 1–6 toward various cancer cell lines also is reported.