Synthesis of N-(methoxycarbonyl or isopropylcarbamoyl- methoxyphosphonyl)-α-amino acid ester and their stereomers

N-(methoxycarbonyl-methoxyphosphonyl)-α-amino add esters (I) were synthesized via the reaction of the corresponding phosphonyl chloride with amino acid ester hydrochlorides in the presence of a base. Compound I was aminated to yield N-(isopropylcarbainoyl-methoxyphosphonyl)-α-amino acid esters (II). With l-amino acids as starting materials, the isomers of products I and II were separated and their configurations were confirmed by the single crystal X-ray diffraction of II.     

有机磷化合物的研究 VIII. 酸性有机磷化合物的气相色谱

Acidic organophosphorus compounds may be identified by GLC via their methyl esters, usually prepared from diazomethane. The wide applications of this mthod are, however, limited by the toxicity of diazomethane. Tetramethyl ammonium hydroxide in methanol solution reacted rapidly with acidic organophosphorus compounds at room temperature to form tetramethyl ammonium salts, which were then converted to the corresponding methyl esters by pyrolysis at 300-350 deg.C. A simple and convenient method for separation and identification of various types of acidic phosphates, phosphonates and phosphinates by GLC has been developed. The GLC behaviours of phosphoric acid dialkyl esters, mono-esters of phenyl-and cyclohexyl-phosphonic acids as well as dialkylphosphinic acids can be represented by corrected retention time (t'R) which correlates linearly with the number of carbon atoms of the alkyl groups in these organophosphorus compounds. The influence of number of carbon atoms and isomerization of alkyl group on t'R values and retention index (I) calculated by Kovats equation was discussed. As shown by our experiments the change in retention index (ΔI) in the homologous series of phosphoric acid dialkyl esters is nearly a constant on lengthening the alkyl group of the esters with methylene linkages.     

Synthesis and Structure Elucidation of Celangulin Derivatives

Celangulins are sesquiterpene polyol esters based on a core structure known as β-dihydroagarofuran from Celastrus angulatus Max. Some of them are environment acceptable-pesticides. In order to find new active compounds and study their SAR, sesquiterpene polyol esters libraries were synthesized based on the basic hydrolysis of the extract of the root bark of Celastrus angulatus which could offer the β-dihydroagarofuran polyol by combinatorial chemical method and the compounds with insecticidal activity were isolated by bioassay-guided fractionation. Two new compounds with insecticidal activity against Mythimna separata, were isolated and elucidated as 2β,6α,8β, 13-tetraisobutanoyloxy-1β,4,9α-trihydroxy-β-dihydroagarofuran (A) and 1β,2β,6α,8β, 13-pentaisobutanoyloxy-4α,9α-dihydroxy-β-dihydroagarofuran (B) mainly by 1H NMR, 13C NMRH-HCOSY, HMQC, HMBC and HRMS spectral data. A: [α]20D -7.3 (c 0.12, CHCl3), B: [α]20D -34.6 (c 0.8,CHCl3).     

SYNTHESIS OF 1-O-ACYL-2,3,4-TRI-O-ACETYL-β-D-XYLO-AND ARABINOPYRANOSES BY PHASE TRANSFER CATALYSIS

The acetylated xylo-and arabinopyranosyl esters(1-8) were obtained in high yields with stereoselectivity by phase-transfer catalyzed (PTC) synthesis, and their structures were confirmed by elemental analysis and IR, ~1H-NMR spectral data.     

Syntheses of imidazolium-bridged cyclodextrin dimers and their catalytic properties in the hydrolytic cleavage of p-nitrophenyl alkanoates

Two imidazolium-bridged cyclodextrin dimers 3a and 3b were prepared by reacting 6-deoxy-6-N-imidazolyl-β-CD (2) with bis(bromomethyl)benzene. The catalytic properties of 2, 3a and 3b in the hydrolytic cleavage of p-nitrophenyl alkanoates, in the form of acetate (PNPA) , butanoate (PNPB) , hexanoate (PNPH) and octanoate (PNPO), were examined. CD dimeis showed middling rate enhancements around neutrality. Catalytic rate constants ( kc) in the presence of 3a or 3b did not vary much with chain length of esters. In contrast, dissociation constants ( Kd) and selectivity factors (kc/Kd) for "long-chain" esters were much smaller and significantly larger than those for short-chain ones respectively, indicating CD dimers 3a and 3b have good dimensional recognition ability and substrate selectivity in the hydrolytic cleavage of p-nitrophenyl alkanoates . Their kinetic consequences are briefly interpreted.     

Interaction of straight chain alcohol vapors with self-assembled MOF film by surface plasmon resonance sensing and imaging

Interaction of straight chain alcohol vapors with MOF-199-functionalized films was studied by SPR.The signals had linear relationships with the concentration of alcohols over a wide range from 0 to 70%(v/v) and were reversible in proportional to the chain length,with R~2 all above 0.99.     

Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide) synthesized by ATRP

Novel Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide),PEG-b-(PNIPAM)_2,were successfully synthesized through atom transfer radical polymerization(ATRP).A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly(ethylene glycol) monomethyl ether(PEG).The copolymers were obtained via the ATRP of N-isopropylacrylamide(NIPAM) at 30℃with CuCl/Me_6TREN as a catalyst system and DMF/H_2O(v/v = 3:1) mixture as solvent.The resulting copo...     

Two New Sesquiterpenes from Euonymus nanoides

Two new dihydroagarofuran sesquiterpenes with a novel substitution pattern:1α-(α-methyl)-butanoyl-2α,15-diacetoxy-4β-hydroxy-9β-(β-)furancarboxy-β-dihydroagarofuran (1) and 1α,2α-di-(α-methyl)-butanoyl-4β-hydroxy-9β-(β-)furancarboxy-15-acetoxy-β-dihydro-agaro-furan (2) were isolated from Euonymus nanoides. Their structures were elucidated by means of ^1H and ^13C NMR spectroscopic studies, including 2D NMR technique.     

Efficient CO2 capture on low-cost silica gel modified by polyethyleneimine

In this work,a series of polyethyleneimine(PEI) functionalized commercial silica gel were prepared by wet impregnation method and used as CO 2 sorbent.The as-prepared sorbents were characterized by N 2 adsorption,FT-IR and SEM techniques.CO 2 capture was tested in a fixed bed reactor using a simulated flue gas containing 15.1% CO 2 in a temperature range of 25-100 C.The effects of sorption temperature and amine content on CO 2 uptake of the adsorbents were investigated.The silica gel with a 30 wt% PEI loading manifested the largest CO 2 uptake of 93.4 mg CO 2 /g adsorbent(equal to 311.3 mg CO 2 /g PEI) among the tested sorbents under the conditions of 15.1%(v/v) CO 2 in N 2 at 75 C and atmospheric pressure.Moreover,it was rather low-cost.In addition,the PEI-impregnated silica gel exhibited stable adsorption-desorption behavior during 5 consecutive test cycles.These results suggest that the PEI-impregnated silica gel is a promising and cost-effective sorbent for CO 2 capture from flue gas and other stationary sources with low CO 2 concentration.     

Nematogenic and smectogenic liquid crystals from new heterocyclic isoflavone derivatives:Synthesis,characterization and X-ray diffraction studies

A new series of liquid crystals comprising eight heterocyclic isoflavone esters,7-alkanoyloxy-3-[4’-(3-methylbutyloxyphenyl)]- 4H-1-benzopyran-4-ones exhibiting enantiotropic nematic(N) and smectic C(SmC) phases were synthesized and investigated.The mesomorphic properties of all derivatives were investigated by means of differential calorimetry and polarized optical microscopy. Wide angle X-ray diffraction technique was employed to investigate the molecular packing associated with the intermolecular interaction as well as the correlation between the thermal behaviour of these compounds with their anisotropy properties within a mesophase.     

Asymmetric synthesis of syn-aryl-(2S,3R)-2-chloro-3-hydroxy esters via an engineered ketoreductase-catalyzed dynamic reductive kinetic resolution

We report here a generic, green synthesis of 17 valuable syn-aryl-(2S,3R)-2–chloro-3–hydroxy esters(syn-(2S,3R)-1) in 73%-99% isolated yields along with 6.1:1–83:1 dr and 31%～>99% ee, through dynamic reductive kinetic resolution of racemic aryl α–chloro β-keto esters(2) catalyzed by an engineered ketoreductase which was obtained via ep PCR-based directed evolution. The hectogram scale synthesis of syn-(2S,3R)-1b at a substrate concentration of 120 g/L showcased the application potential of th...     

RADICAL PHOTOPOLYMERIZATION USING ARYLIODONIUM SALT/TERTIARY AMINE COMPLEX SYSTEM AS THE PHOTOINITIATOR

The diphenyliodonium salt (DPIOC)/triethylamine (TEA) is used as photoinitiator for radical photopolymerization. It was found that a ground state CT complex formed between DPIOC as electron acceptor and TEA as electron donor, which results in extending the photosensitivity range of DPIOC/TEA system up to above 500nm compared with DPIOC alone. The kinetic studies on photopolymerization of methyl methacrylate (MMA) were carried out in CH_3CN: H_2O (14: 1, v/v) mixture solution at 30℃by dilatometer. The results obtained show that the polymerization rate (R_p) increases with increasing concentrations of DPIOC and TEA with exponent 0. 65 and 0. 62 respectively. The activation energy E_a and k_p/k_~(1/2) value were determined to be 4.1 Kcal mol~(-1) and 0.045 respectively. The other influence factors and reaction mechanism were also discussed.     

Baeyer-Villiger oxidation of ketones with hydrogen peroxide catalyzed by Sn-aniline complex

Sn-aniline complex was prepared by a simple procedure.Cyclic and acyclic ketones were oxidized into lactones or esters with very high selectivity and yield with 30% hydrogen peroxide in the presence of Sn-aniline complex.     

Chiral Borated Esters in Asymmetric Synthesis： 1. The First Asymmetric Reaction Catalyzed by Chiral Spiroborated Esters with an O3BN Framework

The first asymmetric reaction catalyzed by chiral spiroborated esters with an O3BN framework was reported. In the presence of 0.1 equivalent of (R,S)-1 or (S,S)-1, acetophenone was reduced by 0.6 equivalent of borane in THF at 0-5℃ for 2 h to give (R)-1-phenylethanol of up to 76% ee and 73% isolated yield. Influence of reaction conditions on the stereoselectivity of the reduction was investigated and a possible catalytic mechanism of the chiral spiroborated esters toward the reduction was also suggested.     

Enantioselective Addition of Allyltrichlorosilane to Bulky-substituted Aldehydes Catalyzed by Axial N,N'-Dioxide Pivalate

Allylation of bulky-substituted aromatic aldehydes with allyltrichlorosilanes were catalyzed by axial biscarboline N.N-dioxide esters with high enaiitioselectivities up to 92% e.e. for l-(4-chlorophenyl)-9-methyl-9Hpyrido[3,4-b]indole-3-carbaldehyde and 90% e.e.for 1-(3-methoxyphenyl)-9-methyl-9H-pyrido[3,4-b]indole-3-carbaldehyde, respectively.Total 22 aldehydes were tested with good yields and enantioselectivities.Catalyst 4f exhibited good catalytic enantioselectivity.     

Synthesis and Properties of u-Oxamido Heterobinuclear Cu(Ⅱ)-Co(Ⅱ) Complexes

Three heterobinuclear complexes were synthesized, namely [Cu (oxpn) Co (L)2] (ClO4)2·xH2O(L= 2,2'-bipyridyl(bpy), 1,10-phenanthroline(phen) , and 5-nitro-1, 10-phenanthroline (NO2-phen)), where oxpn represents N, N'-bis(3-aminopropyl) oxam-ido. Based on 1R, elemental analysis, conductivity measurement and electronic spectra, these complexes were characterized by an extended oxamido-bridged structure with Cu(Ⅱ) in a planar environment and Co(Ⅱ) in a octahedral environment. The symmetry of the cation is very close to C2v.The complexes were also characterized with variable temperature (4~300K) magnetic susceptibility, and the data were fit for the susceptibility equation derived from spin Hamilton, H= -2JS1.S2-DSx12 by least square strategy. The exchange integral, J, was found to be -22.36 cm-1 (for bpy);-15.45 cm-1 (for phen); -19. 10cm-1(for NO2-phen), indicating that there is a weak antiferromagnetic spin-exchange interaction between the metal ions.     

First total synthesis of ocimarin

<正>A facile approach for the first synthesis of ocimarin,naturally occurring coumarins,was developed by employing a cerium(Ⅲ) chloride heptahydrate-catalyzed Pechmann condensation of phenols andβ-keto esters in a solvent-free system as key step,by which ocimarin was achieved by three steps starting from acetylacetic ether and resorcinol with total yield 23.2%.All structures of new compounds were confirmed by IR,~1H NMR and MS.     

Synthesis and Antimicrobial Studies of Novel Billogical Heterocycles

The synthetic route of sildenafil promoted us to synthesize new object molecules. New analogues containing a 4-thiazolidinone ring bonded to the phenyl moiety at the 2-position, 7-(substituted anilino)-6-fluoro-2-(p-meth- oxy-m-{[2-(p-hydroxyphenyl)-4-oxo-1,3-thiazolidin-3-yl]aminocarbonyl}phenylsulfonamido)benzothiazoles (4a—4l) have been synthesized by cyclization with thioglycollic acid of Schiff bases 3a—3l from corresponding 7-(substituted anilino)-6-fluoro-2-(p-methoxy-m-hydrazinocarbonyl phenylsulfonamido)benzothiazoles (2a—2l). Compounds 2a—2l in turn were prepared by dehydroxyhalogenation followed by condensation with hydrazine hydrates of acids 1a—1l. Compounds 1a—1l in turn were prepared by chlorosulfonation of o-methoxy benzoic acid followed by condensation with 6-fluoro-7-(substituted anilino)-2-aminobenzothiazoles. Final compounds have been characterized by their elemental analysis, IR, NMR and mass spectra. All the synthesized compounds have been screened for their antimicrobial activities. Some of them showed good activities.     

Antiviral stereoisomers of 3,5-bis(2-hydroxybut-3-en-1-yl)-1,2, 4-thiadiazole from the roots of Isatis indigotica

Four stereoisomers of 3,5-bis(2-hydroxybut-3-en-1-yl)-1,2,4-thiadiazole, named insatindigothiadiazoles A–D(1a–1d), were isolated from the roots of Isatis indigotica. Their structures were determined by spectroscopic analysis; specifically, the absolute configurations were assigned by using the MPA determination rule based on Δδ~(RS)values of MPA esters, and supported by electronic CD(ECD)calculations. Proposed biosynthetic pathways and preliminary investigations of the biological activities of 1a–1d against influenza virus A(H3N2), Coxsackie virus B3, and/or HSV-1 are also discussed.     

Detailed investigation of optimized alkali catalyzed transesterification of Jatropha oil for biodiesel production

The non-edible oils are believed to be one of the major feedstock for the production of biodiesel in future.In the present study,we investigated the production of Jatropha oil methyl esters(JOMEs) via alkali-catalyzed transesterification route.The biophysical characteristics of Jatropha oil were found within the optimal range in accordance with ASTM standards as a substitute diesel fuel.The chemical composition and production yield of as-synthesized biodiesel were confirmed by various analytical techniques such as FT-IR,1H NMR,13 C NMR and gas chromatography coupled with mass spectrometry.A high percentage conversion,～96.09%,of fatty acids into esters was achieved under optimized transesterification conditions with 6 :1 oil to methanol ratio and 0.9 wt% Na OH for 50 min at ～60°C.Moreover,twelve fatty acids methyl esters(FAME) were quantified in the GC/MS analysis and it was interesting to note that the mass fragmentation pattern of saturated,monounsaturated and diunsaturated FAME was comparable with the literature reported values.