bluuebunny/crossref_metadata_2025 huggingface dataset:
Photophysics and Acid‐Base Chemistry of Re(CH3bpyCOOH)(CO)3X (X=Cl−, and Imidazole) Complexes
Authors: Lin Ren‐Jay , Chang I‐Jy
Published: May 2015

Rheniumtricarbonyl(4′‐methyl‐2,2′‐bipyridine‐4‐carboxylic acid)X (where X is Cl− and imidazole) complexes have been prepared. These two complexes exhibit similar spectroscopic properties. The metal‐ to‐ligand charge‐transfer (MLCT) absorption and the corresponding emission are observed. This charge transfer band is highly solvent dependent. Due to the stronger electron‐withdrawing ability of the ‐COOH (in comparison to the ‐COO− group), the MLCT band has red‐shifted during protonation. Emission quantum yields are dramatically reduced while life time remains similar upon protonation. These behaviors are typical in static quenching mechanism by protons. The ground state pKa of Re(CO)3 (CH3bpyCOOH)Cl obtained from the pH titration curve of the complex absorption at 409 nm was 2.5.
Kinetics of Acid‐Catalyzed Dissociation of Nickel (II) N‐Alkyl‐Substituted Diamino Diamide Complexes
Authors: Chao Min‐Shiun
Published: May 2015

The dissociation kinetics of the nickel (II) complexes of 4‐methyl‐4,7‐diazadecanediamide (4‐Me‐L‐2,2,2), 4,7‐dimethyl‐4,7‐diazadecanediamide (4,7‐N, N′‐Me2‐L‐2,2,2), 4‐ethyl‐4,7‐diazadecanediamide (4‐Et‐ L‐2,2,2), and 4‐methyl‐4,8‐diazaundecanediamide (4‐Me‐L‐2,3,2) have been studied at 25.0 °C and μ = 4.0 M (NaClO4 + HClO4) by the stopped‐flow method. These reactions are specific‐acid catalyzed; however, the rate constants of these reactions do not depend on the concentrations of acetic, chloro acetic, and dichloroacetic acids. At pH values be low 1.0, both the proton‐assisted and the direct protonation path ways make contributions to the rates. The ratios of the rate constant of dissociation by the direct protonation path way to the rate constant by the proton‐assisted path way for the complexes in aqueous solution were measured and discussed.
Formal Synthesis of (±)‐Isodihydronepetalactone
Authors: Chang Meng‐Yang , Chang Bo‐Rm , Chang Chung‐Ho , Chen Shui‐Tein , Chang Nein‐Chen
Published: May 2015

A formal synthesis of (±)‐isodihydronepetalactone (1) from cyclobutenone 5 was de scribed. Baeyer‐Villiger lactonization of cyclobutanone 8 followed by decholorination led to lactone 4, which under went a series of functional group trans formations, furnished cyclopentanone derivative 15. Shapiro reaction on hydrazone derivative in the presence of excess dry ice gave lactone 2. Lactone 2 had previously been converted to isodihydronepetalactone (1).
The Constituents and Synthesis of Cryptamygin‐A from the Stem Bark of Cryptocarya Amygadalina
Authors: Charf Yu‐Yi , Wu Chia‐Hung , Wu Shwu‐Jen , Wu Tian‐Shung
Published: May 2015

Three new benzenoid compounds, namely cryptamygin‐A, ‐B and ‐C together with eleven known compounds were isolated from the stem bark of Cryptocarya amygadalina. Their structures were elucidated by spectral analysis. The synthesis of cryptamygin‐A is also described.
Role of Nitrite on Nitration of 2′‐Deoxyguanosine by Nitryl Chloride
Authors: Chen Hauh‐Jyun Candy , Wang Tze‐Fan , Chen Yuan‐Mao
Published: May 2015

Nitryl chloride and peroxynitrite are reactive nitrogen species generated by activated phagocytes against invading pathogens during infections and inflammation. In our previous report, formation of 8‐nitroxanthine and 8‐nitroguanine was observed in reaction of 2′‐deoxyguanosine or calf thymus DNA with nitryl chloride generated by mixing hypochlorous acid (HOCl) with nitrite (NC2−). The present study investigates factors control ling the yields of 8‐nitroxanthine and 8‐nitroguanine formation in nitration of 2′‐deoxyguanosine by nitryl chloride. We found that the yields of 8‐nitroxanthine and 8‐nitroguanine in reaction of 2′‐deoxyguanosine with nitryl chloride were highly dependent on the ratio of NO2− versus HOCl concentration. The yields of 8‐nitroxanthine and 8‐nitroguanine reached a plateau when the ratio of NC2− versus HOCl concentration was higher than 2. A possible mechanism was postulated to explain this observation. While 8‐nitroguanine is not stable in the presence of peroxynitrite, 8‐nitroxanthine is sensitive to HOCl. The stability of these two nitrated ad ducts might be a factor on their final yields in this reaction. Since HOCl is produced by neutrophils at sites of inflammation where the level of NC2− is elevated, it is conceivable that nitryl chloride contributes to DNA base nitration in vivo, forming 8‐nitroxanthine and 8‐nitroguanine.
Raman Spectroscopy of Galactosemic Rat Lens Crystalline: Correlation of Microscopic Changes of Lens Proteins at Molecular Levels with Gross Cataractous Alteration
Authors: Ho Yuh , Huang Fu‐Yung
Published: May 2015

Near‐Infrared Fourier trans form (near‐IR FT) Raman spectros copy has been used to study the structural changes of lens proteins both in cortex and nucleus of galactosemic rat lenses. It was found that tyrosine doublet ratio of Raman bands, I832/I855, in creased more rapidly in the cortex than in the nucleus during a 5‐week period of galactose feeding, i.e., from 0.86 to 1.1 for the cortex and 0.88 to 0.92 for the nucleus. The ratio obtained for lens nucleus suggests that a lower ratio of less than 1 does not necessarily reflect the apparent transparent state of lens morphology. More over our results for the in crease of tyrosine doubletratio with the extent of cataract formation in galactosemic lens appear to indicate that there is more hydration in crystallins of the cortex than the nucleus since the in creased ratio of tyro sine doublet has been shown to be due to the hydrogen‐bond formation of hydroxyl groups in various tyrosines of proteins with water. The tryptophan band ratio at 880 cm−1 and 757 cm− (I880/I757) under went a precipitous de crease in the cortex and a rather gradual de crease in the nucleus, suggesting buried tryptophan residues become more exposed in the cortex than in the nucleus during galactose‐induced cataractogenesis. Based on the changes of the two ratios, I832/I855 and I880/I757, the change of lens protein environment induced by galactosemic feeding appeared to take place in the cortex first, which was consistent with the observation that the development of an opaque lens be gins in the cortex. While no sulfhydryl (‐SH) signal was detected, there was a slow in crease of disulfide (‐S‐S‐) signal in the cortex of galactose‐fed lenses as compared to control lenses with out galactose. This suggested that a loss of lens glutathione occurred early and oxidation of cysteines in crystallins started in the first week, i.e., be fore the onset of cortical cataract. In contrast, for nucleus of galactosemic lenses the signal of the‐SH group was detected and yet the ‐S‐S‐signal of crystallins could not be found. In this study, we have conclusively demonstrated using Raman vibrational band shift that galactosemic cataract be gins in the cortex, and that the lens cortex suffers more structural alteration in crystallins than the nucleus.
Syntheses of 5‐(3‐Arylsydnon‐4‐yl)Tetrazole Derivatives
Authors: Shih Mei‐Hsm , Lee Mei‐Jin , Yeh Mou‐Yung
Published: May 2015

3‐Arylsydnone‐4‐carbohydroximic acid chlorides (1) could react with sodium azide to produce the corresponding 3‐arylsydnone‐4‐carbazidoximes (2), but not 1‐hydroxytetrazoles 3. Treatment of 3‐arylsydnone‐4‐carbazidoximes (2) with acid chlorides such as acetyl chloride (4a), propionyl chloride (4b) and benzoyl chloride (4c) in the presence of excess triethylamine generated the derivatives of the azidoximes 5. To obtain the desired tetrazoles, the azidoximes 2 should first cyclize directly with acetyl chloride (4a) or propionyl chloride (4b) to afford the acetyl or propionyl derivatives 6. The cyclized tetrazole derivatives 6 underwent deacylation upon heating in ethanol to give 1‐hydroxy‐5‐(3‐arylsydnon‐4‐yl)tetrazoles (3).
Synthesis and Antibacterial Activities of 2‐(1‐Aryl‐5‐Methyl‐1,2,3‐triazol‐4‐yl)‐1,3,4‐Oxadiazole Derivatives
Authors: Zhang Yan , Qiao Ren‐Zhong , Xu Peng‐Fei , Zhang Zi‐Yi , Wang Qin , Mao Li‐Min , Yu Kai‐Bei
Published: May 2015

Eighteen novel 2‐(1‐aryl‐5‐methyl‐1,2,3‐triazol‐4‐yl)‐1,3,4‐oxadiazole derivatives and two acylhydrazone intermediate compounds were synthesized by various pathways starting from 1‐aryl‐5‐methyl‐1,2,3‐triazol‐4‐formhydrazide (1). All products were identified by spectroscopic analysis, and 2‐(1‐aryl‐5‐methyl‐1,2,3‐triazol‐4‐yl)‐5‐benzalthio‐1,3,4‐oxadiazole was further validated by X‐ray crystallography. Results from primary antibacterial activity tests indicated that most of the compounds were effective against E. coli, P. aeruginosa, B. subtilis and S. aureus.
A Synthesis of Thalidomide
Authors: Chang Meng‐Yang , Chang Chung‐Ho , Chen Shui‐Tein , Chang Nein‐Chen
Published: May 2015

A synthesis of racemic thalidomide (1) was described and the important formal [3+3] cycloaddition strategy was a keystep. The total yield of thalidomide (1) was 18% in five steps from known 3.
Gold(III)‐Induced Oxidation of Amino Acids and Malonic Acid: Reaction Pathways Studied by NMR Spectroscopy with Isotope Labelling
Authors: Zou Juan , Parkinson John A. , Sadler Peter J.
Published: May 2015

Reactions of Au(III) with biomolecules are of interest in relation to understanding the mechanism of action of therapeutic gold compounds. NMR investigations of 13C and 15N isotopically‐labelled glycine and alanine show that Au(III) induces deamination and subsequent decarboxylation of both amino acids with the same mechanism. For comparison, reactions of Au(III) with sarcosine and the dicarboxylic acid malonic acid were also investigated. The major intermediates and products have been identified.
Flotation Separation of Lead with Sodium Nitrate‐Potassium Iodide‐Cetyltrimethyl Ammonium Bromide System
Authors: Li Quanmin , Xing Yun , Shen Yiyang
Published: May 2015

The flotation separation behavior of lead with Sodium Nitrate‐Potassium Iodide‐Cetyltrimethyl Ammonium Bromide system and the conditions for the separation of lead with other metal ions are studied in this research. With 0.1 M potassium iodide, 1.0 × 10−2 M Cetyltrimethyl Ammonium Bromide and 1.0 g/10 mL of sodium nitrate, Pb(II) can form an ion‐association complex (PbI42−) (CTMAB+)2 and be separated completely from Zn(II), Fe(III), Co(II), Ni(II), Mn(II) and Al(III) by flotation at pH = 1.0–3.0.
Electroreduction of Polychlorobenzenes Using Either Lead or Copper Electrodes
Authors: Lin Shaw‐Tao , Chao Richard Yung‐Ho , Lin Sun‐Che , Lin Shu‐Fan
Published: May 2015

Polychlorobenzenes can be reduced electrolytically to dichlorobenzenes by using either lead or copper as the electrodes in a MeOH/THF solution. Among the resultants of dichlorobenzenes, 1,4‐dichlorobenzene is a major product that might be due to a low enthalpy of formation. A chlorine atom situated at the ortho position of another chlorine atom in the benzene ring is removed prior to others. However, the sequence of reactivities of the polychlorobenzenes for electroreducing by lead electrodes in this study is as follows: 1,2,3,4‐C6H2Cl4 > 1,3,5‐C6H3Cl3 > C6HCl5 ∼ 1,2,4,5‐C6H2Cl4 > 1,2,3,5‐C6H2Cl4 ∼ 1,2,3‐C6H3Cl3 > 1,2,4‐C6H3Cl3 >C6Cl6.
First Total Synthesis of (±)‐Celaphanol A
Authors: Bie Pingyan , Zhang Chenglu , Li Anpai , Peng Xuanjia , Wu Tongxing , Pan Xinfu
Published: May 2015

The first total synthesis of (±)‐Celaphanol A was accomplished starting from α‐cyclocitral and 3,4‐dimethoxy benzyl chloride in six steps. The intramolecular cyclization with BF3·Et2O and enolization in t‐BuOK/t‐BuOH were the key steps. The process of intramolecular cyclization afforded an all‐cis isomer intermediate for synthesis of aromatic tricyclic diterpenes.
Determination of Organochlorine Pesticides in Sediments from Authie Bay Using Microwave Assisted Solvent Extraction
Authors: Calvez Nicolas Le
Published: May 2015

The aim of this study was to develop an analytical method to determine the organochlorine concentrations in sediments. Combination of Microwave assisted Solvent Extraction (MASE) and capillary gas chromatography with specific detection (electron capture detector) was a viable approach for the determination of pesticides in solid matrixes. In this study, MASE development was focused on the selection of a suitable extraction solvent for all the target analytes. MASE procedure was validated by comparison with conventional methods such as Soxhlet and sonication extraction. The proposed method was then applied to determine the organochlorine insecticides concentrations in samples from Authie Bay (France). Environmental water samples were analysed and five target analytes were detected in concentrations from 0.03 to 0.56 ng/g of dry sediment. These investigations showed the accumulation and the persistency of these products in sediments in spite of the fact they were banned a few decades ago.
Micellar Formation Study of Crown Ether Surfactants
Authors: Chou Fang‐Fei , Shih Jeng‐Shong
Published: May 2015

Fluorescence probe and nuclear magnetic resonance (NMR) methods were employed to investigate the micellation of prepared crown ether surfactants, e.g. decyl 15‐crown‐5 and decyl 18‐crown‐6. Pyrene was employed as the fluorescence probe to evaluate the critical micellar concentration (CMC) of these surfactants in aqueous solutions while spin lattice relaxation times (T1) and chemical shifts of H‐1 NMR were applied in non‐aqueous solutions. Decyl 15‐crown‐5 with lower CMC forms micelles much easier than decyl 18‐crown‐6 with higher CMC in aqueous solutions, whereas decyl 18‐crown‐6 forms micelles easier than decyl 15‐crown‐5 in nonaqueous solutions. Comparison of the CMC of crown ether surfactants and other polyoxyethylene surfactants such as decylhexaethylene glycol was made. Effects of salts and solvents on the micellar formation were also investigated. In general, additions of both alkali metal salts and polar organic solvents into the aqueous surfactant solutions increased in the CMC of these surfactants. The formation of micelles in organic solvents such as methanol and acetonitrile was successfully observed by the NMR method while it was difficult to study these surfactants in organic solutions by the pyrene fluorescence probe method. The NMR study revealed that the formation of micelles resulted in the decrease in all H‐1 spin lattice relaxation times (T1) of hydrophobic groups, e.g. CH3 and CH2, and hydrophilic group OCH2 of these surfactants. However, upon the micellar formation, the H‐1 chemical shifts (δ) of these surfactant hydrophobic groups were found to shift to downfield (increased δ) while the chemical shift of the hydrophilic group OCH2 moved to up‐field. Comparison of the spin lattice relaxation time and H‐1 chemical shift methods was also made and discussed.
Tunneling Ionization Rates of Atoms and Molecules
Authors: Mishima K. , Hayashi M. , Yi J. , Lin S. H. , Selzle H. L. , Schlag E. W.
Published: May 2015

We present a review of our recent work on the improvements of the photoionization rate formulas of Keldysh theory (Zh. Eksp. Teor. Fiz. 47, 1945 (1964) [Sov. Phys. JETP 20, 1307 (1965)]. It is shown that a simple contour integration can be done for evaluating the transition amplitude, instead of the original saddle‐point method. The electron momentum dependence of the pre‐exponential factors is incorporated. Using the second order corrected Coulomb‐Volkov function for the continuous spectrum, more exact expressions are obtained. From our formulas, it is found that the first order Coulomb correction serves to lower the ionization potential and enhance the photoionization rates compared with that in the absence of the Coulomb correction. In addition, the second order correction modifies the Keldysh parameter, decreases the binding energy, and increases the photoionization rate relative to that of the first order Coulomb correction. The target systems in this work are one‐electron hydrogen‐like atoms and randomly oriented diatomic molecules.
Comparative Study between Carbonic and Sulfurous Acids for Dissociation Reaction
Authors: Lin Chiu‐Ling , Chu San‐Yan
Published: May 2015

The conversion between carbonic acid and carbon dioxide plus water is of special significance in many biological and geochemical systems. In this work, we give a theoretical comparison study between H2CO3 and H2SO3 for the dissociation reaction in the environment of microsolvation with the size of the water cluster up to three water molecules,

H2XO3 + (n‐1)H2O ⇌ XO2 +nH2O n = 1, 2, 3 X=C, S

From the calculation of B3LYP/6‐31+G, we conclude that H2SO3 is more unstable than H2CO3 kinetically due to a smaller bond angle change of ∠OXO. It is also more unstable thermodynamically due to better solvation for the product XO2.
Chalcogen‐Bridging Iron Carbonyl Complexes: Cluster Growth and Reactivity Comparison
Authors: Shieh Minghuey , Lai Yun‐Wen
Published: May 2015

Quite a number of chalcogen‐containing iron carbonyl clusters have been synthesized and structurally characterized, and the interesting structural transformations and reactivities of these clusters have been systematically investigated as well. In this short review, we would like to describe the recent developments on iron carbonyl incorporated chalcogen atom (E = Te, Se, S) clusters in our laboratory and will focus on the systematic synthesis, reactivity, and cluster growth in this exciting system.
The Electrochemical Properties of Water‐soluble Polyaniline‐V2O5 Nanocomposites
Authors: Wu Chun‐Guey , Hsu Shui‐Sheng , Hwang Jiunn‐Yih , Chung Ming‐Hau
Published: May 2015

Flexible, conducting water‐soluble polyaniline/V2O5 nanocomposites: (PAPSA)xV2O5, (PSA)xV2O5, and (PAPSAH)xV2O5 were prepared by simply mixing water soluble polyaniline, poly(aniline‐co‐N‐(4‐sulfophenyl)aniline) (PAPSA), poly(N‐(4‐sulfophenyl)aniline) (PSA), and poly(aniline‐co‐N‐propanesulfonic acid‐aniline) (PAPSAH) with V2O5 wet gel at room temperature. XRD data showed that the interlayer spacing of polyaniline/V2O5 nanocomposites is equal to 11∼13 Å which is slightly bigger than that of pristine V2O5 which has one mole of water molecules in its layer gallery. Depth profile SIMS and Auger analysis revealed that the mixing of water‐soluble polyaniline and V2O5 is very homogeneous although there was no direct evidence showing that alternative layer of water‐soluble polyaniline and V2O5 was formed. Cyclic voltammograms of the nanocomposite films showed two pairs of red‐ox peaks with good reversibility. The redox potentials of the nano composites are different from those of water‐soluble polyaniline or V2O5. The color of the films can be yellowish green, green, brown, orange or purple, depending on the applied potentials and stoichiometry of the composites. The optical density ratio (ΔOD) of the nano composite films (< 4500 Å) is better than that of polymer and V2O5, due to the synergic effect of two electrochromic materials. ΔOD increased as the film thickness increased, and it is greater than 0.3 when the thickness of the composite film is larger than 2000 Å, indicating the potential application in electrochromic devices.
Synthesis and Properties of Novel Fluorinated Polyamides Based on 2‐Trifluoromethyl‐4,4′‐Diaminodiphenylether
Authors: Yang Chin‐Ping , Chen Ruei‐Shin , Chen Kuei‐Hung , Chen Ya‐Ping
Published: May 2015

A series of soluble fluorinated polyamides (4a‐h) were synthesized from 2‐trifluoromethyl‐4,4′‐diaminodiphenylether (2) with various aromatic diacids (3a‐c) and imide‐containing diacids (3d‐h) via direct polycondensation with triphenyl phosphite and pyridine. Diamine 2 was prepared through nucleophilic substitution reaction of 2‐chloro‐5‐nitrobenzotrifluoride and 4‐nitrophenol in the presence of anhydrous K2CO3 to yield the dinitro compound, followed by catalytic reduction with hydrazine and Pd/C. These polymers had inherent viscosities ranging from 0.85 to 1.12 dL/g. All of the polyamides were soluble in aprotic polar solvents such as NMP, DMAc, DMF, and DMSO. Polymer films 4a‐h had tensile strengths of 77–95 MPa, elongations to break of 8–40%, and initial moduli of 1.6–2.2 GPa. The glass transition temperatures of these polymers were in the range of 235–268 °C, and the amount of carbonized residues of the polymers at 800 °C in nitrogen atmosphere were above 52%.
Rate Study of Haloadamantane Reduction by Samarium Diiodide
Authors: Lin Tzuen‐Yeuan , Fuh Ming‐Ren , Chen Yu‐Yu
Published: May 2015

Rate constants directly measured by GC/MS‐analyzed method for reduction of haloadamantanes by SmI2 in presence of HMPA and H2O were obtained. HMPA exhibits stronger catalytic effect than H2O does. The result of faster reaction rate of 1‐bromoadamantane than that of 2‐bromoadamantane can be used to confirm the formation of alkyl radical as the rate limiting step of this reduction.
Detailed Structural Characterizations of SBA‐15 and MCM‐41 Mesoporous Silicas on a High‐Resolution Transmission Electron Microscope
Authors: Lin Hong‐Ping , Tang Chih‐Yuan , Lin Ching‐Yen
Published: May 2015

Using high‐resolution transmission electronic micrograph (HR‐TEM) observation, one can clearly see the pore geometry of the MCM‐41 and SBA‐15 mesoporous silicas to determine that their pore shapes are hexagonal and round, respectively. With the perpendicular orientations of the nanochannels to the electron beam, parallel line images of the (100) and (110) repeating spacings were observed. In the SBA‐15 mesoporous silicas, there are byproducts of the granular silica and disordered mesostructures, attributed to the weak hydrogen interactions between Pluronic 123 blockcopolymer and the silica species. There are also many different and significant +π disclination defects in SBA‐15 and MCM‐41 surfactant‐silica composites. The SBA‐15 with a thicker silica wall is more stable under irradiation by high‐energy electron beams compared to MCM‐41, which has thinner wall thickness. Some carbon nanostructure impurities were found in some carbon films on the metal grids.
Preparation of the Solid Electrolytes Li4+xAlxSi1‐xO4‐yLi3PO4 and Their Ionic Conductivity
Authors: Chen Ru‐Fen , Song Xiu‐Qin , Liu Hua‐Ting
Published: May 2015

The ion conductors Li4+xAlxSi1‐xO4‐yLi3PO4 (x = 0 to 0.5, y = 0 to 0.6) were prepared by the Sol‐Gel method. The powder and sintered samples were characterized by DTA‐TG, XRD, SEM, and AC impedance techniques. The conductivity and sinterability increased when y increased from 0 to 0.4 in the Li4+xAlxSi1‐xO4‐yLi3PO4. The particle size of the powder samples is about 0.13 μm. The maximum conductivity at 20 °C is 3.128 × 10−5s cm−1 for Li4.4Al0.4Si0.6O4‐0.4 Li3PO4.
Spectrophotometric Determination of Selected Antibiotics Using Prussian Blue Reaction
Authors: Farhadi Khalil , Ghadamgahi Sedigheh , Maleki Ramin , Asgari Feridoun Salek
Published: May 2015

A simple, sensitive and accurate spectrophotometric method has been described for the determination of ampicillin(I), amoxicillin trihydrate(II) and cefazolin sodium(III). The procedure is based on the formation of Prussian Blue (PB) complex. The reaction between the acidic hydrolysis products of antibiotics (T = 60 °C) with mixture of Fe3+ and hexacyanoferrate(III) ions was evaluated for the spectrophotometric determination of the mentioned drugs. The maximum absorbance of the colored complex occurs at λ = 700 nm and the molar absorptivity is 3.0 × 104 1 mol−1cm−1. The effect of various parameters such as concentration of K3Fe(CN)6 and Fe3+, nature and amount of acids used, temperature and time of heating were investigated. Under optimum conditions the linear range of calibration graph was 2.0–12.0, 5.0–13.5 and 3.0–12.0 μg mL−1 for ampicillin, amoxicillin and cefazolin, respectively. The relative standard deviation for the determination of 10 μg mL−1 of antibiotics was about 0.5–1.5%. The proposed method was successfully applied to the determination of selected antibiotics from pharmaceutical preparations. The validity of the method was tested by the official methods and by the recovery studies of standard addition to pharmaceuticals.
1,8‐Diazabicyclo[5.4.0]undec‐7‐ene: A Remarkable Base in the Debromination of 4‐ or 5‐Substituted N‐Benzyl α‐Bromo‐α‐p‐Toluenesulfonylglutarimide
Authors: Chang Meng‐Yang , Lin John, Yi‐Chung , Chen Shui‐Tein , Chang Nein‐Chen
Published: May 2015

Debromination of N‐benzyl 4‐ or 5‐substituted α‐bromo‐α‐p‐toluenesulfonylglutarimides is achieved with 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) to give the N‐benzyl 4‐ or 5‐substituted α‐p‐toluenesulfonylglutarimides. The DBU/THF system is applied to a new methodology for the synthesis of bicyclic glutarimide skeleton in moderate yields.
Regioselectivity in Reactions of Bis‐Hydrazonoyl Halides with Some Bifunctional Heterocycles
Authors: Shawali Ahmad S. , Abdallah Magda A. , Zayed Mohie E. M.
Published: May 2015

Bis‐hydrazonoyl chloride 1 reacts regioselectively with 3‐mercapto‐1,2,4‐triazole 2a, 2,3‐dihydro‐3‐thioxo‐1,2,4‐triazin‐5(4H)‐one 2b and 2‐mercaptobenzimidazole 2c to give the hitherto unknown annelated 2,3‐bis‐(phenylhydrazono)thiazoles 6a‐c, respectively. Reactions of 1 with the methylthio derivatives of such heterocycles afforded the annelated 3,3′‐bis‐(1,2,4‐triazoles) 11a‐c, respectively. Similar reaction of 1 with 2‐phenylamino‐4(3H)‐pyrimidinones 4 gave 2,3‐bis(phenylhydrazono)imidazo[1,2‐a]pyrimidin‐5(1H)‐ones 16. Oxidation of 6c yielded the corresponding bis(phenylazo) derivative 15. The regiochemistry of the studied reactions is discussed.
Cyclization Reactions of 5‐Aminopyrazoles with β‐Ketoesters, Enamines and β‐Keto Anilides: New Synthetic Routes to Pyrazolo[1,5‐a]Pyrimidine Derivatives
Authors: El‐Taweel F. M. A. , Elmaati T. M. Abu
Published: May 2015

The pyrazolo[1,5‐a]pyrimidines 4, 10, 11 and 14 were synthesized from reaction of 4‐aryazo‐2,5‐diaminopyrazoles 1 with cyclic β‐ketoesters 2a,b or cyclic β‐ketoesters 7, 8 or acetoacetanilide 12, respectively. The reaction of 1 with the enamines 15, 16 and 17 yielded also the pyrazolo[1,5‐a]pyrimidines 18, 20 and 21, respectively.
Synthesis of Substituted Pyrazolo[3,4‐b]Pyridines
Authors: Khalil Mohamed A.
Published: May 2015

The synthesis of different substituted pyrazolo[3,4‐b]pyridines by the reaction of 3‐amino‐5‐chloro‐1‐phenylpyrazole‐4‐carboxaldehyde 1 as starting material with some active methylene reagents has been reported.
A Combined Effect of Thermal and Enzymatic Racemization for d‐Aspartic Acid to l‐Aspartic Acid by High‐Performance Liquid Chromatography Assay
Authors: Cheng Cheanyeh , Wu Shouh‐Chawn
Published: May 2015

The racemization of d‐aspartic acid to l‐aspartic acid has been successfully performed with a coupled enzyme system at 90 °C and a pH of about 4.0 by the assay of high‐performance liquid chromatography. This coupled enzymatic racemization is a successive two‐step reaction first induced by d‐amino acid oxidase and a subsequent coupled reaction by an aminotransferase clonezyme with the help of coenzyme pyridoxal 5′‐phosphate and cosubstrate l‐glutamate. Due to the very high temperature, part of the l‐aspartic acid is produced by the thermal effect. In fact the thermal racemization for aspartic acid can proceed from either d‐ or l‐aspartic acid via an intermediate fumaric acid and leads to the formation of d,l‐malic acid. The formation of α‐oxalacetic acid formed irreversibly from d‐aspartic acid with d‐amino acid oxidase can induce a side reaction to l‐alanine. The thermal effect may also be responsible for the production of d‐, and l‐alanine.
Halogenated Monoterpenes Having a Cyclohexadienone from the Red Alga Portieria Hornemanni
Authors: Kuniyoshi Masayuki , Oshiro Naomasa , Miono Takayuki , Higa Tatsuo
Published: May 2015

Five new ochtodane class monoterpenes have been isolated from two collections of the red alga Portieria hornemanni and their structures elucidated by spectroscopic analysis. These compounds contained 4,4‐dimethylcyclohexa‐2,5‐dienone in common and differed in the C2 side chain structure. Some of them showed mild cytotoxicity. Also discussed is the mechanism of the transformation of 2‐chloro‐1‐hydroxyochtoda‐3(8),5‐dien‐4‐one, a related labile compound reported previously, into 4,5‐dimethylbenzo[b]furan.
A Carbazole Derivative Synthesis for Stabilizing the Quadruplex Structure
Authors: Chang Cheng‐Chung , Wu Jin‐Yi , Chang Ta‐Chau
Published: May 2015

A new molecule of 3,6‐Bis(1‐methyl‐4‐vinylpyridium iodine)carbazole (BMVC) was synthesized for stabilizing the quadruplex structure of human telomeric sequence of d(T2AG3)4 in vitro. Mixing BMVC with the DNA can raise the melting temperature of the d(T2AG3)4 by ∼ 13 °C, implying that BMVC could be a useful telomerase inhibitor. In addition, the fluorescence of the BMVC increased significantly upon interacting with the d(T2AG3)4 which may be useful as a G‐quadruplex specific marker.
Synthesis of α,β‐Unsaturated Ketones and Esters Using Polymer‐supported Selenium Bromide
Authors: Sheng Shou‐Ri , Liu Xiao‐Ling , Wang Xing‐Cong
Published: May 2015

Treatment of the polymer‐supported α‐phenylseleno ketones and esters prepared from polymer‐supported selenium bromide with ketone and ester enolates with hydrogen peroxide afford α,β‐unsaturated ketones and esters in good yields and high purities.
New Triterpenoid Fatty Acid Esters from the Small Twigs of Viburnum Odoratissimum
Authors: Shen Ya‐Ching , Prakash Chaturvedula Venkata Sai , Wang Li‐Tang , Chien Ching‐Te , Hung Meng‐Chieh
Published: May 2015

α‐Amyrin margarate (1), moretenyl margarate (2) and moretenyl palmitate (3), three triterpenoid fatty acid esters, have been isolated from the acetone extract of the small twigs of Viburnum odoratissimum in addition to the three known compounds, α‐amyrin palmitate (4), ursolic acid (7) and vibsanin‐K (8). The structures of compounds 1–3 were elucidated based on extensive spectroscopic analysis and alkaline hydrolysis. Preliminary pharmacological studies revealed that vibsanin‐K and ursolic acid exhibited significant cytotoxicity against human gastric (NUGC) and oral epidermoid (HONE‐1) tumor cells at a concentration of 50 μg/mL while compounds 1–3 were inactive.
An Ethylenedioxy Flavonoid Carboxylic Acid from Limnophila Indica
Authors: Brahmachari G. , Sohel S. M. A. , Mondal D. Gorai S. , Misrti B.
Published: May 2015

The hexane extract of the aerial parts and roots of Limnophila indica yielded a new flavone, 3′,4′‐ethylenedioxy‐5‐hydroxy‐3‐(1‐hydroxy‐1‐methylethyl)‐6,7‐dimethyl‐5′‐methoxyflavone‐8‐carboxylic acid (1), characterized by spectral studies.
Formal Total Synthesis of (±)‐Dimethyl Secologanoside
Authors: Tai Huo‐Mu , Huang Ming‐Hsing , Yang Chau‐Chen
Published: May 2015

A formal total synthesis of the iridoid monoterpene (±)‐dimethyl secologanoside (6) is described. The Norrish I type fragmentation of bicyclo[2.2.1]heptannone 9 is the key step.
New Dolabellanes from the Taiwanese Soft Coral Clavularia Inflata
Authors: Shen Ya‐Ching , Pan Yu‐Ling , Ko Chin‐Lien , Kuo Yao‐Haur , Chen Ching‐Yeu
Published: May 2015

Bioassay‐directed fractionation of the acetone extract of Clavularia inflata collected in Green Island has afforded two new dolabellane diterpenoids, designated as clavinflols A (4) and B (5) in addition to the reported (1R*,12R*)‐dolabella‐4(16),7,10‐triene‐3,13‐dione (1), stolonidiol (2) and stolonidiol monoacetate (3). The structures of compounds 4 and 5 were determined on the basis of 1D and 2D‐NMR techniques including COSY, HSQC, HMBC and NOESY experiments, and acetylation which yielded derivatives 6 and 7, respectively. Pharmacological study revealed that compounds 1–3 and 5 exhibited cytotoxicity against human oral epidermoid carcinoma (KB) cells while compound 4 showed selective activity toward human Hepa cells.
Computational Studies of the Growth Mechanism of Small Fullerenes: A Ring‐Stacking Model
Authors: Lin Wen‐Hsin , Mishra Rama K. , Lin Ying‐Ting , Lee Shyi‐Long
Published: May 2015

A ring‐stacking model for the fullerene growth mechanism has been analyzed using the semiempirical AM1 scheme. Following different routes, small fullerenes C28 (Td and D2), C26 (D3h) and C24 (D6d) have been constructed from monocyclic/polycyclic precursors and circumscribing them with appropriate carbon belts. The deformation energies (DE) and the average bond lengths  of the precursors have been computed. The DE values suggest that there is a chance of bond cleavage of the polycyclic precursors as the growth process proceeds towards the cage formation. On the other hand, the monocyclic precursors are found to have significantly lower deformation energies than the polycyclic precursors. Further analyzing  values of the polycyclic and monocyclic cases at different stages, it is observed that the  values of the polycyclic cases decrease gradually, depicting a shrink in the precursors which may be detrimental to the growth process, whereas monocyclic precursors tend to swell, corroborating the tendency of the system to grow, which may be conducive for the growth process.
Calibration of Relativistic Energy‐Consistent Small‐Core Pseudopotentials for 3d‐Transition Metals
Authors: Sheu Jeng‐Horng , Lee Shyi‐Long , Dolg Michael
Published: May 2015

The generation of two‐component relativistic energy‐consistent small‐core ab initio pseudopotentials based on multi‐configuration all‐electron Dirac‐Hartree‐Fock reference data is briefly described for the 3d‐transition metals Sc to Ni. The one‐component scalar‐relativistic pseudopotentials generated by averaging over spin are tested in large‐scale correlated calculations for atomic excitation and ionization energies using even‐tempered uncontracted 25s20p15d10f8g6h valence basis sets. Comparision to experimental data demonstrates the accuracy of the pseudopotentials. In addition, preliminary results of a molecular calibration study for the spectroscopic constants of ScO in its 2Σ+ ground state are presented (Re = 1.666 Å, De ≈ 6.94 — 7.02 eV, ωe = 984 cm−1) and confirm the good transferability of the atom‐adjusted pseudopotentials to a molecular environment.
Integral Representation of Heisenberg Operators and the Semiclassical Approximation
Authors: Shao Jiushu
Published: May 2015

A simplified formulation of the semiclassical Heisenberg operator based on the forward‐backward evolution methodology is worked out. A new representation related to the Husimi form is suggested to remove its problem, which may also offer a new way to improve the Herman‐Kluk semiclassical propagator.
Magnetic Exchange Interaction in [BNITPhOPr] and [Cu(Cl2CHCO2)2(NITpPy)2(H2O)]: A Density Functional Theory Study
Authors: Ren Jie , Wei Hai‐Yan , Wang Fan , Chen Zhi‐Da , Zhao Qi‐Hua
Published: May 2015

The magnetic exchange interaction and electronic structures for the nitronyl nitroxide free radical (1), (4,4,5,5‐tetramethyl‐4,5‐dihydro‐1H‐imidazolyl‐1‐oxyl 3‐oxide), nitronyl nitroxide biradical, [BNITPhOPr] (2), (1,3‐[di‐2‐(4,4,5,5‐tetramethyl‐4,5‐dihydro‐1H‐imidazolyl‐1‐oxyl 3‐oxide)phenoxy]propane) and CuII‐nitronyl nitroxide radical complex, [Cu(Cl2CHCO2)2(NITpPy)2(H2O)] (3), (NITpPy=2‐(4‐pyridyl)‐4,4,5,5‐tetramethyl‐2‐imidazoline‐1‐oxy 3‐oxide) were studied by the broken symmetry (BS) approach within the density functional theory (DFT), combined with the spin‐Hamiltonian full‐matrix diagonalization method. The theoretically calculated magnetic coupling constant J values (‐0.10 (2), −12.9 (3)) are approximately consistent with experimental results (‐0.24 (2) and‐11.5 (3)). For the complex 3, the magnetic coupling constant j (‐0.85) between two terminal radical ligands is also obtained, which has not been characterized experimentally. In contrast to radical 1, the nitronyl nitroxide radicals in the biradical 2 and complex 3 behave as a more localized spin‐center. However, CuII ion of the complex 3 exhibits a local‐spin delocalization to the surrounding atoms. Spin population analyses suggest that the intramolecular antiferromagnetic coupling for the biradical 2 is governed by the weak spin polarization through the bridging ligand and that the antiferromagnetic coupling interaction between the CuII ion and nitronyl nitroxide radicals in the complex 3 is dominated by both the local‐spin delocalization on the CuII ion and the global spin polarization mechanism.
Trapping of Tricarbonyl(η1,η2‐homoallyl)iron and Tricarbonyl(η3‐allyl)iron Anion Intermediates with 2‐(Phenylsulfonyl)‐3‐phenyloxaziridine
Authors: Yeh Ming‐Chang P. , Ho Jin‐Xuan , Hsueh Peng‐Yu
Published: May 2015

The addition of reactive carbanions to (η4‐1,3‐diene)Fe(CO)3 complexes at −78 °C and 25 °C produced putative homoallyl and allyl anion complexes, respectively. Reaction of the reactive intermediates with 2‐(phenylsulfonyl)‐3‐phenyloxaziridine afforded nucleophilic substituted (η4‐1,3‐diene)Fe(CO)3 complexes.
Studies with Heterocyclic β‐Enaminoniriles: A Simple Route for the Synthesis of Polyfunctionally Substituted Thiophene, Imidazo[1,2:1′,6′]pyrimido[5,4‐b]thiophene and Thieno[3,2‐d]pyrimidine Derivatives
Authors: Raslan M. A. , Sayed S. M.
Published: May 2015

Reaction of 3,5‐diaminothiophene‐2‐carbonitrile derivatives 3a‐c with ethoxycarbonylmethyl isothiocyanate and/or N‐[bis(methylthio)methylene]glycine ethyl ester led to formation of 7‐substituted‐8‐amino‐5‐thioxo‐6H‐imidazo[1,2:1′,6′]pyrimido[5,4‐b]thiophene‐2(3H)‐one derivatives 6a‐c and 7‐substituted‐8‐amino‐5‐(methylthio)imidazo[1,2:1′,6′]pyrimido[5,4‐b]thiophene‐2(3H)‐one 7a‐c, respectively. Also, the synthetic potential of the β‐enaminonitrile moiety in 3a‐c has been explored; it proved to be a promising candiate for the synthesis of 1,6‐disubstituted‐2,4‐diamino‐7,8‐dihydro‐8‐oxopyrrolo[1,2‐a]thieno[2,3‐e]pyrimidine derivatives 10a‐f and pyrido[2′,3′:6,5]pyrimido[3,4‐a]benzimidazole derivatives 12a,b.
Ene Reaction of Pummerer‐type Reaction Intermediate of (Methylthio)Acetonitrile: Synthesis of Dienenitriles
Authors: Huang Hsin‐Yu , Wang Huey‐Min , Kang Iou‐Jiun , Chen Ling‐Ching
Published: May 2015

Pummerer‐type reaction intermediate 2 of (methylthio)acetonitrile (1) has been found to react with 1‐alkenes to afford ene adducts 3. Dienenitriles (4) were synthesized from adducts 3.
Intramolecular Sulfenylation Using Sulfides Synthesis of 5H‐Pyrrolo[1,2‐a][3,1]benzothiazines
Authors: Huang Hsin‐Yu , Wang Huey‐Min , Kang Iou‐Jiun , Chen Ling‐Ching
Published: May 2015

Treatment of N‐[2‐(methylsulfanylmethyl)aryl]pyrroles (4) with phenyliodine(III) bis(trifluoroacetate) containing trifluoroacetic acid resulted in an interrupted Pummerer‐type reaction to give 5H‐pyrrolo[1,2‐a][3,1]benzothiazines (5) rather than the normal Pummerer‐type products.
Heterocycles Derived from 5‐(2‐Aminothiazol‐4‐yl)‐8‐hydroxyquinoline: Synthesis and Antimicrobial Activity
Authors: Abdel‐Mohsen Shawkat A.
Published: May 2015

5‐(2‐Aminothiazol‐4‐yl)‐8‐hydroxyquinoline 2 has been synthesized by treating thiourea with 5‐chloroacetyl‐8‐hydroxyquinoline 1. The amine 2 was treated with aromatic aldehydes to furnish schiff bases 6a‐c which on treatment with phenyl isothiocyanate gave the corresponding thiazolo‐s‐triazines 7a‐c. Reaction of 2 with phenyl isothiocyanate gave the corresponding aminocarbothiamide derivative 8 which on reaction with malonic acid in acetyl chloride afforded thiobarbituric acid derivative 9. Coupling of 9 with diazonium salt gave the phenyl hydrazono derivative 10. However, reaction of 2 with carbon disulphide and methyl iodide afforded dithiocarbamidate 12 which on treatment with ethylenediamine, o‐aminophenol and/or phenylenediamine gave the aminoazolo derivatives 13–15, respectively. Other substituted fused thiazolopyrimidines 16–20 have been also prepared by the reaction of 2 with some selected dicarbonyl reagents. The characterisation of synthesized compounds has been done on the basis of elemental analysis, IR, 1H‐NMR and mass spectral data. All the newly synthesized compounds have been screened for their antimicrobial activities.
Studies on Liquid/liquid Extraction of Copper Ion with Room Temperature Ionic Liquid
Authors: Wei Guor‐Tzo , Chen Jin‐Chu , Yang Zusing
Published: May 2015

Room temperature ionic liquids are regarded as “Green solvents” for their nonvolatile and thermally stable properties. They are employed to replace traditional volatile organic solvents in organic synthesis, solvent extraction, and electrochemistry. In this work, a water immiscible room temperature ionic liquid, 1‐butyl‐3‐methylimidazolium hexafluorophosphate [C4mim][PF6], was used as an alternative solvent for liquid/liquid extraction of copper ions. Metal chelators, including dithizone, 8‐hydroxyquinoline, and 1‐(2‐pyridylazo)‐2‐naphthol, were employed to form neutral metal‐chelate complexes with copper ions so that copper ions were extracted from aqueous solution into [C4mim][PF6]. The parameters that affect the extraction of copper ions with this biphasic system were investigated. The extraction behavior in this novel biphasic system is shown to be consistent with that of traditional solvents. For example, the extraction with this biphasic system is strongly pH dependent. So, the extraction efficiency of coppers ion from an aqueous phase can be manipulated by tailoring the pH value of the extraction system. Hence, the extraction, separation and preconcentraction of copper ions can be accomplished by controlling the pH value of the extraction system. It appears that the use of ionic liquid as an alternate solvent system in liquid/liquid extraction of copper ions is very promising.
Study on the Gas Permeability of Nickel(II) Polyurethane Complexes
Authors: Chao Min‐Shiun
Published: May 2015

Ionic polyurethanes (PUs) were prepared from hydroxyl‐terminated polybutadiene (HTPB) and 4,4′‐dicyclohexylmethane diisocyanate (H12MDI) by a two‐stage method. The ionic group was introduced by adding 4,8‐diazaundecanediamide (L‐2,3,2) as the chain extender of which the tertiary amines and carbonyl groups were complexed with nickel ions. It was found that the binding of hard segments and the flexibility of soft segments had subtle effects on the gas permeability. The effects of hard segment content and the amount of nickel ion on the gas permeability and morphological properties were investigated. Fourier transform infrared (FTIR) spectroscopy was utilized to identify the segregation between hard and soft segments and structure change, which affect the transport properties. The hydrogen bonding index (HBI), frequency difference, and shift as a measure of the phase segregation and the average strength of the interpolymer hydrogen bonds were utilized to study the intermolecular interaction and transport property of the prepared PUs. The oxygen and nitrogen permeabilities of membranes were determined by using gas permeability analyzer. The results of FTIR, differential scanning calorimetry and thermogravimetric analysis measurements explain the complexation and, hence, the gas permeability.
Fused Triazines Via a Tandem Wittig/Ring Closure Strategy: Synthesis of Pyrazolo[5,1‐c]‐1,2,4‐Triazines and 1,2,4‐Triazolo[5,1‐c]‐1,2,4‐Triazines
Authors: Barsy Magda A.
Published: May 2015

A new method for the synthesis of azolo[5,1‐c]‐1,2,4‐triazine ring systems is reported by the sequential formation of triazine ring based on the regioselective formation of the azophosphoranes from hydrazonyl chlorides, followed by the intermolecular Wittig reaction with carboxylic acid chlorides, phenylisocyanate, and carbon disulfide.
The Synthesis of Some New N‐[1‐(2,5‐Dichlorophenyl)‐5‐Methyl‐1,2,3‐Triazol‐4‐yl]‐Carbamic Acid Ester Derivatives
Authors: Dong Heng‐Shan , Jia Wei , Cui Ji‐Dong , Wang Qing‐Lian
Published: May 2015

The synthesis of some new N‐[1‐(2,5‐dichlorophenyl)‐5‐methyl‐1,2,3‐triazol‐4‐yl]‐carbamic acid ester derivatives are reported in this paper. The yielded products 6a‐l were confirmed by Elemental analyses, NMR, MS, and IR spectra.
Liquid Phase Friedel‐Crafts Alkylation over Mixed Metal Oxide Catalyst
Authors: Shinde Manish M. , Sawant Manohar R.
Published: May 2015

Liquid phase Friedel‐Crafts alkylation of benzene with benzyl chloride was carried out over various ferrites viz. CuFe2O4, NiFe2O4, CoFe2O4, ZnFe2O4, and MgFe2O4. Among the various ferrites ZnFe2O4 showed the highest activity. These ferrites were prepared by co‐precipitation technique. The effect of variation of catalyst, speed of agitation and reaction temperature has been studied. Benzylation of other substrates such as toluene, anisole and chlorobenzene was also studied. The catalyst ZnFe2O4 was found to be reusable. The acid base properties of the catalyst were studied by cyclohexanol dehydration reaction and the data was correlated with activity.
Cetyltrimethylammonium Bromide as a Regulator in Paper Separation of Pentachlorophenol Herbicide and Methyl Orange Dye
Authors: Wang Wan‐Kung , Liu Chih‐Hsien
Published: May 2015

An experimental investigation is presented for separation of pentachlorophenol (PCP) and methyl orange (MO) from an aqueous solution by use of cetyltrimethylammonium bromide (CTAB) as a regulator in the paper capillary permeation adsorption process (PCPA). The effects of pH, concentration of CTAB, and ionic strength on the separatability of the molecules were studied. The maximum separatability of nearly 100% PCP and MO was obtained in the optimum pH range 5–11 and 7–11, respectively. The ionic strength has an appreciable effect on separatability. The recovery of PCP and MO from paper by elution with acetone: isooctane solvent gradients was also studied. The selective separation of PCP and MO admixed in aqueous solution by a developed solvent elution technique was also reported. It was believed that PCP and MO were separated as their ion pairs with CTA cations by adsorption on the fiber surface.
Structure‐Reactivity Relationships as Probes to Acetylcholinesterase Inhibition Mechanisms by Aryl Carbamates. I. Steady‐State Kinetics
Authors: Lin Gialih , Lai Cheng‐Yue , Liao Wei‐Chung , Liao Pei‐Shin , Chan Chung‐Hwey
Published: May 2015

From enzyme kinetics, 4‐nitrophenyl‐N‐substituted carbamates 1 are characterized as pseudo‐substrate inhibitors of acetylcholinesterase. However, the activity of the carbamyl enzyme does not recover in the presence of a competitive inhibitor, edrophonium. Therefore, carbamates 1 should be called as the “pseudo‐pseudo‐substrate” inhibitors of the enzyme. Moreover, the ‐logKi, logkc, and logki values are linearly correlated with Taft‐Ingold equation, log (k/ko) = ρ*σ* + δ Es. A three‐step AChE inhibition mechanism by carbamates 1 is proposed. The first step is the pre‐equilibrium protonations of carbamates 1 with ρ* value of −1.4 from pKa‐σ*‐correlation. The second step is the enzyme‐carbamates 1 tetrahedral intermediate formation from nucleophilic attack of the active site Ser200 on the protonated carbamates 1. The ρ* value for the ‐logKi‐σ*‐Es‐correlation indicates that the true ρ* value for the second step is 0.5 [= −0.9 ‐ (‐1.4)]. The δ value of 0.56 for the ‐logKi‐σ*‐Es‐correlation indicates that carbamates 1 with bulky substituents retarded the formation of enzyme‐inhibitor tetrahedral intermediates. The third step (kc step) is the carbamylation step and is the carbamyl enzyme conjugate formation from the enzyme‐carbamates 1 tetrahedral intermediate. The ρ* value of 0.21 for the logkc‐correlation indicates that the transition state for the carbamylation step is more negative charge than the enzyme‐carbamates 1 tetrahedral intermediate. Moreover, the kc step is insensitive to substituent effects since there is a cancellation of electronic demands for bond‐making and bond‐breaking components, like SN2 reactions. The δ value of 0.00 for the logkc‐correlation indicates that the kc step is independent of substituent steric effect. Therefore, the product of this step carbamyl enzyme conjugate is as crowded as the enzyme‐carbamates 1 tetrahedral intermediate and is likely bound to the leaving group, p‐nitrophenol.
Neolignans from the Parasitic Plants. Part 1. Aeginetia Indica
Authors: Ho Jiau‐Ching , Chen Chiu‐Ming , Row Lie‐Ching
Published: May 2015

Two new neolignans, namely balanophonin 4‐O‐β‐d‐glucopyranoside and aegineoside together with four known neolignans have been isolated from the whole plant of Aeginetia indica Linn. (Orobanchaceae). Their structures were established by spectroscopic and chemical methods.