bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of the Reductions of (Ethylenediaminetetraacetato)cobaltate(III) by 4,4‐Dipyridylamine Complexes of Pentacyanoferrate(II) and Pentaammineruthenium(II)
Authors: Chien Chiu‐Feng , Yeh Andrew 
Published: May 2015

AbstractThe reactions of Fe(CN)5dpa3− and Ru(NH3)5dpa2+ (dpa = 4,4′‐dipyridylamine) with Co(edta)− have been investigated kinetically. For Fe(CN)5dpa3− complex, a linear relationship was observed between the pseudo‐First‐order rate constants and the concentrations of Co(edta) which leads to a specific rate 0.876 ± 0.006 M−1S−1 at T = 25°C., μ = 0.10 M and pH = 8.0. For the Ru(NH3)5dpa2+ system, the plots kobs vs [Co(edta)−] become nonlinear at concentrations of Co(edta) greater than 0.01 M and the reaction is interpreted on the basis of a mechanism involving the formation of an ion pair between Ru(NH3)5dpa2+ and Co(edta)− followed by electron transfer from Ru(II) to Co(III). The nonlinear least squares fit of the kinetic results shows that Qip = 10.6 ± 0.7 M−1 and ket = 93.9 ± 0.7 s−1 at pH = 8.0,μ = 0.10 M and T = 25°C.
Synthesis of Tetracyclo[6.2.2.23,6.02,7]tetradeca‐4,9,11,13‐Tetraene
Authors: Lin Cheng‐Tung , Hwang Bai‐Ping , Chou Teh‐Chang 
Published: May 2015

AbstractThe title hydrocarbon 3, a C14H14 tetracyclic tetraene of C2v‐symmetry, was synthesized by new routes starting from 1,8,9,10‐tetrachloro‐11,11‐dimethoxytricyclo[6.2.1.02,7]undeca‐3,5,9‐triene (1). The Diels‐Alder cycloaddition of 1 with 2‐chloroacrylyl chloride, a ketene equivalent, followed by subsequent reduction, dechlorination and deacctalization afforded the ketol 12 as a key intermediate. Elaboration of target compound 3 was carried out by either the method of ring enlargement of 12 or (better) the route of Diels‐Alder reaction of decarbonylated 12 with trans‐1,2‐bis(phenylsulfonyl)ethcnc, an acetylene equivalent, to give trienol 17, followed by dehydration. Upon irradiation, 3 underwent intercyclic [2 + 2]‐addition to caged hexacyclic diene 4. At 120°C, 3 decomposed into barrelene and benzene quantitatively.
Dibenzo[b,e][1,4]diazepin‐1‐Ones, Synthesis and Derivatization
Authors: Rashed N. , Sayed M. , El Ashry E. S. H. 
Published: May 2015

AbstractSeveral linearly fused tricyclic 6,7,6‐systems were prepared. Reaction of 1,2‐diamino‐4‐nitrobenzene with 5,5‐dimethylcyclohexan‐1,3‐dione gave 3‐(2‐amino‐5‐nitroaniIino)‐5,5‐dimethylcyclohex‐2‐en‐1‐one (8). Reaction of 8 and its analogue 6 with various aldehydes gave 2,3,4)5,10,11‐hexahydro‐3,3‐dimethyl‐11‐substituted‐1H‐dibenzo[b,e][1,4]diazepin‐1‐ones 9 and 10. Acetylation of 9 and 10 gave the corresponding N‐acetyl derivatives. Spectral data of the products are discussed.
Microbial Transformation of Ceanothic Acid and Derivatives by Mycobacterium sp. (NRRL B‐3805)
Authors: Lee Shoei‐Sheng , You Bih‐Jing , Wang Kuang‐Chao 
Published: May 2015

AbstractCeanothic acid (1) is the major triterpene isolated from Parliurus ramosissitnus (Rhamnaceae) which possesses three methyl groups corresponding to the 4,4,14α‐trimethyl groups in lanosterol (5). Microbial transformation of 1 and its 3‐dehydro‐2,28‐dimethyl ester derivative (3) with Mycobacterium sp. (NRRL B‐3805) resulted in the methylation of the carboxylic functions and C‐1 epimerization, respectively. Although this work indicates that 1 is not a suitable substrate for 4,4,14α‐tridemethylation, esterification of the carboxylic function and the C‐1 epimerization reaction in ceanothic acid and its derivative is the first observation with this microorganism.
Surface Study of Polymers by Static Secondary Ion Mass Spectrometry Using a Magnetic‐Sector Mass Spectrometer
Authors: Lin Y. P. , Ling Y. C. 
Published: May 2015

AbstractResults from static SIMS analysis of six thermoplastic polymers — polytetrafluoroethylene (PTFE), polyethylene (PE), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polystyrene (PS) and polycarbonate (PC) — using a magnetic‐sector SIMS instrument and O2+ primary beam are presented. For PTFE as a representative sample, the charging effect is reduced only with a metal grid when analyzing positive secondary ions. When negative secondary ions are analyzed, excessive charges are self‐compensated with a normal‐incidence electron gun. Positive‐ion spectra collected agree with spectra obtained using either a quadrupole or time‐of‐flight SIMS instrument and noble‐gas ion beams. The agreement is objectively demonstrated by means of the capability to compare spectra in the NIST/EPA/MSDC mass spectral database. The merits of the use of high‐mass resolution, of which magnetic‐sector SIMS is inherently capable, to provide analytical information about the molecular species native to the sample are demonstrated in distinguishing three ambiguous peaks with nominal mass ratios m/z = 27, 39 and 59 from PMMA.
Extraction by Mixed Solvent and Spectrophotometric Determination of Sodium Dodecyl Sulfate in Sea Water
Authors: Ho Wu‐Hsiung , Hsiao Suh‐Mei , Chen Jin‐Han 
Published: May 2015

AbstractMixed solvent was used to extract ion pairs formed from suitable cationic dye and sodium dodecyl sulfate in sea water. The extracts were used for spectrophotometric determinations. The extraction of ion pairs of various combinations is discussed. Ethyl violet and a mixture (1:1) of p‐xylene and toluene are the most useful combination as the cationic dye and the extraction solvent. The extracts were determined spectrophotometrically at 611.2 nm; the molar absorptivity is 1.27 × 105 M−1 cm−1. The detection limit is 2.0 ppb in water based on three times the standard deviation of the blank. Extraction with this mixed solvent is as rapid and sensitive as with the best single solvent.
Electrooxdation of Tricarbonyl(N,N‐Diphenylcyclohexadienecarboxamide)Iron Complexes. Reversibility of Electron Transfer and Free Energy Change
Authors: Hwang Wen‐Shu , Lee Liangshiu , Yu Wei‐Ren 
Published: May 2015

AbstractQualitative and quantitative criteria of irreversibility of electron transfer in cyclic voltammetry (CV) of tricarbonyl(N,N‐diphenylcyclohexadienecarboxamide)iron complexes were investigated. The measurement of the heterogeneous rate constants for electron transfer according to CV data over an extended range of free energy change ( ΔG) for these complexes are described. Kinetic analyses of the electrochemical technique demonstrates that when the applied potential exceeds the standard potential E°, the experimental rate constant ke represents an accurate measurement of the intrinsic rate constant k1 for electron transfer. However, as the applied potential is less than E°, the reversibility of the electron‐transfer process becomes increasingly more important, and the rate constants for reverse electron transfer k‐t and decomposition k2 of the electrogenerated intermediate have to be taken into account.
Synthesis of Azo‐Sulfa Drugs Based on 2‐Pyridinone and 2‐Pyridinethione
Authors: Abdel Hafez Ali A. , Awad Ibrahim M. A. , Ahmed Ragaa A. 
Published: May 2015

AbstractSome new azo sulfa drugs 3‐cyano‐4,6‐diphenyl‐1‐[4‐(N‐substituted)sulfamyl]phenylazo‐2‐pyridinone dyes (1‐6) and 3‐cyano‐4,6‐diphenyl‐1‐[4‐(N‐substituted)sulfamyl]phenylazo‐2‐pyridinethione dyes (1′‐6′) were synthesized by coupling of 4‐(N‐substituted)sulfamylbenzene diazonium salts with 3‐cyano‐4,6‐diphenyl‐2‐pyridinone and/or with 3‐cyano‐4,6‐diphenyl‐2‐pyridin‐ethione. The corresponding iron (1a‐6a, 1′a‐6′a), copper (1b‐6b, 1′b‐6′b) and mercury (1c‐6c, 1′c‐6′c) chelates wvere also prepared. All synthesized compounds were screened in vitro for antibacterial and antifungal activities.
Alkaloids from Houttuyniae Cordata
Authors: Jong Ting‐Ting , Jean Meei‐Yueh 
Published: May 2015

AbstractThe crude extract of Houttuyniae cordata showed potent anti‐platelet and cytotoxic activities. The constituents of this plant, two pyridine alkaloids 1 and 2, along with three aporphine related alkaloids, cepharanone B (3), cepharadione B (4) and 7‐choloro‐6‐demethyl cepharadione B (5) were characterized by spectral methods. Among them, long chain substituted pyridine alkaloids 1 and 2 are rare in nature, and the 7‐choloro‐6‐demethyl cepharadione B (5) is isolated for the first time.
Limonoids from the Stem Bark of Clausena Excavata
Authors: Wu Tian‐Shung , Huang Shiow‐Chyn , Lai Jeng‐Shiow 
Published: May 2015

AbstractA new pentanortriterpenoid, 1‐O‐methylclausenolide (1) and a known limonoid, zapoterin (4) were isolated from the stem bark of Clausena excavata (Rutaceae). Their structures were elucidated by spectral analysis and chemical transformation.
Functionalized Porphyrin Discotic Liquid Crystals: Photoinduced Charge Separation and Trapping
Authors: Fox Marye Anne , Bard Allen J. , Pan Horng‐Long , Liu Chong‐Yang 
Published: May 2015

AbstractIndividual members of a family of highly absorptive porphyrins bearing symmetrically positioned flexible side chains form discotic liquid crystalline mesophases at modest temperature ranges. The order of this phase is preserved when a thin layer of this self‐assembled material is cooled to room temperature. Exposure of such films to visible excitation, with or without an externally applied electrical field, produces photovoltaic effects and/or charge trapping. The latter effect constitutes the basis for optoelectronic information storage.
Kinetics and Mechanism of the Reaction of Chloroplatinum(II) Complexes with Alkyl Radicals
Authors: Chen Wen‐Jang , Espenson James H. , Bakac Andreja 
Published: May 2015

AbstractThe reaction between certain platinum(II) complexes and alky radicals produces an unstable organoplatinum(III) intermediate, {PtIII ‐R}. The kinetics of this step were evaluated by laser flash photolysis with ABTS2 (2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonate) ion) and TMPD (tetramethylphenylenediamine) as kinetic probes. The rate constants for PtCl42− are: kPt/108 L mol−1 s−1 = 5.2, 2.8 and 0.27 for CH3, C2H5, and CH2Cl in aqueous solution at pH 1. Those with cis‐Pt(NH3)2Cl2 are somewhat smaller, and those for Pt(NH3)42+ too small to measure will) this technique. The product analysis indicates that the decomposition of organoplatinum takes place by hydrolysis and (for R = C2H5 only) by β‐elimination, The kinetic isotope effect on die β‐elimination of DCH2CH2PtC4,2− is kH/kD = 1.2. The β‐elimination step produces a PtIII‐hydride that releases hydrogen gas and forms {PtIII‐OH}. The short‐lived Pt(III) intermediate may disproportionate or oxidize the CoII complex that is produced in the radical‐generating step.
Rate Coefficients of the Reactions of CN and NCO with O2 and NO2 at 296 K
Authors: You Yih‐Yuan , Wang Niann S. 
Published: May 2015

AbstractThe rate coefficients of the reactions of CN and NCO radicals with O2 and NO2 at 296 K: (1) CN + O2 → products; (2) CN + NO2 → products; (3) NCO + O2 → products and (4) NCO + NO2 → products have been measured with the laser photolysis‐laser induced fluorescence technique. We obtained k1 = (2.1 ± 0.3) × 10−11 and k2 = (7.2 ± 1.0) × 10−11 cm3 molecule−t s−1 which agree well with published results. As no reaction was observed between NCO and O2 at 297 K, an upper limit of k3 < 4 × 10−17 cm3 molecule−1 S−1 was estimated. The reaction of NCO with NO2 has not been investigated previously. We measured k4 = (2.2 ± 0.3) × 10−11 cm3 molecule−1 s−1 at 296 K.
Spectrophotometric Determination of Palladium(II) with n‐Hydroxy‐N,N‐Diphenylbenzamidine and 1 ‐(2‐Pyridylazo)‐2‐Naphthol
Authors: Jha Anju , Mishra R. K. 
Published: May 2015

AbstractA spectrophotometric method to determine palladium(II) at trace levels is based on the extraction of palladium(II) as a binary complex with N‐hydroxy‐N,N′‐diphenylbenzamidine (HDPBA) in chloroform at pH 5.0 ± 0.2. The complex shows maximum absorbance at 400 nm with molar absorptivity 6.4 × 103 L mol−1 cm−1. The sensitivity of the Pd(II)‐HDPBA complex was enhanced by the addition of l‐(2‐pyridylazo)‐2‐naphthol (PAN). The green coloured complex shows maximum absorbance at 620 nm with molar absorptivity 1.58 × 104 L mol−1 cm−1. Sandell's sensitivity and the detection limit of the method are 0.0067 μg cm−2and 0.1 μg Pd(II) mL−1, respectively. Most common metal ions associated with palladium metal do not interfere. The effects of various analytical parameters on the extraction of the metal are discussed.
Magnetic Hyperfine Mössbauer Spectra of Ferrocenyaldimines‐FeCl3 Adducts
Authors: Lee Chiu‐Jhen , Wei Ho‐Hsiang 
Published: May 2015

AbstractFerrocenylaldimines (Fc‐CH=N‐R) were prepared by condensation of Schiff base of formylferrocene with polyacenylamines RNH2; R = naphthyl, anthracenyl and pyrenyl groups. This step was followed by oxidation with FeCl3 to give [Fc‐CH=NR]‐FeCl3 adducts. The electronic state of iron in these adducts was investigated by means of 57Fe Mössbauer spectra except for [Fc‐CH=N‐Pyr]‐FeCl3 showed that only a doublet was observed at ambient temperature. As the temperature was decreased below 200 K, additional magnetic hyperfine splitting was observed characteristic of ferric oxide.
Structure and Reactivity of Iron(0)‐Phenyltellurolate [PPN][PhTeFe(CO)4]
Authors: Liaw Wen‐Feng , Chiou Show‐Jen , Lee Way‐Zen , Lee Gene‐Hsiang , Peng Shie‐Ming 
Published: May 2015

AbstractAnionic iron(0) tetracarbonyl with terminal phenyltellurolate ligand PhTe−, [PhTeFe(CO)4]−, has been synthesized and characterized. The title compound was obtained by addition of (PhTe)2 to [PPN][HFe(CO)4] THF solution dropwise. [PPN][PhTeFe(CO)4] crystallizes in the monoclinic space group C c, with a = 16.119(4) Å, b = 13.141(3) Å, c = 19.880(8) Å, β = 93.04(3)°, V = 4205(2) Å3, and Z = 4. The [PhTeFe(CO)4]− anion is a trigonal‐bipyramidal complex in which the phenyltellurolate ligand occupies an axial position with Fe‐Te bond length 2.630(5) Å and the Fe‐Te‐C(Ph) angle is 103.4(5)°. The neutral iron(0)‐telluroether compound, (PhTeMe)Fe(CO)4, was prepared by alkylation of the [PhTeFe(CO)4]−. Protonation of [PhTeFe(CO)4]−and reaction of H2Fe(CO)4 and PhTe)2 ultimately lead to formation of the known dimer Fe2(μ‐TePh)2(CO)6 and H2.
Reactivity of fac‐[PPN][Fe(CO)3(TePh)3]: Structure of Fe2(μTePh)2(NO)4
Authors: Liaw Wen‐Feng , Homg Yih‐Chern , Ou Der‐Shiaw , Lee Gene‐Hsiang , Peng Shie‐Ming 
Published: May 2015

AbstractAddition of NOBF4 to fac‐[PPN][Fe(CO)3(TePh)3] in THF at ambient temperature results in formation of Fe2(μ‐TePh)2(NO)4l Fe2(−TePh)2(CO)6 and organic products. Methylation of fac‐[PPN][Fe(CO)3‐ (TePh)3] by Mel or [Me3O][BF4] leads to the known dimer Fe2(μ.‐TePh)2(CO)6 and organic products. Fe2(μ‐TePh)2(NO)4 crystallizes in the orthorhombic space group P bca, with a = 12.701(5) Å, b = 6.7935(16) Å, c = 21.299(9) Å, V = 1837.8(11) Å3, and Z = 4. The core geometry of Fe2(μ‐TePh)2(NO)4 is best described as a Fe2Te2 planar rhombus with Te‐Fe‐Te bond angle 112.09(4)°. A Fe‐Fe bond (length 2.827(2) Å) is proposed for Fe2(μ‐TePh)2(NO)4 on the basis of the 18‐electron rule. The iron atom adopts a distorted tetrahedral geometry with acute bridge Fe‐Te‐Fe angles 67.91(3)°, and bridging Fe‐Te bond of length 2.53(1) Å.
Synthesis of Five Coordinate Spirocyclic Germanium(IV) Complexes Containing Diethanol Amine
Authors: Chen Deng‐Hai , Chiang Hung‐Cheh 
Published: May 2015

AbstractReaction of dihydroxo(2,2′‐iminodiethanolato‐AWO′) germanium(IV) (A) or dihydroxo(2,2′‐methyliminodiethanolato‐N,O.O′) germanium(IV) (B) with bidentate ligands, e.g. diol, α‐hydroxy acid, oxalic acid, 2,6‐pyridinedicarboxylic acid, or 2‐aminophenol in a mixture of ethanol and xylene mixture yielded a series of unsymmetrical spiro‐germanium complexes 1‐6. These complexes were characterized by NMR, IR, mass spectra and elementary analysis. The 1H NMR spectrums of all these compounds show the existence of an intramolecular N–Ge bond. X‐ray analysis of compound 6 shows a short N–Ge bond (2.08 Å).
The Total Synthesis of (±)‐Camphor and (±)‐Epicamphorenone from Methylcyclopentadiene
Authors: Chang Nein‐Cben , Chiu Chih‐Tsao 
Published: May 2015

AbstractThe total synthesis of (±)‐carnphor and (±)‐epicamphorenone from methylcyclopentadiene are described.
Synthesis and Crystal Structures of Nickel(II) and Copper(II) Complexes of Meso‐3,6,6,9‐Tetramethyl‐4,8‐Diazaundecane‐2,10‐Dione Dioxime
Authors: Fun Hoong‐Kun , Lee Tsong‐Jen , Tahirov Tahir , Lu Tian‐Huey , Luh Hung , Chung Chung‐Sun 
Published: May 2015

AbstractThe nickel(II) and copper(II) complexes of meso‐3,6,6,9‐tetramethyl‐4,8‐diazaundecane‐2,10‐dione dioxime (meso‐HM‐PAO) have an intramolecular hydrogen bond between cis oxime groups. [Cu(meso‐HM‐PAO‐H)(H2O)](NCS) crystallizes in space group P21/n with a = 7.692(1), b = 12.028(2), c=20.235(3) Å, β=93.03(1)°, Z = 4 and Dc=1.46 g/cm3. The final R value for this complex was 0.034 for 2223 observed reflections with I ≥ 2.5σ (I). The Cu(II) coordination is a distorted square pyramid. The Cu(II) ion is five‐coorinated with the diazadioxime N atoms equatorial and water O atom axial. The Cu(II) is 0.12 Å from the equatorial plane towards the hydrate. The equatorial Cu‐N distances span a narrow range, 1.953(3)‐1.999(3) Å. The axial Cu‐O distance is 2.314(3) Å. The thiocyanate group is almost linear. The intramolecular O ⃛O hydrogen bond length is 2.479(4) Å. [Ni(meso‐HM‐PAO‐H)](ClO4) crystallizes in space group P21/c with a = 14.774(3), b = 12.752(3), c = 20.035(4) Å, β = 92.94(3)°, Z = 8 and Dc = 1.51 g/cm3. The final R value for the complex was 0.053 for 4794 observed reflections with F ≥ 4σ (F). The coordination about Ni(II) is a slightly distorted square plane. The Ni(II) ion is 0.0673(7) Å from the best plane of the four donor nitrogen atoms away from the perchlorate ion. The Ni‐N distances span a narrow range 1.863(4)‐1.927(4) Å. There are two molecules per asymmetrical unit resulting in eight molecules being packed in an unit cell; they are bound together by van der Waals interactions. The O‐H ⃛O bonds of these complexes give characteristic infrared absorptions as well as chemical shift of the 1H NMR signal (Ni complex).
A Facile Synthesis of Stable Precursors to 2‐Alkylated‐3‐(phenylthio)‐1,3‐Butadienes
Authors: Chou Shang‐Shing P. , Tai Hai‐Ping 
Published: May 2015

Abstract3‐Sulfolenes 3 which are stable precursors to 2‐alkylated‐3‐(phenylthio)‐1,3‐butadienes (4) are conveniently prepared.
Calculations on Heterofullerenes: C24N4, C36N4 and C52N4
Authors: Wang Bo‐Cheng , Yu Liang‐Jye , Wang Wen‐Jwu 
Published: May 2015

AbstractAccording to geometrical considerations, a method is devised to show a geometric relationship between the tetrahedron and the small heterofullerenes below C60: C24N4, C36N4 and C52N4 all of which belong to the Td point group. These simple geometric relationships also allow us to predict the possible structures of heterofullerenes consisting of more than sixty carbons with the Td symmetry. The number of hexagonal faces (besides the 12 pentagonal faces), vertices and edges of these heterofullerenes are obtained by applying Euler's theorem. Calculated by means of molecular mechanics MM2(87), the minimum energy structure, the bond lengths, the bond angles and the torsion angles for such heterofullerenes were generated. The simple Hückel MO calculations are used to determine the HOMO, LUMO and the energy gap between HOMO and LUMO of C24N4 and C36N4 heterofullerenes. The heats of formation of C28 and C40, C24N4 and C36N4 were calculated according to the MNDO method. The ionization energies, die Δϵ (LUMO‐HOMO) and the resonance energies were investigated with semiempirical MNDO methods for comparison with the stabilities of C28, C24N4 and C28H4. The kinetic and thermodynamic stabilities of such tetrahedral derivatives of heterofullerenes were predicted based on the energy gaps and heats of formation.
Extraction of Betel Quid with Supercritical Carbon Dioxide
Authors: Su Sue‐Guane , Tai Dar‐Fu , Shih In‐Lung , Chiou Tzyy‐Wen 
Published: May 2015

AbstractSupercritical extraction with CO2 as solvent was adopted to remove alkaloids and safrole from the betel quid. The extraction efficiency was significantly affected by the operating pressure and temperature. Results of sensory evaluation showed that the eating qualities of the betel quid decreased but still satisfied the chewer after the extraction treatment.
Chemical Constituents from the Aerial Part of Rosa Transmorrisonensis
Authors: Kao Shu‐Fang , Fang Jim‐Min , Cheng Yu‐Shia 
Published: May 2015

AbstractThe aerial part of Rosa transmorrisonensis Hayata contains chemical constituents of long‐chain alkanes, linolcnic acid, squalenc, catechin, sitosterol, sitosteryl‐)β‐D‐glucoside, 3,4,5‐trimethoxyphenyl‐(β‐D‐glucoside, 9‐glucosyl‐4,7E‐megastigmadien‐3‐one, oleanolic acid and eight ursolic acid derivatives. Among them, the new compound 14a was determined to be 2,3,4,6‐tetraacetyl‐(19α‐hydroxy‐2α,3α,24‐triacetoxyurs‐12‐en‐28‐oyl)‐β‐D‐glucopyranoside by spectral methods.
Fluorescence Quenching of Aminopeptidase‐I from Pronase
Authors: Wu Chien‐Hou , Lin Wann‐Yin 
Published: May 2015

AbstractAminopeptidase‐I from pronase contains five tryptophan residues, determined by modification with N‐bromosuccinimide and MCD measurments. The fluorescence of the enzyme is quenched by acrylamide, a neutral quencher, but not by iodide, an anionic quencher. The quenching constant for acrylamide is about one tenth that of acctyltryptophan in aqueous solution because of the steric effect of the large protein molecule. The inaccessibility of iodide to the tryptophans is probably due to the anionic environment of the fluorophores created by the large content of Asp and Glu in the enzyme. Aminopeptidase‐I is quenched by Cu(II) and Co(II) through the formation of a nonfluorescent ground‐state complex. The results indicate that there are three accessible tryptophans for Cu(II) and two for Co(II) suggesting that some tryptophans are buried inside the enzyme and are thus inaccessible to the quencher. In the presence of a competitive inhibitor, the enzyme contains one fewer accessible tryptophan for Cu(II) indicating that this tryptophan is located in the active center. The CD spectrum of the enzyme in the far UV region is unaltered by the presence of Ca(II), whereas that in the aromatic region is enhanced significantly. The perturbation of the CD spectrum probably results from the local conformational change induced by Ca(II) or from the rigidity of the tryptophan being enhanced by the bound Ca(II).
“Truncated” Pagodanes — Synthesis of Functionalized [1.1.1.1] and [1.1.1.0] Pagodanes
Authors: Pracht Thomas , Weber Klaus , Fritz Hans , And Lothar Knothe , Prinzbach Horst 
Published: May 2015

Abstract“Truncated” [1.1.1.1] pagodanes like the [1.1.0.0] and [0.0.0.0] homologues3 and 4 (EStr = 146.1 – 171.5 kcal mol−1, MM2) are potential precursors of unusual unsaturated homoconjugated radical cations and σ‐bishomoaromatic dications. Attempts are presented toward the synthesis of 3 ‐ starting out from [1.1.1.1] pagodane‐4,9‐dione 9 and diaza [2.2.1.1] pagodadiene 11 by cycloelimination (unsuccessful) and by Favorskii‐type ring contraction methodologies. Control experiments with the model diketone 19 documented the limitations for α,α′‐difunctionalization of 9 as the prerequisite for one‐pot double Favorskii‐type ring contraction. A de novo synthesis for such α,α′‐disubstituted derivatives of 9(54) was not sufficiently expeditious to open a practical access to 3. Sequential double bridgehead hydroxylation of 9, successfully practized with model 19, similarly suffered from inherent cage effects and allowed only limited yields of [1.1.1.0] pagodanone 10, the intermediate on the way to 3.
Mass Spectra of Substituted N‐Alkylpyrroles and Related Compounds
Authors: Lin Shaw‐Tao , Shiue Gong‐Yih , Kuo Yueh‐Hsiung , Shih Kae‐Shyang 
Published: May 2015

AbstractUnder El conditions, substituents on N‐alkylpyrroles affect fragmentation of the alkyl groups. The electron‐withdrawing character of the cyano group retarded formation of a N‐methylene cation, and a labile substituent, i.e., ‐CHO, ‐CH2COOMe, competed with an N‐alkyl group to be a initial fragmentation center, MNDO calculation of the heat of formation of possible fragment ions showed that protonated pyridine is the most stable among the isobaric ions.