bluuebunny/crossref_metadata_2025 huggingface dataset:
Isomerization and Disproportionation of 1,2,4‐Trimethylbenzene over HY Zeolite
Authors: Ko An‐Nan , Kuo Ching Tung
Published: May 2015

The conversion of 1,2,4‐trimethy]benzene (1,2,4‐TMB) over HY zeolite was studied at atmosoheric pressure and 200–300 °C by using a fixed‐bed, integral‐flow reactor. The types and initial selectivities of various products were obtained from plots of product selectivity according to the time‐on‐stream theory. The primary reaction included the isomerization and the disproportionation; the former led to the simultaneous formation of 1,2.3‐ and 1,3,5‐TMB whereas the latter produced all isomers of xylene and tetramethylbenzene. The relative initial rate of disproportionation to isomerization decreased from 12.6 at 200 °C to 5.47 at 300 °C. The activation energies for the primary reactions were estimated and compared with those in the reaction of 1,2,3‐TMB.
The Chemistry of Binor‐S and its Cyclopropyl Ring Transformations
Authors: Yang Ya‐Ping , Ding Mei‐Fang , Wang Yu‐Wen , Cheng Shu‐Chun , Li Chun‐Lien , Chen Yao‐Jung , Wen Yuh‐Sheng , Jiang Tsong‐Shing , Chow Tahsin J.
Published: May 2015

Selective ring opening of the cyclopropyl moiety of binor‐S was accomplished by several methods including acidic hydrolysis, bromination, and bydrobromination. The crystal structure of dibromide adduct 3 was solved by X‐ray diffraction analysis. Debrominations of 3 yielded either 1 or 4a, whereas dehydrobromination yielded a 3‐substituted monobromide 6a. The mechanism of conversion of 3 to 6a is depicted as involving intermediate 7; the existence of 7 is supported by the isolation of olefin 8. Oxidation of alcohol 4c produced ketone 11a which was either oxidized to lactone 12 or transformed to a methylene derivative 11b. Hydroboration of 11b followed by quenching with hydrogen peroxide produced a hydroxymethyl derivative 14.
Electrochemical Oxidations of Central Nervous System Indoleamines, Catecholamines and Alkaloids: Potential Significance into Neurodegenerative Diseases
Authors: Wrona Monika Z. , And Fa Zhang , Dryhurst Glenn
Published: May 2015

The serotonergic neurotransmitter 5‐hydroxytryptamine (5‐HT), the catecholaminergic neurotransmittcr dopaminc (DA) and various tetrahydroisoquinoline (TIQ) and tetrahydro‐β‐carboline (THβC) alkaloids are all easily oxidized compounds. Aberrant oxidative transformations of 5‐HT and other central indoles might be involved in neurodegenerative Alzheimer's Disease (AD). Changes in the oxidation chemistry of DA appear to be fundamental in substantia nigra neurons in Parkinson's Disease (PD). Various TIQ and THβC alkaloids are elevated in the brain as a result of ethanol drinking. Recent studies into the electrochemical oxidation chemistry of 5‐HT, DA and various TIQ and THβC alkaloids have been reviewed. The potential roles of the oxidation chemistry of these compounds in neurodegenerative AD, PD and alcoholism are discussed.
Classical Cascade Calculations on the Analysis of Surface Bonding Structures by Secondary Particle Mass Spectrometry
Authors: Chang Che‐Chen
Published: May 2015

The application of secondary particle mass spectrometry to analyze the atomic bonding configuration on a surface was investigated with computer calculations of particle sputtering from an Ar‐bombarded surface of Ag{111}. In contrast to the prediction from the present sputtering theory, better resolved structure in the angular distribution was not observed for particles of high energy sputtered from the surface. These particles ejected to a wide angle and their angular distribution may not reflect well the atomic bonding geometry on the surface. The analytical capability of secondary particle mass spectrometry to determine surface structures can be significantly improved by selecting for detection only those particles that have prolonged collisions. The preferred directions of ejection and the relative sputtering intensity in the distribution of azimuthal angle between major open channels on the surface vary insignificantly with the duration of collision in the regime of long collisions. The results provide the first evidence that at small energies of sputtering the particles emitted from the surface may contain information about only the top two surface layers. Secondary particle mass spectrometry can thus be extremely surface sensitive for analysis of properties of solid surfaces.
Solid‐State Oxygen and Hydrogen Sensing Devices Based on Copper Dicyanoanthraquinone Diimines
Authors: Wang Chong Mou , Lin Huh‐Lerng , Wang Wehn‐Ying , Cheng Hwang Yaw , Liu Lilian Kao
Published: May 2015

Substituted dicyanoanthraqumone diimines (DCNAQI) and their related copper complexes, Cu(DCNAQI), have been synthesized and characterized. Most Cu(DCNAQI) complexes possess an activation energy 80–400 meV and strongly absorb in the IR range. Electrochemical investigations with polycrystailine electrodes as thin films reveal that Cu(DCNAQI) behaves as an n‐type semiconductor. Under bandgap excitation (4000 cm−1), the photoconductance measured with these Cu(DCNAQI) electrodes was greatly promoted under nitrogen, but very sensitive to O2 or H2. When the conductance difference, Δσ/σdark = (σlight ‐ σ dark)σ dark, was plotted vs the partial pressure of the target molecule, a nearly linear relationship was observed. Among Cu(DCNAQI), Cu(β‐methyl‐DCNAQI) gave the greatest senstivity for detection of hydrogen, but Cu(α,α′‐dichloro‐DCNAQI) appeared most sensitive toward oxygen. This remarkable relationship is likely due to retardation of the mobility of electron or hole by interaction with oxygen or hydrogen at the Cu(DCNAQI) electrode surface; a solid‐state oxygen/hydrogen sensing device based on these organic semiconductors is proposed.
Conformational Analysis of Biphenyl‐2,2′‐Diacetate
Authors: Lin Gialih , Chen Show‐Jane , Wu Fang‐Chen
Published: May 2015

Conformational analysis of biphenyl‐2,2′‐diacetate by dynamic NMR and UV spectra and by plots of enzyme activity vs temperature plots is described. From dynamic NMR spectra of the biphenyl‐2,2′‐diacetate with a chiral shift reagent, the coalescence temperature (Tc), the Gibbs energy of activation (ΔG≠), and the rate coefficient (k) of bipbenyl‐2,2′‐diacetate were −5 °C, 59.5 kJ/mol, and 13.3 s−1, respectively. From analysis of the conformational break in the UV spectra and the discontinuity in the plots of enzyme activity vs temperature, the racemerization temperature of bipbenyl‐2,2′‐diacetate is about 5°C.
Comparison of Stereoselectivity of Intramolecular Cyclization of Aldehydes Tethered with Conjugated Esters Induced by O‐Stannyl and O‐Samarium Ketyls to Form the Tetrahydrofuran Ring Systems
Authors: Hon Yung‐Son , Sun Pei‐Pei , Lu Hui‐Ling , Chang Nein‐Chen
Published: May 2015

Several (E)‐ and (Z)‐ω‐formyl‐5‐oxa‐2‐substituted‐α,β‐unsaturated esters (6Za‐6Zc; 6Ea‐6Ec; 6Eb′‐6Ec′; 6Zb′‐6Zc′) were prepared in high yields. They were subjected to cyclization of their intramolecular ketyl radicals induced by either samarium(II) iodide or tributyltin hydride. These two reagents gave distinct stereoselectivities. More bicylic lactone than monocyclic hydroxy‐ester was formed when tributyltin hydride was used, but the opposite stereoselectivity was obtained when samarium(II) iodide was used. The effect of double‐bond configuration, heteroatom and substituent on stereoselectivity is described.
Ab Initio Calculations of Structure and Energetics of the Hypermetalated Hydrogen Oxide Molecules: Li2NaOH and LiNa2OH
Authors: Shie Yi‐Shiau , Ho Jia‐Jen
Published: May 2015

We made ab initio electronic calculations of the structure and energetics of mixed hypermetalated hydrogen oxides, Li2NaOH and LiNa2OH. There exist five equilibrium geometries for each complex. In all levels of calculation the global minimum structure for Li2NaOH has C2v symmetry and a large distance between sodium and oxygen, 4.24 Å (MP2/6‐31G*). The dissociation energies to all possible products were also calculated. Li2NaOH → Na + Li2OH δH = +25.33 kcal/mol (at MP4/6‐311++G**//6‐31G* + ZPE scaled by 0.9). All other dissociation processes are highly endothermic. Similar procedures were applied to LiNa2OH. The global minimum structure for LiNa2OH belongs to point group Cs. It is also endothermic to all possible dissociation paths. LiNa2OH →Na + LiNaOH δH = +12.72 kcal/mol (at MP4/6‐311++G*//6‐31G* + ZPE scaled by 0.9). The nuclear repulsion energy is crucial in energetics of the structures. The distribution of electron density and bonding properties for these equilibrium structures were analyzed.
Muttiphoton Ionization of Benzene‐Ammonia Clusters: Intracluster Reaction and Cluster Ion Stability
Authors: Tsai Wen‐Chin , Yen Wei‐Hung , Tzeng Wen‐Bih
Published: May 2015

Neutral benzene‐ammonia clusters, prepared in a supersonic expansion, were ionized using multiphoton ionization. The cluster ions were investigated with a time‐of‐flight mass spectrometer. The observed major cluster ions, under 355‐nm laser irradiation, resulting from prompt intracluster ion‐molecule reaction and fragmentation following ionization are (C6H6)m(NH3)nH+, m = 1–6, n = 1–4 and (C6H6)m+, m = 1–3. The results of isotopic labeling experiments clearly indicate that C6H6 does not participate in intracluster ion‐molecule reactions to form (C6H6)m(NH3)nH+. A local maximum appears at n = 2 in the intensity distribution of (C6H6)m(NH3) nH+ for each value of m under all experimental conditions. This finding indicates that (C6H6)m(NH3)2H+ is more stable than any other (C6H5)m(NH3)mH+ (n = 1,3,4) for m = 1–6.
Rotational Phenomena on Substituent Phenyl Rings of (η5‐Cyclopentadienyl)(η4‐Tetraphenylcyclobutadiene)Cobalt
Authors: Lo Shih‐Chun , Keng Mei‐Yun , Chang Yuan‐Terng , Hong Fung‐E
Published: May 2015

We used extended Hückel calculations, variable‐temperature, homonuclear long‐range shift‐correlated 2‐D 1H NMR and dynamic NOE measurements to investigate rotational phenomena of substituent phenyl rings on (η5‐cyclopentadienyl)(η4tetraphenylcyclobutadiene)cobalt (1). Two closely related compounds, (η5‐cyclopentadienyl)(η4‐1,3‐diphenylcyclobutadiene)cobalt (A) and (η5‐cyclopentadienyl)(η4‐1,2‐diphenylcyclobutadiene)cobalt (A′), were prepared. Energy minima appeared at conformations of which the dihedral angles between phenyl and cyclobutadiene rings are about 30° for I and 0° for A according to extended Hückel calculations. In 1, ortho protons of phenyl rings belong to one set of multiplet in 1H NMR; meta and para protons belong to the other. It was supported by a long‐range coupling 2‐D 1H NMR and NOE experiments. A sharp line due to phenyl rings was observed in the low‐temperature 1H NMR spectrum of A, which indicates that the five protons are magnetically equivalent at that temperature.
Kinetics of Oxidation of Diphenylmethane and Derivatives with Ce(IV) in Aqueous Acidic Acetonitrile
Authors: Lin Hong‐Ping , Leu Jeng Rong , Jwo Jing‐Jer
Published: May 2015

In aqueous acidic acetonitrilc solution cerium(IV) oxidizes diphenylmethane (Ph2CH2) to produce diphenylmethanol (Ph2CHOH) first and then benzophenone (Ph2CO). With the organic reductant in great excess, both the Ce(IV)‐Ph2CH2 and Ce(IV)‐Ph2CHOH rcactions follow second‐order kinetics. The rates of both reactions increase nonlinearly with increasing [H+] or with decreasing [H2O]. Both kinetic and spectrophotometrc results indicate that replacement of water molecules by complex formation through the phenyl or hydroxyl group plays an important role in activating the reaction. Under similar conditions, the order of relative reactivities toward Ce(IV) oxidation is PhCH2OH > CH3CH2OH > Ph2CHOH > Ph2CH2 > PhCH3> (Ph2CO, C6H6). Mechanistic interpretations of the kinetic results are presented.
Monitoring of Atmospheric Sulfur Dioxide by Fluorescence Monitoring System
Authors: Chen Yehn‐Cherng , Lo Jiunn‐Guang , Wang Jough‐Tai
Published: May 2015

A fluorescence monitoring system was used to measure gaseous sulfur dioxide at Taoyuan Agricultural Farm. A gas‐diluting system and gas chromatograph equipped with a sulfur chemiluminescence detector used to audit the accuracy of diluted sulfur dioxide are described. The accuracy was −8% and −2%, respectively, for the preparation of 10 and 50 ppb SO2 standard gas. The pattern of variation of SO2 concentration at Taoyuan Agricultural Farm is reported. In summer at Taoyuan Agricultural Farm, the concentration of SO2 varied with a pattern of night concentration (15‐20 ppb) greater than that in the afternoon (0–2 ppb). Computer‐analyzed wind trajectories in Taiwan for this pattern are reported.
Electrochemical Study on Decomposition of Hydrogen Peroxide with Fe(II)
Authors: Kao Jing Yi , Wang Chong Mou
Published: May 2015

Decomposition of H2O2 with Fe2+ was studied with SnO2 electrodes. By chronoamperometric and voltammetric techniques, the diffusion coefficients of Fe3* and H 2O2 were estimated to be 5 × 10‐6 and 2 × 10−5 cm2/s, respectively; the rate of decomposition of H2O2 with Fe2+ was proportional to [H2O2]1/2·[Fe2+]2 at a smaller concentration of Fe2+, but to [H2O2]1/2·[Fe2+] when [Fe2+] was increased, indicating the formation of ferryl ion and the electron exchange between it and Fe2+ playing important roles. This catalytic decomposition. was dependent on pH; the maximum rate was observed to occur about pH = 1.5.
Reactions of Tris(acetonitrile)tricarbonylchromium with Trimethylsilylarenes
Authors: Lin See , Liu Lin‐Kang
Published: May 2015

The reactions of tris(acetonitrile)tricarbonylchromium 1 with trimethylsilyl derivatives 2–5 of phenalene, indene, 1,2‐dihydronaphthalene and trans‐β‐methylstyrene gave products 10‐13, respectively, containing no trimethylsilyl groups. The reactions of 1 with trimethylsilyl derivatives 6–8 of benzene, toluene and cycloheptatriene gave products 14–16, respectively, containing trimethylsilyl groups. The reaction of 1 with 1,2‐bis(trimethylsily‐1,2‐dihydro)naphthalene 9 gave product 17 in which only trimethylsilyl at the allylic position was cleaved. Compound 10 crystallizes in the orthorhombic system, space group Pbca, with a = 12.228(4), b = 14.288(1), c = 15.128(3) Å, Z = 8, RF= 0.046, and Rw = 0.047. X‐ray crystallographic data confirm that the Cr(CO)3 moiety is bonded to phenalene in a η6‐mold.
Fragmentation of α‐Acetoximino Ketoesters in Polyphosphoric Acid
Authors: Zee Sheng‐Hsu , Chou Shan‐Yen
Published: May 2015

Fragmentations of various α‐acetoximino ketoesters in neat polyphosphoric acid medium to form acylium ions were studied. The resulting acylium ions were trapped by benzene rings either intermolecularly or intramolecularly.
Acetals of Dehydro‐L‐Ascorbic Acid 2‐Hydrazones. Access to the Chiral Building Block (R)‐Glycerol Acetonide
Authors: El Ashry E. S. H. , Rashed N. , Mousaad A.
Published: May 2015

5,6‐O‐Isopropylidene, cyclohexylidene and benzylidene derivatives of L‐threo‐2,3‐hexodiulosono‐1,4‐lactone 2‐phenylhydrazone were prepared. Reduction of the isopropylidcne derivative was followed by treatment with base, and then periodate oxidation and reduction to give (R)‐glycerol acetonide. Hydrogen bonding in the hydrazones has a role in forming geometrical isomers.
Pyrolytic Chemistry of Benzyl Benzoate
Authors: Chen Ping‐Shu , Chou Chin‐Hsing
Published: May 2015

Flash vacuum pyrolysis of benzyl benzoate (3) at temperatures in the range 750–900 °C and at 102 torr gave diphcnylmethane (5) as the major product with toluene (6) and eight other trace products, namely bipbenyl (7), dibenzyl (8), 2‐, 3‐, 4‐phenyltoluenes (9,10,11, respectively), fluorcne (12), benzyl alcohol (4) and benzaldehyde (13). The mechanism of formation of these products is proposed to involve benzyl and phenyl radicals.
Bicyclo[3.2.1]octenones as Building Blocks in Natural Product Synthesis (IV): Formal Synthesis of (±)‐Hydroxyloganin Aglucone
Authors: Chang Chi‐Peng , Yin Wei‐Kung , Chang Nein‐Chen
Published: May 2015

A formal synthesis of (±)‐hydroxyloganin aglucone from bicyclo[3.2.1]octenone 1 is described. Ring opening of syn‐8‐(methanesulfonyloxy)‐1‐phenylthiotricyclo[4.2.1.03,7]non‐4‐en‐2‐one 14 with potassium hydroxide is the key reaction.
Bridgehead Nitrogen Heterocycles: Facile Synthesis of Imidazo [2,1‐b]‐1,3,4‐Thiadiazoles Using Hypervalent Iodine
Authors: Mohan Jag , Singh Virender , Kataria Sangeeta
Published: May 2015

2,6‐Diarylimidazo [2,1‐b]‐1,3,4‐thiadiazoles (3) were synthesized by reactions of either α‐haloketones with 2‐aminothiadiazoles (1) or directly with acetophenones in the presence of [hydroxy(p‐tosyloxy)iodo]benzene. The latter method is convenient and versatile.
Charge Density Studies of Thiathiophthene. 4 Theoretical Studies on 2,5‐Dimethyl Thiathiophthene and 2,4‐Diphenyl Thlathiophthene with Density Functional Method
Authors: Hwang Tsong Song , Chong Delano P. , Wang Yu
Published: May 2015

The distribution of deformation density of 2,5‐dimethyl thiathiophthene and 2,4‐diphenyl thiathiophthene are calculated via density functional method. The results are in good agreement with the corresponding experimental and theoretical distributions from an ab initio method. The ionization potentials obtained in this calculation on 2,5‐dimethyl thiathiophthene are in good agreement with those obtained experimentally from photoelectron spectroscopy, it is in better agreement than those VIPs based on ab initio calculations. Net atomic charges are compared with the experimental multipole refinement and with those calculated with ab initio and DFT methods for various atomic partitions.
A Theoretical Study of Aluminium Substitution in MFI Zeolites
Authors: Fêng Ming‐Hsiang , Chao Kuei‐Jung
Published: May 2015

The substitution of aluminium for silicon in sodium and proton forms of MFI zeolites has been studied by theoretical force field calculations. The parameters of the cff91_czeo force field developed by Hill and Sauer for zeolites were adopted in this calculation. The molecular structure was optimized according to an energy minimization algorithm with the Newton‐Raphson method. The results indicate that mere seems little energetic preference for aluminium location in Na‐MFI, and that the smaller is the Si‐O‐Al angle, the smaller is the proton‐aluminium substitution energy in H‐MFL The acidity is related to the framework structure and the strong acid sites are correlated with large Si‐O‐Al angles. These conclude that the electrostatic interaction plays a minor role in aluminium substitution and the locations of aluminium atoms and of Brönsted acid sites depend mainly on the framework geometry.
Impedance Analysis of Charge Transport and Redox Reactions of Polypyrrole at Polypyrrole‐coated Electrodes
Authors: Chang Cmur‐Min , Song Chi‐Shyang , Huang Hsuan‐Jung
Published: May 2015

Charge transport accompanying the redox reactions of polypyrrole at a polypyrrole‐coated electrode was investigated with systems containing selected electrolytes. From cyclic voltammeiric and impedance data, we found transport of anions into and from the polymer film to be responsible for the charge‐transfer process accompanying the oxidation and reduction of polypyrrole. With parameters such as charge‐transfer resistance, Rel, low‐frequency polymer resistance, Rl limiting capacitance, Cl and diffusion coefficient, Del estimated, the electrochemical behaviour of polypyrrole as an electronic insulator and conductor is explicitly identified.
Synthesis and Application of Long‐Chain Carboxylate Crown‐Ether Ionophores for Transport of Metal Cations
Authors: Jane Yih‐Song , Shih Jeng‐Shong
Published: May 2015

Alkyl‐substituted sym‐dibenzo‐16‐crown‐5‐oxyacetic acid and sym‐dibenzo‐16‐crown‐5‐oxydodecanic acid were synthesized and applied as ion transport carriers in liquid and film membranes. Increasing crown‐ether lipophilicity decreased acid dissociation constants and solubilities of crown‐ether carboxylic acids in water but enhanced the solubility and transport ability of the carboxylic anion‐K+ complex through a liquid organic (CH2Cl2) membrane. Transport phenomena of the cations alkali‐metal ions, alkaline‐earth metal ions and transition‐metal ions through liquid membranes based on these crown‐ether carriers were investigated, Effects of anions, crown‐ethers and pH on ion transport are discussed. A mechanism of ion transport through a crown‐ether membrane is proposed to include [OH] and [H+] in both source and target layers. Ion transport through a polymer/crown‐ether film membrane was more efficient than through a liquid membrane.
Synthesis and Crystal Structure of Metal Complexes of N‐phenyl‐o‐benzoquinonediimine (M = Ru2+, Co3+, Ni2+)
Authors: Cheng Hei‐Ying , Lin Cheng‐Chen , Tzeng Biing‐Chiau , Peng Shie‐Ming
Published: May 2015

Electron‐delocalized quinoid‐like complexes — [RuII(bipy)2(N‐ph‐bqdi)]2+, cw‐[CoIII(N‐ph‐s‐bqdi)2(py)]+ and trans‐[NiII(N‐ph‐s‐bqdi)2] (N‐ph‐bqdi = N‐phenyl‐o‐benzoquinonediimine, N‐ph‐s‐bqdi = N‐phenyl‐o‐semi‐benzoquinonediimine) were synthesized that display reversible multi‐electron redox couples. The respective cis‐ and trans‐ conformation of the Co and Ni complexes are controlled by the steric effect of the substituent phenyl group. The Ni complex forms one‐dimensional stacks in crystals. The crystal and molecular structures of three compounds are reported. [Ru(bipy)2(N‐ph‐bqdi)](PF6)2: space group P2l/c, a = 13.292(2), b = 18.785(4), c = 13.959(2) Å; β = 97.42(1)°, V = 3456(1) Å3, Z = 4, Rf = 0.047, Rw = 0.044; cis‐[Co(N‐ph‐s‐bqdi)2(py)](OAc)(H2O): space group P21/n, a = 12.752(4), b = 13.303(2), c = 16.683(3) Å; β = 102.27(2)°, V = 2765(1)Å3 Z = 4, Rf = 0.035, Rw = 0.035; and trans‐[Ni(N‐ph‐s‐bqdi)2]: space group P‐1, a = 9.771(2), b = 10.417(1), c = 11.541(2) Å; α = 92.24(1), β = 104.04(1), γ = 117.94(1)°, V = 990.6(3) Å3, Z = 2, Rf = 0.030, Rw = 0.031. Infrared, 1H NMR, 15N NMR and electronic absorption spectra, elemental analyses, magnetic and cyclic voltammetric data are presented.
Syntheses of α‐Haloformylarylhydrazines and Their Self‐dimerizations
Authors: Kuo C. N. , Wu M. H. , Chen S. P. , Li T. P. , Huang C. Y. , Yeh M. Y.
Published: May 2015

α‐Haloformylarylhydrazine hydrohalides 1 were prepared through ring opening of 3‐aryl‐4‐halosydnones 7 with hydrohalic acids in EtOAc in moderate yields. Reactions between compounds 1 and primary alcohols gave alkyl 1‐arylhydrazinecarboxylates 12 and 14, important intermediates in syntheses of antiinflammatory drugs. Compounds 16,4‐aryl‐2‐(arylhydrazin‐1‐y1)‐1,3,4‐oxadiazolin‐5‐ones, and compounds 18, 1,4‐diaryl‐1,4‐dihydro‐1,2,4,5‐tetrazine‐3,6(2H,5H)‐diones, were synthesized by self‐dimerization of compounds 1. Compounds 18 were also converted to compounds 17 via intramolecular rearrangement. Structural elucidation and verification of the reaction mechanisms are presented.
Triplex Formation of Oligonucleotides Containing 2′‐O‐Methylurldine, 5‐Bromo‐2′‐OMethyluridine and 2′‐0‐Methycytidine
Authors: Ono Akira , Kan Lou‐Sing
Published: May 2015

The influence of 5‐bromo and 2′‐O‐methyl substitution of pyrimidine bases on nucleic acid triplex formation was examined by thermal denaturation and circular dichroism spectra with the following oligomers: 5′‐(Um) (I, Um = 2′‐O‐methyluridine), 5′‐(BUm)15T (II, BUm = 5‐bromo2′‐O‐metnyluridine), 5′‐(CmUm)6Cm‐T (III, Cm = 2′‐O‐methylcytidine), and 5′‐(CmUm)6Cm T (IV). Both I and II form triplexes with dA16 (A) or 5′‐d(C2A16C2)‐5′‐d(G2T16G2) (D), but III and IV form triplexes with 5′‐d(AG)8 (G). Triplex formation involving two unmodified oligomers, dT16 (T) and 5′‐d(CT)7 (C), was used for comparison. The orders of melting temperatures (Tm) of triplexes were II A II (Tm = 48 °C) > I A I (34 °C) > T A T (22 °C); II D (Tm= 30 °C) > I D (22 °) > T D (12 °C); and IV G IV (Tm= 82 °C) > III G III (72 °C) > C G C (55 °C). The pKa of IVG IV, III G III, and C G C were determined by CD to be 6.5,6.3, and 6.2, respectively. Triplexes formed by oligonucleotides containing both 2′‐O‐methyl and 5‐bromo substitutions are more stable and have a greater pKa than those formed by oligonucleotides with 2′‐O‐methyl substitution only; which in turn are more stable and have a greater pKa than those formed by unmodified oligonucleotides.
Photolysis of (7R)‐7‐Methoxycarbonyl‐1,5‐di‐f‐butylbicyclo[2.2.2]oct‐5‐ene‐2,3‐dione at Various Temperatures
Authors: Lin Yu‐Min , Ueng Yin‐Gang , Wu Sean‐Nan
Published: May 2015

Upon irradiation at room temperature, the title compound 1 isomerized selectively and quantitatively into a cyclobutanedione 2 which underwent quantitatively bisdecarbonylation to afford a cyclohexadiene 3. Thermolysis of 2 produced 1 and a bicyclo[2.2.1]heptenone 4. Compound 4 was prepared in 70% yield by irradiation of 1 in refluxing dry toluene.
Transfer Chemical Potentials, Solubility and Reactivity of Psoralen and 8‐Hydroxypsoralen in Binary Aqueous Methanol Mixtures
Authors: Alsehaibani Hamad A. , Abu‐Gharib Ezz‐Eldin A.
Published: May 2015

Solubilities are reported for psoralen and 8‐hydroxypsoralen in binary aqueous mixtures at ambient pressure and 298 K, with organic cosolvent methanol. Gibb's energies of transfer of there two compounds are calculated from their solubilities. Transfer chemical potentials of both compounds are stabilised by increasing prapartion of organic cosolvent because of their markedly hydrophobic character.

Basic hydrolysis of psoralen and 8‐hydroxypsoralen in aqueous methanol mixtures was examines kinetically, yielding Gibb's energies of activation. Derived transfer parameters are used in analysis of kinetic data to describe the influence of solvent composition on initial and transition states. Derived transfer chemical potentials for a single ion such as hydroxide ion lead to an interesting comparison of the effects of extrathermodynamic assumptions, Wells estimates and TATB assumption, on the initial and transition states. The analysis comfirm the important role played by the choice of extrathermodynamic assumption in determining the overall kinetic pattern. We describe misgivings concerning procedures used by wells to derive transfer chemical potential for single ions.
Simultaneous Determination of Nickel(II) and Cobalt(II) by Second‐Derivative Spectrophotometry
Authors: Ho Wu‐Hsiung , Chen Chien‐Lung , Chen Huey‐ru
Published: May 2015

4‐(2‐Pyridylazo) resorcinol, PAR, is shown to be useful for simultaneous determination of cobalt(II) and nickel(II) using second‐derivative spectrophotometric method with controlled experimental parameters. This method allows the determination of 0.20‐1.25 ppm of nickel(II) and 0.25‐1.50 ppm of cobalt(II) in mixtures with good precision and accuracy. This method has advantages of simplicity, speed and requires no prior separations.
Cyclopentylidene Ketals of C‐Glycerolyl Heterocycles
Authors: Abdel Hamid H. , El Habrouk M. , El Ashry E. S. H.
Published: May 2015

Cyclopentylidene ketals of 3‐(D‐erythro and L‐threo‐glycerol‐1‐yl) of l‐phenyl‐2‐pyrazoline‐4,5‐dione‐4‐phenylhydrazone and 1 ‐phenylflavazole were prepared. The location of the ketal ring on the glycerolyl residues was determined by NMR spectral analyses.
Pulsed, Crossed, Supersonic Molecular Beam Studies of Refractory Atom Reactions
Authors: Naulin Christian , Costes Michel
Published: May 2015

Dynamics of refractory atom reactions have been studied with a crossed beam apparatus combining two pulsed, supersonic molecular beam sources, a pulsed UV laser for creating the refractory atoms in the gas phase by laser ablation, and a pulsed dye laser to probe the reaction products by laser‐induced fluorescence. Examples of the A1(2Pj) + O2(X3∑g)→ A10(X2∑+) + O(3Pj), Mg(1So) + N2O(X1∑+) → MgO(X1∑+,a3Π) + N2(X1∑g+) andC(3Pj) + NO(X2Πr) → CN(X2∑+) + 0(3Pj) systems are given. Comparisons with the studies performed using the conventional steady‐state beam approach are made.
Magnetic Analysis of Atomic and Molecular Beams. Recent Applications
Authors: Aquilanti Vincenzo , Ascenzi Daniela , Cappelletti David , Pirani Fernando
Published: May 2015

A progress report is given on recent advances in the magnetic analysis techniques for atomic and molecular beams. The cases of halogen atoms and of oxygen molecules are considered in detail. Applications are outlined to discharge plasma diagnostics, to the measurements of molecular alignment in seeded beams and to scattering studies of the interaction of open shell atoms.
Chemical Reconstruction of Pt‐Rh(100) Alloy and Pt/Rh(100), Rh/Pt(100) Bimetallic Surfaces
Authors: Tanaka Ken‐Ichi , Nieuwenhuys B. E. , Tamura Hiroyuki
Published: May 2015

When Cu(110), Ni(l 10), Ag(110) surfaces are exposed to O2 at room temperature, one dimensional metal‐oxygen strings grow in the < 001 > direction of the (110) surfaces. A similar phenomenon occurs in the adsorption of H2 on Ni( 110) surface at room temperature, where the one dimensional strings grow along the < 110 > direction. These phenomena are undoubtedly different from the adsorption induced reconstruction but are explained by the chemical reconstruction involving the formation of quasi‐compounds and their self‐ordering on the metal surfaces. The chemical reconstruction is indispensablly important to understand the structure and catalysis of alloy and bimetallic surfaces.

Pt0.25Rh0.75(100) alloy surface being active for the reaction of NO with H2 is an interesting example. When the Pt‐Rh(100) alloy surface is exposed to NO or O2 at arround 500 K, a p(3 × 1) ordered Rh‐O over‐layer is obtained on a Pt‐enriched 2nd layer by the chemical reconstruction. Ordering of Rh‐0 in the p(3 × 1) structure on the Pt(100) surface was reproduced by heating a Rh/Pt(100) bimetallic surface in O2, and the chemical reconstruction making the p(3 × 1) Rh‐O overlayer on a Pt enriched 2nd layer was also proved by heating a Pt/Rh(100) bimetallic surface in O2 or NO. The activation mechanism of the Pt‐Rh alloy and the Pt/Rh bimetallic surfaces by the chemical reconstruction was evidently shown by using a Pt deposited Rh(100), Pt/Rh(100), surface. That is, the Pt/Rh(100) is not so active for the reaction of NO with H2, but the reconstructed p(3 × 1)Rh‐O/Pt‐layer/Rh(100) surface is very active for the reaction. Therefore, it was concluded that the chemical reconstruction of the Pt‐Rh catalyst makes the active surface which is composed of Rh‐O and a Pt layer.
Internal Rotation of the Methyl Group in Cations of Toluene Derivatives
Authors: Fujii Masaaki , Takazawa Ken , Ito Mitsuo
Published: May 2015

The potential of the internal rotation of the methyl group was determined for o‐, m‐, and p‐fluorotoluene cations by pulsed field ionization spectroscopy. The potential of the internal rotational motion was also surveyed for other toluene derivative cations. It was found that the barrier height generally increases by ionization. The increase in the barrier height has been discussed in connection with the reduction of the internal rotational constant B by ionization. The geometrical distortion of the methyl group during the internal rotation has been suggested.
Characteristics and Dynamics of Superexcited States of Molecules
Authors: Nakamura Hiroki
Published: May 2015

Characteristics and dynamics of superexcited states of molecules are interpreted by emphasizing their significant roles in various molecular dynamic processes. The states are expected to open a new field of physics and chemistry; but because of their complexity, they should be investigated by using the possible multifarious means from the various view points. The interplays between theory and experiment and also between the two theories, dynamics theory and quantum chemistry, are crucial to reveal this world. More systematic studies are required for the superexcited states of polyatomic molecules.
Ejection of Cluster Ions from a Liquid Beam of an Aniline‐Propanol Solution Following Laser Photoionization
Authors: Mafuné Fumitaka , Kobno Jun‐Ya , Kondow Tamotsu
Published: May 2015

A simple technique of preparing a continuous laminar liquid flow in vacuum (liquid beam) was developed and combined with multiphoton ionization and a time‐of‐flight mass spectrometer. This technique was applied to the study on resonance photoionization of an aniline (AN)‐propanol (PrOH) solution (0.1 – 0.3 M). Binary cluster ions of aniline and propanol, AN+(PrOH)n (n ≤ 1), and protonated propanol cluster ions, H+(PrOH)n (n ≤ 1), were observed as product ions in the gas phase. The relative intensities of AN+PrOH and those of H+(PrOH)2 were measured as functions of the excitation laser power and the concentration of aniline in the propanol solution. The dependences of the ion intensities on the laser power and the AN concentration are explained in terms of a Coulomb ejection model, where the ions are ejected from the surface by Coulomb repulsion exerted from neighboring ions. It is also concluded that H+(PrOH)n is produced by a proton transfer reaction from an aniline ion to solvent molecules in the solution.
Parahydrogen Induced Polarization: A New Magnifying Glass for Examining Reactions with Hydrogen
Authors: Eisenberg Richard
Published: May 2015

Parahydrogen‐included polarization (PHIP), its occurrence and mechanistic implications in homogeneous hydrogenation chemistry, and its appearance in the oxidative addition of H2 to transition metal centers are described and analyzed. The PHIP phenomenon, which is characterized by unusual NMR absorptions and emissions in product spectra, arises when para‐enriched H2 is employed in hydrogenation of unsaturated organic substrates with a homogeneous metal catalyst or when para‐enriched H2 is added to a metal complex to form a metal dihydride. Examples of PHIP are found in ruthenium phosphine‐catalyzed hydrogenations, catalysis by binuclear rhodium complexes, and in H2 oxidative addition to Ir(I) complexes. The decay of polarization has been shown in the case of asymmetric hydrogenation catalyzed by Rh(chiraphos)+ to correlate well with the measured rate of reaction. For asymmetric hydrogenation of aprotic substrates using Noyori's Ru(BINAP)(OAc)2 catalyst (1), PHIP is observed indicating a pairwise hydrogen transfer mechanism. Through the signal enhancement of PHIP, it has been possible to observe Rh hydride species never previously detected including binuclear complexes in the reaction of H2 with RhCl(CO)(PR3)2 (R = Ph, Me) and in hydrogenation catalysis promoted by RhCl(PPh3)3. Also observed in the hydrogenation catalysis is the putative olefin dihydride catalytic intermediate.
1H NMR Study on the pH‐Dependent Polymorphism of a DNA Triplex with Oligonucleoside Methylphosphonate Analogues
Authors: Lin Leh‐Jame , Lin Shwu‐Bin , Wu Cheng‐Wen , Kan Lou‐Sing
Published: May 2015

Triplex formation in various stoichiometric mixtures of oligonucleoside methylphosphonates d‐Ap(GpAp)7G (A) and d‐Cp(TpCp)7 (B) (p = methylphosphonate) was studied by measuring the NH‐N hydrogen bonded NMR resonance in relation to temperature and pH. Only a duplex or a triplex was observed for the mixture at pH 6.8 or 3.83 respectively, but both duplex and triplex coexist at pH 4.75. Thus the polymorphism of the mixture is close related to the pKa (4.30) for protonation of B. The triplex starts to dissociate when pH < 2. All data indicate that the duplex and triplex formed by A and B are less stable than those formed by d‐A‐(G‐A‐)7G (C) and d‐C‐(T‐C‐)7T (D) (‐ = phosphodiester). The conformation of the triplex A·B2 is the same at pH 3.83 as that of the corresponding triplex C·D2 at pH 4.50, but different at pH 4.75. Thus, the A·B2 triplex must be able to exist in various conformations, depending on the acidity of the solution. Furthermore, no diastereoisomeric effect was observable on duplex and triplex formation as similar chemical shifts of all NH resonances from C+, G, and T bases were recorded from a mixture of myriad steric isomers.
Circular Dichroism Measurements on C‐Terminal Fragment of Heat Shock Protein from Rat
Authors: Tsay L. M. , Hu S.‐M. , Wang C. , Lee W. S. , Lin L. J. , Kan Lou‐Sing
Published: May 2015

The secondary structure of the C‐terminal fragment (10 kDa) of rat hsc70 (a. a. #546–646) was analyzed according to circular dichroism spectra. In the pH range 5–9 and at concentrations of Na+ up to 0.18 M, the protein is estimated to contain 32‐34% a helix, 18–16% of β sheet, approximately 25% for both turns and disordered structures. This protein is most stable at pH between 6 and 7 in solution with 0.055 M Na+ concentration. However, all Tm are relatively large (57–73 °C) and alterations from one condition to another are small. Thus, the C‐fragment (10 kDa) of hsc70 is a stably folded protein under physiological conditions.
Determination of Butyltins in Sea Water by Gas Chromatography with Flame Photometric Detection
Authors: Lu Te‐Chang , Whang Chen‐Wen
Published: May 2015

Use of a gas chromatograph with a flame‐photometric detector (GC‐FPD) is described to determine butyltin compounds in sea water. The butyltins in an acidified water sample (pH 3.0) are first complexed with tropolone, followed by solid‐phase extraction (SPE) with a tropolone‐treated C18 cartridge. HCI at a small concentration is then added to the concentrated SPE eluate before GC analysis. This procedure is simple and off‐column derivatization of analytes is not required. The organotins, viz. mono‐, di‐ and tributyltin, are separated as their respective chlorides on a capillary column (HP‐1) and are detected with a flame‐photometric detector and an interference filter at 610 nm. Recoveries of the three butyltin species are quantitative (> 90%). Based on a sea water sample 200‐mL, the detection limits for mono‐, di‐ and tributyltin are 6,4 and 3 ng tin L−1, respectively. This method is applied to analysis of trace butyltins in various samples of sea water.
A Mild and Efficient Method for Selective Acetylation of Amines
Authors: Yang Shyh‐Chyun , Wang Huey‐Min , Chen Ling‐Ching
Published: May 2015

Primary and secondary amines were acetylated under mild conditions by means of 3‐acetyl‐1,3‐thiazolidine‐2‐thione [ATT(1)]. The reaction was successfully applied to selective acetylation of a primary amino group of diamines containing a primary and a secondary amino groups or exclusive N‐acetylation of amino alcohols.
Palladium‐Catalyzed Synthesis of Tetrahydrocarbazoles
Authors: Wang Huey‐Min , Chou Hui‐Ling , Chen Ling‐Ching
Published: May 2015

The synthesis of tetrahydrocarbazoles from bromoenaminones derived from β‐diketones is described. The reaction proceeds by intramolecular cyclization of bromoenaminones involving arylpalladium complexes.
Nucleophilic Solvent Intervention in Benzylic Solvolyses. The Use of YBnx Scales in Grunwald‐Winstein Type Correlation Analysis
Authors: Liu Kwang‐Ting
Published: May 2015

New YBnX scales of solvent ionizing power are developed and considered superior to Yx scales for benzylic bromides, chlorides, p‐nitrobenzoates and tosylates in Grunwald‐Winstein type correlation analysis of solvolytic reactivities. The YBnX values, with addition and revision, are summarized. Evidence for nucleophilic solvent intervention in the solvolysis transition state for secondary and tertiary benzylic substrates is given. The advantages of employing this tool to understand solvolysis mechanisms are discussed.
Medicinal Chemical Studies of Anti‐Inflammatory and Analgesic Natural Products
Authors: Shen Tsung‐Ying
Published: May 2015

Following the discovery of salicylates and its conversion to aspirin, natural products research has provided many promising leads for further modification as anti‐inflammatory and analgesic agents. Recent studies have focused on biosynthesis inhibitors of eicosanoids and receptor antagonists of the platelet activating factor, including a new class of dual functional inhibitors derived from neolignans. The highly potent analgesic alkaloid epibatidine from the frog skin has been synthesized and recharacterized as a very strong acetylcholine nicotinic receptor agonist. Some novel epibatidine analogs have shown promise as potential CNS drugs and research probes for clarifying the anti‐addictive property of the African alkaloid ibogaine.
Syntheses of Chiral Acyclic Natural Products from Sugar
Authors: Li Jin‐Cui , Li Yun‐Long , Peng Zhi‐Hui , Sun Xiao‐Ling , Wang Yan‐Fang , Wu Wen‐Lian , Wu Yu‐Lin , Yao Zhu‐Jun
Published: May 2015

The syntheses of several biologically interesting acyclic natural products such as LTA, 1, LTB4 8, mosquito oviposition attractant pheromone 46 and cytotoxic annonaceous acetogenin corossolone 57 and corossoline 58 from sugars in our laboratory are reviewed.
Transition Metal Cation Salts in Organic Synthesis
Authors: Chuang Chong‐Nan , Chuang Li‐Wen , Yeh Ming‐Chang P.
Published: May 2015

Reaction of lithium diisopropylamide (LDA) with (η4‐1,3‐cyclohexadiene)Fe(CO)3 complexes bearing functionalized side chains at C‐5, under an atmosphere of carbon monoxide, gives bridged bicyclo[3,2,1]octene and bicyclo[3,3,1]nonene systems after electrophilic quenching. Under the same reaction conditions, intramolecular cyclization of acyclic (η4‐ 1,3‐butadiene)Fe(CO)3 complexes with functionalized side chains at the terminal position of the diene ligands furnishes fused bicyclo[3.3,0]octanone and bicyclo[4.3.0]nonanone derivatives after acid quenching. The addition of a variety of the highly functionalized zinc‐copper reagents RCu(CN)ZnI to the (η7‐cycloheptatrienyl)Cr(CO) gives (η6‐cyclohepta‐1,3,5‐triene)Cr(CO)3 complexes with a functionalized side‐chain at the C‐7 position of the ring. Intramolecular cyclization of ester‐subsbtuted adducts using lithium diisopropylamide generates fused bicyclo[5.3.0]decane and bicyclo[5.4.0]undecane derivatives. The addition of a variety of the highly functionalized zinc‐copper reagents RCu(CN)Znl to the (η4‐cyclohexa‐1,3‐diene)Mo(CO)2(Cp) at the terminus of the coordinated diene ligand gives [Mo(π‐allyl)(CO)2(Cp)](Cp = cyclopentadienyl) complexes with the functionalized side‐chain at the C‐4 position of the ring. Intramolecular cyclization of the (π‐allyl)molybdenum complex containing a pendant propanoic acid unit generates the δ‐lactone derivative.
Biologically Active Metabolites from Marine Organisms
Authors: Su Jingyu , Zeng Longmei , Zhong Yongli , Fu Xiong
Published: May 2015

The authors' chemical studies on the secondary metabolites from marine organisms are summarized. From marine sponges, algae and soft corals grown in the South China Sea, thirty five compounds were isolated. Their structures were elucidated mainly on the basis of spectral evidence. The biological activities of dysamides, 1–6, stelletin 21 and lactone 23 are reported.
Synthesis and Reactions of Enediynes and Enyne‐Allenes
Authors: Wang Kung K.
Published: May 2015

The thermal cycloaromatization reactions of (Z)‐3‐hexene‐1,5‐diynes (enediynes) and (Z)‐1,2,4‐heptatrien‐6‐ynes (enyne‐allenes) provide easy entries to a variety of carbon biradicals. Several new synthetic routes to these highly unsaturated compounds were developed by using multifunctional reagents properly substituted with combinations of boron, silicon, and tin appendages. Condensation of γ‐(trialkylsilyl)allenylboranes 1 and 2 with conjugated acetylenic and allenic aldehydes followed by the elimination step of the Peterson olefination reaction furnished enediynes and enyne‐allenes with high geometric purity. Convenient procedures for the synthesis of enediynes and enyne‐allenes were also developed by using alkenylboronic ester 28 and the trimethyltin‐substituted alkenylboranes 34 for cross‐coupling reactions. On heating, acyclic enyne‐allene 22 underwent a sequence of intramolecular transformations through biradical intermediates to form 26, providing a new example of a one‐step 0 → ABCD ring construction of the tetracyclic‐steroidal skeleton.
Constituents of Antrodia Cinnamomea
Authors: Wu De‐Peng , Chiang Hung‐Cheh
Published: May 2015

We describe identification of seven components from Antrodia cinnamomea. Their structures were determined on the basis of spectral analysis and comparison with authentic samples. These compounds include two steroids (1, 2) (β‐sitosterol and eburicol), two new steroids (3, 4) [methyl‐4α‐methylergost‐8,24(28)‐dien‐3,7,11‐trion‐26‐oate and methyl‐4α‐methylergost‐8,24(28)‐dien‐3,11‐dion‐26‐oate], two lignans (5, 6) [(+)‐sesamin and 4‐hydroxysesamin], and one long chain methyl ester (7) (methyl oleate). Among them, compounds 3 and 4 are first isolated from nature.
Synthesis and in Vitro Evaluation of New Cephalosporins Exhibiting Antimicrobial Activity against Gram‐Positive Bacteria, in Particular Methicillin‐Resistant Staphylococci
Authors: Lin Ho‐Shen , Rampersaud Ashraff A. , Flokowitsch Jane E. , Alborn William E. , Wu Ernie C. Y. , Preston David A.
Published: May 2015

The preparation and biological evaluation of 7β‐[[2‐(phenyl)thiazol‐4‐yl]acetamido]cephalosporins and 7β‐[[(2‐(pyridin‐2‐yl)thiazol‐4‐yl]acetamido]cephalosporins, 9a‐o, substituted at the 3‐position with acetyloxymethyl, chlorine, hydrogen, and methyl are described. Hantzsch's thiazole synthesis is employed to provide thiazoleacetic acids 5a‐e, subsequently followed by Morpho CDI‐assisted amidation to complete the synthesis of target cephalosporins 9a‐o. These compounds display activity selectively against Gram‐positive bacteria, but are inactive against most Gram‐negative bacteria tested. Those with acetyloxymethyl at the 3‐position, i.e., 9a, 9e, 9i, 9m, and 90, exhibit activity with minimal inhibitory concentrations of 16 (μg/mL or lower against four strains of methicillin‐resistant staphylococci, namely Staphylococcus aureus X400 and S13E and Staphylococcus epidermidis 270 and 222. Notably, 9a displays an activity profile similar to that of vancomycin regarding its spectrum and potency.
Synthesis and Characterization of ASnOAsO4(A = K and Rb)
Authors: Lin Kuan‐Jiuh , Lin Hong‐Cheu , Lii Kwang‐Hwa
Published: May 2015

Crystals of two alkali‐metal tin(IV) arsenates, KSnOAsO4 and RbSnOAsO4, were grown from a flux and structurally characterized by single‐crystal X‐ray diffraction. Crystal data: RSnOAsO4, orthorhombic, Pna21 (No. 33), a = 13.406(3) Å, b = 6.678(1) Å, c = 10.921(2) Å, Z = 8, R = 0.037 for 1173 independent reflections with I > 2.5ó(l); RbSnOAsO4, as above except a = 13.567(3) Å, b = 6.791( 1) Å, c = 10.891(2) Å, R = 0.035 for 1958 independent reflections. The two compounds are isostructural with the nonlinear optical material KTiOPO4. The oxygen frameworks of both tin compounds approximate closely to a centrosymmetric arrangement, as indicated from the analysis of atomic coordinates. Second harmonics were generated in powdered RbSnOAsO4 to confirm the absence of a center of symmetry in the structure.
Direct Measurement of Enantiomeric Excess of Synthetic Tert‐Leucine with a Chiral‐Ligand‐Exchange Chromatography
Authors: Wang Shwu‐Huey , Kao Hsin‐Yi , Chen Shui‐Tein , Wang Kung‐Tsung
Published: May 2015

Racemic tert‐leucine can be completely resolved by ligand exchange chromatography (LEC) using a Chiralpak WH column. The retention time of the tert‐leucine was decreased by increasing concentration of Cu2+, or decreasing pH of the eluent whereas it was unaffected by varying the temperature of eluent. Optimal conditions for complete separation of the D.L‐tert‐leucine were found to be (Cu2+, 5.0 mM, pH 5.5, 25 °C). The enantiomeric excess of synthetic tert‐leucine, a chiral auxiliary reagent, was determined.
A Practical Route to Chiral Phenylalanine via the Condensation of Keto Acids with Amides and Asymmetric Hydrogenation
Authors: Chau Tay‐Yuan , Tsui Jian‐Hou , Lin Chi‐Ching , Chan A. S. C.
Published: May 2015

The condensation of β‐phenylpyruvic acid with amides gave olefinic intermediates in good yields (75‐80%). The asymmetric catalytic hydrogenation of α‐acetamidocinnamic acid with high enantioselectivity is described.
The Bonding Nature of the Canonical Molecular Orbitals in Simple Diatomic Molecules
Authors: Chang Tse‐Chiang
Published: May 2015

The bonding nature of the canonical molecular orbitals 2σg, 2σu and 3σg in the molecules N2,O2, F2 and the related analogous molecular orbitals in the molecules P2 and CO, is analysed using Weinhold's natural bond orbital set. When the canonical molecular orbitals can be well localized into natural bond orbitals, the covalent bond can be completely attributed to the bonding type natural bond orbitals. The decomposition of canonical molecular orbitals into the natural bond orbital basis then gives the weighted bond order as the component of the bonding portion in the canonical molecular orbital. The weighted bond order results match the photoelectron spectroscopy assignment quite satisfactorily.