bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and the Acid Hydrolysis of N-(2-Hydroxyethyl)ethylenediamine-N,N′,N′-triacetate Complex of Di-μ-oxo-bis(oxomolybdenum(V))
Authors: Sasaki Yoichi , Morita Tomoji S
Published: July 2006

A hedta (H3hedta=N-(2-hydroxyethyl)-ethylenediamine-N,N′,N′-triacetic acid) complex of molybdenum(V), Mo2O4(hedta)(H2O)−, has been prepared and characterized. The rate of acid hydrolysis of this complex in an aqueous perchloric acid solution ([H+]=0.5–2.0 mol dm−3; I=2.0) is of similar magnitude to that of Mo2O4(edta)2−(H4edta=ethylenediaminetetraacetic acid), increasing with increase in [H+].
The Conformations of Nickel(II) Complexes with edda-Type Optically Active Polyamino Carboxylic Acids in Aqueous Solutions
Authors: Murakami Tasuku , Hirako Ichiro , Hatano Masahiro
Published: July 2006

Circular dichroism (CD) and proton magnetic resonance (PMR) spectra of nickel(II) complexes containing a series of ethylenediamine-N,N′-diacetic acid (H2edda)-type optically active quadridentate ligands were measured in aqueous solutions. The epro complex which is an edda-type optically active ligand containing l-proline residues is found to exhibit the same CD spectrum as complexes of other edda-type ligands containing l-alanine, l-valine, l-phenylalanine, and l-serine residues. The CD and PMR spectra of the mixed complexes of these edda-type ligands having an oxalate ion was also measured. From the CD and PMR spectral data, it is concluded that these complexes stereospecifically take the Δ-s-cis form in solution. The large contact shift observed for the a protons of the amino acidate moieties indicates that the substituent groups become axial to the chelate plane.
A New Synthetic Approach to Esters of β-Keto Thiocarboxylic SAcids
Authors: Wakui Toshimitsu , Yamaguchi Haruzo , Motoki Shinichi
Published: July 2006

Esters of β-keto thiocarboxylic S-acids (5) were synthesized from S-ethyl bromothioacetate (1), through a reaction sequence involving the reduction of sulfonium ylides (4) with zinc in acetic acid.
Tungsten Hexachloride-catalyzed Decomposition of Diazo Compounds. A Novel Oxazole Synthesis
Authors: Kitatani Katuzi , Hiyama Tamejiro , Nozaki Hitosi
Published: July 2006

Benzoylphenyldiazomethane and diazoacetophenone react with several nitriles in the presence of WCl6 catalyst to produce 2-substituted 4,5-diphenyloxazoles (1a–d) and 2-methyl-5-phenyloxazole (2) in good yields. The remarkable catalysis is ascribed to the good affinity of tungsten with carbenes. The catalytic decomposition of diphenyldiazomethane yields diphenylcarbenium ion, which is transformed into triarylmethanes in aromatic solvents.
Synthesis of 2-Alkoxy-3,4,6-trihydroxyacetophenones
Authors: Hatakeda Kiyotaka , Saito Norio , Ito Shota , Asano Takashi
Published: July 2006

2-Alkoxy-3,4,6-trihydroxyacetophenones have been prepared from 2,3,4,6-tetrakis(benzyloxy)acetophenone (II) in good yields by the following reactions: hydrolysis of II to 2-hydroxy-3,4,6-tris(benzyloxy)acetophenone (IIIa), alkylation of IIIa to 2-isopropoxy and 2-ethoxy-3,4,6-tris(benzyloxy)acetophenones (IVa and VIb), and hydrogenolysis of IVa and IVb to the corresponding 2-alkoxy-3,4,6-trihydroxyacetophenones (Va and Vb).
An MO Calculation of the Reaction Path of a Symmetry-Disfavored 1,3-Sigmatropic Rearrangement
Authors: Minato Tsutomu , Inagaki Satoshi , Fujimoto Hiroshi , Fukui Kenichi
Published: July 2006

The path of suprafacial 1,3-sigmatropic rearrangement is studied with the INDO-CI and INDO LMO methods. The methyl migration has been found to be represented by successive 1,2-shifts with a biradicaloid transition state. The interaction between the singly occupied MO’s of allyl and methyl fragments is suggested to be responsible for the determination of the path. A subsidiary orbital also plays a part. On the other hand, the chlorine migration has been shown to be a direct 1,3-shift. The interaction between the lowest unoccupied MO of the allyl cationic part and the highest occupied MO of the remaining part, chloride anion, has been found to govern the path of chlorine migration. The lone pair electrons of the migrating fragment makes the successive 1,2-shifts quite unlikely in the 1,3-suprafacial chlorine rearrangements.
Determination of the 63P1→63P0 Transition Rate of Hg in CO and NO by a Modulation Technique
Authors: Horiguchi Hiroyuki , Tsuchiya Soji
Published: July 2006

In order to determine the branching ratio for Hg(63P1) deactivation to the 63P0 and 61S0 states in CO or NO, a modulation technique was utilized. The intensity of 253.7-nm radiation was modulated at a frequency in the range from 0.1 to 20 kHz, and the resulting a.c. component of the Hg(63P1 or 63P0) concentration was measured by monitoring the absorption of the 435.8- or the 404.7-nm emission line from an Hg discharge lamp. The lower detection limit of excited Hg atoms was 107 cm−3 in this experimental method. On the basis of the Hg(63P0) concentration relative to that of Hg(63P1) in an Ar+CO or NO mixture including information on the phase delay, the 63P1→63P0 transition rate could be determined; the 63P1→63P0 cross section was found to be 22.4 Å2 for CO and 7.1 Å2 for NO and the 63P0→61S0 cross section to be 1.80 Å2 for CO and 37 Å2 for NO at room temperature.
The Electron Capture by Bromobenzene in the γ-Radiolyses of Cyclohexane and 2,2,4-Trimethylpentane
Authors: Karasawa Hidetoshi , Kim Eung-Ryul , Sato Shin
Published: July 2006

The γ-radiolyses of cyclohexane and 2,2,4-trimethylpentane have been reinvestigated. Bromobenzene was used as the electron scavenger. The analysis of the G-values of benzene obtained at high concentrations of bromobenzene showed that the empirical formula proposed by Hummel for the electron scavenging

G=G_fi+G_gi{1-exp(-√‾αS)}

is better than that proposed by Warman et al. The values of Gfi+Ggi thus obtained were 3.7±0.3 for cyclohexane and 3.5±0.2 for 2,2,4-trimethylpentane. The bromobenzene-concentration dependence of the G-values of hydrogen and methane from 2,2,4-trimethylpentane was well explained by the hypothesis that the lifetimes of the 2,2,4-trimethylpentane ion for the decomposition are in the same order as the time needed for the geminate recombination.
Heat Capacities of Aqueous Solutions of Glutaric and Malonic Acids
Authors: Kawaizumi Fumio , Noguchi Tuneyuki , Miyahara Yutaka
Published: July 2006

Using a calorimeter composed of a Dewar vessel and a Beckmann thermometer, the specific heat capacities of aqueous solutions of glutaric and malonic acids were measured at 30 °C. Techniques for establishing the temperature gadient between the solution in the Dewar and the outer air bath were adopted. The partial molar heat capacities at infinite dilution were estimated assuming a relation of the form mφCp=bm+cm2. The contributions of the –CH2– and –COOH groups to the partial molar heat capacities in aqueous solution are roughly additive: for –CH2– a positive contribution and for –COOH a negative one. The Δ(=‾Cp2°–Cp2(pure state)) were also calculated and positive and negative values were obtained for Δ(–CH2–) and Δ(–COOH), respectively.
An Interpretation of Delayed Fluorescence Behavior of Naphthalene in Biphenyl Host in the Lower Temperature Region
Authors: Kusumoto Yoshihumi , Gondo Yasuhiko , Sato Hiroyasu , Kanda Yoshiya
Published: July 2006

Temperature and concentration dependences of the delayed luminescence observed in the naphthalene (guest)–biphenyl (host) mixed crystal system have been studied. The presence of the temperature-independent delayed fluorescence (TIDF) and its significance in the evaluation of activation energy have also been confirmed in this system as in the case of the benzo[f]quinoline–biphenyl system previously reported, and the generality of the existence of TIDF as well as its significance in relation to activation energy has been suggested. In addition, some remarks have been made on the nature of TIDF and the decay behavior.
A Chlorine NQR Study of Trichloromethyl Derivatives. I
Authors: Hashimoto Masao
Published: July 2006

The chlorine NQR frequencies of several benzene derivatives with –CCl3 groups were measured at temperatures above 77 K. For all the compounds studied, the NQR signals of the –CCl3 groups were observed to fade out; the fade-out temperatures (Tf) were in the temperature range of 130–370 K. It was found that the most important factors involved in determining the Tf value are the intramolecular steric hindrance, hyper conjugation, and intermolecular interactions. In some compounds, an increase in the NQR frequency was found to be caused by the intramolecular steric hindrance.
The Microwave Spectrum of 1-Propanethiol
Authors: Ohashi Osamu , Ohnishi Mamoru , Tagui Akira , Sakaizumi Takeshi , Yamaguchi Ichiro
Published: July 2006

The microwave spectra of 1-propanethiol and its deuterated species (CH3CH2CH2SD) were measured in the frequency region from 8.5 to 35 GHz. Several a-type R-branch transitions for the ground and excited vibrational states of the normal species and for the ground state of the deuterated species were identified, and the following rotational constants in MHz were obtained: A=23429±653, B=2345.29±0.03, and C=2250.18±0.03 for the ground state of the normal species; A=24483±945, B=2346.30±0.04, and C=2253.91±0.04 for the excited state of the normal species, and A=21758±461, B=2306.71±0.03, and C=2217.79±0.03 for the ground state of the deuterated species. The spectrum assigned to the ground vibrational states has been attributed to the T–G rotational isomer, and the excited vibrational state has been ascribed to the –CH2–CH2– torsional motion.
Intrachain Charge-Transfer Complex in Ethanol Solution on a Polysarcosine Chain Having a Terminal Electron Donor and a Terminal Electron Acceptor Groups
Authors: Takagi Hiroaki , Sisido Masahiko , Imanishi Yukio , Higashimura Toshinobu
Published: July 2006

Polysarcosine having a terminal electron donating group (p-dimethylaminoanilide group) and a terminal electron accepting group (3,5-dinitrobenzoyl group) was synthesized. An ethanol solution of the polymer showed a distinct charge-transfer absorption band around 435 nm. With use of the extinction coefficient determined for the low-molecular-weight model compounds, the fraction of polymers forming an intrachain complex was evaluated to be about 0.08 for \barn=6 (\barn is the degree of polymerization of the polysarcosine chain). The fraction decreased with rise in temperature and increase in chain length. The fraction experimentally observed was considerably larger than that estimated from the Monte Carlo calculation on polysarcosine chain, indicating that the cyclic conformations are greatly stabilized by the intrachain charge-transfer interaction. Thermodynamic parameters were determined for the intrachain complex. The chain length dependence of the parameters in ethanol was the opposite of that obtained previously in a chloroform solution. The difference was explained in terms of the difference of the conformations of polysarcosine chain in chloroform and in ethanol solutions. This was evidenced by the NMR spectra recorded in the solvents.
The New Schizandrin-type Lignans, Kadsurin and Kadsurarin
Authors: Chen Yuh-Pan , Liu Rolan , Hsu Hon-Yen , Yamamura Shosuke , Shizuri Yoshikazu , Hirata Yoshimasa
Published: July 2006

Two new lignans, kadsurin and kadsurarin, were isolated from Kadsura japonica Dunal, and their structures were established. The stereostructures of the schizandrin-type lignans including their conformations were elucidated by measurements of intramolecular nuclear Overhauser effects.
Synthesis of Methyl-substituted 1-Cyclopentene-1-carboxylates and Related Compounds
Authors: Takeda Akira , Shinhama K\={o}ichi , Tsuboi Sadao
Published: July 2006

The treatment of methyl-substituted 1-chloro-2-oxo-1-cyclohexanecarboxylic esters (7a–e) with anhydrous Na2CO3 in refluxing xylene gave the corresponding methyl-substituted 1-cyclopentene-1-carboxylic esters (1a–e). Several intermediates important in the synthesis of natural products, such as 4,4-dimethyl-1-cyclopentene-1-carbaldehyde (9), 5-methyl-1-cyclopentene-1-carbaldehyde (12), α-(3-methyl-1-cyclopentenyl)propionic acid (16), and ethyl 2-methyl-3-oxo-1-cyclopentene-1-carboxylate (17), have been prepared starting from esters 1e, 1d, 1b, and 1a, respectively.
ESR Studies of N-(Arylthio)-t-butylaminyls
Authors: Miura Yozo , Asada Hidetsugu , Kinoshita Masayoshi
Published: July 2006

It was found that N-(arylthio)-t-butylaminyls (2) are easily generated by the photolysis of N-t-butylbenzene-sulfenamides (1). The ESR spectra of 2 were split into a 1 : 1 : 1 triplet by the interaction with the nitrogen nucleus (11.70–11.89 G), and each of the triplet was further split by the ring protons (ao-H: 0.89–1.07 G). The g-values of 2 lie in the range from 2.0068–2.0073. The radicals persist in benzene and it appears that they are not sensitive to the atmospheric oxygen.
Inositol Derivatives. 10. Isopropylidenation of 1,2-O-Cyclohexylidene-myo-inositol Derivatives and Preparation of Unaccessible Blocked Inositols
Authors: Ogawa Seiichiro , Oki Shuichi , Kunitomo Hideo , Suami Tetsuo
Published: July 2006

Isopropylidenation of 1,2-O-cyclohexylidene-myo-inositol and its 3-O-tosyl- and 3-O-benzoyl derivatives with 2,2-dimethoxypropane in N,N-dimethylformamide in the presence of acid catalyst gave the corresponding 4,5- and 5,6-O-isopropylidene derivatives. Selective benzoylation of 1,2-O-cyclohexylidene-4,5-O-isopropylidene-myo-inositol with benzoyl chloride in pyridine gave mainly the 3-O-benzoate, whereas with benzoic anhydride the 6-O-benzoate. Several unaccessible blocked inositols were prepared by displacement reaction of the protected sulfonyl derivatives with sodium benzoate.
Catalytic Behavior of Sulfonium Trihalides in the Low-temperature Liquid-phase Oxidation of Tetralin
Authors: Ohkubo Katsutoshi , Aoji Teruo , Yoshinaga Kohji
Published: July 2006

Homogeneous oxidation of nonpolar tetralin catalyzed by sulfonium trihalides was found to proceed via a radical chain mechanism in which the trihalide catalysts promoted the reaction through the activation of molecular oxygen.
The Reactions of Several Anilides with Phosphoryl Chloride
Authors: Fukuda Masahiro , Okamoto Yoshiki , Sakurai Hiroshi
Published: July 2006

Chloroacetanilide and p-methylchloroacetanilide reacted with phosphoryl chloride to give 2-chloromethyl-3-chloro-4-anilinoquinoline and 2-chloromethyl-3-chloro-4-(p-toluidino)-6-methylquinoline respectively. In the case of propionanilide, 2-ethyl-3-methyl-4-anilinoquinoline was obtained when the reaction was carried out at 20–30 °C. On the other hand, when the reaction temperature was raised to 80–100 °C, N-(1-chloro-1-propenyl)-N,N′-diphenylacetamidine was obtained.
Reaction of Camphene with Chloroacetic Acid and the Synthesis of 2-(8-Camphenyl)ethanol
Authors: Kishimoto Takao , Ishihara Hiroshi , Matsubara Yoshiharu
Published: July 2006

Camphene (1) reacts with chloroacetic acid (2) or its polymer, polyacetoxamer; α-chloro, ω-carboxy in the presence of potassium bromide at reflux temperature to give the 2,2-dimethyl-exo-3-hydroxynorbornane-endo-3-propanoic acid lactone and the 2,2-dimethyl-endo-3-hydroxynorbornane-exo-3-propanoic acid lactone in a 50% yield. The synthesis of 2-(8-camphenyl)ethanol from 1 was simplified by utilizing this reaction.
The Intramolecular Cyclization Reaction of Unsaturated Acid with Palladium(II) Salt
Authors: Kasahara Akira , Izumi Taeko , Sato Kazuhiro , Maemura Mitsugi , Hayasaka Tomohide
Published: July 2006

The stoichiometric reaction of sodium salts of 3-butenoic acid, 3-pentenoic acid, 4-pentenoic acid, and 4-hexenoic acid with lithium tetrachloropalladate(II) affords 2-buten-4-olide, 4-methyl-2-buten-4-olide (2b), 2b, and 4-ethyl-2-buten-4-olide respectively. Similarly, the reaction of 2-styrylbenzoic acid with palladium(II) salt leads to the formation of 3-phenylisocoumarin.
Electronic Structures of Meso-ionic Azapentalenes Studied by X-Ray Photoelectron Spectroscopy
Authors: Ohta Toshiaki , Yoshida Masayuki , Kuroda Haruo
Published: July 2006

X-Ray photoelectron spectra of meso-ionic azapentalenes were observed in the solid phase. The charge distributions in these molecules were investigated by using the observed chemical shifts of core-electron levels, employing Siegbahn’s electrostatic potential model and the results of CNDO/2 calculations.
Kinetics of the Oxidation of Ethylenediaminetetraacetato and Aqua Complex of Dimeric Molybdenum(V) by the μ-Hyperoxo-bis[pentaamminecobalt(III)] Ion in Aqueous Perchloric Acid Solution
Authors: Sasaki Yoichi
Published: July 2006

Kinetics of the oxidation of double-bridged Mo(V) complexes, [Mo2O4(edta)]2− (H4edta=ethylenediaminetetraacetic acid) and [Mo2O4(aq)]2+ with [(NH3)5CoO2(−)Co(NH3)5]5+ has been studied in aqueous perchloric acid solution at 25–50 °C. The oxidation of [Mo2O4(edta)]2− is characterized by the electron transfer within the ion-pair formed between the two reactants. The first order rate constants for the electron transfer process (ke) are independent of [H+] ([H+]=0.05–0.1 M; I=0.1–2.0 M) (M=mol dm−3). At 40 °C and I=0.1 M, ke is equal to (1.34±0.08)×10−3 s−1 and the corresponding activation parameters are ΔH\eweq=28±4 kcal mol−1 and ΔS\eweq=18×11 cal K−1 mol−1. The rate of oxidation of [Mo2O4(aq)]2+ is independent of the oxidant concentration and accelerated by halide ions and Mo(VI). The rate-determining step is the formation of a single-bridged Mo(V) dimer (A) prior to electron transfer. The first order rate constants for the formation of A (k1) are reciprocally dependent on [H+] ([H+]=0.5–2.0 M; I=2.0 M). k1 is (4.3±0.3)×10−6 s−1 at 25 °C and for [H+]=1.0 M. The difference in the oxidation mechanism of the two complexes has been discussed in terms of the charge of the complex, stabilization of the Mo2O4-unit by the ligands, and the role of coordinated water.
The Chemistry of Phenalenium Systems. XXIII. Syntheses and Properties of Cyclohepta[cd]phenalen-6-one and the Cyclohepta[cd]phenalenium Ion
Authors: Yamamoto Kagetoshi , Kayane Yutaka , Murata Ichiro
Published: July 2006

The syntheses of cyclohepta[cd]phenalen-6-one (8) and the cyclohepta[cd]phenalenium tetrafluoroborate (1) are reported. As expected, it is apparent that in the transition from 10,11-dihydrocyclohepta[cd]phenalen-6-one to the fully conjugated ketone 8, all the vinyl protons move downfield by 0.22 to 0.53 ppm. The plausible explanation suggests that these shifts arise from deshielding due to the existence of a diamagnetic ring current induced in the 14π periphery of 8. In accord with theoretical prediction, the cation 1 is extremely stable. The substantial thermodynamic stability of 1 is reflected to its pKR+ of 8.4. The ion 1 can be regarded as a perturbed [15]annulenium ion weakly coupled with a localized central vinyl crosslink.
Syntheses of 4-Phenylcoumarins Containing a Dimethylpyran Ring
Authors: Matsui Takanao , Nishimura Shinji , Nakayama Mitsuru , Hayashi Shûichi , Fukui Kenji
Published: July 2006

Three isomers of 2H,8H-benzo[1,2-b: 3,4-b′]dipyran and 2H,8H-benzo[1,2-b: 5,4-b′]dipyran, were synthesized by dehydrogenation of the dihydrobenzodipyran derivatives using DDQ or NBS and by dehydration of the secondary alcohol prepared by reduction of 4-phenylcoumarin derivatives bearing dihydropyranone ring with sodium borohydride.
Synthesis and 13C NMR Spectra of endo-5-(4-Imidazolyl)bicyclo[2.2.2]oct-endo- and exo-2-yl trans-Cinnamates
Authors: Utaka Masanori , Akiyama Mamoru , Takeda Akira
Published: July 2006

The Synthesis of endo-5-(4-imidazolyl)bicyclo[2.2.2]oct-endo- and exo-2-yl trans-cinnamates was carried out starting from 2-butyn-1,4-diol. The key intermediate, endo-5-(4-imidazolyl)bicyclo[2.2.2]octan-2-one, was obtained by oxidation of endo-5-(4-imidazolyl)bicyclo[2.2.2]oct-2-ene with palladium chloride, the oxidation being stereo- and regiospecific. The mode of 2,5 disubstitution and endo, exo stereochemistry were determined by means of 13C chemical shifts of the bicyclo[2.2.2]octane framework.
The Isolation and Structure of Toxic Principles, Milliamines A, B, and C, from Euphorbia Millii
Authors: Uemura Daisuke , Hirata Yoshimasa
Published: July 2006

Toxic compounds were isolated from Euphorbia Millii Ch. des Moulins (Euphorbiaceae). The structure of the milliamines was established from chemical and spectral evidence. Furthermore, the acute toxicity of milliamine A was examined.
Synthesis of Corticotropin Peptides. XIV. The Synthesis of Two Octadecapeptides Corresponding to the Amino Acid Sequence 22–39 of Porcine and Human Corticotropins
Authors: Watanabe Kunio , Inouye Ken
Published: July 2006

The syntheses are described of two octadecapeptides, H–Val–Tyr–Pro–Asn–Gly–Ala–Glu–Asp–Glu–Leu–Ala–Glu–Ala–Phe–Pro–Leu–Glu–Phe–OH (Ip) and H–Val–Tyr–Pro–Asn–Gly–Ala–Glu–Asp–Glu–Ser–Ala–Glu–Ala–Phe–Pro–Leu–Glu–Phe–OH (Ih), corresponding to a tryptic fragment (positions 22–39) of porcine corticotropin (αp-ACTH) and that of human hormone (αh-ACTH), respectively. The porcine pep tide and the corresponding human peptide are prepared simultaneously by an identical synthetic procedure except for the introduction of amino acid residue in position 31. Synthetic peptide Ip is compared with the authentic αp-ACTH (22–39), which has been isolated from a tryptic hydrolysate of natural αp-ACTH, in terms of chemical and physicochemical properties to establish their identity. These data as well as those obtained with human peptide Ih prove the satisfactory synthesis of the two octadecapeptides.
Synthesis of Amino Compounds under Phase Transfer Conditions
Authors: Nakajima Yosuke , Kinishi Ryo-ichi , Oda Jun’ichi , Inouye Yuzo
Published: July 2006

The phase transfer process was applied to the reaction of organic bromides with azide anion. The reduction of intermediary azide derivatives gave the corresponding amino compounds, benzylamine, glycine, alanine, butyrine, and serine in fairly good yields. Effective catalytic activity was demonstrated by the difference in chemical yields in the case of methyl bromoacetate and ethyl α-bromopropionate. In order to examine the role of phase transfer catalyst, two bromohydrins (methyl β-hydroxy-α-bromopropionate and styrene bromohydrin) were subjected to the present reaction. Methyl β-hydroxy-α-bromopropionate afforded serine exclusively in the presence of 18-crown-6 and tetrabutylammonium bromide, but in the absence of the catalyst a mixture of serine and isoserine was obtained. A different regioselectivity was observed in the case of styrene bromohydrin.
Hydration of Aza-aromatic Aldehydes. I. Isolation of the Solid Hydrates and the Thermodynamic Properties in Dimethyl Sulfoxide
Authors: Abe Kazuhisa , Hirota Minoru , Takeuchi Isao , Hamada Yoshiki
Published: July 2006

The covalent hydration forming geminal diol is shown to be general in six-membered aza-aromatic aldehydes substituted by a formyl group at ortho or para-position to the nitrogen atom, and the equilibrium constants and thermodynamic quantities of the reaction are determined by NMR spectroscopic measurements. The results are compared with those of their hemiacetal formation. In several cases, solid monohydrates are isolated and identified.
The Cycloaddition of Dispiro[2.2.2.2]deca-4,9-diene with the Styrene Derivatives. The Syntheses and Spectral Properties of the [4.2]Paracyclophane Derivatives
Authors: Shibata Tohru , Tsuji Takashi , Nishida Shinya
Published: July 2006

The thermal cycloaddition of dispiro[2.2.2.2]deca-4,9-diene 1 with the styrene derivatives has afforded [4.2]paracyclophane derivatives, 3. A reaction mechanism by way of the biradical intermediates, involving the initial homolytic cleavage of the cyclopropane ring in 1 followed by the addition to the styrene molecule, is proposed. In the reaction of 1 with styrene, and methyl α-phenylacrylate, the yields of 3 were improved with the dilution of the reactants, while in the reaction with trans-stilbene, no appreciable dependence on the reactant concentration was observed. The mass spectra of the substituted [4.2]paracyclophanes show a predominant fragmentation to the substituted p-xylene-α,α′-diyl (or elements thereof) ion radical. [4.2]Paracyclophane exhibited a temperature-dependent NMR spectrum which could be ascribed to the rapid equilibration between two structurally equivalent conformers. Bulky substituents on C-1 and C-2 shifted the equilibrium to one side.
Induced Circular Dichroism Spectra of Cobalt(III) Complexes in a Chiral Medium Containing (+)589-Diethyl Tartrate
Authors: Taniguchi Yutaka , Hidaka Jinsai , Shimura Yoichi
Published: July 2006

The induced circular dichroism (CD) spectra of 21 achiral or racemic cobalt(III) complexes have been measured in a chiral medium containing (+)589-diethyl tartrate in the region of the first d-d transition bands. The absolute value of the molar circular dichroism (Δε) observed for these complexes is in the range of about 0.04–0.3 cm−1 mol−1 dm3. The induced CD spectra of the racemic complexes show a different pattern from the natural CD spectra of their resolved enantiomers. The observed induced CD spectra have been discussed in relation to the stereochemistry of the complexes.
Pressure Effect on the Base Hydrolysis Rate of [Co(NH3)5Cl]2+ in a Carbonate Buffer
Authors: Kitamura Yoichi
Published: July 2006

The pressure effect on the base hydrolysis reaction rate of [Co(NH3)5Cl]2+ in a 0.0133 M Na2CO3–0.0200 M NaHCO3 buffer solution was measured up to 1500 kg cm−2 (M=mol dm−3). The activation volume (ΔV\eweq) was found to be 33.4 ml mol−1. This value is consistent with that expected from the Dcb mechanism.
INDO-UHF-CI Calculations of the Electronic Structure of Formaldehyde–Hydrogen Systems
Authors: Mizutani Kimiko , Izumi Toyoo , Matsumoto Shiro
Published: July 2006

The electronic structures were calculated for the ground and several excited states of systems composed of a formaldehyde molecule and a hydrogen atom at various relative positions by means of an INDO-UHF-CI method, in order to elucidate the hydrogen-abstracting process of excited carbonyl compounds. The results were presented and discussed by means of the adiabatic potential energy curves, by means of configuration analysis using the various states of the non-interacting component species as reference, and by means of electron-density maps. The results showed in a concrete way that the process may proceed through an intermediate charge-transfer state, and the electron-density maps had features suggesting an attractive force acting on the positively charged hydrogen atom.
Effect of the Third Virial Coefficient on the Intensity of Light Scattered by Mixed Aqueous Solution of Poly(vinylpyrrolidone) and Sodium Dodecyl Sulfate
Authors: Nakagaki Masayuki , Shimabayashi Saburo
Published: July 2006

It was found that the reduced intensity of scattered light, Rθ, increases and then decreases with polymer concentration, becoming maximum for a certain concentration of the polymer, when the third virial coefficient, A3, is positive. The theoretical concentration of polymer for the maximum Rθ is (3A3M2)−1⁄2, where M2 is the molecular weight of the polymer. This was observed in the case of the aqueous solution of poly(vinylpyrrolidone) (PVP) mixed with sodium dodecyl sulfate (SDS). In the mixed solution, PVP and SDS form a complex which behaves like a polyelectrolyte with or without a simple salt of low concentration. Such a solution often has higher-order virials. The value of the polymer concentration for the maximum scattered light intensity agreed with the theoretical value.
Intramolecular Catalytic Substitution Reaction of N-(ω)-Bromoalkyl)pyridinium Bromide with Potassium Cyanide
Authors: Yamada Masahide , Sakakibara Tohru , Takamoto Tetsuyoshi , Sudoh Rokuro
Published: July 2006

It was found by means of NMR spectrometric and potentiometric titration technique that the intramolecular catalytic substitution of N-(ω-bromoalkyl)pyridinium bromide with KCN proceeds in the range n=2–6 of methylene chain on the pyridinium salt and the intermolecular substitution in n=7 and 9, and the addition of cyanide anion to the pyridine ring takes place only for n=1.
Active Sites of MoO3 and MoO3–SiO2 Catalysts for Isomerizaiton of Butenes. Characterization by Tracer Study
Authors: Hattori Hideshi , Maruyama Kazumasa , Tanabe Kozo
Published: July 2006

Deuterium atom distribution of butenes in the coisomerization of cis-2-butene d0/d8 over MoO3 and MoO3–SiO2 indicates that the reaction involves intermolecular hydrogen transfer for both catalysts. Butenvs produced over deuterium-exchanged MoO3–SiO2 contain deuterium atoms, those produced over deuterium-exchanged MoO3 none.
Radical Reaction in a Silent Electric Discharge of Ethylene
Authors: Itoh Junichi , Takimoto Kazuto , Tsuda Satoru
Published: July 2006

In the silent electric discharge of ethylene, it was revealed, by studying the effects of various scavengers on the formation of gaseous products, that the radical reaction plays an important role, unlike as in the reaction in radiolysis. Furthermore, the existence of several intermediates was directly or indirectly demonstrated by using an ESR technique and by adding iodine as a radical scavenger.
Ligand-Substitution Reaction of Bis(acetylacetonato)copper(II) and Bis(acetylacetonato)zinc(II) with 2-(2-Pyridyl)benzimidazole
Authors: Kondo Michio
Published: July 2006

The reaction of bis(acetylacetonato)copper(II) with 2-(2-pyridyl)benzimidazole (1) in ethanol was studied by means of absorption, fluorescence, and 1H NMR spectroscopies, and it was found that one of the acetylacetonate anions in the complex is replaced by the anion of 1. Bis(acetylacetonato)zinc(II) reacts with 1 in a similar manner. Neither acetylacetonate reacts with 2-(3-pyridyl)- or 2-(4-pyridyl)benzimidazole.
Vilsmeier Reaction of Phenols. I. Synthesis of Aryl Formates
Authors: Morimura Syoji , Horiuchi Hideo , Murayama Keisuke
Published: July 2006

The reaction of phenol and o-t-butylphenols with N,N-dimethylformamide–phosphoryl chloride complex in dimethylformamide afforded the corresponding formates in fairly good yields. The scope and limitation of o-formylation of highly sterically hindered phenols with the complex were also examined.
A New Synthesis of 4-Methoxy-6-valeryl-5,6-dihydro-2-pyrone
Authors: Takeda Akira , Amano Eiichiro , Tsuboi Sadao
Published: July 2006

The reaction of ethyl 2-acetoxy-3-oxoheptanoate with γ-bromo-β-methoxy-cis-crotonate in the presence of sodium ethoxide afforded diethyl 3-methoxy-5-hydroxy-5-valeryl-2-hexenedioate (7) in 65% yield. Treatment of 7 with a dilute aqueous NaOH in acetone gave (±)-4-methoxy-6-valeryl-5,6-dihydro-2-pyrone, a key intermediate leading to pestalotin, in 41% yield.
Mono S-Acylated 1,8-Naphthalenedithiol. Isolation and Characterization of Tetrahedral Intermediate in the Intramolecular Acyl Transfer Reaction
Authors: Takagi Makoto , Ishihara Ryoji , Matsuda Tsutomu
Published: July 2006

The tetrahedral intermediate in the intramolecular acyl transfer reaction of mono-S-acylated 1,8-naphthalenedithiol was found to be sufficiently stable to allow isolation or direct characterization by spectroscopy. Formation of carbenium ion from the intermediate is suggested in sulfuric acid.
Utilizing Emulsification in the Synthesis of Dihydro-exo-dicyclopehtadienyl Ethers and Their Esters
Authors: Hatano Akira , Iwase Yoshiyuki
Published: July 2006

Alcohols and carboxylic acids were subjected to an addition reaction with dicyclopentadiene, using dodecylbenzenesulfonic acid both as the emulsifying agent and the acid catalyst. Dihydro-exo-dicyclopentadienyl ethers and their esters were syntheized in good yields and found to be free of undesirable side reactions.
Isolated Molecule Approach to the Orbital Study of Chemical Reactions. I. Bimolecular Nucleophilic Substitution
Authors: Fujimoto Hiroshi , Kosugi Nobuhiro
Published: July 2006

A method of analyzing chemical interactions between two systems is presented and applied to the bimolecular nucleophilic substitution of methylfluoride by fluoride ion. In order to get a clear insight into the mechanisms of chemical interactions, the interacting system has been represented by a combination of various electron configurations of the reactants involved. The matrix elements necessary for the configuration interaction have been obtained by transforming the MO’s of the isolated reactants into a set of orthogonalized functions. The change in the energy and the redistribution of the electrons due to the interaction in the reaction have been calculated by the use of the ab initio (STO-3G) MO’s and have been divided into the Coulomb, exchange, delocalization, and polarization interactions. A comparison of the results with the results of the SCF CI calculations of the composite system has shown the utility of the method in studying weak and moderately strong interactions between two systems.
Switching in Copper-Phthalocyanine Films
Authors: Sadaoka Yoshihiko , Sakai Yoshiro
Published: July 2006

Bistable switching between two impedance states was observed in copper-phthalocyanine films. The turn-on can be interpreted in terms of the steady thermal breakdown model. The stable high conductivity in the on-state is attributed to the partly carbonized copper-phthalocyanine which was formed by Joule heating along the filamentary paths. The J-V characteristic in the off-state and the threshold-field strength were found to be expressed as J∝V6|d3.8 and Eth∝1|d0.46 respectively.
The Dimorphism and Electronic and Vibrational Spectra of 2-Anilino-1,4-naphthoquinones
Authors: Matsunaga Yoshio , Miyajima Nobuhiko , Togashi Atushi
Published: July 2006

Dimorphic forms were isolated for over ten derivatives of 2-anilino-1,4-naphthoquinone, 2-anilino-3-chloro-1,4-naphthoquinone, and 2-anilino-3-bromo-1,4-naphthoquinone carrying substituents on the phenyl ring. One of the two forms exhibits a relatively sharp vibrational band near 3300 cm−1, the other, a relatively broad band at a lower wave number. The spectra in the region from 700 to 1700 cm−1 are often markedly different from each other. In several instances, the two forms are differently colored. This difference is attributed to the appearance of, or a change in the intensity of, an intermolecular charge-transfer absorption band. Not only the dimorphic forms, but also most of the derivatives examined, could be classified into two groups on the basis of the location and the sharpness of the vibrational band appearing in the region from 3150 to 3350 cm−1.
Shock Tube Study of the H–D Exchange Reaction between Acetylene and Deuterium
Authors: Ogura Hiroo
Published: July 2006

H–D exchange reaction between acetylene and deuterium has been investigated in a single-pulse shock tube in the temperature range 1200–1500 K. Empirically, in the C2HD appearance the order with respect to acetylene was 0.25±0.09, and that with respect to deuterium 1.14±0.15. The rate constant of 1.39 th order for the C2HD increase was obtained as; k(cm1.17 mol−0.39 s−1)=(24.4±7.5)×1011exp((−51200±2400)⁄RT). The isotopic distributions of acetylene and hydrogen as determined by mass spectrometry suggest that C2D2 and H2 are formed by the subsequent reactions of C2HD and HD, respectively. A free-radical chain mechanism initiated by the same bimolecular reaction of acetylene, viz. 2C2H2→C4H3+H, as in the pyrolysis and hydrogenation of acetylene was proposed. A steady-state treatment of the proposed mechanism shows that the empirical rate and concentration dependence of the C2HD increase are in line with those of the steady-state rate.
The Transition to Detonation from Deflagration in Ethylene–Oxygen Systems
Authors: Inomata Tadaaki , Suzuki Momotaro
Published: July 2006

The flames of ethylene and oxygen mixtures (initial pressure, 50–500 mmHg, and ethylene content, 20–40%) were studied, especially for the transition to detonation from deflagration. The flames may roughly be divided into four groups: A, a flame without any shock wave generation; B, a flame with a shock wave generation; C, a flame with many shock waves and much turbulence of the flame, and finally D, the detonation produced by the collision of a flame and a reflected shock wave at the bottom of the tube. The flame transit to detonation from deflagration is a linear relation between the velocities of the flames at the point of detonation and DID, or the distance from the point of ignition to the detonation for all the sorts of flames given above, in spite of several apparent differences.
The Molecular Structure of μ-Carbonyl-di-μ-diphenylmethylene-bis(π-cyclopentadienylrhodium), [(π-C5H5)2Rh2{C(C6H5)2}2(CO)]
Authors: Ueda Hiroshi , Kai Yasushi , Yasuoka Noritake , Kasai Nobutami
Published: July 2006

The molecular structure of [(π-C5H5)2Rh2{C(C6H5)2}2(CO)] has been determined from three-dimensional X-ray diffraction data (R=0.040 for 2394 reflections). The crystal belongs to the monoclinic system, space group A2/a, with four formula units in a cell of dimensions: a=19.967(5), b=10.343(1), c=16.526(4) Å, and β=123.05(2)°. The molecule has C2 symmetry: the two-fold axis passes through the bridge carbonyl group, being perpendicular to the Rh–Rh bond (Rh–Rh=2.548(1) Å). The diphenylcarbene moieties bridge between rhodium atoms. The planar cyclopentadienyl rings lie 1.94 Å from the nearest rhodium atom and exihibit the usual π-bonded geometry.
The Synthesis of Dimethyl dl-3-Ethyl-4-methyl-1,2-cyclopentanedicarboxylates
Authors: Ito Shosuke , Hirata Yoshimasa
Published: July 2006

The four 3,4-cis-stereoisomers of dimethyl dl-3-ethyl-4-methyl-1,2-cyclopentanedicarboxylates (1a, 1b, 1c, and 1d) have been synthesized and their configurations established. A comparison of the spectral data and the GLC behaviors has shown that the corresponding ester, one of the key degradation products of ikarugamycin, has the r-1, t-2, c-3, c-4-configuration (1a). The r-1, t-2, c-3, t-4-stereoisomer (1f) has also been prepared.
The Isotope Effect on the Quenching of the Cadmium Triplet State by Methanol
Authors: Tsunashima Shigeru , Morita Kuniko , Sato Shin
Published: July 2006

The isotope effect on the Cd-photosensitized emission of methanol has been investigated using CH3OH, CH3OD, CD3OH, and CD3OD. The relative quenching efficiencies for the 326.1 nm resonance line were 1 : 0.3 : 0 .9 : 0.3 in the order of CH3OH, CH3OD, CD3OH, and CD3OD. The emission intensities from the intermediate complex between an excited cadmium and methanol were also measured. The band-shape was not affected by the substitution of D atoms. The intensity ratio was 1 : 3.1 : 1.1 : 3.1 in the order of CH3OH, CH3OD, CD3OH, and CD3OD, when the incomplete quenching was corrected. These results were explained by the following quenching processes:

Cd^*+CH_3OH & →Cd···H···OCH_3

&→Cd···O<_CH_3^H

where Cd* represents Cd(3P1) and/or Cd(3P0). The D/H kinetic isotope effect on the former process was estimated to be 0.3
A Temperature-Jump Study of the Formation Reactions of Nickel(II)–Pyridine Complexes in Aqueous Solutions
Authors: Tamura Kiyoshi , Harada Shoji , Yasunaga Tatsuya
Published: July 2006

A temperature-jump study reveals two relaxation phenomena in aqueous nickel (II)–pyridine solutions. One is observed in a metal-rich and low-concentration system, while the other is found only in a ligand-rich and high-concentration system. The relaxation processes are ascribed to the complex formation reactions:

Ni^2++py\oversetk_1\undersetk_-1\ightleftharpoonsNi(py)^2+ and Ni(py)_2^2++py\oversetk_3\undersetk_-3\ightleftharpoonsNi(py)_3^2+

The rate constants reported are: 3.6×103 M−1 s−1 for k1 and k3, 37 s−1 for k−1 and 760 s−1 for k−3, at 25 °C. The effect of the coordinated pyridine molecules on the reactivity of the metal is discussed.
The Effect of a Solvent on the Carbonylation of Methanol Catalyzed by Rhodium Complexes in the Presence of Methyl Iodide
Authors: Matsumoto Toshio , Mori Kunio , Mizoroki Tsutomu , Ozaki Atsumu
Published: July 2006

In the synthesis of acetic acid by the carbonylation of methanol catalyzed by RhCl3·3H2O or Rh2Cl2(CO)4in the presence of methyl iodide, it was found that ketone solvents, such as acetophenone and benzophenone, keep both the catalytic activity and selectivity high, even at an elevated temperature. The kinetic results in acetophenone are in agreement with the mechanism proposed by Paulik and Roth. The effect of the ketone solvent was discussed by taking account of the competitive oxidative addition of hydrogen iodide with methyl iodide.
Studies of Peptide Antibiotics. XXXVI. Synthesis and Biological Activity of [5,5′-Leucine]-gramicidin S
Authors: Abe Okitoshi , Utsumi Yoko , Izumiya Nobuo
Published: July 2006

An analog of gramicidin S, in which 5,5′-proline residues were replaced by leucine, was prepared in order to investigate the effect of the introduction of hydrophobic side groups on the antibacterial activity and on the conformation. Also the solubility problems encountered during the synthesis of this analog are described. No significant effect was observed on the cyclization reaction by the replacement of 5,5′-proline to leucine residues. This analog exhibited comparable biological activity and the similar conformation to the natural gramicidin S. These studies suggested that the imino groups of 5,5′-proline residues have no significant roles on both antibacterial activity and conformation of this antibiotic.
The Photobromination of β-Styrenesulfonamides and Syntheses of 2-Arylacetylene-1-sulfonamides
Authors: Hasegawa Kiyoshi , Hirooka Syuzi , Kawahara Hiroshi , Tanaka Atsushi , Nomura Masahiro , Hori Yutaka
Published: July 2006

The photobromination of trans-β-styrenesulfonamides in acetic acid at 16–18 °C gave about 75 : 25 mixtures of threo (cis adducts)- and erythro-1,2-dibromo-2-arylethane-1-sulfonamides (trans adducts). A similar photobromination of cis-β-styrenesulfonamide afforded a 33 : 67 mixture of the threo (trans adduct)- and the erthro-dibromides (cis adduct). The diastereomers could be separated by fractional recrystallization. The cis adducts were shown to be formed neither by secondary isomerization nor by (presumably) ionic addition. The trans dehydrobromination of the threo- and the erythro-dibromides with Et3N gave (Z)- and (E)-β-bromo-β-styrenesulfonamides respectively, which underwent further facile dehydrobromination with aqueous 1 M NaOH at 45–50 °C to afford 2-arylacetylene-1-sulfonamides. They were also prepared from (Z)-α-chloro-β-styrenesulfonamide by an analogous procedure.
Diphosphine–Rhodium Complex-Catalyzed Hydroformylation of α,β-Unsaturated Esters
Authors: Tanaka Masato , Hayashi Teruyuki , Ogata Ikuei
Published: July 2006

The product distribution in the hydroformylation of α,β-unsaturated esters (ethyl acrylate, methyl methacrylate, methyl crotonate, and methyl tiglate) catalyzed by Rh2Cl2(CO)4 was studied at 150 °C under 100 atm of synthesis gas (CO/H2=1/1) in the absence or presence of various additional phosphorus ligands. In order to attain a high selectivity of α-formylation (>80%), the addition of shorter methylene-chained diphosphines (R2P(CH2)nPR2, R=phenyl or cyclohexyl, n=2–4) to the reaction system was essential, while the use of Rh2Cl2(CO)4 alone or in combination with triphenylphosphine or a longer diphosphine, Ph2P(CH2)5PPh2, resulted in a very low α-selectivity. The effects of the reaction variables on the product distribution were also examined for acrylate and methacrylate using Ph2P(CH2)4PPh2 and Ph2P(CH2)2PPh2, respectively, as additional ligands.
Syntheses of 4′-Deoxykanamycin and 4′-Deoxykanamycin B
Authors: Miyake Toshiaki , Tsuchiya Tsutomu , Umezawa Sumio , Umezawa Hamao
Published: July 2006

4′-Deoxykanamycin (9) was prepared from kanamycin via  N-benzyloxycarbonylation, 4″,6″-O-cyclohexylidenation, selective benzoylation at 2′,3′, and 2″-hydroxyl groups, 4′-O-mesylation, 4′-iodination, 4′-hydrogenation, and removal of the protective groups. 4′-Deoxykanamycin B (19) was analogously prepared from kanamycin B. 4′-O-Tosyl derivative of kanamycin B was also led to 19. Selective formylation of the 3′-hydroxyl group of a protected kanamycin B derivative with N,N-dimethylformamide-tosyl chloride followed by mesylation of the unstable 3′-O-formyl derivative also led to 4′-deoxykanamycin B. Throughout the syntheses, the 4′-hydroxyl group of the protected kanamycins was found to be least reactive for benzoylation among the 2′,3′,4′, and 2″-hydroxyl groups. The 13C NMR spectrum of 9 was also measured. It was concluded that 4′-deoxygenation of antibiotics structurally related to kanamycin caused the resonances of 13C-6′ downfield shift.
The Reaction of Nucleophilic Reagents at the β-Position of 3-Bromo-4-nitropyridine N-Oxides
Authors: Matsumura Eizo , Ariga Masahiro
Published: July 2006

The reactions of 3-bromo-4-nitro-2-R1-6-R2-5-X-pyridine N-oxides (1a:R1=H, R2=Me, X=H; 1b:R1=R2=Me, X=H; 1c: R1=R2=H, X=Br) with diethyl sodiomalonate, ethyl sodiocyanoacetate, and ethyl sodioacetoacetate have been carried out. The treatment of 1a, 1b, and 1c with diethyl sodiomalonate gives 3-[bis(ethoxycarbonyl)methyl]-4-nitro-2-R1-6-R2-5-X-pyridine N-oxides (2a, 2b, and 2c) and 4-[bis(ethoxycarbonyl)methyl]-3,5-dibromopyridine N-oxides (3c). With ethyl sodiocyanoacetate, 3-[cyano(ethoxycarbonyl)methyl]-4-nitro-2-R1-6-R2-pyridine N-oxides (4a and 4b) and 4-[cyano(ethoxycarbonyl)methyl]-3,5-dibromopyridine N-oxide (5c) are obtained. With ethyl sodioacetoacetate, 1a and 1c give 3-[acetyl(ethoxycarbonyl)methyl]-6-methyl-4-nitropyridine N-oxide (6a) and/or 3-ethoxycarbonyl-2-methyl-6-R1-7-X-furo[3,2-c]pyridine N-oxides (7a and 7c), but 1b is unaffected by ethyl sodioacetoacetate under the given conditions. The electronic and steric effects of methyl and bromo groups for the reactions are discussed.
Synthesis of Streptolidine Lactam, a Guanidine-contain ing Amino-acid Lactam Moiety of Streptothricin Antibiotic Group
Authors: Kinoshita Mitsuhiro , Suzuki Yoshiharu
Published: July 2006

Streptolidine lactam (3) present in streptothricin antibiotics was stereospecifically synthesized. 3,4-Anhydro-1,2 : 5,6-di-O-isopropylidene-d-iditol (4) was converted into the 3,4-bis(benzyloxycarbonylamino)-3,4-dideoxy-d-mannitol derivative 7  via the 3,4-diazido-3,4-dideoxy-d-mannitol derivative 6. De-O-protection of 7 followed by two-stage oxidation with periodate-bromine afforded 2,3-bis(benzyloxycarbonylamino)-2,3-dideoxy-d-arabono-1,4-lactone (8), which was transformed into the azide lactone 9. Selective hydrogenolysis of 9 with Raney Ni gave the N-protected amino sugar lactam 10. O-Tetrahydropyranylation of 10 followed by hydrogenolysis afforded the O-protected amino sugar lactam 12. Treatment of 12 with cyanogen bromide in water gave the O-tetrahydropyranylated streptolidine lactam 13, which on mild acid hydrolysis afforded 3 (hydrochloride). The amino sugar lactam 14 obtained by hydrogenolysis of 9 with palladium black was also treated with cyanogen bromide to yield 3 (hydrobromide). Acid hydrolysis of 3 gave streptolidine (2) (dihydrochloride) identical with that derived from the antibiotics.
Studies on Separation of Amino Acids and Related Compounds. VIII. Preparative Separation of Isomeric l-Aspartyl-l-phenylalanine Methyl Esters and Related Dipeptide Esters by Ion-Exchange Chromatography
Authors: Yasutake Akira , Aoyagi Haruhiko , Izumiya Nobuo
Published: July 2006

Authentic peptides, α- and ω-isomers of l-aspartyl (or l-glutamyl)-l-phenylalanine (or l-tyrosine) methyl ester, were synthesized by conventional methods. Among these eight peptides, α-l-glutamyl-l-phenylalanine methyl ester showed the tendency to convert to the corresponding dipeptide anhydride even under mild conditions. The experiments on a small column of Dowex 50 cation exchange resin were carried out with a model mixture composed of the α- and ω-isomers, and the optimum conditions for the complete separation of both isomers were determined. A synthetic mixture composed of the α- and ω-isomers was prepared readily through the coupling of benzyloxycarbonyl-l-aspartic acid (or glutamic acid) anhydride with l-phenylalanine (or l-tyrosine) methyl ester and subsequent hydrogenation. The synthetic mixture was separated by the use of a large ion exchange column and each isomer was obtained in a good yield.