bluuebunny/crossref_metadata_2025_split huggingface dataset:
Racemization of Optically Active Aromatic N-Acetylamino Acids and Asymmetric Transformation of N-Acetyl-2-(4-hydroxyphenyl)glycine via Salt Formation with Optically Active α-Methylbenzylamine
Authors: Shiraiwa Tadashi , Sakata Shinji , Natsuyama Hisashi , Fujishima Keiko , Miyazaki Hideya , Kubo Satoru , Nitta Tomohisa , Kurokawa Hidemoto 
Published: July 2006

Abstract
The racemization rates of N-acetyl-(S)-tyrosine, N-acetyl-(S)-phenylalanine, N-acetyl-(R)-2-(4-hydroxyphenyl)glycine [(R)-AcHpg], N-acetyl-(R)-2-phenylglycine, and N-acetyl-(S)-alanine were measured by use of (RS)-α-methylbenzylamine [(RS)-MBA] as a base-catalyst. The first-order rate constant for racemization tended to increase with an increase in the polar substituent constant of the N-acetylamino acid side chain. The racemization appeared to be subject to the inductive effect by the side chain. An asymmetric transformation of (RS)-AcHpg by using (R)-MBA, based on the result of racemization, gave an optically pure salt of (R)-AcHpg with (R)-MBA by successive use of the filtrate as the solvent. Optically pure (R)-2-(4-hydroxyphenyl)glycine [(R)-Hpg] was separated from the salt in 87–90% yield based on the starting (RS)-AcHpg. In addition, the asymmetric transformation of (R)-AcHpg was achieved by using (S)-MBA to give optically pure (S)-Hpg in 80% yield after purification of the salt of (S)-AcHpg with (S)-MBA followed by hydrolysis.
Efficient Synthesis of 2-Vinyl-γ-butyrolactones and 2-Vinyl-γ-butyrolactams by Palladium-Catalyzed Decarboxylative Carbonylation
Authors: Bando Takashi , Tanaka Shuji , Fugami Keigo , Yoshida Zen-ichi , Tamaru Yoshinao 
Published: July 2006

Abstract
4-Vinyl-1,3-dioxan-2-ones (cyclic carbonates) undergo decarboxylation-carbonylation by the catalysis of Pd(0) species under CO (in most cases, 1 atm) to provide 2-vinyl-γ-butyrolactones in good yields. The course of the reaction of 6-vinyltetrahydro-2H-1,3-oxazin-2-ones (cyclic carbamates) depends on the substituent on the nitrogen atom. When it is H or Ts (and COPh), 2-vinyl-γ-butyrolactams or 6-amino-3-hexenoic acid esters are obtained. Cyclic N-benzylcarbamates are unreactive. trans-2,3-Disubstituted lactones and lactams arise stereoselectively from carbonates and carbamates, irrespective of their stereochemistry, respectively.
A Novel Configuration-Controlled Stereoselectivity in Enol Silylation of Ketones. Stereochemistry of Amine-Promoted Enol Silylation of Meso and Racemic α,α′-Dichloro Ketones and of Ketonization of the Resultant Enol Silyl Ethers
Authors: Shimizu Nobujiro , Matsuno Sho-ichiro , Tanaka Masayuki , Tsuno Yuho 
Published: July 2006

Abstract
Stereochemistry in amine-promoted enol trimethylsilylation of meso- and dl-α,α′-dichloro ketones, RCHClCOCHClR (1a; R = Me and 1b; R = i-Pr), and in ketonization of the resultant enol silyl ethers (2a and 2b) has been studied. The Et3N-promoted silylation of 1 in benzene shows a marked diastereoselectivity; the racemic isomer exhibits 84% and 98% (E)-selectivities for 1a and 1b, while the meso isomer, 97% and 98% (Z)-selectivities respectively. Both stereo- and diastereo-selectivities markedly depend upon solvent polarity and base strength. For example, both meso- and dl-1a showed small (Z)-selectivities in DMF. The diastereoselectivity markedly decreased with increasing base strength; both 1a and 1b exclusively gave the (E)-isomer of 2 irrespective of the configuration of the ketone when treated with lithium diisopropylamide in the presence of chlorotrimethylsilane at −78 °C. The ketonization of 2a and 2b was also diastereoselective in the direction opposite that observed in the forward reaction; the (E)-isomer predominantly gave the meso ketone (24% d.e.), while the (Z)-isomer, the racemic ketone (ca. 70% d.e.) upon protonation with concd hydrochloric acid in THF.
Total Synthesis of Siastatin B and Its Enantiomer Using Carbohydrate as a Chiral Educt
Authors: Nishimura Yoshio , Wang When-mei , Kudo Toshiaki , Kondo Shinichi 
Published: July 2006

Abstract
The enantioselective synthesis of siastatin B, an inhibitor of neuraminidase and its antipode from d-ribono-γ-lactone has stereospecifically been achieved. The total synthesis elucidated the absolute configuration of siastatin B as (3S,4S,5R,6R)-6-acetamido-4,5-dihydroxy-3-piperidinecarboxylic acid.
FeS2-Catalyzed Hydrocracking of Di(1-naphthyl)methane. Efffects of Hydrogen Pressure, Catalyst Feed and Reaction Temperature, and Kinetic Study
Authors: Wei Xian-Yong , Ogata Eisuke , Niki Etsuo 
Published: July 2006

Abstract
Hydrocracking of di(1-naphthyl)methane (DNM) in the temperature range of 150–300 °C was studied. In the presence of FeS2 and pressurized hydrogen, DNM hydrocracking took place over 175 °C. FeS2 selectively catalyzed the cleavage of C–C linkage in DNM to give 1-methylnaphthalene and naphthalene. The rate for DNM hydrocracking strongly depended on hydrogen pressure, FeS2 feed and reaction temperature. Kinetic study indicates that DNM hydrocracking in the temperature range of 200–300 °C could be considered as a first order reaction. Under the reaction condition (DNM 7.5 mmol, decalin 30 ml, FeS2 0.5 g, sulfur 0.05 g, initial hydrogen pressure 10 MPa), the activation energy and frequency factor for DNM hydrocracking were 19 kcal mol−1 and 5.3 × 107 h−1, respectively.
Sequence Dependent Cyclization-Cleavage of Dipeptides from the Oxime Resin and Its Prevention
Authors: Nishino Norikazu , Xu Ming , Mihara Hisakazu , Fujimoto Tsutomu 
Published: July 2006

Abstract
The rates of cyclization-cleavage of dipeptides with various sequences assembled on the Kaiser’s oxime resin were determined. cyclo(–Ala–Ala–) was liberated from the H–Ala–Ala–oxime resin with the apparent first-order rate constant, kapp, 1.8 × 10−1 min−1 under basic conditions. While cyclo(–Ala–Pro–) was much more rapidly formed (kapp = 1.5 min−1) from the H–Ala–Pro–resin, cyclo(–Ala–Val–) was produced with kapp, 2.2 × 10−2 and 5.5 × 10−2 min−1 from H–Ala–Val–resin and H–Val–Ala–resin, respectively. During the coupling reaction for tripeptides by the dicyclohexylcarbodiimide/1-hydroxybenzotriazole or the symmetrical anhydride method was observed significant loss of dipeptides by cyclization, which was successfully prevented by the [(benzotriazol-1-yl)oxy]tris(dimethylamino)phosphonium hexafluorophosphate (BOP) method except in the case of H–Ala–Pro–resin. In consequence of elucidating the defect and describing the method for the prevention, the reliability of the oxime resin was increased to be widely used in the practical synthesis of protected peptides.
Preparation and Characterization of Iridium(III) Complexes Containing (2-Aminoethyl)dimethylphosphine (edmp) or (2-Aminoethyl)diphenylphosphine (edpp). Structures of fac-[Ir(edmp)3]Cl3·5H2O and trans(Cl,Cl),cis(P,P)-[IrCl2(edpp)2]BF4 and Comparisons of Their Properties with Those of the Cobalt(III) and Rhodium(III) Analogs
Authors: Suzuki Takayoshi , Rude Mette , Simonsen Kim P , Morooka Mitsuo , Tanaka Hitoshi , Ohba Shigeru , Galsbøl Frode , Fujita Junnosuke 
Published: July 2006

Abstract
The iridium(III) complexes containing (2-aminoethyl)dimethylphosphine (edmp) or (2-aminoethyl)diphenylphosphine (edpp) were prepared. Crystal structures of fac-[Ir(edmp)3]Cl3·5H2O (2), trans(Cl,Cl),cis(P,P)-[IrCl2(edpp)2]BF4 (3), and Δ(lel3)- and Λ(ob3)-[Ir(R,R-chxn)3](NO3)3·3H2O (4 and 5; chxn = trans-1,2-cyclohexanediamine) were determined by single-crystal X-ray diffraction. Crystal data and final R values are: for 2, FW = 703.7, triclinic, , a = 11.718(2), b = 13.199(1), c = 9.482(1) Å, α = 91.44(1), β = 105.86(1), γ = 90.53(1)°, V = 1410.0(2) Å3, Dx = 1.66 Mg m−3, and Z = 2, R = 0.039 for 5410 reflections. For 3, FW = 808.5, triclinic, , a = 11.465(1), b = 13.694(1), c = 10.049(1) Å, α = 94.764(6), β = 92.197(8), γ = 102.807(8)°, V = 1530.5(2) Å3, Dx = 1.75 Mg m−3, and Z = 2, R = 0.035 for 5978 reflections. For 4, FW = 774.9, hexagonal, P63, a = 13.005(1), c = 10.221(2) Å, V = 1497.1(3) Å3, Dm = 1.71(2), Dx = 1.72 Mg m−3, and Z = 2, R = 0.020 for 1063 reflections. For 5, hexagonal, FW = 774.9, P63, a = 13.359(1), c = 9.848(2) Å, V = 1522.0(3) Å3, Dm = 1.70(2), Dx = 1.69Mg m−3, and Z = 2, R = 0.015 for 1105 reflections. The average Ir–N bond length of 2.167(6) Å in 2 is longer by 0.077(6) Å than those in 4 and 5. The structural data of the corresponding cobalt(III) and rhodium(III) complexes show that the order of the strength of the trans influence of the –PMe2 group in edmp is CoIII &lt; IrIII &lt; RhIII. In 3, the elongation of the metal–nitrogen bond length by the trans influence of the –PPh2 group in edpp is smaller than that of the –PMe2 group in 2, and the elongation is nearly the same as those in the corresponding cobalt(III) and rhodium(III) complexes. The absorption spectra of the two series of complexes, fac-[M(edmp)3]3+ and trans(Cl,Cl),cis(P,P)-[MCl2(edpp)2]+ (M = CoIII, RhIII, and IrIII) are compared and Shimura’s spectrochemical parameters for iridium(III) are discussed.
Suppression of Methemoglobin Formation by Glutathione in a Concentrated Hemoglobin Solution and in a Hemoglobin-Vesicle
Authors: Sakai Hiromi , Takeoka Shinji , Seino Yuriko , Tsuchida Eishun 
Published: July 2006

Abstract
The suppression of methemoglobin (metHb) formation by glutathione (GSH) is difficult because GSH is oxidized not only by the reduction of metHb, but also by oxygen to generate active oxygen species, such as superoxide (O2−•) and hydrogen peroxide (H2O2), which contribute to metHb formation. An effective nonenzymatic reduction of metHb was achieved at a high concentration of Hb (40 wt%, 2.48 × 10−2 M subunits (1 M = 1 mol dm−3)) because the reduction of metHb was accelerated, and at a low partial pressure of oxygen (pO2 = 40 Torr (1 Torr = 133.322 Pa)) because the oxidation of GSH was effectively suppressed. Hb-vesicles, which encapsulate concentrated Hb (40 wt%, 2.48 × 10−2 M subunits), transport oxygen in the blood stream at relatively low pO2 (110 Torr in artery and 40 Torr in venous, 58 Torr in average). The rate of metHb formation in Hb-vesicles was effectively decreased from 3.8 × 10−7 to 1.6 × 10−7 M s−1 by coencapsulating GSH at 58 Torr.
Synthesis of β-Hydroxy Nitriles via Indium-Induced Coupling of Bromoacetonitrile with Carbonyl Compounds
Authors: Araki Shuki , Yamada Masafumi , Butsugan Yasuo 
Published: July 2006

Abstract
The organoindium reagent, derived from indium metal and bromoacetonitrile, reacted with carbonyl compounds in the presence of chlorotrimethylsilane to give, after hydrolysis, β-hydroxy nitriles. The coupling proceeded with high chemoselectivity, though the diastereoselectivity was low.
Friedel–Crafts Transannular Alkylation of Aromatic Compounds with Nonconjugated Cyclic Dienes
Authors: Tateiwa Jun-ichi , Aoki Ikuo , Suama Masakazu , Uemura Sakae 
Published: July 2006

Abstract
Friedel–Crafts transannular alkylation of aromatic compounds with nonconjugated cyclic dienes such as (Z,Z)-1,5-cyclooctadiene (1,5-COD), bicyclo[2.2.1]hepta-2,5-diene (norbornadiene), and 1,4-cyclohexadiene was studied. The five to six isomers of phenylbicyclooctanes were produced in the alkylation of benzene with 1,5-COD in the presence of either Brönsted acid or Lewis acid as the catalyst. The isomer ratios depended on the nature and the amount of catalyst, the reaction time, and the reaction temperature. In the AlCl3-catalyzed reaction of 1,5-COD with toluene it was disclosed that an initial para-rich isomer distribution of the products shifted to a meta-rich one in a prolonged reaction. With norbornadiene a transannular cyclized compounds was obtained, while with 1,4-cyclohexadiene no transannular cyclization was observed.
Conformation of Methyl trans-3-Arylpropenoates in Triplet States and Their Reactivities
Authors: Nakabayashi Kenichi , Ohashi Kyouko , Takamuku Setsuo 
Published: July 2006

Abstract
The photochemical cis–trans isomerization and cycloaddition of methyl trans-3-arylpropenoates in benzene via triplet state were investigated. The results of triplet sensitized cis–trans isomerization clearly indicated that the most stable conformation for methyl 3-phenylpropenoate is a twisted form while methyl 3-(4-biphenylyl)propenoate and methyl 3-(2-naphthyl)propenoate are in the equilibrium states between the trans-planar triplet and twisted form. Photoirradiation of these methyl 3-arylpropenoates in relatively high concentrated benzene solutions gave two isomeric cyclodimers of dimethyl t-3, t-4-diaryl-r-1, c-2-cyclobutanedicarboxylate and dimethyl c-3, t-4-diaryl-r-1, t-2-cyclobutanedicarboxylate as main products. The reactivities of cycloaddition are relatively high where the most stable conformation is twisted form.
Photooxygenation of Diphenanthro[5,4,3-abcd : 5′,4′,3′-jklm]perylene
Authors: Ohshima Shigeru , Uchida Akira , Horiguchi Seiji , Suzuki Atsushi , Fujisawa Shoji , Oonishi Isao 
Published: July 2006

Abstract
The photooxygenation of diphenanthro[5,4,3-abcd : 5′,4′,3′-jklm]perylene (DPP) due to visible-light irradiation was investigated by measuring the absorption spectra and applying semi-empirical molecular orbital methods. It was shown theoretically that molecular oxygen attaches to the central benzene ring of DPP to give an endo-peroxide. The oxygen gradually detaches from the endo-peroxide at room temperature, reproducing DPP. The activation energies for both the reactions of oxygen attachment and detachment were determined based on the temperature dependences of the reaction rates in benzene; 10.0 ± 5.5 kJ mol−1 for the attachment reaction and 83.8 ± 2.5 kJ mol−1 for the detachment reaction.
An Extractive Spectrophotometric Method of Determination of Molybdenum(VI) Using 3-Hydroxy-2-(4-methoxyphenyl)-6-methyl-4H-chromen-4-one
Authors: Dass Rameshwar , Mehta Jaswant Ram 
Published: July 2006

Abstract
3-Hydroxy-2-(4-methoxyphenyl)-6-methyl-4H-chromen-4-one (HL) behaved as a sensitive spectrophotometric reagent for molybdenum(VI). The metal ion formed a yellow complex with the reagent in acetic acid medium. The complex was extractable into 1,2-dichloroethane and the absorbance values remained unchanged for more than one week. Spectral data showed the formation of 1 : 2 species with λmax value at 411 nm. Beer’s law was obeyed over the concentration range of 0—2.3 ppm. The molar absorptivity and Sandell’s sensitivity were calculated to be 5.61 × 104 dm3 mol−1 cm−1 and 0.0017 μg Mo cm−2 respectively, at 411 nm. The effect of as many as 41 cations and 28 anions and complexing agents was studied. Out of these only Sn(II), Ce(IV), citrate, oxalate, disodium dihydrogen ethylenediaminetetraacetate, and hydrogen peroxide interfered seriously. For ten replicate determinations of 1 μg Mo cm−3 the standard deviation was 0.008 with a relative mean error of ±0.09%. The method is simple, selective, precise and rapid. It has been applied satisfactorily to the determination of molybdenum in steels, waters and flue dust samples.
Immunochemistry of Lysosomal Storage Disorders
Authors: Parkinson-Lawrence Emma , Fuller Maria , Hopwood John J , Meikle Peter J , Brooks Doug A 
Published: July 2006

Abstract
Background: Lysosomal storage disorders are a group of genetic diseases, each with a broad spectrum of clinical presentation that ranges from attenuated to severe. The immunochemical analysis of patient samples is aimed at several key aspects of patient management, including early detection of the disorder, prediction of clinical severity, determining the most appropriate therapeutic regimen, and monitoring of patients on therapy.
Methods: In this study, we review the current and emerging technology available to achieve these assessments.
Results: Immune assays have direct practical application for the early detection, diagnosis and prognosis of lysosomal storage disorder patients. Multiplexing of these assays may provide a platform to allow newborn screening for multiple lysosomal storage disorders.
Conclusions: We have reviewed the immunochemical techniques available for the analysis of lysosomal storage disorder patient samples and advise that these may be used in conjunction with other technologies for effective patient management.
Standards for Plasma and Serum Proteomics in Early Cancer Detection: A Needs Assessment Report from the National Institute of Standards and Technology-National Cancer Institute Standards, Methods, Assays, Reagents and Technologies Workshop, August 18–19, 2005
Authors: Barker Peter E , Wagner Paul D , Stein Stephen E , Bunk David M , Srivastava Sudhir , Omenn Gilbert S 
Published: July 2006

Abstract
NIST and the National Cancer Institute cosponsored a workshop on August 18–19, 2005, to examine needs for reference materials for early cancer detection. This meeting focused on standards, methods, assays, reagents, and technologies. Needs for plasma and serum proteomics, DNA methylation, and specimen reference collections were discussed, and recommendations from participants were solicited. This report summarizes the discussion and recommendations for proteomics reference materials.
Cell-Free Plasma DNA as a Novel Marker of Aseptic Inflammation Severity Related to Exercise Overtraining
Authors: Fatouros Ioannis G , Destouni Aspasia , Margonis Konstantinos , Jamurtas Athanasios Z , Vrettou Christina , Kouretas Dimitrios , Mastorakos George , Mitrakou Asimina , Taxildaris Kiriakos , Kanavakis Emmanouel , Papassotiriou Ioannis 
Published: July 2006

Abstract
Background: Circulating free plasma DNA is implicated in conditions associated with tissue injury, including exercise-induced inflammation, and thus is a potential marker for athletic overtraining.
Methods: We measured free plasma DNA along with C-reactive protein (CRP), creatine kinase (CK), and uric acid (UA) in 17 recreationally trained men participating in a 12-week resistance training regimen (8 resistance multi-joint exercises selected to stress the entire musculature: bench press, squat, leg press, snatch, hang clean, dead lifts, barbell arm curls, and rowing), consisting of 4 training periods (t1, t2, t3, and t4).
Results: Plasma DNA concentrations increased markedly after t1, t2, and t3 and returned to baseline after t4. There were substantial differences between t2 and t1 and between t3 and t2 plasma DNA concentrations. CRP increased by 300% after t2 and by 400% after t3 (there was no difference between t2 and t3 CRP values) compared with baseline (t0). CK increased only after t3. UA increased after t2 and t3, with a greater increase after t3.
Conclusions: This study demonstrates that, after chronic excessive resistance exercise, plasma DNA concentrations increase in proportion to training load, suggesting that plasma DNA may be a sensitive marker for overtraining-induced inflammation.
Use of Frozen Sera for FT4 Standardization: Investigation by Equilibrium Dialysis Combined with Isotope Dilution-Mass Spectrometry and Immunoassay
Authors: Van Uytfanghe Katleen , Stöckl Dietmar , Ross H Alec , Thienpont Linda M 
Published: July 2006

Abstract
Background: Serum-free thyroxine (FT4) testing is recommended for diagnosis or monitoring of thyroid dysfunction, particularly in cases of hormone binding abnormalities. However, the poor intermethod agreement among commercial FT4 assays suggests a need for standardization with a hierarchically higher measurement procedure. To that purpose, we applied equilibrium dialysis (ED) in combination with isotope dilution-liquid chromatography/tandem mass spectrometry (ID-LC-tandem MS).
Methods: After ED, we collected dialysate into tubes containing [13C6]-T4 for ID and [13C9]-T4 as carrier, purified the samples by solid-phase extraction, and analyzed them with LC/tandem MS. We evaluated the procedure’s analytical performance and tested its suitability for measurement of hypo-, eu-, and hyperthyroid serum FT4 concentrations. We conducted a pilot method comparison study with 3 commercial assays to investigate whether frozen sera could be used for the purpose of FT4 standardization.
Results: The within-run, between-run, and total CVs (inclusive ED) were 3.7%, 4.2%, and 5.6%, respectively (17.7 pmol/L; n = 20). The mean accuracy, estimated from recovery experiments with dialysate and dialysis buffer supplemented at 8.7, 18.7, and 33.5 pmol/L, and from analysis of certified sera gravimetrically diluted to 9.8, 19.2, and 34.8 pmol/L, was 98.0% to 102.8%. The procedure’s limit of detection and limit of quantification were 0.5 and 1.3 pmol/L, respectively. The method comparison demonstrated the suitability of the selected sera for standardization of FT4 assays and confirmed the lack of assay comparability.
Conclusions: We demonstrated that the described ED-ID-LC/tandem MS procedure and the selected type of sera qualify for standardization of FT4 measurements.
Multiple planar coincidences with N-fold symmetry
Authors: Baake Michael , Grimm Uwe 
Published: July 2006

Abstract
Planar coincidence site lattices and modules with N-fold symmetry are well understood in a formulation based on cyclotomic fields, in particular for the class number one case, where they appear as certain principal ideals in the corresponding ring of integers. We extend this approach to multiple coincidences, which apply to triple or multiple junctions. In particular, we give explicit results for spectral, combinatorial and asymptotic properties in terms of Dirichlet series generating functions.
Decagon covering model and equivalent HBS-tiling model
Authors: Gummelt Petra 
Published: July 2006

Abstract
For decagonal Al—Co—Ni quasicrystals, coverings based on a single decagonally shaped columnar 20 Å-cluster as well as tilings of so-called hexagon-, boat- and star-tiles are used to model the atomic structure. We introduce geometrically defined local transformation rules which enable us to replace a covering of overlapping congruent decagons by an equivalent HBS-tiling at the same scale and vice versa. Starting from an obvious one-to-one correspondence in case of idealized, perfect Penrose order, we show that there is a very similar relation also for random decagon coverings with slightly relaxed structure. The proofs given here complete our statements announced in previous work.