bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass-spectrometric Measurement of Activities in Both Solid and Liquid Solutions of the KCl–NaCl System
Authors: Itoh Mitsuru , Sasamoto Tadashi , Sata Toshiyuki 
Published: July 2006

Abstract
The activities of the KCl–NaCl system were mass-spectrometrically determined by the ion-current-ratio method in the temperature range From 793 to 1083 K. As a result, the activities of KCl or NaCl in the solid solution showed greatly positive deviations from Raoult’s law while the liquid solution at 1083 K gave slightly negative values. The heats of mixing in the solid solution were calculated from the temperature dependence of the modified ion-current ratios, [(INa2Cl+/XNaCl2)/(IK2Cl2/XKCl2)]. The excess entropy of mixing in the solid solution was attributed to the change in the vibrational spectrum, and the vibrational contribution to the heat of mixing was evaluated.
Catalytic Activity of V–Sn Oxides for Oxidation Reactions
Authors: Ono Takehiko , Nakagawa Yoshiro , Kubokawa Yutaka 
Published: July 2006

Abstract
The rate of oxidation of C3H6, C2H4, C3H8, and CO has been investigated over V–Sn oxides of various compositions. The rate shows two maxima at V–Sn(V/Sn=2/1) and (1/8) oxides. Comparison between the rate of reduction of the oxides with C3H6 and that of the corresponding catalytic oxidation suggests that the oxygen species responsible for oxidation differs for V–Sn(2/1) and V–Sn(1/8) oxides. The amount of oxygen desorbed in the temperature range 400–530 °C varies with the composition of the V–Sn oxides, showing a maximum at V–Sn(2/1) oxide. With V–Sn(1/8) oxide, little or no oxygen desorption is observed. On the basis of these results together with those of structural studies, it is concluded that the rate maximum with V–Sn(2/1) oxide arises from formation of an amorphous material from which lattice oxygen is easily released, while the rate maximum with V–Sn(1/8) oxide is associated with the presence of V4+ ions dissolved in SnO2.
Photoreaction of N,N′-Dibromo-2,5-piperazinedione
Authors: Sera Akira , Itoh Kuniaki , Yamada Hiroshi , Aoki Ryuichi 
Published: July 2006

Abstract
The photolysis of N,N′-dibromo-2,5-piperazinedione in dichloromethane gave an unstable photoproduct. The alcoholysis of the photoproduct in the presence of a small amount of hydrogen bromide yielded 3,6-diethoxy-2,5-piperazinedione and its alcoholyzed products, ethyl diethoxyacetate, ethyl 2-(diethoxyacetylamino)-2-ethoxyacetate, N-(1-ethoxy-1-ethoxycarbonylmethyl)oxamide, and ethyl N-(diethoxyacetyl)glycinate. The reactions of the photoproduct with other nucleophiles also gave the corresponding substituted 2,5-piperazinediones. The structure of the primary photoproduct was deduced to be 3,6-dibromo-2,5-piperazinedione on the basis of these observations.
Branched-chain Sugars. XXIII. Stereoselectivities in the Addition of Nucleophiles to Several 4-Uloses
Authors: Matsuzawa Masafumi , Sato Ken-ichi , Yasumori Toshio , Yoshimura Juji 
Published: July 2006

Abstract
The stereoselectivities in the 1,2-addition of nucleophiles such as methylmagnesium iodide, vinylmagnesium bromide, and 2-lithio-2-methyl-1,3-dithiane to seven kinds of 4-uloses were examined. The configurations of C-vinyl derivatives obtained were determined from the chemical shifts of α-carbons in 13C-NMR spectra.
Oxidation of Olefins into α-Phenylseleno Carbonyl Compounds. Highly Regioselective anti-Markownikoff Type Oxidation of Allylic Alcohol Derivatives
Authors: Shimizu Makoto , Takeda Ryo , Kuwajima Isao 
Published: July 2006

Abstract
By using (C6H5Se)2–t-BuOOH or (C6H5Se)2–(C6H5SeO)2O system, oxoselenenylation reactions of C=C bonds have been examined with allylic and homoallylic alcohol derivatives, and substituted cyclohexenes, and allyl t-butyldimethylsilyl ethers are found to undergo regioselective conversion into β-siloxy α-phenylseleno carbonyl compounds in high yields.
Absolute Intensity Measurement of the ν4 Band of Fluoroform by the Use of a Tunable Diode-laser Source
Authors: Sofue Susumu , Kawagughi Kentarou , Hirota Eizi , Fujiyama Tsunetake 
Published: July 2006

Abstract
The absolute infrared absorption intensities have been measured for the P35(35) and P36(36) lines, which belong to the ν4 fundamental of fluoroform, by the use of a tunable diode-laser source. The observed intensity, Γ, was 5360+220 cm2 mol−1. This intensity value was compared with that observed by the conventional method.
Effects of Intermolecular Hydrogen-bonding on the Luminescence Properties of Acetophenone, Characterization of Emission States
Authors: Ghoshal Suniti Kumar , Sarkar Susil Kumar , Kastha Gouranga Sundar 
Published: July 2006

Abstract
The effects of intermolecular hydrogen-bond formation by protic solvents on the absorption and luminescence properties of acetophenone have been investigated. It has been concluded from analysis of the T←S0 absorption, phosphorescence excitation spectra and the emission characteristics that the lowest triplet state of acetophenone in its vapor phase and in nonpolar as well as in moderately polar solvents (e.g., ethanol, EPA etc.) is of n-π* character. In rigid polar media, acetophenone exhibits a very weak 1π-π*→S0 fluorescence and a weak 3π-π*→S0 phosphorescence superposed with the principal 3π-π*→S0 emission. A progressive enhancement of both of these emissions with increasing polarity of the solvent has been observed. It is shown that the fluorescence and the dual phosphorescence emissions from acetophenone in rigid polar media arise as a result of decreased efficiencies of the spin-orbit and vibronic coupling interactions due to intermolecular hydrogen-bond formation by the protic solvents.
Oxidation of Copper in Nitrogen Dioxide
Authors: Takasu Yoshio , Tomo-oka Teruhide , Matsuda Yoshiharu 
Published: July 2006

Abstract
Thermal microgravimetry, mass spectrometry, and X-ray diffractometry were used to investigate the ability of NO2 to oxidize copper. NO2 oxidizes a copper plate with formation of oxide film consisting of Cu2O (predominant) and CuO. The oxidation obeys a cubic law, and proceeds faster than in oxygen. An oxidation mechanism is presented on the basis of kinetic and structural data.
Stereochemistry of Friedel-Crafts Alkylation of Benzene with Optically Active 2-Chlorobutane
Authors: Suga Sohei , Segi Masahito , Kitano Kiyoyuki , Masuda Shinji , Nakajima Tadashi 
Published: July 2006

Abstract
The alkylation of benzene with (+)-2-chlorobutane (1) by Lewis acid catalyst gave stereospecifically (−)-2-phenylbutane (2) with inversion of configuration at low temperature for short reaction times. A lowering of the stereospecificity of the reaction was found to be partly due to the racemization of (+)-1 and (−)-2.
Fused Heterocycles. IV. Synthesis of 7-(o-Hydroxyphenyl)-3,5-dimethyl-7,8-dihydro-6H-isoxazolo[4,5-b]azepines
Authors: Malla Reddi Kooturu , Janakirama Rao Citineni , Krishna Murthy Ananthula 
Published: July 2006

Abstract
Michael addition of acetylacetone to 3-methyl-4-nitro-5-(o-hydroxystyryl)isoxazoles gives 4-(o-acetoxyphenyl)-5-(3-methyl-4-nitro-5-isoxazolyl)-2-pentanones (4). Reductive cyclization of 4 with tin(II) chloride and concentrated hydrochloric acid leads to 7-(o-hydroxyphenyl)-3,5-dimethyl-7,8-dihydro-6H-isoxazolo[4,5-b]azepines. The formation of 4 has been rationalized through ortho effect. NMR and mass spectra of products have been discussed.
The Precursors of Phenols Produced in the γ-Radiolysis of Aromatic Hydrocarbons in Liquid Carbon Dioxide
Authors: Karasawa Hidetoshi , Yugeta Rei , Yamaguchi Akira , Sato Shin 
Published: July 2006

Abstract
The γ-ray-induced oxidation of toluene in liquid carbon dioxide has been reinvestigated. In order to discuss the precursors of the main products: three kinds of cresols and benzyl alcohol, 1-butene was used as the scavenger of oxygen atoms. The formation of cresols and benzyl alcohol was well explained by the participation of two precursors: one is oxygen atoms and the other is ionic species, O− or/and CO3− ions. The ratio of the G-value of oxygen atoms to that of the sum of O− and CO3− ions initially formed was estimated to be 4 : 1 for pure liquid carbon dioxide. The spur model previously proposed was applied to explain the formation of O− and CO3− ions.
The Molecular Structures of Thiomethoxymethylbis(triphenylphosphine)-palladium Hexafluorophosphate and Perchlorate at −160 °C
Authors: Miki Kunio , Kai Yasushi , Yasuoka Noritake , Kasai Nobutami 
Published: July 2006

Abstract
The molecular structures of [Pd(CH2SCH3)(PPh3)2]PF6(3a) and [Pd(CH2SCH3)(PPh3)2]ClO4(3B) at −160°C were determined by means of X-ray diffraction. Crystals of both complexes belong to the monoclinic system: 3a, a=11.535(2), b=17.990(4), c=17.754(2) Å and β=101.07(1)°, space group P21/c with Z=4; 3b·CH2Cl2 solvate, a=11.496(5), b=20.872(9), c=15.056(6) Å and β=94.77(4)°, space group P21/n with Z=4. Both structures were solved by the heavy atom method and refined by the least-squares procedure to R=0.141 for 3906 reflections and R=0.102 for 4595 reflections for 3a and 3b respectively. The geometry around the Pd atom in each complex is essentially planar. However, the coordination behavior of the CH2SCH3 group in 3a and in 3b seems to be different. In 3a, the CH2SCH3 group is bonded to the Pd atom through the Pd–C σ-bond and the donation of the sulfur to the metal atom, forming a Pd–C–S three-membered ring [Pd–CH2=2.06(4), Pd–S=2.367(8), CH2–S=1.77(4) and S–CH3=1.78(4) Å]. On the other hand, the CH2SCH3 group in 3b is coordinated to the metal atom as a methylenemethylsulfonium ion, containing a C=S double bond[Pd–CH2=2.208(13), Pd–S=2.303(6), CH2–S=1.678(14) and S–CH3=1.86(4) Å].
An Analysis of the CF2 Emission Spectrum in a CF2Cl2 Plus Metastable He System
Authors: Ishiguro Takahiko , Hamada Yoshiaki , Tsuboi Masamichi 
Published: July 2006

Abstract
Ultraviolet chemiluminescence caused by a reaction of metastable He and CF2Cl2 was observed. Laserexcited single-vibronic-level fluorescence of the CF2 ？dical thus produced was also examined. The main feature in the 250–400 nm region was explained as the CF2 \ ildeA1B1-\ ildeX1A1 transition. The observed vibrational-level population of CF2(\ ildeA1B1) resulting from this reaction exhibits a maximum near v′2=5. This fact implies that the product has a FGF angle of about 104°, which is nearly equal to the FCF angle (105.4°) of the reactant (CF2Cl2) molecule, rather than to the equilibrium FCF angle (122°) of the CF2 (\ ildeA1B1) itself.
The Crystal and Molecular Structure of trans-2,2-Diphenyl-3,4-dichlorothietane
Authors: Kumakura Shigekazu 
Published: July 2006

Abstract
The crystal structure of the title compound has been determined by means of X-ray diffraction. The space group is P\bar1 with a=11.665(4), b=8.775(4), c=7.092(2) Å, α=95.73(3), β=84.36(3), γ=104.90(2)°, and Z=2. The structure was refined to R=0.048 for 1770 reflections collected on a four-circle diffractometer. The thietane ring is puckered with dihedral angles, C(2)SC(4)/C(2)C(3)C(4) and SC(2)C(3)/SC(4)C(3), of 150.1° and 149.9° respectively. The conformation of the C–Cl bonds with respect to the thietane skeleton is (3e4e), consistent with that in solution derived from the dipole moments. The average distance of the two C–Cl bonds is 1.781 Å. The C(2)–S, C(4)–S, and C(2)–C(3) bond distances are 1.872(4), 1.811(5), and 1.545(6) Å respectively; agreeing well with the corresponding bond distances observed in the cis isomer of the compound; however, the C(3)–C(4) of 1.506(6) Å is much shorter. The bisector of the bond angle formed by the ring substituents at each of the ring atoms is tilted out of the corresponding CCC or CCS planes within the thietane ring so as to increase the staggering of the neighboring substituents. The angle of tilt at Cβ is larger than those at the Cα’s. The intermolecular S···S contact of 4.080(5) Å is normal in view of the usual van der Waals radii.
The Solvent Extraction of Alkali Metal Picrates by Benzo-15-crown-5
Authors: Takeda Yasuyuki , Wada Yoshimasa , Fujiwara Shizuo 
Published: July 2006

Abstract
Benzo-15-crown-5 (B15C5) extracted alkali metal picrates (MA) into benzene by forming M(B15C5)A or M(B15C5)2A complexes and moreover, in the presence of tributyl phosphate (B), B15C5 extracted rubidium and caesium picrates by forming M(B15C5)BA complexes. The extractability sequences of the M(B15C5)A, M(B15C5)2A, and M(B15C5)BA complexes are Na+&gt;K+&gt;Rb+&gt;Li+&gt;Cs+,K+&gt;Rb+&gt;Cs+&gt;, and Rb+&gt;Cs+ respectively. The extraction equilibrium constants for these complexes have been determined at 25 °C, and the synergistic formation constants of the M(B15C5)2A and M(B15C5)BA complexes in the benzene solution have been calculated. The synergistic effects for the alkali metal ions for the B15C5 system were compared with those for the 15C5 system.
The Crystal Structure of cis-Diammine(orotinato)platinum(II)
Authors: Solin Takaaki , Matsumoto Kazuko , Fuwa Keiichiro 
Published: July 2006

Abstract
From the reaction of cis-[Pt(NH3)2(H2O)2] with orotic acid, yellow needle crystals, green needle crystals, and dark-blue microcrystalline crystals were obtained. The results of elemental analyses, the IR absorption spectra, and X-ray Weissenberg photographs showed that the yellow and green needles are identical, whereas the dark-blue microcrystalline compound exhibits slight difference in the elemental analyses and IR spectra. Green needle crystals of cis-diammine(orotinato)platinum(II), cis-[Pt(NH3)2(C5H2N2O4)], were subjected to X-ray single crystal analysis. The crystals belong to the monoclinic system, with the space group P21/c, and the cell dimensions are a=7.468(5), b=7.537(3), c=15.618(9) Å, and β=107.90(7)°, with Z=4. The structure was solved by the heavyatom method and refined to the final R value of 0.0567 for 1918 non-zero reflections. The complex is almost planar, and the platinum atom is coordinated by the orotic acid at N1 and carboxylic oxygen, forming a fivemembered chelate ring. The structure of the pyrimidine ring of the orotic acid is compared with free and coordinated uracil and thymine. No definite explanation for the color difference was obtained.
The Complex Formation of the Copper(II) Ion with Ethylenediaminetetraacetic Acid and N-(2-Hydroxyethyl)ethylenediamine-N,N′,N′-triacetic Acid
Authors: Yamaguchi Shuichiro , Oyama Noboru , Ikeda Kazuo , Matsuda Hiroaki 
Published: July 2006

Abstract
The complex formation of the Cu(II) ion with ethylenediaminetetraacetic acid (EDTA) and N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (HEDTA) has been studied potentiometrically and polarographically over the wide pH range from 1 to 11 in aqueous solutions containing 1.0 mol dm−1 NaClO4 at 25.0 °C. Both the emf data obtained by potentiometric titrations and the pH-dependence of reversible half-wave potentials were explained in terms of the formation of the following complex species: for the Cu–EDTA complexes, CuL2− (logβ101=17.28±0.04), CuHL− (logβ111=20.15±0.04), CuH2L(logβ121=22.73±0.04), CuH3L+(logβ131=24.12±0.04), and CuH−1L3− (logβ1−11=6.83±0.05); for the Cu–HEDTA complexes, CuL− (logβ101=16.30±0.05), CuHL (logβ111=18.76±0.04), CuH2L+ (logβ121=19.85±0.04) and CuHL−1L2− (logβ1−11=6.35±0.05), where βpqr=[CupHqLr]/[Cu2+]p[H+]g[L]r, and where L denotes the unprotonated molecule of EDTA or HEDTA.
Dimerization of Tryptophan Derivatives in Trifluoroacetic Acid
Authors: Hashizume Kazunari , Shimonishi Yasutsugu 
Published: July 2006

Abstract
Side-products are formed when Ac–Trp–OMe, Ac–Gly–Trp–OMe, or Ac–Trp–Trp–OMe is stored in trifluoroacetic acid. Two products from each of Ac–Trp–OMe and Ac–Gly–Trp–OMe and one product from Ac–Trp–Trp–OMe are isolated by the column chromatography on silica gel and confirmed for homogeneity by the highperformance liquid chromatography. As confirmed by 1H-NMR and mass spectral analyses, they have dimerized structures through the α-carbon to α′-carbon binding of two indole rings. One of the two products from each of Ac–Trp–OMe and Ac–Gly–Trp–OMe is the trans-isomer(s) and the other the cis-isomer(s). Only a trans-isomer(s) is obtained from Ac–Trp–Trp–OMe.
The Crystal Structure of Dibromobis(iminodiacetamide)palladium(II)
Authors: Sekizaki Masao 
Published: July 2006

Abstract
The crystals are triclinic, P\bar1. R is 0.047 for 1617 independent non-zero reflections. The complex has a centrosymmetric square-planar coordination, with two imino nitrogen and two bromine atoms in trans positions.
Abnormal LiAlH4 Reduction of 4,4-Diphenyl-3-cyano-2-methyl-2-pyrrolin-5-one
Authors: Akabori Sadatoshi , Takahashi Kazue , Ohtomi Michiko , Sakamoto Yohko 
Published: July 2006

Abstract
The reduction of 4,4-diphenyl-3-cyano-2-methyl-2-pyrrolin-5-one with lithium aluminum hydride yields three unexpected reduction products, together with the usual product.
Vacuum UV Photoelectron Intensity of Gaseous Compounds. II. Experimental Processes of Determination of Differential and Partial Photoionization Cross Sections
Authors: Achiba Yohji , Yamazaki Tomoko , Kimura Katsumi 
Published: July 2006

Abstract
Experimental processes recently developed to determine differential and partial photoionization cross sections of molecules are described in detail, based on photoelectron intensity measurements using a gaseous binary mixture of a sample with a standard gas. The quantities obtained here in these processes are 1) relative photoelectron peak heights, 2) normalized photoelectron spectra, 3) relative photoelectron band areas, and 4) differential and partial photoionization cross sections. Corrections are made for electron collecting efficiency. In connection with the photoelectron intensity determination, we propose here a method of obtaining the mole ratio of the components of a binary mixture entered into the ionization chamber of a photoelectron spectrometer. Satisfactory results on partial photoionization cross sections have been obtained for several testing samples.
Molecular Structures of the Reduced 1,2,4-Triazine Derivative and Its Reaction Product with Electron-deficient Acetylene
Authors: Ayato Hiroshi , Tanaka Isao , Yamane Takashi , Ashida Tamaichi , Sasaki Tadashi , Minamoto Katsumaro , Harada Katsuhiko 
Published: July 2006

Abstract
The molecular structures of 3-methylthio-2-rnethyl-5,6-diphenyl-2,5-dihydro-1,2,4-triazine (1) and its reaction product with dimethyl acetylenedicarboxylate, 5,6-bis(methoxycarbonyl)-2-methyl-1-methylthio-4,8-diphenyl-2,3,7-triazabicyclo[3.3.0]octa-3,6-diene (2), were determined by the X-ray method. The former belongs to the triclinic system P\bar1, with Z=2, a=10.776(2), b=10.203(2), c=8.556(1) Å, α=105.44(2), β=104.94(2), and γ=60.31(2)°; the latter belongs to the orthorhombic system Pca21 with Z=4, a=18.166(2), b=7.444(2), and c=16.080(2) Å. Both structures were solved by the direct method. The final R-factors are 0.075 for 1 and 0.048 for 2. In Compound 1 the dihydrotriazine ring is in the boat form, while in Compound 2 both of the cis-fused five-membered rings are in the envelope form.
Metal Complexes of Amino Acids. XIII. The Relationships between the 13C Chemical Shifts and Ligand Field in the trans(O)-[Co(O)2(N)4] Type Complexes
Authors: Ama Tomoharu , Kawaguchi Hiroshi , Yasui Takaji 
Published: July 2006

Abstract
The relationship between the ligand field of the carboxyl groups and the chemical shift of carboxyl carbon or α-carbon has been investigated on the basis of the absorption and 13C-NMR spectral data of the trans(O)-[Co-(OCO-R)2(en)2]Xn type complexes (OCO-R denotes amino acid or fatty acid coordinating unidentately with the carboxyl group to cobalt (III)). The linear correlations were observed between the \barνmax (1Eg component of the first absorption band) and the chemical shifts of carboxyl- and α-carbons.
Synthesis of (+)-Hinokiol, (+)-Hinokione, (+)-Salviol, and (+)-2-Oxoferruginol
Authors: Matsumoto Takashi , Usui Shuji , Kawashima Hiroyuki , Mitsuki Masanori 
Published: July 2006

Abstract
Reduction of abieta-5,8,11,13-tetraen-3-one with lithium aluminium hydride afforded the corresponding alcohol, which was submitted to catalytic hydrogenation to yield abieta-8,11,13-trien-3β-ol (7) together with its 5βH-isomer. Acetylation of 7, followed by the Friedel-Crafts acylation, afforded 3β-acetoxy-12-acetylabieta-8,11,13-triene. This compound was converted into 3β,12-diacetoxyabieta-8,11,13-triene (11) by the Baeyer-Villiger oxidation. Treatment of 11 with lithium aluminium hydride yielded hinokiol, which was oxidized to hinokione. Subsequently, hinokiol was methylated and the resulting 12-methyl ether was dehydrated to afford 12-methoxyabieta-2,8,11,13-tetraene. The tetraene was then submitted to hydroboration-oxidation to give 12-methoxyabieta-8,11,13-trien-2α-ol (15) which, on demethylation with ethanethiol and anhydrous aluminium chloride, afforded salviol. Oxidation of 15 with pyridinium chlorochromate, followed by demethylation, gave 2-oxoferruginol.
Reaction between Azibenzil and Diarylmethanimine
Authors: Mehrotra Kailash Nath , Prasad Girija 
Published: July 2006

Abstract
The thermal reaction of azibenzil with diarylmethanimine (1) leads to N-(diarylmethylene)diphenylacetamide (2) which from methanol or ethanol yields N-(α-alkoxydiarylmethyl)diphenylacetamide (4). The reduction of 2 with sodium borohydride gives N-(diarylmethyl)diphenylacetamide. The photochemical reaction of azibenzil and 1 results in the formation of cyano ethers besides the amido ethers 4. A mechanism of formation of products is discussed.
Synthesis and Activity of Antitumor Agents, Methyl [N′-(2-Chloroethyl)-N′-nitrosoureido]deoxygentiobiosides
Authors: Fukuda Yoshimasa , Suami Tetsuo 
Published: July 2006

Abstract
Chlorozotocin and GANU are nitrosoureido derivatives of d-glucose, exhibiting remarkable antitumor activities against leukemia L1210 in mice. We wish to report a synthesis of the derivatives of gentiobioside.
The Activities of Sodium Salts of 1-Amino-4-alkylaminoanthraquinone-2-sulfonic Acid in Aqueous Solutions
Authors: Mitsuishi Masaru , Yamaguchi Yuzoh 
Published: July 2006

Abstract
The mean activity coefficients of sodium salts of 1-amino-4-alkylaminoanthraquinone-2-sulfonic acid (alk= Me(MAS), Et, n-Pr, or n-Bu (n-BAS)) in aqueous solutions ranging in concentration from 10−3 to 10−2 mol kg−1 have been determined by means of isopiestic measurements at 50 and 60 °C respectively. It has been found that the mean activity coefficients of these dyes are much smaller than unity, the coefficients of MAS being the largest, and those of n-BAS, the smallest. The coefficients have been found to decrease with an increase in the dye concentration. An examination of the results obtained by Miliceivic treatment suggests that the MAS exists as dimer or trimers, and the other dyes, as tetramers, at 60 °C.
The Crystal Structure of [N-(t-Pentyloxycarbonyl)-l-prolyl]-l-alanylglycine
Authors: Yamada Yasuyuki , Tanaka Isao , Ashida Tamaichi 
Published: July 2006

Abstract
The crystal structure of the title compound was determined by the X-ray method. The space group is P21,with a=18.741(3), b=12.602(1), c=9.553(1) Å, β=118.46(2)°, and Z=4. The structure was determined successfully by the vector-space-search method, using a dimer structure of Boc–Pro–Val–Gly–OH as a rigid group. The final R value was 0.075 for 2025 non-zero reflections. Two independent molecules related by a pseudo twofold axis are linked by β-sheet-type hydrogen bonds. This kind of dimerization commonly occurs in all the Boc–Pro–X–Gly–OH peptides except Boc–Pro–Leu–Gly–OH. The packing similarity of these peptides is discussed.