bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Convenient Synthesis of Naphth[2′,3′ : 5,6]- and [1′,2′ : 5,6]-1,3-oxazino[3,2-b]benzimidazoles and Benzoxazolo[3,2-b] [l,3]quinazolone - Mechanism of Thiophosgene Heteroeyelisation [1]
Authors: Dubey S. K. , Sharma Satyavan , Iyer R. N. 
Published: February 2015

Abstract
Reaction of thiophosgene or phosgene on 2′-aminonaphthanilides (2, 5) gave the corresponding 2-substituted-6-oxonaphth[2′,3′: 5,6]-1,3-oxazino[3,2-b]benzimidazoles (3) and 6-oxonaphth[1′,2′:5,6]-1,3-oxazino[3,2-b]benzimidazoles (6) respectively. The mechanism of such reactions has been studied by carrying reaction between 2′-hydroxy - anthranilide (7 a) and thiophosgene in acidic and basic media.
Darstellung und Raman-Spektrum Preparation and Raman Spectrum of ReO3Cl·SbCl5/ Preparation and Raman Spectrum of ReO3Cl·SbCl5
Authors: Dehnicke Kurt , Liese Werner 
Published: February 2015

Abstract
Rheniumoxychloride forms with antimony pentaehloride a donor-acceptor complex, ReO3Cl·SbCl5. According to the Raman spectrum the complex contains a Re-O-Sb bridge.
Neue Phasen im System Thallium-Eisen-Schwefel/New Phases in the System Thallium-Iron-Sulphur
Authors: Sabrowsky Horst , Mirza Jahangir , Methfessel Christoph 
Published: February 2015

Abstract
The structure and magnetic properties of the new ferromagnetic compounds TlFe1+xS2 (0,25 ≤ x ≤ 0,85) were investigated. A new monoclinic phase Tl3Fe2S4 (a = 1303, b = 1114, c = 738,3 pm, β= 124,5°, Z = 4, space group C5
2h) was characterized by single crystal X-ray techniques.
The Molecular Structure of Allenes and Ketenes, XIII Correlations of Carbon-Proton Spin-Spin Coupling Constants in Allenes with ab initio STO-3G Overlap Populations
Authors: Runge Wolfgang 
Published: February 2015

Abstract
It is shown that substituent effects on one-bond and long-range carbon-proton coupling constants in monosubstituted allenes parallel quantitatively ab initio STO-3G carbon 2s-hydrogen 1 s overlap populations, irrespectively of whether the substituents are bonded to the allenic skeleton via first-row (C, O) or second-row (Si, S, Cl) atoms.
Benzo(c)-1 λ4.2-thiazol, ein neues bicyclisches 10π-System/ Benzo(c)-1 λ4 ,2-thiazol. a New Bicyclic 10π-System
Authors: Klingebiel Uwe , Bentmann Dieter 
Published: February 2015

Abstract
In the reaction of lithiated N-(fluorodimethylsilyl)-2,4,6-trimethylaniline with bis(trimethylsilyl)-sulfurdiimide LiF is eliminated and a benzo(c)-1 λ4 ,2-thiazol is formed. Trifluoroacetic acid reacts with this thiazol to give the trifluoroacetate.
Darstellung und Kristallstruktur von CsAlF4 / Preparation and Crystal Structure of CsAlF4
Authors: Lösch Roland , Hebecker Christoph 
Published: February 2015

Abstract
Single crystals of CsAlF4 have been prepared from a mixture of CsF and AlF3 and investigated by X-ray methods, CsAlF4 crystallizes hexagonally (isostructurally to the new CsCrF4-type) with a = 9.500, c= 3.713 Å, Z= 3, space group P62m-D3h
3, No. 189. AgAlF4 crystallizes orthorhombically (isostructurally to a-RbFeF4) with a = 7.108, b = 7.111, c = 5,568 Å, Z = 4.
Basic Chromium(III) Formate: Reaction of Chromiiim(III) Chloride with Formic Acid
Authors: Paul R. C. , Kapoor P. , Baidya . B. , Kapoor R. 
Published: February 2015

Abstract
Chromium(III) Chloride, Basic Chromium(III) Formate, IR, Thermogravimetry, Magnetic Moment Chromium(III) chloride reacts with anhydrous formic acid to give basic chromium(III) formate [Cr3O(OOCH)6(H2O)2(HCOOH)](OOCH), HCOOH. Its reactions with bases (B) give compounds of the general composition [Cr30(C00CH)6(B)3](00CH). The title compound has been characterized by infrared spectral data, temperature range (266-110K) magnetic moment and thermogravimetry.
Über Additionsreaktionen von zinnorganischen Verbindungen mit N.N′ -Bis(pentafluorphenyl)-sehwefeldiimid / Addition Reactions of Tinorganic Compounds with N,N′-Bis(pentafluorophenyl)sulfurdiimide
Authors: Roesky Herbert W. , Schmieder Wilfried , Ambrosius Klaus 
Published: February 2015

Abstract
The reactions of N,N′ -bis(pentafluorophenyl)sulfurdiimide with [(CH3)3Sn]2NCH3, [(CH3)3Sn]3N and [(CH3)3Sn]2NC6F5 yiels the 1:1 adducts 1-3. 1H and 19 F NMR investigations show, that fluorine atoms in the ortho position of the phenyl ring coordinate to the tin atom. This causes an increase of electron density at tin. A similar interpretation is given for the adduct 4 of N,N′-bis(p-chlorophenylsulfonyl)sulfurdiimide and [(CH3)3Sn]2NCH3, where an oxygen atom of the sulfonyl group is bonded to tin.
The Isolation and Characterization of Molecular Complexes Produced from the Reaction of Nitrophenols with Divalent Metal Oxinates
Authors: Aly M. M. , Shalaby A. M. 
Published: February 2015

Abstract
The reaction of nitrophenols (picric acid, 2,6-dinitrophenol, and 2,4-dinitrophenol) with divalent metal oxinate (metal = Cu, Co, Ni, Mn, and Zn) produced a type of molecular complex, which comprises two molecules of the metal oxinate and one molecule of the nitrophenol. In the case of the Mg complex the ratio is 1:1. A definite charge-transfer band is detected for the Co(II) complex. A hydrogen bonding system O1...H+...O2 is suggested. This includes the proton of the nitrophenol and two oxygen atoms; each is related to a coordinated oxinate of two different metal oxinate molecules. Analytical and spectral evidence are in accordance with the tentatively suggested formulations.
Zur Strukturchemie der Diperoxovanadate(V): Das μ-Hydroxo-bis [oxo-diperoxovanadat(V)] Anion / Studies on Diperoxovanadates: The μ-Hydroxo-bis [oxo-diperoxovanadate(V)] Anion
Authors: Wieghardt Karl , Quilitzsch Udo 
Published: February 2015

Abstract
Depending on the pH and the respective concentrations of solutions containing NH4+/NH3/H2O2/NH4VO3 three yellow ammonium salts can be isolated:
(NH4)4[O(VO(O2)2)2], NH4[VO(O2)2NH3]; and the novel (NH4)3[HV2O11] · 2 H2O. A cesium and potassium salt of the latter anion have been prepared. The infrared spectra of these salts are interpreted assuming a μ-hydroxo-bis[oxo-diperoxovanadate(V)] structure in the solid state.
Photoredox Reaction of trans-4-Stilbenecarboxylatopentaamminecobalt(III)
Authors: Vogler Arnd , Kern Alfred 
Published: February 2015

Abstract
The irradiation (λ = 313 nm) of aqueous [Co(III)(NH3)5TSC]2+(TSC-= trans-4-stilbenecarboxylate) leads to a redox reaction with formation of Co2+ as has been shown previously. The TSC-ligand is oxidized to the radical in the primary photoreaction. At higher complex concentrations (～10-2 M) this TSC radical is oxidized to stable products (Φ = 0.09 ± 0.02) by [Co(NH3)5TSC]2+,which is reduced to Co2+ leading to release of the TSC- ligand (Φ = 0.07 ± 0.02). Co2+ is thus formed by both the secondary and the primary photo chemical reaction (Φ overall = 0.16). At low complex concentrations (< 10-4 M) in the presence of air, the primary TSC radical is scavenged by O2. Benz-aldehyde is an oxidation product. This reduces the formation of Co2+ to Φ = 0.09 ± 0.02, which is taken to be the efficiency of the primary photo chemical step. It is suggested that the photoredox reaction is initiated by an electron transfer from the first excited singlet of the TSC- ligand. As shown by sensitization experiments, the population of the lowest TSC-triplet leads to the usual trans/cis isomerization of the TSC-ligand, but not to the redox reaction.
Synthesen mit Nitrilen, LIV Reduktion von Oximinomalonitril zu Aminomalonitril mittels Raney-Katalysatoren / Syntheses with Nitriles, LIV Reduction of Oximinomalonitrile to Aminomalonitrile Using Raney-Catalysts
Authors: Junek Hans , Mittelbach Martin 
Published: February 2015

Abstract
An improvement of the synthesis of aminomalononitrile (2) can be achieved by using Raney-catalysts for the reduction of oximinimalonitrile at a H2-pressure of 4 atm and 20 °C. Due to the reactivity of oximinomalonitrile some new derivatives of oximinocyanoacetamide are obtained by O-and N-acylation. Condensation of 2 with benzilmonoxime leads to 2-amino-5,6-diphenyl-pyrazine-carbonitrile, with N-phenyl-formamidate 2-amino-2,2-dicyano-1-(N-phenylimino)-acetaldehyde (10) is yielded.
Oximinomalonitrile, Aminomalononitrile, Oximinocyanoacetamide
Organophosphorus Compounds of Expected Biological Activity, Part II Preparation of Thiourea Derivatives and N-Aryl-phosphorothiomonoamidates
Authors: Abdel-Hay F. I. , Omara M. A. , El-Barbary A. A. , El - Badawi M. 
Published: February 2015

Abstract
The examples of cyclodiphosphazanes so far studied do not contain any nuclei of biological interest [1]. In the present investigation we aimed to introduce ethyl p-amino-benzoate, 2-aminopyridine residues in the phosphazane molecule. For this purpose phosphorus pentachloride was treated with ethyl p-aminobenzoate, p-anisidine, 2-amino-pyridine and 5-aminoquinoline to give 1,3-di-p-ethoxycarbonylphenyl-, 1,3-di-p-methoxy-phenyl-, 1,3-di-2-pyridyl-and 1,3-di-5-quinolinyl-2,2,2,4,4,4-hexachlorocyclo-diphos-phazane (1 a-d), respectively. The compounds 1 a-d were treated with potassium thio-cyanate in acetone. The oily products formed were then treated with p-anisidine, ethyl-p-aminobenzoate and 2-aminopyridine whereupon solid products (2 a-h) were obtained. The reaction probably takes place according to the following mechanism [2].
Quenching of Singlet Oxygen by Sodium Azide in Reversed Micellar Systems
Authors: Miyoshi Norio , Tomita Giiti 
Published: February 2015

Abstract
The oxidation reaction of singlet oxygen with 1,3-diphenylisobenzofuran was investigated in cyclohexanic reversed micellar solutions of dodecylammonium propionate, using pyrene as photosensitizer. The furan oxidation was effectively inhibited by azide ion-bound reversed micelles. Empty reversed micelles also inhibited the furan oxidation to some extent. The inhibition of the furan oxidation was due to the quenching of singlet oxygen by azide ion-bound and empty reversed micelles. Such singlet oxygen quenching was dependent on the concentration of water added.
Results obtained were discussed in connection with the polarity in the interior of reversed micelles, micellar size, the state of water solubilized in reversed micelles and the lifetime of singlet oxygen. The heavy atom effect on the quenching of singlet oxygen was also studied using heavy water.
Notizen: AB2X2-Verbindungen des Berylliums mit 2 A - und 5 B-Elementen / AB2X2 Compounds of Beryllium with 2 A - and 5 B - Elements
Authors: Tiburtius Christoph , Schuster Hans-Uwe 
Published: February 2015

Abstract
The new compounds MgBe2P2, MgBe2As2, CaBe2P2 and CaBe2As2 have been prepared. They are supposed to crystallize trigonally in a CaAl2Si2-type structure.
Tetrazen aus Diazen / Tetrazene from Diazene
Authors: Wiberg Nils , Häring Heinz-Wolfgang , Vasisht Sham Kumar 
Published: February 2015

Abstract
The acid-catalyzed decomposition of diazene, formed as an intermediate by the reaction of bis(trimethylsilyl)diazene with acids, leads by dimerisation via tetrazene to ammonium azide.
Zur Kristallstruktur von SrLaNiO4 / On the Crystal Structure of SrLaNiO4
Authors: Pausch H. , Müller-Buschbaum Hk. 
Published: February 2015

Abstract
Single crystals of SrLaNiO4 were prepared with a new high temperature and high oxygen pressure method (CO2-Laser radiation). The X-ray investigation shows, that this compound belongs to the K2NiF4-type (a - 381.3; c = 1268.7 pm; space group D17
4h-I4/mmm), with a stretched octahedral oxygen coordination around Ni3+. The octahedral distortion can only be explained by a geometrical effect.
Darstellung und Kristallstruktur von NH4SbS2 / On the Preparation and Crystal Structure of NH4SbS2
Authors: Volk Klaus , Bickert Peter , Kolmer Raimund , Schäfer Herbert 
Published: February 2015

Abstract
NH4SbS2 has been prepared and its crystal structure determined. The new compound crystallizes triclinic, space group P1̄, with the following cell-constants: a = 1213 pm, b = 641.9 pm, c = 634.0 pm, a = 102.9°, β = 98.9°, γ = 101.2°. In the structure there are ψ-SbS4-trigonal bipyramids connected to chains by common edges.
Darstellung und Kristallstruktur von K2Sb4S7 · H2O / Preparation and Crystal Structure of K2Sb4S7 · H2O
Authors: Eisenmann Brigitte , Schäfer Herbert 
Published: February 2015

Abstract
K2Sb4S7 · H2O crystallizes in the triclinic system with a = 1171.4(5) pm, b = 952.0(5) pm, c = 715.6(5) pm and α = 99.36(5)°, β = 86.80(5)°, γ= 103.48(5)°. One half of the Sb atoms has three sulfur neighbours forming with the free electron pair a ψ-ShS3 tetrahedron, while the other half is coordinated by four S atoms to build a ψ-trigonal SbS4 bipyramid. These polyhedra are connected by common edges and corners to a three-dimensional network with two types of channels, in which either K+ ions only or K+ ions and water molecules are located.
15N-NMR-Spektroskopie bei Kohlenstoffaziden / 15N NMR Spectroscopy of Carbon Azides
Authors: Müller Joachim 
Published: February 2015

Abstract
The following triply 15N labelled azides CH3N3, C6H5N3, O2NC6H4N3, (O2N)3C6H2N3, NCN3, and (NCN3)3 were investigated by 15N NMR and partially by vibrational and 13C NMR specrtoscopy. The signals of the β- and γ-N atom show an overcrossing. 1J(15N -13C) is zero for the arylazides.
Ringöffnung CO+- und COOCH3
+·-substituierter Cyclopropane und CO-Eliminierung aus isomeren C3H5CO+-Ionen / Ring Opening of CO+ and COOCH3
+· Substituted Cyclopropanes and CO Loss from Isomeric C3H5CO+ Ions
Authors: Schwarz Helmut , Wesdemiotis Chrysostomos 
Published: February 2015

Abstract
The non-decomposing molecular ions of methyl cyclopropanecarboxylate (14) are found to rearrange to ionised methyl but-3-enoate (15). For ions with sufficient internal energy to decompose, this isomerization is in competition with · OCH3 loss, via direct cleavage of the ester group. Collisional activation spectroscopy may be used to distinguish between the C3H5CO+ ions formed by · OCH3 loss from the molecular ions of 14, 15 and other isomeric precursors. Four distinct C3H5CO+ species (18-21) can be identified in this way; these C3H5CO+ ions may themselves decompose, via CO elimination. Consideration of the metastable peak shape for CO loss, in conjunction with collisional activation spectroscopy on the resulting C3H5
+ -ions, leads to two main conclusions, (i) Two C3H5
+ ions (22 and 27) exist in potential energy wells. The very narrow metastable peaks for CO loss from 19 and 21 (leading to 22 and 27, respectively) show that these processes are continuously endothermic. In contrast, CO loss from either 18 or 20 gives rise to much broader metastable peaks. This suggests that rate-determining rearrangement of the incipient C3H5
+ cations, to a more stable isomer, occurs prior to decomposition, (ii) Elimination of CO from the [M- · OCH3]+ fragment of 14 gives rise to a composite metastable peak, thus indicating the occurrence of two competing channels for dissociation. These channels are assigned to CO loss from 18 (larger kinetic energy release) and CO loss from 19 (smaller kinetic energy release).
13C-NMR-Spektren einiger Acridon-Derivate [1] / 13C NMR Spectra of Some Acridone Derivatives [1]
Authors: Mester I. , Bergenthal D. , Rózsa Zs. , Reisch J. 
Published: February 2015

Abstract
The 13C NMR spectra of acridone derivatives 3-5, 8-12, melicopicine (14), melicopidine (15) and melicopine (16) are presented. The substituent parameters for OH and OCH3 groups in acridone derivatives have also been given.
Die Kristallstruktur der orientierungsfehlgeordneten kubischen Hochtemperaturphase des Natriumperchlorats NaClO4 / The Crystal Structure of the Orientationally Disordered, Cubic High-temperature Phase of Sodium Perchlorate NaClO4
Authors: Berthold Hans Joachim , Kruska Brigitte Gabriele , Wartchow Rudolf 
Published: February 2015

Abstract
The crystal structure of the orientationally disordered, cubic high-temperature phase of NaC104 has been investigated using single crystal X-ray diffraction data. Space group Fm3m-O5
h, Z = 4, sodium and chlorine as in NaCl, oxygen in position 96 j (occupation factor 1/6).
Beiträge zur Untersuchung anorganischer nichtstöchiometrischer Verbindungen, VIIIa Elektronenmikroskopischer Nachweis neuer, eng begrenzter Defekte bei Blockstrukturen und Berechnung ihrer O/Me-Werte / Contributions to the Study of Inorganic Non-Stoichiometric Compounds, VIIIa Electronmicroscopical Proof of New, Small Area Defects of Block Structures and Calculation of Their O/Me Values
Authors: Heurung Günter , Gruehn Reginald , Brunner Herbert 
Published: February 2015

Abstract
Compounds of the systems Fe2O3-Nb2O5 (O/Me < 2.5) and Nb2O5-WO3 (O/Me > 2.5) were prepared by chemical transport. The block structures of the obtained phases were investigated by high resolution transmission electron microscopy.
The unusual defects observed were nearly identical in both systems. A recently developed method to calculate the O/Me value of block structures [1] was extended and used for these defects.
Derivate des Benzo[1.3]dioxols, 44 [1]Darstellung von p-chinoiden Brenzkatechinmethylenethern / Derivatives of 1,3-Benzodioxoles, 44Preparation of 1,4-Benzoquinones Fused to Cyclic Diethers
Authors: Dallacker Franz , Reichrath Germanus , Schnackers Gerard 
Published: February 2015

Abstract
The preparation of 5,6-dimethyl- (1g), 5-methoxy-6-methyl-1,3-benzodioxole-4,7- quinone(1k), 6,7-dimethyl-1,4-benzodioxan-5,8-quinone (3e), 7,8-dimethyl-3,4-dihydro- 2H-1,5-benzodioxepin-6,9-quinone (4e), 8,9-dimethyl-2,3,4,5-tetrahydro-1,6-benzodioxo- cin-7,10-quinone (5f) and of 9,10-dimethyl-3,4,5,6-tetrahydro-2H-1,7-benzodioxonin-8,11-quinone (6e) by potassiumnitrosodisulfonate-oxidation of the phenols 1f, 1j, 3d, 4d, 5e, and 6d is described. To obtain the phenols by Baeyer-Villigeroxidation of the aldehydes 1e, 1i, 3c, 4c, 5d, 6c, the cyclic ethers are subjected to bromination, bromine-lithium-exchange, and formylation of the lithium-compounds.
Eine neue Synthese von Bis(1.5 -cyclooctadien)platin / A New Synthesis of Bis( 1,5-cyclooctadiene)platinum
Authors: Herberich Gerhard E. , Heßner Bernd 
Published: February 2015

Abstract
Bis(1,5-cyclooctadiene)platinum has been pre­pared in 74-82% yield by reduction of dichloro-(1,5-cyclooctadiene)platinum with bis(cyclopentadienyl)cobalt in the presence of excess 1,5-cyclooctadiene.
Inhaltsstoffe aus Clausena anisata (Willd.)Oliv. (Rutaceae), III [1,2]13C-NMR-Spektren des Mupamins, des Carbazols und einiger Carbazol-Derivate / Constituents of Clausena anisata (Willd.) Oliv . (Rutaceae) , III [1,2] 13C NMR Spectra of Mupamine , Carbazole and Some Carbazole Derivatives
Authors: Mester I . , Bergenthal D. , Reisch J. 
Published: February 2015

Abstract
The fully interpreted 13C NMR spectra of mupamine, carbazole, and of some carbazole derivatives are reported.
Neue bicyclische λ3 -Phosphazane / New Bicyclic λ3 - Phosphazanes
Authors: Zeiss Werner , Endrass Werner 
Published: February 2015

Abstract
Symmetrically 1,5 bridged cyclotetra(λ3 -phosphazanes) 2a, b are formed from cyclotri-(λ3 -phosphazanes) 1a, b and heptamethyldisilazane. Substitution of halogens at P3 and P7 in 2a, b by alkoxy or phenoxy substituents is achieved with alcohols in the presence of triethylamin to give 2c, d. NMR spectroscopy shows 2a, b to exist as isomers A or B, whereas for 2c, d additional asymmetric isomers like C or D are assumed.
Darstellung, Eigenschaften und Kristallstruktur von Tl6Au2I10 / Preparation, Properties, and Crystal Structure of Tl6Au2I10
Authors: Stoeger W. , Rabenau A. 
Published: February 2015

Abstract
Tl6Au2I10 forms black crystals with a golden luster. In a closed system the temperature of decomposition is 276 °C. In vacuum or under inert gas Tl6Au2I10 decomposes above 65 °C forming 1 mol I2. Above 180 °C a second mol I2 is formed giving TlI and gold. The space group is P6̅2c with the lattice constants a = 10.569 and c = 13.431 Å and Z = 2. Tl6Au2I10 is built up by a framework of Tl6I6 with channels parallel to the c-axis. These channels contain Au+ mainly with a trigonal planar coordination or linear I-
3-polyiodide ions and I- ions, resp.
The Reaction of (h5-Cyclopentadienyl)carbonyl(triphenylphosphine)iridium and Bis(pentafluorophenyl)acetylene
Authors: Rausch M. D. , Gastinger R. G. 
Published: February 2015

Abstract
The reaction between (h5-cyclopentadienyl)carbonyl(triphenylphosphine)iridium and bis(pentafluorophenyl)acetylene has been investigated in detail. As in earlier studies involving the analogous cobalt and rhodium complexes, the metallocyclic product 1-(h5-cyclopentadienyl)-1-triphenylphosphine-2,3,4,5-tetrakis-pentafluorophenyl)iridole (3) has been obtained, although in very low yield. A variety of highly fluorinated organic products have also been isolated and identified, including hexakis(pentafluorophenyl)-benzene (5), Zraws-1,2-bis(pentafluorophenyl)ethene (6) and 1,2,3,4-tetrakis(pentafluoro-phenyl)naphthalene (4). The latter product has been synthesized by an independent method. Reaction mechanisms to account for the formation of 4 under these conditions are discussed.
Na6Pt8Ge8, eine ternäre intermetallische Phase mit tetraedrischen Platinclustern / Na6Pt8Ge8, a Ternary Intermetallie Phase with Tetrahedral Platinum Clusters
Authors: Thronberens Werner , Schuster Hans-Uwe 
Published: February 2015

Abstract
Na6Pt8Ge8 was prepared from the elements; it crystallizes in a cubic structure, space group I4̄3m, a= 761.4 pm. The phase contains two structural elements:
The Pt-atoms form tetrahedra, which are covered by bigger Ge-tetrahedra. The Na-atoms build a 3-D-network consisting of chains crossed under right angels.
NMR Studies on Halogeno-cis-bis(phosphine)-nido-pentaboranyl Derivatives of Nickel, Palladium, and Platinum
Authors: Kennedy John D. , Staves John 
Published: February 2015

Abstract
An examination of the 1H-{11B}, 11B, 11B-{1H}, and 31P-{1H} NMR behaviour of the compounds [M(B5H8)(X)(dppe)] has been made [M = Ni, Pd and Pt; X = halogen; dppe = bis(diphenylphosphino)ethane]. Some relaxation phenomena are rationalised, and it is concluded that all the compounds examined have a static metallo -nido-penta -borane structure in which the metal atom occupies a bridging position between two basal boron atoms. Some temperature and solvent effects are also presented and briefly discussed.
Konformationsstudien an Partialsequenzen von ACTH und Analogen. Theoretische Vorhersagen und CD-Untersuchungen an Polyethylenglykol-gebundenen Oligopeptiden / Conformational Studies on Partial Sequences of ACTH and Analogues. Theoretical Predictions and CD Investigations of Polyethylene glycol)-bound Oligopeptides
Authors: Mutter Hildegard , Mutter Manfred , Bayer Ernst 
Published: February 2015

Abstract
Conformational studies on synthetic segments)* of ACTH using circular dichroism (CD) are described. The segments [Val4]-ACTH (1-10) = I, [Pro1, Ala2, Ala3, Val4]-ACTH (1-10) = II and ACTH (11-23) = III have been synthesized according to the Liquid-Phase-Method with polyethylene glycol (PEG) as solubilizing C-terminal protecting group. The peptide PEG esters were studied in water and 2,2,2-trifluoroethanol (TFE) and the dependence of chain length, side chain protection and solvent upon the conformation has been evaluated. From these measurements, I shows partially helical structure in TFE and β-conformation in H2O. The modified 10-peptide II with strong helix formers at the N-terminus shows substantial amounts of helical structure in TFE and in water. A significant increase in helical structure is observed by adding the Pro residue to the N-terminus. The CD spectra of the 13-peptide III ist also typical for partially helical structure, however other types of ordered conformations cannot be excluded. The experimental data are compared with the results from calculations of the secondary structure deduced from the empirical prediction scheme of Chou and Fasman and the more elaborated statistical mechanical treatment of peptide conformations proposed by Tanaka and Scheraga. The agreement between experimental data and theoretical prediction is reason-able for I and II, whereas III is expected to adopt extended conformations beside unordered forms. The experimentally found unique behaviour of Prolin was rationalized by the asymmetric helix nucleation feature of this residue. A model for the most probable conformation of ACTH is proposed and a critical evaluation of the predictive schemes is given.