bluuebunny/crossref_metadata_2025 huggingface dataset:
Chromophore in binuklearen ringförmigen Gold(I)‐Komplexen
Authors: Ludwig Werner , Meyer Walter
Published: December 2004

Annular compounds containing two PAuP‐entities are prepared by reaction of (trialkylphosphine)gold (I) halogenides with diphosphines. With bis (dimethyl‐phosphino)methane (DMPM), 1,2‐bis(dimethylphosphino)ethane (DMPE) and 1,3‐bis(dimethylphosphino)propane (DMPP) we obtained the following 8‐, 10‐and 12‐membered annular binuclear complexes: [Au(DMPM)]2Cl2 H2O, [Au(DMPM)]2(SbF6)2, [Au(DMPE)]2Cl2 2H2O, [Au(DMPE)]2(SbF6)2, [Au‐(DMPP)]2Cl2 and [Au(DMPP)]2(SbF6)2 as identified by conductivity measurements, 1H‐ and 31P‐NMR. spectra and extinction curves. Their absorption spectra differ from those of the isolated linear PAuP‐complexes mainly by a very strong band at low energy which is absent in the latter. There is a strong interaction between the PAuP‐entities only in certain excited electronic states and an understanding of all transitions is only possible, if both chromophores PAuP and (PAuP)2 are taken as a basis of interpretation. Bands of the same spectrum belong apparently to two different electronic systems.

The absorption spectra of isolated linear and annular ylide‐complexes containing one and two CAuC‐entities, respectively, show quite the same behaviour.
Synthesis and Properties of 1, 1‐Dihalogenocycloprop[b]Anthracenes
Authors: M¨︁ller Paul , Rey Michel
Published: December 2004

The synthesis of 1, 1‐difluoro‐1H‐cycloprop[b]anthracene (3) is described. The key step of the synthesis is the cycloaddition of 1,2‐dichloro‐3,3‐difluorocyclo‐propene (6) to 2,3‐dimethylidene‐1,2,3,4‐tetrahydronaphthalene (5). The 13C‐NMR. spectrum of 3 is assigned on the grounds of C,F‐coupling constants, selective H‐decoupling and the resulting residual C,H‐coupling. The 1, 1‐dichloro derivative 4 was synthesized by the same route, but could not be isolated pure. Experiments for the reduction to 1H‐cycloprop[b]anthracene (2) and for the ionization of 3 or 4 to the cation 16 failed.
Ergebnisse der Verfahrensforschung, I. Synthese von o‐{(+)‐D‐2‐[4‐(4‐(Trifluormethyl)phenoxy)phenoxy]propionyl}‐aceton‐oxim
Authors: Imfeld Marquard , Suchý Miloš , Vogt Peter , Lukáč Teodor , Schlageter Markus , Widmer Erich , Boguth Walter
Published: December 2004

Results of process Research I. Synthesis of O‐{(+)‐D‐2‐[4‐(4‐(triluoromethyl)phenoxy)phenoxy]propionyl}‐acetone oxime

Efficient and simple procedures for the preparation of O‐{L‐[(sulfonyl)oxy]‐propionyl}‐oxime derivatives 7b‐e have been developed. The alleviation of 4‐[4‐(trifluoromethyl)phenoxy]phenol (11) with 7d, the final step of a technical synthesis of 1, has been studied in detail.
Alkaloid Production in Catharanthus Roseus Cell Cultures. XI. Biotransformation of 3′, 4′‐Anhydrovinblastine to Other Bisindole Alkaloids
Authors: Kutney James P. , Aweryn Barbara , Choi Lewis S. L. , Kolodziejczyk Pawel , Kurz Wolfgang G. W. , Chatson Kenneth B. , Constabel Friedrich
Published: December 2004

Biotransformation studies of 3′,4′‐anhydrovinblastine (1) in Calharanthus roseus cell suspension cultures are reported. A detailed study of one cell line, coded at „916”︁, has revealed that 1 is transformed to the natural bisindole alkaloids leurosine (2) and Catharine (3) in approximately 25–30 and 9–16% yield, respectively. In 24–48 h, about 40% of 1 is utilized by the cells. Conditions for biotransformation of 1 have not been optimized so the above yields quoted are not final.
Reaktionen von o‐Chinonen mit Aminen und Proteinen. 4. Mitteilung. 7a‐Methyl‐5,6‐dioxo‐5,6,7,7a‐tetrahydroindol‐Derivate aus 4‐Methylbrenzcatechin und Enaminen
Authors: Peter Martin G. , Speckenbach Fritz
Published: December 2004

Reactions of o‐Quinones with Amines and Proteins. 7a‐Methyl‐5,6,7,7a‐tetrahysroindole Derivatives from 4‐Methylcatechol and Enamines

Methyl l‐[2′‐(methoxycarbonyl)ethyl]‐7a‐methyl‐5,6‐dioxo‐5.6.7,7a‐tetrahydro‐indole‐3‐carboxylate (1) was isolated after the oxidation of 4‐methylcatechol with silver (1) oxide in the presence of b̃‐alanine methyl ester in glacial acetic acid. The formation of 1 requires in situ dehydrogenation of the b̃‐aminocarboxylate and addition of the resulting enamine to 4‐methyl‐1,2‐benzoquinone. Reaction of ethyl 3‐(phenylamino)crotonate with 4‐methyl‐1,2‐benzoquinone afforded ethyl 2,7a‐dimethyl‐5,6‐dioxo‐1‐phenyl‐5,6,7,7a‐tetrahydroindole‐3‐carboxylate (6). Despite the fact that the yields are low, the addition of enamines to o‐quinones represents an interesting novel extension of the Nenitzescu‐reaction which is well known in the p‐quinone series. Compound 1 may be considered as a novel model for the crosslinking of proteins by o‐quinones. Formation of 1 was, however, not observed under physiological conditions.
N, N, N′,N′‐Tetrabutyl‐3,6‐dioxaoctan‐dithioamid, ein ionophor mit Cd2+‐Selektivität, Röntgenstrukturanalyse des Cd2+‐Komplexes
Authors: Sauter Hansjürg , Dobler Max
Published: December 2004

N, N, N′,N′‐Tetrabutyl‐3,6‐dioxaoctan‐dithioamid, an Ionophore with Cd2+‐Selectivity

The CdCl2‐complex of N, N, N′, N′‐tetrabutyl‐3, 6‐dioxaoctanedithioamide crystallizes with the composition [Ligand. Cd2Cl4] in space group P1, a= 14.140, b= 10.025, c= 12.173 Å, α = 95.59°. β = 102.06°. γ = 85.50° Z= 2. Each ligand coordinates two Cd2+‐ions. Adjacent cations are bridged by two Cl+‐ions such that infinite bands along the b‐axis are formed.
Structures cristallines et moléculaires des muscs macrocycliques III. La muscone et sa 2,4‐dinitrophénylhydrazone
Authors: Bernardinelli Gérald , Gerdil Raymond
Published: December 2004

Crystal and Molecular Structure of Macrocyclic Musks. III. Muscone and its 2, 4‐Diuitrophenylhydrazone

Muscone (3‐methylcyclopentadecanone C16H30O) forms orthorhombic plastic‐crystals with Z = 2 (a = 5.560(4), b = 8.176(6), c = 17,168(20) Å). Single crystals are obtained by zone melting at 258 °K. The high degree of disorder and the ambiguity of space group have precluded a structural determination by X‐ray diffraction methods.

The crystal structure of muscone 2,4‐dinitrophenylhydrazone (DNPHM; C22H34N4O4, triclinic, space group P¯, a = 8.015 (4), b = 8.235 (2), c = 17.409 (4) Å. α = 102.69 (4), β; = 93.86 (3), γ = 96.03 (3)° Z = 2) was solved by direct methods and refined to a final R of 0.155 (Rω = 0.102). The macrocycle shows static disorder, which could be partially resolved by analysis of the anisotropy of the atomic vibrational parameters. Eight possible conformers with reasonable geometries emerged from the subsequent refinements and were used as starting models in force‐field calculations, which converged to four quinquangular conformations ([25233]; [34233]; [21423*4]; [3423*4]) with similar energies. In the molecular packing, the interactions between macrocycles and substituents are minimized. They are comparable to those described for the cis‐ and trans‐civetone DNPH derivatives [1] [2].
Enrichment of Potassium Isotopes with Macrocyclic Polyether Potassium Complexes
Authors: Schmidhaltcr Beat , Schumacher Ernst
Published: December 2004

Enrichment of the potassium isotopes is achieved by means of the chemical exchange reaction

Where L represents a macrocyclic polyether. Dicyclohexyl‐18‐crown‐6 ((cis‐syn‐cis)‐isomer) was investigated. The single stage‐separation factor a=1+ε was determined according to the method of Glueckauf from the elution curve and iso‐topic assays. One obtains ε‐values of 1.18, 0.84. and 0.74 × 10−3(±5×10−5) at −10, 0 and 10° respectively, in favor of the heavy isotope, indicating an enthalpy of isotopic exchange of −13 ± 4 Joule mol−1.

The technical feasibility of a pre‐enrichment process for 40K starling with basic laboratory data is discussed.
Structural analogues of aporphines. Part II: Synthesis of some isomers of lysergic acid derivatives
Authors: Berney Daniel
Published: December 2004

Isomers of lysergic acid derivatives (3, 22, 23 and 24). analogous to aporphine, have been synthesized from the key intermediate ketone 12.
Serine‐Protease‐Assisted Synthesis of Peptide Substrates for α‐Chymotrypsin
Authors: Bizzozero Spartaco A. , Rovagnati Bruno A. , Dutler Hans
Published: December 2004

δ‐Chymotraypsin catalyzes peptide‐bond formation between acylated amino‐acid and peptide esters as the carboxyl component and amino‐acid and peptide amides as the amino component. The conditions under which enzyme‐catalyzed coupling can be used for fragment condensation in peptide synthesis is investigated. To illustrate the method the synthesis of tetra‐, penta‐ and hexapeptides of the structure Ac‐Lxn …︁ LxlLyl …︁ LymNH2 with Lxl  Tyr, designed as substrates for α‐chymotrypsin, is described.
The Conformation of 1,6‐Diaza‐2,7‐cyclodecadione in Solution
Authors: Winkler Tammo , Leutert Thomas
Published: December 2004

From 1H‐ and 13C‐NMR. data, a crown conformation with trans amide bonds is deduced for 1,6‐diaza‐2,7‐cyclodecadione (1) in solution. Compound 1 was obtained by reaction of 2‐pyrrolidone with POCl3.
A case of highly diastereoselective addition to unsymmetrical ketones: lk‐addition of (2‐alkenyl)triphenoxytitanium derivatives
Authors: Seebach Dieter , Widler Leo
Published: December 2004

(2‐Butenyl)‐, (4‐methyl‐2‐pentenyl)‐, and (2‐heptenyl)triphenoxytitanium (2a–c) add to dialkyl, alkyl aryl‐, and alkinyl aryl ketones to give high yields of tertiary homoallylic alcohols (5–12), which are diastereomerically enriched up to 98%. Configurational assignment by degradation of two of the products to olefins 15 and 18 ‐ through β‐hydroxy acids 13 and 16 and β‐lactones 14 and 17 ‐ leads to the proposal of a general mechanism and of a specification of the relative topicity lk of the process (Scheme 5). The allylic Ti‐compounds 2 can serve as d2‐reagents (see the d2‐synthon II and the aldol‐type structures 1).
Interaction of Ca2+ and Mg2+ with Ionophores Studied by Using a Pair‐Potential Model Based on ab initio Calculations
Authors: Welti Martin , Pretsch Ernö , Clementi Enrico , Simon Wilhelm
Published: December 2004

Atom pair potentials are obtained from ab initio SCF‐LCAO‐MO calculations for model complexes of Mg2+ and Ca2+ with N, N‐dimethylacetamide, and malonamide. The SCF‐LCAO‐MO interaction energies for 271 complexes of Mg2+ and 271 complexes of Ca2+ with these amides were fitted with a simple analytical potential by a least‐square procedure. Interaction energies and optimal ion locations obtained by pair‐potential calculations are compared with values obtained by ab initio calculations for some related amides. The application of the atom pair potentials to the structure of the Mg2+‐complex [MgCl2 (C3H7ON)6] of N‐ethylacetamide is discussed.
On Cardioactive Steroids. VIII. The Synthesis of Bufalin and Resibufogenin Isomers
Authors: Wiesner Karel , Tsai Thomas Y. R. , Jäggi Franz J. , Tsai Connie S. J. , Gray Glenna D.
Published: December 2004

α‐Isobufalin

Systematic names are given at the titles of the Exper. Part.

(1) and β‐isoresibufogenin (3) have been synthesized from testosterone by a method which features a novel oxidative furan to pyrone transformation.
Polar versus steric effects in the solvolysis of 6endo‐substituted 2endo‐norbornyl p‐toluenesulfonates. Norbornanes, Part 8
Authors: Grob Cyril A. , Günther Bettina , Hanreich Reinhard
Published: December 2004

The solvolysis rates and products of the 6endo‐R‐substituted 2endo‐norbornyl toluenesulfonates 6a–6i have been determined. The rates of 6a–6g correlate with the inductive constants σ the 6endo‐substituents and are not related to the size of the latter. It is therefore concluded that polar rather than steric effects control the exo/endo‐rate ratios of norbornyl sulfonates. Products are derived mainly from rearranged 6exo‐R‐norbornyl cations when the substituent is an electron donor and from unrearranged 6endo‐R‐substituted cations when the substituent is an electron acceptor.
Partialsynthesen und Reaktionen von Abietanderivaten (Lanugonen) aus Plectranthus lanuginosus und verwandten Verbindungen
Authors: Schmid Jean Martin , Uchida Masaaki , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Partial Syntheses and Reactions of Abietanoid Derivatives (Lanugones) from Plectranthus lanuginosus and of Related Compounds

Interconversions by partial syntheses of several lanugones establish their absolute configuration at C(15). Unexpected reactions exemplify the unique reactivity of these abietanoic diterpenes, ‐ Lanugone O (4) was prepared in several steps from (15S)‐coleon C (8a; Scheme 2) thus establishing its (15S)‐configuration. One of the intermediates, the 12‐O‐acetyl‐6‐oxoroyleanone 12, through acetyl‐migration sets up an equilibrium with the vinylogous quinone 13 (Scheme 3). ‐ The chirality at C(15) in the dihydrofuran moiety of lanugone Q (16) was proven by acid‐catalyzed conversion of lanugone O (4) to 16. ‐ Instead of the usual nucleophilic attack shown by quinomethanes, lanugone L (1) is electrophilically substituted at C(7) by acetic anhydride/pyridine (Scheme 1). ‐ In a homosigmatropic [1,5]‐H‐shift, lanugone G (17) in solution is converted to the corresponding allyl substituted royleanone 18 (Scheme 4). ‐ Methanolysis of lanugone J (19) leads to the expected royleanone 20 having the 2‐methoxypropyl side chain (Scheme 5). Similar reactions were found in acetolytic reactions. However, treatment‐of spirocoleons with SOCl2/DMF produces mainly 12‐deoxyroyleanones with allyl‐ and 2‐chloropropyl groups, i. e. 19→26 and 27; 28 → 29. The possible natural occurrence of these compounds is emphasized.
The chemistry of thujone. VI. Thujone as a chiral synthon for the synthesis of optically active steroid analogues
Authors: Kutney James P. , Grice Peter , Pascoe Keith O. , Piotrowska Krystyna , Rettig Steven J. , Szykula Jerzy , Trotter James
Published: December 2004

The thujone derived enone 1 is converted in one step to the pentacyclic compound 4. The structure of 4 was determined by X‐ray diffraction analysis. The acid‐catalyzed cyclopropane‐ring opening of 4 and of the model compound 9 are described.
Water Relaxation Measurements on Semiquinones of Various Flavoproteins
Authors: Visser Antonie J. W. G. , De Wit Jan L. , Müller Franz , Berendsen Herman J. C.
Published: December 2004

The water relaxation rates of several flavoproteins in the semiquinone state have been investigated by the spin echo technique. The results indicate a rather unspecific interaction between water and the protein‐bound flavosemiquinones. An average interaction distance of 0.3‐0.5 nm has been estimated. From the temperature dependence of the rate constants the free energy of activation for proton exchange is calculated to be about 17 kJ/mol. The rate of proton exchange is around 1011 s−1 for the flavosemiquinones investigated are accessible to water regardless of their ionic state.

The large difference in relaxation rates of water protons between D‐ and L‐ amino‐acid oxidases is noticeable. Oxynitrilase exhibits the highest whereas Azotobacter vinelandii flavodoxin shows the lowest water relaxation rate of the flavoproteins studied. The results are discussed in relation to the visible‐light absorption properties of the flavoproteins.
Alkoxycarbonyl‐ and Carboxylate‐Group Migrations in the Benzilic Acid Rearrangement of Ethyl Cyclopropane‐2, 3‐dioxopropionate
Authors: Dahn Hans , Dao Lê H. , Hunma Rannoo
Published: December 2004

In alkaline medium C3H5COC (OH)2COOEt (1b) is transformed into C3H5C (OH)(COOH)2 (2a). Labelling experiments show that the cyclopropyl group is not shifted, but only ROOC and/or −O2C groups. GC./MS. and NMR. analysis after incomplete reaction show that both ROOC‐ and −O2C‐groups Migrate; at higher pH (ca. 14) the ester group rearrangement seems to be more important than at pH ca.9‐10.
Rearrangements Involving C8H8F‐Cations of the Cage Type
Authors: Jefford Charles W. , Mareda Jiri , Blaudzun Jean‐Pierre , Burger Ulrich
Published: December 2004

The homo‐l, 4 adduct obtained from difluorocarbene and bicyclo [2.2.1]hepta‐2, 5‐diene (1) was treated successively with HCl, FSO3H and SbF5 in SO2ClF at low temperature. The protic acids underwent electrophilic addition to the cyclopropane part of 1, giving the corresponding derivatives. However, in FSO3H at − 50°, protonation of the gem‐difluoro grouping also occurred to give the 2‐fluoro‐6‐fluorosulfonylbicyclo [3.2.1]oct‐2‐en‐3‐yl cation. The reaction of 1 with SbF5 at −78° led initially to the formation of the 2‐fluorobicyclo [3.2.1 ]octa‐2, 6‐dien‐4‐yl cation, which rearranged to 4‐fluorotricyclo [5.1.0.05,8]oct‐3‐en‐2‐yl cation at −40°. These rearrangements are discussed in the light of those expected for C8H8F square pyramidal cations.
On the Mechanism of the α‐Alkynone Cyclization: A Theoretical Study
Authors: Kaneti José , Karpf Martin , Dreiding André S.
Published: December 2004

The acetylene → carbene rearrangement of three model a‐alkynones, namely propynal (1a), 2‐butynal (1b) and butynone (1c) is studied by ab initio double‐zeta, double‐zeta plus polarization and double‐zeta plus self‐consistent electron pairs calculations. Transition states are located by force‐gradient geometry optimization. Calculated minimum energy reaction paths reveal substituent effects on the activation parameters, which indicate that a H‐atom or an alkyl group competes favorably with an acyl group in the [1,2]‐shift from a‐alkynones 1 to the corresponding acylvinylidenes 5.
Dass Hydrierprodukt eines β‐Nitro‐N‐nitrosoamins ist kein 1,2,3‐Triazolidin, sondern ein β‐Hydroxylamino‐N‐nitrosoamin
Authors: Egger Notker , Hoesch Lienhard , Dreiding André S.
Published: December 2004

The Product of Hydrogenation of a β‐Nitro‐N‐nitrosoamine Is Not a 1,2,3‐Triazolidine, but a β‐Hydroxylamino‐N‐nitrosoamine

It is shown, by spectroscopy, that the product of catalytic hydrogenation of N, 2‐dimethyl‐2‐nitro‐N‐nitrosopropylamine (1) consists of a 5:1 mixture of (E)‐ and (Z)‐2‐hydroxylamino‐N, 2‐dimethyl‐N‐nitrosopropylarnine (3) and does not contain ‐ as had been claimed ‐ any l, 2‐dihydroxy‐1, 2, 3‐triazolidine (2). Thus there is still no evidence for the existence of the N(OH)N(OH) functionality. The structure of intermediates on the way to 1 are also revised.
Additionsreaktionen von 2‐Thiazolin‐5‐thionen mit Acetylenen Vorläufige Mitteilung
Authors: Jenny Christjohannes , Obrecht Daniel , Heirngartner Heinz
Published: December 2004

Addition Reactions of 2‐Thiazolin‐5‐thiones with Acetylenes

The reaction of the 2‐thiazolin‐5‐thiones 1 and 5, respectively, with acetylen carboxylates yields mainly 1, 4‐dithiafulvenes of type 3. In the presence of the acetylenic compounds, the 1, 4‐dithiafulvenes undergo an isomerization to give the corresponding 2, 3‐dihydrothiophene‐2‐thiones 4.
Synthesis of Covalently Linked Viologen‐Metallocenes
Authors: Meyerhans Andreas , Pfau Wolfgang , Memming RÜDiger , Margaretha Paul
Published: December 2004

The synthesis and physical data of the covalently linked viologen‐ferrocenes 3 a and 5 a and of the corresponding ruthenocene 3 b are described.
Geometrisch enantiomorphe Cyclobutan‐Derivate
Authors: Prelog Vladimir , Thix Jean , Srikrishnan Tamarapu
Published: December 2004

Geometrically Enantiomorphic Cyclobutane Derivatives

The concept of geometrical enantiomorphism of unsaturated molecules is generalized to cover other planar rectangular arrangements of four ligands of which two are enantiomorphic.

Three pairs of geometrically enantiomorphic cyclobutane derivatives were prepared, their configurations were established, and their CD. was investigated.

The construction of a catalogue of possible stereoisomers from ligands of different types attached to an achiral core is discussed using a rectangle as example of such a core.
Calf Intestinal Alkaline Phosphatase I. Improved Isolation Method and Molar Composition of the Purified Phosphatase
Authors: Portmann Plato , Jörg Andreas , Furrer Kurt , Walker Hans‐Sepp , Leuthard Peter , Sudan Jean‐François , Perriard FrançOis , Comment Jean‐François , Leva Geneviève , Nell Jean‐pierre
Published: December 2004

A modified and improved method for isolation of calf intestinal alkaline phosphatase is described. By this method 300 to 400 mg of pure enzyme was prepared in a relatively short time. On the basis of the results of ultracentrifugation and of the free, polyacrylamide and immunoelectrophoresis the phosphatase obtained is found to be a homogenous glycoprotein, containing firmly bound zinc, magnesium and phosphoric acid. The molar composition of the enzyme and the catalytic activity were determined with different substrates and buffers.
Nicht‐Berry Pseudorotation beim Carbonylgruppenaustausch von Tetracarbonyl(η‐(Z)‐cycloalken)eisen‐Komplexen
Authors: Cosandey Marcel , von Büren Martin , Hansen Hans‐Jürgen
Published: December 2004

Exchange of Carbonyl Group Sites in Tetracarbonyl(η‐(Z)‐cycloalkene)iron Complexes via Non‐Berry Pseudorotation

The tetracarbonyliron complexes of cyclobutene, cyclopentene, 4,4‐dimethyl‐cyclopentene, 2,5‐dihydrofurane, cyclohexen, (Z)‐cyclohepten, ‐octene, ‐nonene, and ‐decene were prepared by thermal or photochemical reaction of the corresponding olefins with nonacarbonyldiiron and pentacarbonyliron, respectively. The low‐temperature behaviour of the mostly new complexes which can be stored over a longer period only below 250 K and which exhibit four C,O‐stretching frequencies in the IR. spectra (cf. Table 2), indicative for a trigonal bipyramidal structure with the olefin ligand in an equatorial position, was studied in CCl2F2 by 13C‐NMR. spectroscopy between 200 and 115 K. In this temperature range all complexed olefin ligands with the exception of (Z)‐cyclooctene (cf. [11]) show an averaged Cs‐symmetry on the NMR. time scale. About 115 K the tetracarbonyliron group gives rise to three 13C‐signals in a ratio of 1:1:2 for the complexes of (Z)‐cycloheptene, (Z)‐cyclodecene and 2,5‐dihydrofurane (Cf. Table 3). This is an agreement with the fixed equatorial position of the non‐rotating olefin ligands. The complexes of cyclooctene and cyclononene give only two 13C‐signals in a ratio of 1:1 for the carbonyl groups. The temperature dependence of the signals indicates that in these cases the two axial carbonyl groups exhibit accidentally the same chemical shift. In all cases a complete line shape analysis of the 13C‐signals of the carbonyl groups could only be accomplished by using two exchange constants (cf. Tables 4 and 5 as well as Fig. 2–5 and Fig. 8). The same is true for the cyclobutene complex, but only one exchange constant could be determined (at 120 K: two 13C‐signals in a ratio of 1:3 with the beginning of a further coalescence). The cyclopentene and cyclohexene complexes showed only one 13C‐signal even at 115 K. The observed temperature‐dependent line shapes of the 13C‐signals can be interpreted in terms of a Non‐Berry pseudorotation mechanism involving a three site exchange with each of the two diastereotopic axial carbonyl groups and the two equatorial carbonyl groups (for activation parameters see Table 4). The differences in the activation parameters can be explained on steric grounds by assuming a transition state (cf. Fig. 8) similar to the C3b‐structure of tetracarbonyliron which lies about 27 kJmol−1 above its C2v‐structure (cf. [30]) comparable with the ground state of our complexes with weak dπ(Fe),pπ(Olefin) back bonding. The transition state model implies that the reorganization process involving the axial carbonyl group in exo‐position possesses the higher exchange barrier (cf. Fig. 8).
Preparation and Diels‐Alder Reactivity of 2,3,5,6,7,8‐Hexamethylidenebicyclo [2.2.2]octane (‘[2.2.2]Hericene’). Force‐field calculations of exocyclic dienes as a moiety of bicyclic skeletons
Authors: Pilet Olivier , Birbaum Jean‐Luc , Vogel Pierre
Published: December 2004

The [2.2.2]hericene (6), a bicyclo[2.2.2]octane bearing three exocyclic s‐cis‐butadiene units has been prepared in eight steps from coumalic acid and maleic anhydride. The hexaene 6 adds successively three mol‐equiv. of strong dienophiles such as ethylenetetracarbonitrile (TCE) and dimethyl acetylenedicarboxylate (DMAD) giving the corresponding monoadducts 17 and 20 (k1), bis‐adducts 18 and 21 (k2) and tris‐adducts 19 and 22 (k3), respectively. The rate constant ratio k1/k2 is small as in the case of the cycloadditions of 2,3,5,6‐tetramethylidene‐bicyclo [2.2.2]octane (3) giving the corresponding monoadducts 23 and 27 (k1) and bis‐adducts 25 and 29 (k2) with TCE and DMAD, respectively. Constrastingly, the rate constant ratio k2/k3 is relatively large as the rate constant ratio k1/k2 of the Diels‐Alder additions for 5,6,7,8‐tetramethylidenebicyclo [2.2.2]oct‐2‐ene (4) giving the corresponding monoadducts 24 and 28 (k1) and bis‐adducts 26 and 30 (k2). The following second‐order rate constants (toluene, 25°) and activation parameters were obtained for the TCE additions: 3+TCE→23: k1 = 0.591±0.012 mol−1·l·s−1, ΔH≠=10.6±0.4 kcal/mol, and ΔS≠ = −24.0±1.4 cal/mol·K (e.u.); 23+TCE→25: k2=0.034±0.0010 mol−1·l·s−1, ΔH≠ = 10.6±0.6 kcal/mol, and ΔS≠ = −29.7±2.0 e.u.; 4+TCE→26: k1 = 0.172±0.035 mol−1·l·s−1, ΔH≠ 11.3±0.8 kcal/mol, and ΔS≠ = −24.0±2.8 e.u.; 24+TCE→26: k2 = (6.1±0.2)·10−4 mol−1·l·s−1, ΔH≠ = 13.0±0.3 kcal/mol, and ΔS≠ = −29.5±0.8 e.u.; 6+TCE→17: k1 = 0.136±0.002 mol−1·l·s−1, ΔH≠ = 11.3±0.2 kcal/mol, and ΔS≠ = −24.5±0.8 e.u.; 17+TCE→18: k2 = 0.0156±0.0003 mol−1·l·s−1, ΔH≠ = 10.9±0.5 kcal/mol, and ΔS≠ = −30.1 ± 1.5 e.u.; 18+TCE→19: k3=(5±0.2) · 10−5 mol−1 mol−1 ·l·s−1, ΔH≠ = 15±3 kcal/mol, and ΔS≠ = −28 ± 8 e.u. The following rate constants were evaluated for the DMAD additions (CD2Cl2, 30°): 6+DMAD→20: k1 = (10±1)·10−4 mol−1 · l·s−1; 20+DMAD→21: k2 = (6.5±0.1) · 10−4 mol−1 ·l·−1; 21+DMAD→22: k3 = (1.0±0.1) · 10−4 mol−1 ·l·s−1.

The reactions giving the barrelene derivatives 19, 22, 26 and 30 are slower than those leading to adducts that are not barrelenes. The former are estimated less exothermic than the latter. It is proposed that the Diels‐Alder reactivity of exocyclic s‐cis‐butadienes grafted onto bicycle [2.2.1]heptanes and bicyclo [2.2.2]octanes that are modified by remote substitution of the bicyclic skeletons can be affected by changes inthe exothermicity of the cycloadditions, in agreement with the Dimroth and Bell‐Evans‐Polanyi principle.

Force‐field calculations (MMPI 1) of 3, 4, 6 and related exocyclic s‐cis‐butadienes as a moiety of bicyclo [2.2.2]octane suggested single minimum energy hypersurfaces for these systems (eclipsed conformations, planar dienes). Their flexibility decreases with the degree of unsaturation of the bicyclic skeleton. The effect of an endocyclic double bond is larger than that of an exocyclic diene moiety.
Crystal Structure of 1,1,4,4‐Tetrafluorocyclohexane at 95 K
Authors: Dunitz Jack D. , Schweizer W. Bernd , Seiler Paul
Published: December 2004

The crystal structure of 1,1,4,4‐tetrafluorocyclohexane has been determined from X‐ray diffraction measurements at 95 K. Internal motion of the CF2‐group can be discerned from analysis of the atomic vibration tensors. The pattern of bond lengths suggests that an anomeric‐effect type of interaction between antiperiplanar C,C‐ and C,F‐bonds (as well as between C,H‐ and C,F‐bonds) may be operative in this molecule.
β‐Helical structures of Boc‐(L‐Val‐D‐Val)6‐OMe in the crystalline state and in chloroform
Authors: Lorenzi Gian Paolo , Jäckle Hans , Tomasic Lera , Pedone Carlo , Di Blasio Benedetto
Published: December 2004

A conformational study was carried out on Boc‐(L‐Val‐D‐Val)6‐OMe in the crystalline state by X‐ray and IR. and by 1H‐NMR. in chloroform. The dodecapeptide crystallizes from CHCl3/EtOAc with a left‐handed helical structure of the type ↑↓ β5.6, and from CHCl3/MeOH (or MeOH) with a different structure. In chloroform it forms three slowly interconverting species: one is a ↑↓ β5.6 left‐handed helical species, and the other two are most likely single‐stranded β4.4 helical species of opposite handedness. The double‐stranded helical species is predominant in fresh solutions of samples obtained from CHCl3/EtOAc. Because of the slow conversion or formation of this species some hours are needed to reach the conformational equilibrium in chloroform at 25°.
Photochemisch induzierte Reaktionen von 3‐Amino‐2H‐azirinen
Authors: Dietliker Kurt , Heimgartner Heinz
Published: December 2004

Photochemically Induced Reactions of 3‐Amino‐2H‐azirines

Irradiation of 3‐(N‐methylanilino)‐2H‐azirines with a mercury low pressure lamp induces the cleavage of the C(2), C(3)‐ring bond thus affording nitrilio‐methanide dipols, substituted by an amino group at C(1). Depending on the substitution pattern at C(3), these intermediates can be trapped by dipolarophiles to yield five‐membered heterocycles with high regioselectivity, or they undergo a 1,4‐H‐shift forming 2‐azabutadiene derivatives. Further, the dipol is protonated at C(1) even by weak CH–acids.
Kreuzkonjugierte Cyanine und Merocyanine aus Salzen 1‐substituierter 2,3‐Dimethylchinoxaline. 3. Mitteilung. Über die Indikatoreigenschaften der Farbbasen und die Tautomerie der konjugaten Farbsäuren
Authors: Schelz Dieter
Published: December 2004

Crossconjugated Cyanines and Merocyanines, Obtained from Salts of 1‐Substituted 2,3‐Dimethylquinoxalines: On the Properties of the Dye Bases in Acidic Media

UV./VIS. and 1H‐NMR. spectra of the indicator bases 1 in acidic solutions are presented. The solutions of the dye acids N and NN′ (Scheme 2) are in general not stable due to tautomerism. The relative pKa‐values are set in relation to data of equilibria and half‐life periods. The latter ones depend on the substituents and on the acidity of the solutions. An inverse substituent effect observed in protic solvents is ascribed to solvolytic reactions.

The dye base 1S (X = SO3Na, R = C6H5) was synthesized starting with chlorobenzene. The cyanines 2 were obtained on treatment of 1 with HClO4 in CH3CN; solutions of 1 in H2SO4, however, yielded on dilution tautomeric salts that were isolated as the perchlorates 3.
The Structure of C‐Alkaloid‐O, a Constituent of Calabash Curare. Part 187. Papers on organic natural products
Authors: Borris Robert P. , Guggisberg Armin , Hesse Manfred
Published: December 2004

The structure of C‐alkaloid‐O (1=his HCL‐salt) was established on the basis of spectral data and comparison with the analogous compound 2, synthesized from a natural product of known absolute configuration. Internally consistent 13C‐NMR. assignments are given for 1, 2, huntrabrine methochloride (4) and its diacetate derivative 5.
Reinigung der D‐Oxynitrilase aus Mandeln mit Hilfe der Affinitäts‐Chromatographie
Authors: Hochuli Erich
Published: December 2004

A Rapid Purification of D‐Oxynitrilase from Almond Meal by Affinity Chromatography

Oxynitrilase from almond meal is capable of catalyzing the stereospecific addition of cyanide to a variety of aldehydes. Thus, the enzyme is potentially useful in the synthesis of optically active cyanohydrins on a preparative scale [1]. As the currently available purification procedures for this enzyme [2] are rather tedious, we have elaborated a simple and rapid procedure based on affinity chromatography. An inhibitor for the enzyme, methyl p‐(3‐aminopropoxy)benzoate (4), has been synthesized and attached covalently to Sepharose 4B as a solid matrix (5). With this affinity gel it was possible to prepare the D‐oxynitrilase in a simple procedure with high yields.
Tetraazamacrocycles lipophiles: Application à l'extraction liquide‐liquide des ions métalliques
Authors: Handel Henri , Muller Frédéric R. , Guglielmetti Robert
Published: December 2004

Lipophilic Tetraazamacrocycles: Application to Liquid‐liquid Extraction of Metal Ions

Liquid‐liquid extraction of Co2+, N2+, Cu2+, Zn2+, Cd2+, Pb2+, and Ag+ by lipophilic tetraazamacrocycles is reported in different solvents. Extraction efficiency is sensitive to the metal ion identity, the cavity size of the macrocycle and the pH of the aqueous phase. The influence of the organic receiving phase and the anion identity is discussed and expressed in terms of donnor‐acceptor concepts. Further‐more, the lipophilic tetraazamacrocycles exhibit high extraction efficiency towards these transition‐ and heavy‐metal ions.
Die Acylierung von 5‐Amino‐1 H‐1, 2, 4‐triazolen. Eine 13C‐NMR.‐Studie
Authors: Winkler Tammo , Kristinsson Haukur
Published: December 2004

The Acylation of 5‐Amino‐1 H‐1,2,4‐triazoles. A 13C‐NMR. Study

The acylation of 3‐substituted‐5‐amino‐1 H‐1,2,4‐triazoles (1) with methyl chloroformate or dimethylcarbamoyl chloride yielded mainly 1‐acyl‐5‐amino‐1,2,4‐triazoles (2 and 3). Acylation of 3‐methyl‐, 3‐methoxy‐ and 3‐methylthio‐5‐amino‐1 H‐1,2,4‐triazole (1b, 1c and 1d) with methyl chloroformate gave up to 10% of the 1‐acyl‐3‐amino‐1,2,4‐triazoles. For the unsubstituted 5‐amino‐1,2,4‐triazole (1a), a (1:1)‐mixture of the 3‐ and 5‐isomers 2a and 4 was obtained in dioxane in the presence of triethylamine. No 4‐acylated product was detected in contrast to earlier reports. The structures of the reaction products were determined with the aid of proton coupled 13C‐NMR. spectra using the corresponding N‐methyl‐1,2,4‐triazoles as reference compounds.
The Crystal Structure of Methyl β‐orcinol‐carboxylate (= Methyl 2,4‐dihydroxy‐3,6‐dimethylbenzoate)
Authors: Brehm Lotte , Stoeckli‐Evans Helen , Tabacchi Raphael , Bürgi Hans‐Beat
Published: December 2004

The mono‐arylic compound, methyl β‐orcinol‐carboxylate (I) is one of the principal components of lichens which grow on the oak tree. In the crystal structure of I the molecules are H‐bonded to form sheets separated by 3.56 (5) Å. The carbonyl O‐atom of the ester group and the ortho‐hydroxyl group form a strong intramolecular H‐bond. The IR. spectrum of the solid contains two (O‐‐H)‐stretching frequencies which, by comparison with the spectra of the 4‐methoxy and the 2‐methoxy analogues, can be assigned to one intra‐ and one intermolecular H‐bond.
Synthesis of 2‐Norzizaene and 9,10‐Dehydro‐2‐norzizaene (7,7‐Dimethyl‐6‐methylidenetricyclo[6.2.1.01,5]undec‐9‐ene) via Intramolecular Allyl Cation Induced Cycloaddition
Authors: Hoffmann H. M. R. , Henning Rolf
Published: December 2004

7,7‐Dimethyl‐6‐methylidenetricyclo[6.2.1.01,5]undec‐9‐ene (10) has been prepared from allylic alcohol 8 in one step in 16% yield. Selective hydrogenation of 10 with diazene gives the 2‐norzizaenes 1a and 11.
The Calf Intestinal Alkaline Phosphatase. II. Reaction between the metal content and the enzyme activity
Authors: Portmann Plato , Schaller Hubert , Leva Geneviève , Venetz Werner , Müller Thomas
Published: December 2004

Pure alkaline phosphatase (EC 3.1.3.1; 1500 U/mg) was dialyzed at 4° during 168 h against water, 10−4M EDTA or 10−4M o‐phenanthroline. During the dialysis, samples were periodically removed and analyzed for metal content and activity. The results indicate that 1 mol of native calf intestinal alkaline phosphatase contains 4 g‐atom of zinc and 4 g‐atom of magnesium tightly bound, and that both metal ions are necessary for full enzyme activity. The dialyzed, partially demetallized enzyme could be reactivated by the addition of zinc and/or magnesium salts.
Etudes sur les composés organométalliques. XIX. Synthèse et caractérisation de composés alkoxy (alkyl)titane (IV)
Authors: Meyer Edouard Marc , Jacot‐Guillarmod André
Published: December 2004

Studies of Organometallic Compounds. Synthesis and Characterization of Some Alkoxy (alkyl)‐titanium(IV) Compounds

Alkoxy(benzyl)titanium and alkoxy(cyclohexyl)titanium compounds are prepared by alcoholysis of tetrabenzyl‐ and tetracyclohexyltitanium. Structural features are investigated by means of 1H‐NMR.
Synthese stereoisomerer Pinanthromboxane und Evaluation der Verbindungen als Plättchenaggregationsinhibitoren
Authors: Bounameaux Yves , Coffey John W. , O'Donnell Margaret , Kling Klaus , Quinn Ronald J. , Schönholzer Peter , Szente André , Tobias Lawrence D. , Tschopp Thomas , Welton Ann F. , Fischli Albert
Published: December 2004

Synthesis of Stereisomeric Pinanthromboxane Derivatives and Evaluation of the Compounds as Platelet Aggregation Inhibitors

Starting from the two enantiomeric myrtenols ((−)‐1 and (+)‐1; cf. Scheme 1), the synthesis of twelve stereoisomeric pinanthromboxane derivatives ((+)‐ and (−)‐10, ‐11, ‐14, ‐15, ‐21 and ‐22) is described (cf. Schemes 1–4). Biological data from the evaluation as platelet aggregation inhibitors (cf. Table 6 and 7), thromboxane synthetase inhibitors (cf. Table 8) and from the assessment as antagonists of leukotriene E4 induced bronchoconstriction (cf. Table 9) are presented.
Untersuchungen der Reaktionsprodukte von Isocyanaten mit Hydroxylamin
Authors: Becker Alfred , Heizler Werner
Published: December 2004

Investigations of the Products of Isocyanates with Hydroxylamine

The reactions of isocyanates with hydroxylamine give rise to several compounds according to the different conditions involved when starting with the primary reaction products, the hydroxy‐ureas. The pure compounds have been isolated. An interesting reaction of N‐phenyl‐N′‐phenylcarbamoyloxyurea with sodium hydroxide has been observed. This compound is converted to 3‐hydroxy‐1, 5‐diphenylbiuret under conditions described.
Preparation of α‐Bromo‐ and α‐Chlorocarboxylic Acids from α‐Amino Acids
Authors: Olah George A. , Shih Joseph , Prakash G. K. Surya
Published: December 2004

Diazotization of α‐amino acids in 48:52 (w/w) hydrogen fluoride/pyridine along with excess of potassium halide results in the corresponding α‐halocarboxylic acids in good to excellent yields (Table 1 and 2).
Fragmentation of Homoallylic Alkoxides. Preparation of 1‐(3′‐cyclopentenyl)‐2‐alkanones from 2‐substituted bicyclo[2.2.1]hept‐5‐en‐2‐ols
Authors: Snowden Roger L.
Published: December 2004

The potassium 2‐substituted bicyclo[2.2.1]hept‐5‐en‐2‐alkoxides derived from alcohols 2–9 at 30° in hexamethylphosphoric triamide (HMPA) afford 1‐(3′‐cyclopentenyl)‐2‐alkanones 10–19 via heterolytic C(1), C(2)‐allylic bond cleavage in the substrate alkoxide followed by intramolecular protonation of the resultant transient allylic anion.
Hydroxyphenyl‐1‐methylpyridinium‐jodide als potentielle Reaktivatoren von mit Organophosphor‐Verbindungen vergifteten Acetylcholinesterasen
Authors: Riggio Gaetano , Hopff Wolfgang Herbert , Hofmann Alfred André , Waser Peter Gaudenz
Published: December 2004

Hydroxyphenyl‐1‐methylpyridinium‐iodide as Potential Reactivators of Acetylcholinesterase Poisoned with Organophosphorus Compounds.

It was our aim to reactivate acetylcholinesterase poisoned with sarin.

We synthesized 2‐(o‐hydroxyphenyl)‐1‐methylpyridinium‐iodide (9), 2‐(p‐hydroxyphenyl)‐1‐methylpyridinium‐iodide (19) and 4‐(o‐hydroxyphenyl)‐1‐methylpyridinium‐iodide (14) as potential reactivators. All substances showed moderate toxicity against mice; their reactivity potency in vitro and in vivo was negligible.
Notiz zur Synthese von Alkyl‐, Cycloalkyl‐ und Aryl‐(4‐aminophenyl)‐sulfonen
Authors: Courtin Alfred
Published: December 2004

Syntheses of Some Alkyl‐, Cycloalkyl‐ and Aryl‐(4‐aminophenyl)‐sulfones

Syntheses of (4‐aminophenyl)‐alkyl, ‐cycloalkyl and ‐aryl sulfones 2 were achieved both by alkylation of 4‐(acetylamino)‐benzenesulfinic acid (7) to the corresponding acetanilides 9 followed by hydrolysis and by oxidation of the appropriate (4‐nitrophenyl)‐sulfides 11 to (4‐nitrophenyl)‐sulfones 1 with subsequent Béchamp reduction.
The Intramolecular Ramberg‐Bäcklund Reaction: A Convenient Method for the Synthesis of Strained Bridgehead Olefins
Authors: Becker Konrad B. , Labhart Marco P.
Published: December 2004

The stereochemical aspects of the intramolecular Ramberg‐Bäcklund reaction, i.e. the 1,3‐elimination of hydrogen halide followed by sulfur dioxide extrusion, have been studied on the α‐bromosulfones of the 1‐thiadecalin

Throughout this paper ‘1‐thiadecalin’ will be used in place of ‘decahydro‐1‐thianaphthalene’.

series. Whereas the cis,exo‐bromosulfone 23a containing the ideal W‐type arrangement of the reacting atoms undergoes a clean Ramberg‐Bäcklund reaction, the trans,exo‐ and trans,endo‐bromosulfones, 24a and 24b, respectively, lead to an α,β‐unsaturated sulfone by simple 1,2‐elimination of HBr. Application of the Ramberg‐Bäcklund reaction to 9‐bromo‐8‐thiabicyclo[5.2.1]decane‐8,8‐dioxide (17) permits a short synthesis of the Bredt olefin bicyclo[5.1.1]non‐1(8)‐ene (5), which can be isolated but shows the typical high reactivity of other methylene‐bridged (E)‐cyclooctenes.
Notiz über die Reaktion von Methylhydrazin mit N‐Cyano‐azomethinen. Abhängigkeit des Reaktionsverlaufs von der Natur der Abgangsgruppe
Authors: Kristinsson Haukur , Winkler Tammo
Published: December 2004

The reaction of methylhydrazine with N‐cyanoazomethines 1 containing a thioalkyl leaving group yields the 3‐amino‐1,2,4‐triazole derivatives 2, whereas the N‐cyanoazomethines 1 containing an alkoxy leaving group give the isomeric 5‐amino‐1,2,4‐triazoles 3. The yields are excellent and the position selectivity is high. The structures of the 1,2,4‐triazole derivatives were determined with the aid of proton‐coupled 13C‐NMR. spectra.
Cross Conjugated Polyenes Derived from 2‐Vinyl‐butadiene: Electronic States of their Radical Cations, and Triplet Energy
Authors: Bally Thomas , Neuhaus Louis , Nitsche Stephan , Haselbach Edwin , Janssen Johann , Lüttke Wolfgang
Published: December 2004

The doublet states of the radical cations of the cross conjugated polyenes 4,4‐dimethyl‐1‐methylidene‐2,5‐cyclohexadiene 2 and its bis‐derivative 1 have been investigated by photoelectron spectroscopy and by electronic spectroscopy of \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{+\kern-4pt {.} } $\end{document}+, prepared at 77 K in an electron scavenging matrix by γ‐irradiation. Simultaneous consideration of the spectral results shows \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {1}^{+\kern-4pt {.} } $\end{document} to be the second hydrocarbon molecular cation (after 2,2‐dimethyl isoindene) which possesses a first excited doublet state (D1) of non‐Koopmans nature (2B3g). The first Koopmans‐type excited state (2B2g) expected from PE. spectroscopy lies, however, very close in energy. In addition T1 of 1 was observed by electron energy loss spectroscopy at 2.0±0.1 eV. Application of the ‘SDT‐equation’ predicts for this state only 1.05 eV; there is at present no reasonable explanation for this failure.
The Crystal Structure of 1,2‐Didehydrocrotalanine Picrate: A Macrocyclic Pyrrolizidine Alkaloid Analogue
Authors: Stoeckli‐Evans Helen , Robins David J.
Published: December 2004

1,2‐Didehydrocrotalanine (2) is the first synthetic macrocyclic pyrrolizidine alkaloid analogue to be studied by X‐ray crystallography. The crystal structure was solved by multisolution direct methods and refined by full‐matrix least‐squares to R = 0.036 for 693 reflections. The alkaloid analogue has an 11‐membered macrocycle containing two ester groups with their carbonyl groups nearly antiparallel.
3,3‐Dialkyltriazencarbonsäure‐Derivate durch oxydative Hydro‐Acyl‐Elimination von 3,3‐Dialkyltriazan‐1,2‐dicarbonsäure‐Derivaten
Authors: Egger Notker , Hoesch Lienhard , Dreiding André S.
Published: December 2004

3,3‐Dialkyltriazenecarboxylic Derivatives by Oxidative Hydro‐Acyl‐Elimination from 3,3‐Dialkyltriazane‐1,2‐dicarboxylic Derivatives

The preparation and some properties of esters and amides of 3,3‐dialkyltriazenecarboxylic acids (6) are described. These novel triazenes 6 were obtained by treatment of diesters, diamides and ester‐amides of 3,3‐dialkyltriazane‐1,2‐dicarboxylic acids (3) with lead tetraacetate, when an elimination of the COOR‐ or the CONHR‐group at N(2) together with the H‐atom at N(1) took place. The precursor triazanes 3 were readily available from the addition of secondary amines 2 to diesters, diamides or ester‐amides of diazenedicarboxylic acid (1). The spectral properties of the triazanes 6, including the 15N‐NMR signals of one example, are compared with those of the triazanes 3. They express the structural features due to conjugation in 3,3‐dialkyltriazenecarboxylic derivatives, including the resistance to rotation around the N(2), N(3)‐bond.
1H‐NMR Spectroscopy of Gold Drugs. High‐Resolution Studies of β‐D‐Thioglucosetetraacetate Phosphine Complexes of Au(I)
Authors: Pregosin Paul S. , Becker Edwin D.
Published: December 2004

1H‐NMR data (11.74 Tesla) for the gold(I) complexes [R3P‐Au‐(2,3,4, 6‐tetra‐O‐acetyl‐1‐thio‐β‐D‐glucopyranosido‐S)] (R = Et, Cyclohexyl, C6H5, p‐CH3OC6H4) with sulfur coordination to gold, are reported. The resonances associated with the sugar protons have been assigned although these have similar chemical environments. The coordination chemical shifts, Δδ, for the AuSCH proton are ≈︁ 0.6 ppm, and support S‐coordination to gold.
Conjugative, Exciton and Charge‐Resonance Interactions in D2d‐9,9′‐Spirobifluorene and D2d‐Tetrabenzotricyclo [5.5.0.02,8]dodeca‐3,5,9,11‐tetraene. Photoelectron and Polarized Absorption Spectra
Authors: Spanget‐Larsen Jens , Gleiter Rolf , Haider Rudolf
Published: December 2004

Photoelectron spectroscopy, polarized electronic absorption spectroscopy in stretched polymer sheets, and semiempirical theoretical methods have been applied to investigate the valence electronic structures of the two title compounds 1 and 2, considering fluorene (3) as a reference compound. The results are analyzed in terms of ‘through space’ and ‘through bond’ conjugative effects and exciton and charge‐resonance interactions. Spiro‐conjugation in 1 is found to play a similar role as ‘through bond’ interaction via the cyclobutane ring in 2. In contrast to the results of a recent investigation, exciton coupling is found to be relatively insignificant, while charge‐resonance effects are important. The transition close to 41 000 cm−1 in the absorption spectra of 1 and 2 has no obvious counterpart in the spectrum of 3; it is assigned to a 1E− state with large charge‐resonance character, involving promotion of an electron from the HOMO of one half‐chromophore to the LUMO of the other.
Synthesis of β‐pyrazinyl‐L‐alanine (Paa) and of peptide derivatives
Authors: Petermann Claudia , Fauchère Jean‐Luc
Published: December 2004

The title compound was prepared via a malonic ester synthesis starting with α‐chloromethylpyrazine [2], and ending, after an asymmetric enzymatic hydrolysis of the racemic N‐acetyl‐β‐2‐pyrazinylalanine to the L‐form of the new amino acid. The optical purity was ascertained by 1H‐NMR analysis at 360 MHz of the diastereoisomeric dipeptides L‐pyrazinylalanine‐L‐leucine and D‐pyrazinylalanine‐L‐leucine. Hydrophobic, steric and electronic parameters for its side chain were also estimated, which can be useful for the quantitative study of structure‐activity relationships of biologically active peptide derivatives. The new amino acid could be introduced in the place of phenylalanine in the enkephalin‐like pentapeptide [D‐alanyl2, leucine5]enkephalin, thus showing good stability towards the classical methods of peptide synthesis.
Tétraazamacrocycles lipophiles: Extraction d'ions métalliques par une résine imprégnée
Authors: Muller Frédéric R. , Handel Henri , Guglielmetti Robert
Published: December 2004

Lipophilic Tetraazamacrocyles: Extraction of Metal Ions by Impregnated Resin

Extraction of Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+ and Ag+ by lipophilic tetraazamacrocycles dispersed on a solid matrix (Amberlite XAD7) is reported. Extraction efficiency is sensitive to the metal ion identity and the cavity size of the macrocycle. The influence of kinetic factors upon extraction efficiency is discussed.
Mesomorphic properties of some 6‐n‐alkyl‐2‐(4′‐cyanophenyl)naphthalenes. Preliminary Communication
Authors: Lauk Urs , Skrabal Peter , Zollinger Heinrich
Published: December 2004

The synthesis of the title compounds 4 is described and their transition temperatures are compared with the nematic phases of the respective 6‐n‐alkoxynaphthalene derivatives.
Azimine. VII. Herstellung durch Oxydation von Triazanen
Authors: Egger Notker , Hoesch Lienhard , Dreiding André S.
Published: December 2004

Azimines. VII

Teil VI, s. [1].

.
Preparation by Oxidation of Triazanes

A novel method for the preparation of certain azimines 4 by oxidation of 1,2,3‐trisubstituted triazanes 3 is described. Treatment of 3‐aryl‐triazane‐1,2‐diesters 3a‐3c with lead tetraacetate afforded the 3‐aryl‐azimine‐1,2‐diesters 4a‐4c. The precursor triazanes 3a‐3c were prepared by addition of p‐substituted anilines to diisopropyl diazene‐1,2‐dicarboxylate 1b. A comparison of the spectral properties of the azimines 4 with those of the correspondingly substituted triazanes 3 reveals the unsaturated and dipolar nature of the azimines 4.