bluuebunny/crossref_metadata_2025 huggingface dataset:
Base Hydrolysis of Pentaaminecobalt(III) Complexes: The [CoX(dien) (dapo)]n+ system. Part 1. Syntheses, structures, configuration, and spectroscopy
Authors: Comba Peter , House Donald A. , Jackson W. Gregory , Marty Werner , Stoeckli‐Evans Helen , Zipper Luc
Published: December 2004

Oxygentation of aqueous solutions of CoIII in presence of stoichiometric amounts of N‐(2‐aminoethyl)ethane‐1,2‐diamine (dien) and 1,3‐diaminopropan‐2‐ol (dapo) produces μ‐peroxocobalt(III) dimers. Acid cleavage (HCI) yields mer‐exo(H)‐, mer‐endo (H)‐, unsym‐fac‐exo(OH)‐, and unsym‐fac‐endo(OH)‐[CoCl(dien)(dapo)]2+ (A–D)(X = Cl), resp. and unsym‐fac‐[Co‐(dien)(dapo‐N,N′,O)]3+ (G). Isomer seperation was achieved by fractional crystallization as ZnCl and ClO salts and by ion‐exchange chromatography. The corresponding bromo, azido, nitrito‐O, nitro‐N, thiocyanato, hydroxo, and aqua complexes were also synthesized. Optically resolved samples were prepared for chiral compounds, and the complexes were structurally characterized by X‐ray analyses (\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\it \Lambda} \limits^ \to $\end{document}(−)436(CD)‐A (X = N3)), (\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\it \Delta} \limits^ \to $\end{document}(−)436(CD)‐B). (X = N3), \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\it \Delta} \limits^ \to $\end{document} (+)436(CD)‐B by their chiroptical properties, and by 13C‐NMR spectroscopy supported by 1H‐NMR, IR, CD, and UV/VIS spectroscopy. \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\it \Lambda} \limits^ \to $\end{document}(−)436(CD)‐mer‐exo(H)‐[Co(N3)(dien)(dapo)](hydrogen di‐O‐benzoyl‐L‐tartrate)2.4 H2O crystallizes in the orthorhombic space group P212121, a = 7.676(1) Å, b = 19.457(1) Å, c = 34.702(2) Å. \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\it \Lambda} \limits^ \to $\end{document}(−)436(CD)‐mer‐endo(H)‐[Co(N3)(dien)(dapo)] (hydrogen di‐O‐benzoyl‐L‐tartrate)2.2.75 H2O crystallizes in the triclinic space group P1, a = 8.062(3) Å b = 10.296(1) Å, c = 15.056(2) Å, alpha = 80.55(1)°, β = 85.18(2)°, γ = 89.10(2)°. \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\it \Delta} \limits^ \to $\end{document}(+)436(CD)‐mer‐endo(H)‐[Co(N3)(dien)(dapo)](hydrogen di‐O‐benzoyl‐L‐tartrate)2. 5.75 H2O crystallizes in the triclinic space group P1, a = 7.742(1) Å, b = 10.014(1) Å, c = 18.045(2) Å, α = 99.57(1)°, β = 92.87(1)°, γ = 102.56(1)°. The absolute configurations of the three cations were determined unambiguously. Interconversions of the various isomers and derivatives and structural, configurational, and spectroscopic aspects are discussed in detail.
Benzene Oxidation by ‘Bare’ FeO+ in the Gas Phase
Authors: Schröder Detlef , Schwarz Helmut
Published: December 2004

Bare FeO+ reacts in the gas phase with benzene at collision rate (k = 1.3 × 10−9 cm3 molecule−1 s−1), giving rise to the formation of Fe(C6H4)+/H2O(5%), Fe(C5H6)+/CO(37%), Fe(C5H5)+/CO/H. (2%), and Fe+/C6H5OH (56%). Neither the reaction rate nor the product distribution are subject to a significant kinetic isotope effect, thus, ruling out several mechanistic variants described in the literature to the operative for ‘analogous’ arene oxidation processes in solution. A mechanism is suggested which is in keeping with the experimental findings, and which also accounts for some remarkable results obtained, when two [Fe, C6,H6H6O]+ isomers are generated and subjected to a neutralization‐re‐ionization experiment in the gas phase.
Stereoselectivity in Reactions of Metal Complexes. Part XV. Structure and stability of chiral cobalt(III) complexes with pentadentate ligands
Authors: Bernauer Klaus , Stoeckli‐Evans Helen , Hugi‐Cleary Deirdre , Hilgers Hermann J. , Abd‐el‐Khalek Habib , Porret Joëlle , Sauvain Jean‐Jacques
Published: December 2004

The syntheses and characterization of four new linear pentadentate ligands and their CoIII complexes are described: N,N′‐[(pyridine‐2,6‐diy)bis(methylene)]bis[sarcosine] (sarmp), N,N′‐[(pyridine‐2,6‐diyl)bis(methylene)]bis[(R)‐ or (S)‐proline] ((R,R)‐ or (S,S)‐promp), N,N′‐[(pyridine‐2,6‐diyl)bis(methylene)]bis[N‐(methyl)‐(R)‐ or (S)‐alanine] ((R,R)‐ or (S,S)‐malmp); 2,2′‐[pyridine‐2,6‐diyl]bis[(S)‐ or rac‐N‐(acetic acid)pyrrolidine] ((S,S)‐ or rac‐bapap). The complexes were characterized and, with but one exception, complex formation is stereospecific: Δ‐exo‐(R,R) (or Λ‐exo‐(S,S)) for promp and Λ‐(R,R) (or Δ‐(S,S)) for bapap. The exception is [Co((R,R)‐ or (S,S)‐malmp)H2O]ClO4 for which two forms are obtained, to which Λ‐endo‐(R,R) (or Δ‐endo‐(S,S)) and, tentatively, Δ‐unsymmetric‐(R,R)‐ (or Λ‐unsymmetric‐(S,S)‐) configurations are assigned. X‐Ray crystal structures are presented for the complexes [Co(sarmp)H2O]ClO4, [Co((S,S)‐promp)H2O]ClO4, [Co(rac‐bapap)H2O]ClO4 and endo‐[Co(rac‐malmp)H2O]ClO4. Ligand acid dissociation and CoII and FeII complex‐formation constants are reported.
Nucleotides. Part XXXIX Synthesis of arabinonucleoside phosphoramidite building blocks
Authors: Resmini Matthias , Pfleiderer Wolfgang
Published: December 2004

High‐yield chemical syntheses of phosphoramidite building blocks of the four arabinonucleosides aUrd (1), aCyd (2), aAdo (3), and aGuo (4), suitable for (3′–5′)oligoarabinonucleotide synthesis are described. The problem of 2′‐hydroxy group protection was solved by introduction of the versatile 2‐(4‐nitrophenyl)ethoxycarbonyl (npeoc) residue, which was also used for aglycon protection.
Carbocyclic Analogs of Nucleosides. Part 3. Synthesis of a new sulfone analog of cyclic adenosine 3′,5′‐monophosphate
Authors: Jenny Thomas F.
Published: December 2004

The novel uncharged analog 2 of adenosine 3′,5′ ‐monophosphate (1) was prepared in its racemic form. To increase membrane permeability, the phosphate diester monoanion group of 1 was replaced by a dimethylene sulfone unit ( = methanosulfonylmethano group), and the 2′‐OH group was removed. To decrease lability against acid‐catalyzed depurination, the ring O‐atom was replaced by a CH2 group. All three modifications are also expected to increase the stability of analog 2 towards enzymatic degradation. The carbocyclic skeleton of 2 was constructed from trinorbornenecarbaldehyde 3 (see Scheme 1–3), and the adenine precursor 6‐chloropurine was introduced in the carbocyclic unit via an SN2 reaction based on Mitsunobu chemistry (Schemes 4 and 5).
Synthese chiraler Kobalt‐Komplexe mit planoid‐tetradentatem Ligand‐System
Authors: Härter Ralph , Wegmuth Christophe , Scheffold Rolf , Engel Peter , Linden Anthony
Published: December 2004

Synthesis of Chiral Cobalt Complexes with Planoid‐Tetradentate Ligand System

The synthesis of a series of Cbl‐related, achiral CoIII complexes 9a–c as well as enantiomerically pure, C2‐symmetric CoIII complexes 15 and 18, is reported (Schemes 3, 5, and 7). The crystal structures of 9c and 15 were determined. Complex 18 acts as an enantioselective catalyst in the isomerization of 1,4‐epiperoxides to hydroxycycloalkenones.
Synthesis and Electronic Properties of Intensely Coloured Iron(II) complexes with new 4‐substituted planar tridentate nitrogen ligands analogous to 2, 2′: 6′, 2″‐terpyridine
Authors: Bochet Christian G. , Piguet Claude , Williams Alan F.
Published: December 2004

The para‐substituted tridentate ligands 2,6‐bis[1‐(3,5‐dimethoxybenzyl)benzimidazol‐2‐yl]‐4′‐X‐phenyl)‐pyridine (X = H: L3; X = NO2: L4; X = NEt2: L5) have been synthesized in six steps using Kröhnke reactions. Spectroscopic results show that the electronic properties of the ligands are strongly influenced by the nature of the substituent bound to the pyridine ring and extended Hückel calculations performed on 4‐(X‐phenyl)pyridine fragments give a qualitative insight into the factors responsible for the striking differences observed in the absorption spectra. Upon complexation to FeII, the ligands L2–L5 give intensely coloured pseudo‐ocatahedral low spin [Fe(Ln)2]2+ (n = 2–5) complexes in acetonitrile solution. Electrochemical and spectroscopic measurements show that the particular electronic characteristics associated with each substituent strongly influence the properties of the resulting FeII complexes as demonstrated by the very intense MLCT transition (ϵ > 50000 M−1 cm−1) observed in the green complex [Fe(L5)2]2+.
Synthesis of Thiazole and Fused Thiazolo Derivatives
Authors: Urleb Uroš , Neidlein Richard , Kramer Walter
Published: December 2004

The syntheses of thiazole and fused thiazolo derivatives 2–4, 6–8, 10a–11b, 13–16 from heterocylic isothiocyanates 1, 5, 9, and 12 bearing an ortho ester group and bifunctional reagents, such as substituted propargylamines, is described. Different regioselectivity of intramolecular nucleophilic attack of the thiourea S‐atom on the C  C bond, resulting in the formation of both thiazolo and thiazino derivatives, as well as NMR structure elucidation are discussed.
Structure and Highly Stereoselective Formation of 1:2 Metal‐to‐Ligand complexes with triamine 2,6‐bis(pyrolidin‐2‐yl)pyridine. meso‐[2,6‐bis(pyrrolidin‐2yl)pyridine]nickel(II) (meso‐[Ni(bpp)2]2+), a Metal Complex with S4 Symmetry
Authors: Bernauer Klaus , Gretillat François , Stoeckli‐Evans Helen , Warmuth Ruth
Published: December 2004

The X‐Ray structures of the 1:1 copper(II) complexes with racemic and opticall active (+)‐(R,R)‐(2,6‐bis(pyrrolidin‐2‐yl)pyridine ((+)‐bpp; (+)‐I) were determined. Whereas the perchlorate 1 of racemic complex contains the monomeric units with perfect C2 symmetry, the sulfate of the optically active compound crystallizes as a coordination polymer composed of sequences of three different five‐coordinate units linked by sulfate bridges around a threefold screw axis (see 2). Formation of the 1:2 complexes of nickel(II) with (±)‐bpp is shown to be highly stereoselective. Acidimetric titrations and CD measurements indicate that the equilibrium mixture contains 99% of the meso‐complex 3 belonging to the point group S4 and only 0.5% of each enantiomer of the C2‐symmetric optically active forms. The S4 symmetry of meso‐[Ni{(+)‐bpp}{(−)‐bpp}]ClO4)2 (3) was confirmed by X‐ray analysis. The formation of binary complexes of cobalt(II), zinc(II), and cadmium(II) with (±)‐bpp shows an excess of 28, 34, and 8%, respectively, of the meso‐form over the statistical amount. CD and UV/VIS measurement show a pH‐dependent high spin/low spin equilibrium between the octahedral [Ni(bpp)(H2O)3]2+ and the square‐planar [Ni(bpp)OH]+ in aqueous solution.
Vitamin‐B12‐Catalyzed C,C‐Bond Formation. Synthesis of a california red scale pheromone
Authors: Auer Lucas , Weymuth Christophe , Scheffold Rolf
Published: December 2004

A Mixture of (3S,6R)‐ and (3R,6R)‐3‐methyl‐6‐(1‐methylethenyl)dec‐9‐enyl acetate (1a and 1b, respectively)–1a being a pheromone of the California red scale – is synthesized in 14 steps from (+)‐(R)‐limonene (4). The key step is the reductive vitamin‐B12‐catalyzed coupling of (R)‐5‐(2‐iodoethyl)‐6‐mehtylhept‐6‐en‐2‐one ethylene acetal (8) and methyl crotonate (3).
Carbocyclic Analogs of Nucleosides. Part 4. Preparation of enantiomerically pure analogs of purine nucleosides for the synthesis of sulfone‐linked oligonucleotide analogs
Authors: Jenny Thomas F. , Benner Steven A.
Published: December 2004

Cyclopentane derivatives bearing a 3‐(hydroxymethyl) group, a 4‐(2‐hydroxyethyl) functionality, and a nucleoside base are carbocyclic variants of nucleoside analogs previously described as building blocks for the preparation of oligonucleotide analogs having dimethylene sulfone (= methanosulfonylmethano) linking groups replacing the phosphodiester linking units found in natural oligonucleotides. These carbocyclic nucleoside analogs (e.g. 17 and 20) are stable to both acid‐catalyzed depurination and base‐catalyzed hydrolysis, in contrast with most non‐ionic analogs of oligonucleotides. Furthermore, they can be prepared with complete control over the stereochemistry at the ‘anomeric’ center. A procedure is given for preparing these purine‐nucleoside analogs via the construction of an enantiomerically pure carbocyclic skeleton (Schemes 1–3), followed by a Mitsunobu‐type reaction to introduce the purine‐base derivatives (Scheme 4). Furthermore, preliminary results for the coupling of these analogs to yield nucleoside dimers (e.g. 26) are also reported (Scheme 5).
Physicochemical and Structural Properties of Non‐Steroidal Anti‐inflammatory Oxicams
Authors: Tsai Ruey‐Shiuan , Carrupt Pierre‐Alain , Tayar Nabil El , Giroud Yvan , Andrade Pedro , Testa Bernard , Brée Françoise , Tillement Jean‐Paul
Published: December 2004

Using the five therapeutic oxicams 1–5, we showed that isosteric replacements result in remarkable changes in the physicochemical and structural properties of congeners. Thus, the acidity of the phenolic OH group is relatively higher in the oxicams containing a pyridinyl moiety, i.e. in piroxicam (1), tenoxicam (2), and lornoxicam, (3), due to their zwitterionic nature. This consequently influences their lipophilicity profile at different ionization states. Furthermore, partitioning behaviour in octan‐l‐ol/H2O and heptane/H2O systems suggests an internal H‐bond between the enolic OH and the amide CO group. The anionic oxicams readily partition into the octanol phase at pH 7.4 and not at all into the heptane phase. Only the partition coefficients of oxicams measured in the heptane/H2O system, but not in the octanol/H2O system, correlate with their transfer across the blood‐brain barrier. This implies that only the neutral form of oxicams crosses the blood‐brain barrier.
Epoxidierung von Cucurbitaxanthin A: Herstellung von Cucurbitaxanthin B und seines 5′,6′‐Epimeren
Authors: Deli József , Matus Zoltán , Molnár Péter , Tóth Gyula , Décsy Zoltán , Eugster Conrad Hans
Published: December 2004

Epoxidation of Cucurbitaxanthin A: Preparation of Cucurbitaxanthin B and of Its 5′,6′‐Epimer

Cucurbitaxanthin A (= (3S,5R,6R,3′S)‐3,6‐epoxy‐5,6‐dihydro‐β,β‐carotene‐5,3′‐diol; 1) isolated from red pepper (Capsicum annuum var. longum nigrum) was trimethylsiylated and then epoxidized with monoperphthalic acid. After deprotection and chromatographic separation, cucurbitaxanthin B (= (3S,5R,6R, 3′S,5′R,6′S)‐3,6:5′,6′‐diepoxy‐5,6,5′,6′‐tetrahydro‐β,β‐carotene‐5,3′‐diol; 2) and 5′,6′‐diepicucurbitaxanthin B (= (3S,5R,6R, 3′S,5′S,6′R)‐3,6:5′,6′‐diepoxy‐5,6,5′,6′‐tetrahydro‐β,β‐carotene‐5,3′‐diol; 5) were obtained and carefully characterized. They show mirror‐like CD spectra and, therefore, emphasize the importance of the torsion angle of C(6)–C(7) on the electronic interaction between the polyene chain and the chiral end group.
Synthesis of (−)‐Pinidine via asymmetric, electrophilic enolate hydroxyamination/nitrone reduction
Authors: Oppolzer Wolfgang , Merifield Eric
Published: December 2004

Enantiomerically pure(−)‐pinidine (1) has been synthesized in 18.5% overall yield by a nine‐step sequence starting from keto‐ester 2. The key step 5 → 6 involves an asymmetric, electrophilic enolate hydroxyamination. Diastereoselective hydrogenation of nirtone 6 ensures the cis‐relation between the substituents at C(2) and C(6) in piperidine 7.
Synthesis and Structure of η4‐Enone Complexes of Ruthenium(0)
Authors: Marcuzzi Alessandro , Linden Anthony , von Philipsborn Wolfgang
Published: December 2004

A variety of [Ru(CO)2L(η4enone)] complexes (L = phosphines, phosphites, and arsines, enone = (E)‐4‐phenylbut‐3‐en‐2‐one) have been synthesized. 1H‐, 13C‐, and 31P‐NMR spectra are reported and the X‐ray structures of two Ru complexes with L  Ph3P(7), Et3P (10) and one Fe complex with L  Ph3P (14) are presented. All three compounds crystallize in the same monoclinic space group P21/n with a = 10.575(2) Å, b =9.213(2) Å, and c = 27.608(5) Å, β = 100.04(2)°, Z = 4 for 7, a = 10.276(3) Å, b = 12.935(3) Å, and c = 14.854(2) Å, β = 96.96(2)°, Z = 4 for 10, and a = 10.492(2) Å, b = 9.232(3) Å, and c = 27.129(3) Å, β = 98.67(2)°, Z = 4 for 14. The structures of the Ru complexes are compared with the Fe analogues. In the case of M  Ru and L  (EtO)3P, (MeO)3P, and (i‐PrO)3P (9, 11, and 13, respectively) stereoisomers could be detected by 31P‐NMR at room temperature, wich arise from rotation at the coordinated metal centre.
The 2H,2H‐INADEQUATE experiment: Detection of One‐ and Two‐Spin Double Quantum Coherences
Authors: Mons Hans‐Egbert , Bergander Klaus , Günther Harald
Published: December 2004

The INADEQUATE experiment for spin‐1 nuclei has been extended to deuteron spin systems of the AX, AA′ XX′, and AA′MM′X type. Measurements with (3,3‐D2)norcampher, 4‐chloro(2,3,5,6‐D4)pyridine, and (D5)pyridine revealed correlation peaks due to two‐spin double quantum coherences and additional one‐spin double quantum peaks with coordinates F1 = 2 ωi, F2 =(ωii = A, X) which were not observed in the 6Li, 6Li,‐INADEQUATE experiment described earlier.
Improved Purification of C60 and Formation of σ‐ and π‐Homoaromatic methano‐bridged fullerenes by reaction with alkyl diazoacetates
Authors: Isaacs Lyle , Wehrsig Arno , Diederich François
Published: December 2004

A rapid and inexpensive method for the large‐scale purification of C60 is the simple filtration of the toluenesoluble extract of commercial fullerene soot through a short plug of charcoal/silica gel with toluene as the eluent. Reactions of C60 with ethyl and tert‐butyl diazoacetates in refluxing toluene lead to the formation of the (alkoxycarbonyl)methylene‐bridged isomers 1a–3a and 1b–3b, respectively, which can be equilibrated, upon further heating, into the single compounds 1a and 1b, respectively. Isomers 1a/b possess the methano bridge at the 6–6 ring junction, whereas structures 2a/b and 3a/b are bridged at the 6–5 junction. A dramatic influence of local and π‐ring current anisotropic effects of the fullerene sphere on the NMR chemical shifts of the methine protons in the bridge is observed: the chemical shifts of the protons located over a pentagon ring in 2a/b and over a hexagon ring in 3a/b differ by Δδ = 3.47 and 3.45 ppm, respectively. The analysis of the 13C‐NMR chemical shifts of the bridgehead C‐atoms and the 1J(C,H) coupling constants for the methano‐bridge atoms reveals conclusively that the 6‐5‐ring‐bridged structures 2a/2b and 3a/3b are π‐homoaromatic (‘open’ transannular bond) and the 6‐6‐ring‐bridged structures 1a/b are π‐homoaromatic (‘closed’ transannular bond). The electronic absorption spectra show that π‐homoconjugation in 2a/b and 3a/b represents a much smaller electronic perturbation of the original C60 chromophore than σ‐homoconjugation in 1a/b. The results of this study demonstrate an impressive linkage between the chemistry of methano‐bridged annulenes and methano‐bridged fullerenes.
An Efficient Enantioselective Synthesis of (—)‐Serricorole
Authors: Oppolzer Wolfgang , Rodriguez Inès
Published: December 2004

The cigarette beetle pheromone (–)‐serricorole (1) has been synthesized in 23% overall yield by an eight‐step sequence starting from N‐propionylsultam 3. The synthesis features asymmetric anti‐ and syn‐aldolizations 3 → 4 and 8 → 9, a non‐destructive N‐acylsultam cleavage with lithiated ethylphenylsulfone (10 → 12), and the smooth, Ti‐mediated cyclization of β‐acyloxy‐ketone 2 to dihydropyranone 14.
Stereocontrolled Syntheses of Polysubstituted 2,3‐Dihydro‐4H‐pyran‐4‐ones by cyclocondensation of β‐ acyloxy‐ketones
Authors: Oppolzer Wolfgang , Rodriguez Inés
Published: December 2004

syn‐β‐Acyloxy‐ketones 6 and an anti‐β‐acyloxy‐ketone 17 undergo smooth intramolecular enolate/ester condensations 6 → 18 and 17 → 19 when treated with TiCl4/EtN(i‐Pr)2. Thus, tri‐ and tetrasubstituted cis‐ or trans‐2,3‐dihydro‐4H‐pyran‐4‐ones are easily prepared in a stereoselective manner.
Lanthanide‐nitrate interaction in anhydrous acetonitrile and coordination numbers of the lanthanide ions: FT‒IR study
Authors: Bünzli Jean‐Claude G. , Milicic‐Tang Anita , Mabillard Catherine
Published: December 2004

The interaction between lanthanide ions LnIII (Ln = La, Nd, Sm–Dy, Er, Yb) and nitrate ions is investigated by FT‐IR spectroscopy in dilute anhydrous MeCN solution. The work is performed for ratios R = [NO]t/[LnIII]t ranging from 0 to 8 and for solutions generally 0.05M in LnIII, prepared from anhydrous lanthanide perchlorates Ln(ClO4)3. When nitrate is progressively added to the Ln(ClO4)3 solutions, the formation of [Ln(NO3)n](3−n)+ species is clearly evidenced by the FT‐IR spectra. All the NO3− ions are coordinated and bidentate. A quantitative study was performed using the v1 and v6 vibrational modes for coordinated NO ions. The average coordination numbers estimated for Nd, Eu, Tb, and Er in solutions of trinitrates are 9.0, 9.1, 8.3 and 8.2, respectively (±0.3 unit). In presence of an excess NO, these numbers become 9.8, 10.2, 10.0, 9.8, 9.9, and 9.9 (±0.3 unit) for La, Nd, Eu, Tb, Er, and Yb, respectively. No hexanitrato species forms under the experimental conditions used (R up to 8). The structural aspect of the various nitrato species is also investigated. In the pentanitrato species, all the ligands appear to be equivalent, while large inequivalences are observed for Ln(NO3)3 solutions. Since for the latter most of the absorption bands assigned to nitrate vibrations contain several components, a curve‐fitting procedure has been used for decomposing the v2, v4 and v6 vibrations. There is a considerable difference between LnIII ions, the nitrate inequivalences being larger in the middle of the series.
Ilwensisaponins A, B, C, and D: Triterpene Saponins from Scrophularia ilwensis
Authors: Çaliş İhsan , Zor Murat , Başaran A. Ahmet , Wright Athony D. , Sticher Otto
Published: December 2004

From the aerial parts of Scrophularia ilwensis, four new triterpene saponins, ilwensisaponins A–D (1–4) were isolated. The structures of the compounds were elucidated using chemical and spectral data as 13β, 28‐epoxy‐3‐β‐{{[β‐D‐glucopyranosyl‐(1→2)]‐[α‐L‐rhamnopyranosyl‐(1→4)‐β‐D‐glucopyranosyl‐(1→3)]‐β‐D‐fucopyranosyl}‐oxy} olean‐11‐en‐23‐ol (1), 3‐β‐{{[β‐D‐glucopyranosyl‐(1→2)]‐[α‐L‐rhamnopyranosyl‐(1→4)‐β‐D‐glucopyranosyl‐(1→3)]‐β‐D‐fucopyranosyl}oxy}olena‐11, 13(18)‐diene‐23, 28‐diol (2), 3‐β‐{{[β‐D‐glucopyranosyl‐(1→2)]‐[α‐L‐rhamnopyranosyl‐(1→4)‐β‐Dglucopyranosyl‐(1→3)]‐β‐Dfucopyranosyl}oxy}‐11α‐methoxyolean‐ 12‐ene‐23, 28‐diol (3), and 3‐β‐{{[β‐D‐glucopyransoyl‐(1→2)]‐[α‐L‐rhamnopyranosyl‐(1→4)‐β‐D‐glucopyranosyl‐(1→3)]‐β‐D‐fucopyranosyl}oxy}olean‐12‐ene‐11α,23,28‐triol(4).
Why Pentose‐ and Not Hexose‐Nucleic Acids??. Part VII. Pyranosyl‐RNA (‘p‐RNA’). Preliminary communication
Authors: Pitsch Stefan , Wendeborn Sebastian , Jaun Bernhard , Eschenmoser Albert
Published: December 2004

Qualitative conformational analysis of the entirety of conceivable hexo‐ and pentopyranosyl oligonucleotide systems derived from the diastereoisomeric aldohexoses (CH2O)6 and aldopentoses (CH2O)5 predicts the existence of a variety of pairing systems which have not been experimentally investigated so far. In particular, the analysis foresees the existence of a ribopyranosyl isomer of RNA (‘p‐RNA’), containing the phosphodiester linkage between the positions C(4′) and C(2′) of neighboring ribopyranosyl units. Double strands of p‐RNA oligonucleotides are expected to have a linear structure and to show purine‐pyrimidine and purine‐purine (Watson‐Crick) pairing comparable in strength to that observed in homo‐DNA. Experimentally, synthetic β‐D‐ribopyranosyl (4′→2′)‐oligonucleotides derived from adenine and uracil confirm this prognosis: adenine‐uracil pairing in p‐RNA duplexes is stronger than in the corresponding RNA duplexes. Importantly, adenine in p‐Ribo(A8) does not show (reverse‐Hoogsteen) self‐pairing, in sharp contrast to its behavior in the homo‐DNA series. The sheer existence of strong and selective pairing in a system that is constitutionally isomeric to RNA and can be predicted to have a linear structure has implications for the problem of RNA's origin. In this context, a comprehensive experimental study of the pairing properties of p‐RNA, of its potential for constitutional assembly, self‐replication, and intra‐duplex isomerization to RNA seems mandatory.
Stereoselectivity in Reactions of Metal Complexes. Part XVII. Synthesis of three new optically active triamines: 2,6‐Bis{[(2S)‐2‐(hydroxymethyl)pyrrolidin‐1‐yl]methyl}pyridine, 2,6‐bis{[(2S)‐2‐(methoxymethyl)pyrrolidin‐1‐yl]methyl}pyridine, and 2,6‐bis{{(2S)‐2‐[(benzyloxy)methyl]pyrrolidin‐1‐yl}methyl}pyridine. X‐ray structure and equilibrium behaviour of their copper(II) complexes
Authors: Bernauer Klaus , Chuard Thierry , Stoeckli‐Evans Helen
Published: December 2004

The three new optically active triamines derived from 2,6‐bis(aminomethyl)pyridine, i.e. 2,6‐bis{[(2S)‐2‐(hydroxymethyl)pyrrolidin‐1‐yl]methyl}pyridine (3a), 2,6‐bis{[(2S)‐2‐(methoxymethyl)pyrrolidin‐1‐yl]methyl}‐pyridine (3b), and 2,6‐bis{{(2S)‐2‐[(benzyloxy)methyl]pyrrolidin‐1‐yl}methyl}pyridine (3c), were synthesized. The equilibrium behaviour in solution and CuII complex formation were studied by acidimetric titration and by UV/VIS and CD measurements. It was found that in aqueous solution, 3a can coordinate one of the CH2OH groups to CuII upon deprotonation. X‐Ray crystal structures were determined for the complexes [Cu(3a)Cl]ClO4·H2O, [Cu(3b)Cl]ClO4, and [Cu(3c)Cl]ClO4. In the solid state, coordination of both the OH and the alkoxy groups was observed, and the three ligands are pentacoordinated.
Tritium Labelling of Naltrindole, a δ‐Receptor‐Selective Opioid Antagonist via 1‐Bromonaltrexone
Authors: Tóth Géza , Ötvös Ferenc , Hosztafi Sándor
Published: December 2004

The synthesis of [1,5′‐3H2]naltrindole (9) with labels at both the morphine skeleton and the indole moiety was carried out by catalytic tritiodehalogenation of 1,5′‐dibromonaltrindole (8) resulting in a specific activity of 46.1 Ci/mmol (1705 GBq/mmol). The brominated precursor was prepared by the Fischer indole synthesis starting from 1‐bromonaltrexone (7) and (4‐bromophenyl)hydrazine.
Investigation of an Olfactoryly Active Ring‐Like Conformer of a Chain‐Type Odorant, (3S)‐3,7‐dimethyloctanal, by computer calculation and graphics
Authors: Yoshii Fumiko , Hirono Shuichi , Moriguchi Ikuo
Published: December 2004

The odor of (3S)‐3,7‐dimethyloctanal, a chain‐type odorant, has some resemblance to that of ethyl (1 R, 6S)‐2,2,6‐trimethylcyclohexane‐1‐carboxylate, a ring‐type odorant. We investigated the ring‐like conformers of (3S)‐3,7‐dimethyloctanal. Two approaches, (i) systematic conformational analysis and (ii) construction of the initial structure by referring to the structure of the ring‐type odorant, were considered in the search for ring‐like conformers of the chain‐type odorant. As a result, it was found that two stable ring‐like conformers of (3S)‐3,7‐dimethyloctanal, obtained from the two approaches, resembled conformers of ethyl (1R, 6S)‐2,2,6‐trimethylcyclohexane‐1‐carboxylate in their three‐dimensional structural features. The shapes of the two ring‐like ones were not exactly the same but were quite similar. Therefore, the two ring‐like conformers were considered to approximate the olfactoryly active conformer that binds and stimulates the same odor receptor as that for ethyl (1R,6S)‐2,2,6‐trimethylcyclohexane‐1‐carboxylate. In addition, ring‐like conformers of another chain‐type odorant, 2‐methylpent‐2‐enal, were investigated to check the validity of the calculation method used.
Self‐Replication of Oligonucleotides in Reverse Micelles
Authors: Böhler Christof , Luisi Pier Luigi , Bannwarth Willi
Published: December 2004

The coupling between the tri(deoxynucleotides) d[(MeO)C‐G‐Ap] (1) and d[(NH2)Td5′‐C‐G‐] (2) to yield the phosphoramidate‐linked (hexadeoxy‐nucleotide) d[(MeO)C‐G‐Anh5′Td5′‐C‐G] (3) was investigated both in aqueous solution and in reverse micelles constituted of CTAB (cetyl(trimethyl)ammonium bromide) in hexane/pentan‐1‐ol 9:1. No siginificant difference was found concerning the yield and the kinetics of the reaction in the two systems. The coupling between 1 and 2 was also carried out in the presence of the template d[(MeO)C‐G‐A‐T‐C‐G] (4), an analogue of 3, so as to reproduce the conditions of template‐directed self replication. It was shown that the trinucleotide coupling in the presence of a template obeys the so‐called square‐root law both in H2O and in reverse micelles. No significant difference of the time course of the reaction in H2O and in reverse micelles was observed. This shows that self‐replication of oligonucleotides occurs within geometrically bounded structures, which represents a step forward in the mimicking of minimal life processes.
The Homoconjugated Electron‐Releasing Carbonyl Group of 1‐Methylbicyclo[2.2.1]hept‐5‐en‐2‐one. Regioselective syntheses of 5‐chloro‐ and 6‐chloro‐1‐methylbicyclo[2.2.1]hept‐5‐en‐2‐one
Authors: Kernen Philippe , Vogel Pierre
Published: December 2004

Syntheses of (±)‐2‐exo‐cyano‐1‐methyl‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐endo‐yl acetate (1) and of (±)‐1‐methyl‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐one (2) are reported. The additon of PhSeCl to 1 afforded (±)‐5‐endo‐chloro‐2‐exo‐cyano‐1‐methyl‐6‐exo‐(phenylselenenyl)‐7‐oxabicyclo[2.2.1]hept‐2‐endo‐yl acetate (6), whereas 2 added to PhSeCl with the opposite regioselectivity giving (±)‐6‐endo‐chloro‐1‐methyl‐5‐exo‐(phenylselenenyl)‐7‐oxabicyclo[2.2.1]heptan‐2‐one (7). These adducts were converted into 5‐chloro‐1‐methyl‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐one (9) and 6‐chloro‐1‐methyl‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐one (10), respectively.
2‐(Tributylstannyl)‐1‐{[2‐(trimethylsilyl)ethoxy]methyl}‐1H‐indole: Synthesis and use as a 1H‐indol‐2‐yl‐anion equivalent
Authors: Palmisano Giovanni , Santagostino Marco
Published: December 2004

Pd‐Catalyzed reaction of 2‐(tributylstannyl)‐1‐{[2‐(trimethylsilyl)ethoxy]methyl}‐1H‐indole (5) with a variety of aryl, heteroaryl, vinyl, and allyl halides provides an efficient entry to the corresponding cross‐coupled products (see Table).
Synthesis and Characterization of (5′‐Deoxyadenosin‐5′‐yl)cobalamin ( = ‘Adenosylcobalamin’) Analogues Mimicking the Transition‐State Geometry of Coenzyme‐B12‐Dependent Rearrangements
Authors: Poppe László , Rétey János , Hull William E.
Published: December 2004

A convergent synthesis of the five novel analogues 1a–e of (5′‐deoxyadenosin‐5′‐yl)cobalamin ( = ‘adenosylcobalamin’) is described. The analogues 1a–e carry oligomethylene chains (C3–C7) inserted between the central Co‐atom and the 5′‐O‐atom of the adenosine moiety and are thought to mimick the transition‐state geometry in coenzyme‐B12‐catalyzed rearrangement. All five analogues were characterized by NMR, UV, and FAB mass spectrometry.
Photochemistry of 6,6‐Dimethyl‐ and 2,2,6,6‐Tetramethyl‐2H,6H‐pyran‐3‐one
Authors: Er Erhan , Margaretha Paul
Published: December 2004

The title compounds 1a and 1b have been synthesized in two steps from the saturated pyran‐3‐ones 2a and 2b, respectively. Upon irradiation (254 nm or 350 nm) in dilute solutions (10−3−10−2M), compounds 1 undergo a formal [4 + 2] cycloreversion from the excited triplet state to give (2‐methylprop‐1‐enyl)ketene (11) and either formaldehyde or acetone, ketene 11 being trapped by H2O or MeOH to afford 4‐methylpent‐3‐enoic acid (5) or its methyl ester 4 in 75–85% isolated yield. In this (monomolecular) photoreaction, heterocycles 1 differ from their alicyclic counterparts, i.e., 4,4‐dimethylcyclohex‐2‐enone (10a) and 4,4,6,6‐tetramethylcyclohex‐2‐enone (10b), as no rearrangement to a 4‐oxabicyclo[3.1.0]hexan‐2‐one occurs. On the other hand, the photochemical behavior of pyranone 1a in bimolecular reactions (cyclodimerization, [2 + 2] cycloaddition to 2,3‐dimethylbut‐2‐ene) resembles that of enone 10a.
Syntheses of Segmental Heteroleptic Ligands for the Self‐Assembly of Heteronuclear Helical Supramolecular Complexes
Authors: Piguet Claude , Bocquet Bernard , Hopfgartner Gérard
Published: December 2004

The development of a modified Phillips reaction allows the synthesis of complicated heteroleptic ligands based on pyridine and 1H‐benzimidazole moieties. The key‐step formation of aromatic 1H‐benzimidazole rings from N‐(2‐nitroaryl)arenecarboxamides significantly improves the possibilities of the classical intermolecular Phillips reactions and can be applied to the synthesis of large oligo‐multidentate units. Segmental heteroleptic ligands containing two different bidentate coordinating units (see 14) or bidentate and terdentate sites connected by ‘diphenylmethane’ ( = methylenebis(phenylene)) spacers (see 15 and 16) were obtained in fair to good yield by using multistep syntheses following this strategy. Heterotrileptic ligands (bidentate‐terdentate‐bidentate, see 19 and 20; terdentate‐terdentate‐terdentate, see 23) requiring the simultaneous formation of four 1H‐benzimidazole rings in one step were prepared and demonstrate the extended possibilities of this methodology. Data are presented to show that the milder conditions used for this modified Phillips reaction together with its flexibility are essential for the development of ligands adapted for the self‐assembly of heteronuclear helical complexes.
Synthesis of Linear Oligomers of (R)‐3‐Hydroxybutyrate and Solid‐State Structural Investigations by electron microscopy and X‐ray scattering
Authors: Seebach Dieter , Bürger H. Michael , Müller Hans‐Martin , Lengweiler Urs D. , Beck Albert K. , Sykes Kathy E. , Barker Phil A. , Barham Peter J.
Published: December 2004

Repetitive treatment of the biopolymer P(3‐HB) (molecular weight > 105 Dalton, storage or s‐P(3‐HB)), with lithium hexamethyl disilazanid (LHMDS) at −70° in THF leads to a mixture of oligomers with increasingly sharp distribution around a 15‐, 30‐, and 45mer. Discrete fragments are also isolated when P(3‐HB) is heated under reflux (89°) in neat Et3N. Linear oligo(3‐HB) derivatives (3‐7) containing up to 96 3‐HB units are synthesized using an exponential segment‐coupling strategy. These oligomers are used to calibrate size‐exclusion chromatography columns for the analysis of oligo(3‐HB) samples from the different sources. The linear oligo‐(3‐HB) derivatives also served as a model with respect to the physical properties of high molecular weight P(3‐HB) and were investigated as such by transmission electron microscopy (TEM) and by small‐ and wide‐angle X‐ray scattering (SAXS and WAXS). The thicknesses of the lamellar crystallites (long periods) formed by the 8mer, 16mer, and 32mer, are ca. 26, 52, and 53 Å, respectively, indicating that the 32mer molecules are folded once, very tightly, into a ‘hair‐pin’‐type conformation. High‐molecular‐weight P(3‐HB), which was crystallized in a similar way, also has a lamellar crystallite thickness of ca. 50–65 Å. Thus, the treatment of P(3‐HB) with LHMDS at low temperature causes etching of the amorphous regions, an effect well known in polymer science for studying the regularity of chain folding. The ca. 50‐Å packing within the tight folds of P(3‐HB) is discussed in view of its possible function in ion transport through cell membranes.
Glycosylidene Carbenes. Part 17. Glycosidation of benzyl β‐D‐ and β‐L‐ribopyranosides. Further evidence for the effect of stereoelectronic control on the regioselectivity of glycosidation
Authors: Uhlmann Peter , Vasella Andrea
Published: December 2004

The H‐bonds of the enantiomeric ribosides 4 and 5 and their glycosidation by the diazirine 1 are described. HO–C(2) and HOC(4) of 4 and 5 form a ‘flip‐flop’ H‐bonding system, with HOC(3) acting as a H‐bond donor to OC(2) or OC(4). HOC(2) and HOC(4) of monomeric 4 and 5 are thus the most strongly acidic OH groups. Glycosidation of 4 and 5 by 1 depends on the solvent, the temperature, and the concentration. It yields up to 91% of a mixture of anomeric pairs of the 1,2‐, 1,3‐, and 1,4‐linked disaccharides 8–13 and 20–25, respectively, which were characterized as their diacetates 14–19 and 26–31 (Scheme). Glycosidation in CH2Cl2 and in dioxane yielded mostly the 1,3‐linked disaccharides 10/11 and 22/23 (α/β ca. 4:1), while glycosidation in THF leads mostly to the 1,2‐ and 1,4‐linked regioisomers (β>α). There are small, but significant differences in the glycosidation of 4 and 5. These, the regio‐, and the stereoselectivities are rationalized as the consequences of the stereoelectronic control of both the H‐transfer from HOC(2) or HOC(4) to the intermediate carbene and of the formation of the glycosidic CO bond, and of the coordination of the intermediate oxycarbenium ion with THF.
Novel Cholic‐Acid‐Type Sterones of Deltocyathus magnificus, a deep‐water scleractinian coral from the Loyalty Islands, SW Pacific
Authors: Guerriero Antonio , D'Ambrosio Michele , Zibrowius Helmut , Pietra Francesco
Published: December 2004

Cholic‐acid‐type 3‐keto steroids 1–8, all isolated from Deltocyathus magnificus (2–8 after CH2N2 treatment), are the first secondary metabolites obtained from a deep‐water scleractinian. Steroids 1–3, 5, and 7 are new, their main structural oddities being loss of C(24) (see 5) or hydroxylation in the side chain (see 3 and 7). Steroids 4, 6, and 8, from the same coral, were previously known from other marine organisms.
Synthesis and Circular Dichroism of Both Enantiomers of 2‐deuterofluoroacetic acid ( Fluoro[2H1]acetic acid)
Authors: Gartz Dagmar , Reed Jennifer , Rétey János
Published: December 2004

Sharpless epoxidation of (E)‐1‐(trimethylsilyl)[1‐2H1]oct‐1‐en‐3‐o1 (3a) yielded (1S,2S,3S)‐ and (1R,2R,3R)‐1‐(trimethylsilyl)‐1,2‐epoxy[1‐2H1]octan‐3‐ols (4a and 4b, resp.) which were converted in three steps into (S)‐ and (R)‐fluoro[ 2H1]acetic acid (7a and 7b, resp.) in good yields. Their high isotopic and optical purity was established by 1H‐ and 19F‐NMR, mass, and circular‐dichroism spectroscopy.
Synthesis of 1,3,4,5‐Tetrahydro‐2‐benzoxepin Derivatives as Conformationally Restricted Analogues of cyclamenaldehyde‐type compounds and as intermediates for highly odour‐active homologues
Authors: Skouroumounis Georges , Winter Béat
Published: December 2004

Nine 1,3,4,5‐tetrahydro‐2‐benzoxepin derivatives have been prepared as mimics of the folded (gauche) conformation of cyclamenaldehyde (1) and related compounds, but none of them showed the typical lily‐of‐the valley (muguet) odour activity. However, conversion of these substances to previously unknown analogues of 1 having a Me substituent on the aromatic ring in an ortho position to the side chain led to new fragrance substances with remarkable properties. The results indicate that the extended (anti) conformation is more likely to be the ‘bioactive’ one at the receptor site(s).
A Ring Enlargement from Seven‐ to Ten‐Membered‐Ring sulfonamide derivatives
Authors: Orahovats Alexander S. , Bratovanov Svetoslav S. , Linden Anthony , Heimgartner Heinz
Published: December 2004

The reaction of 3‐(dimethylamino)‐2,2‐dimethyl‐2H‐azirine (1a) with 4,5‐dihydro‐7,8‐dimethoxy‐1,2‐benzothiazepin‐3‐one 1,1‐dioxide (4) in dioxane at room temperature gave the correspondingly substituted 4H‐1,2,5‐benzothiadiazecin‐6‐one 1,1‐dioxide 5a in 64% yield (Scheme 2). The structure of this novel ten‐membered ring‐enlargement product was established by X‐ray crystallography (Fig.). Under more vigorous conditions (refluxing dichloroethane), 5a was formed together with the isomeric 6a, both in low yield. The 3‐(dimethylamino)‐2H‐azirines 1b and 1c reacted sluggishly to give the two isomeric ring‐enlargement products of type 5 and 6 in yields of 24–29% and 2–4%, respectively (Table 1). Even less reactive is 2,2‐dimethyl‐3‐(N‐methyl‐N‐phenylamino)‐2H‐azirine (1d), which reacted with 4 in MeCN only at 65°. Under these conditions, besides numerous decomposition products, only traces of 5d and 6d were formed. No ring enlargement was observed with the sterically crowded 1e, which bears an isopropyl group at C(2).
Electrochemical Behaviour and Antioxidant Activity of Some Natural Polyphenols
Authors: Born Markus , Carrupt Pierre‐Alain , Zini Roland , Brée Françoise , Tillement Jean‐Paul , Hostettmann Kurt , Testa Bernard
Published: December 2004

A number of natural polyphenols (chlorogenic acid (9), cordigol (11), cordigone (12), danthrone (1), 1,5‐dihydroxy‐3‐methoxyxanthone (2), eriosematin (7), flemichin D (8), frutinone A (6), mangiferin (4), quercetin (5), 1,3,6,7‐tetrahydroxyxanthone (3) and verbascoside (10)) were investigated for their redox properties using cyclic voltammetry. The antioxidant properties of these compounds were also examined in two models, namely lipid peroxidation in rat synaptosomes and AAPH‐mediated oxidation of serum albumin. Compounds with a catechol group (9, 4, 5, 3 and 10) were oxidized below 0.4 V and inhibited lipid peroxidation with IC50 values between 2 and 8 μM. Compounds having one or more isolated phenolic groups and showing an oxidation potential between 0.45 and 0.8 V (11, 12 and 8) inhibited lipid peroxidation with IC50 between 7 and 9 μM, except 2 (0.45 V), danthrone (0.96 V) and eriosematin which showed no or modest antioxidant activity. Some of the investigated compounds also protected albumin from oxidation, but no structure‐activity relationship was apparent, suggesting that other factors beside redox potential influence this activity.
Preparation of N‐Fmoc‐Protected β2‐ and β3‐Amino Acids and their use as building blocks for the solid‐phase synthesis of β‐peptides
Authors: Guichard Gilles , Abele Stefan , Seebach Dieter
Published: December 2004

N‐Fmoc‐Protected (Fmoc = (9H‐fluoren‐9‐ylmethoxy)carbonyl) β‐amino acids are required for an efficient synthesis of β‐oligopeptides on solid support. Enantiomerically pure Fmoc‐β3‐amino acids β3: side chain and NH2 at C(3)(= C(β)) were prepared from Fmoc‐protected (S)‐ and (R)‐α‐amino acids with aliphatic, aromatic, and functionalized side chains, using the standard or an optimized Arndt‐Eistert reaction sequence. Fmoc‐β2‐ Amino acids (β2 side chain at C(2), NH2 at C(3)(= C(β))) configuration bearing the side chain of Ala, Val, Leu, and Phe were synthesized via the Evans' chiral auxiliary methodology. The target β3‐heptapeptides 5–8, a β3‐ pentadecapeptide 9 and a β2‐heptapeptide 10 were synthesized on a manual solid‐phase synthesis apparatus using conventional solid‐phase peptide synthesis procedures (Scheme 3). In the case of β3‐peptides, two methods were used to anchor the first β‐amino acid: esterification of the ortho‐chlorotrityl chloride resin with the first Fmoc‐β‐amino acid 2 (Method I, Scheme 2) or acylation of the 4‐(benzyloxy)benzyl alcohol resin (Wang resin) with the ketene intermediates from the Wolff rearrangement of amino‐acid‐derived diazo ketone 1 (Method II, Scheme 2). The former technique provided better results, as exemplified by the synthesis of the heptapeptides 5 and 6 (Table 2). The intermediate from the Wolff rearrangement of diazo ketones 1 was also used for sequential peptide‐bond formation on solid support (synthesis of the tetrapeptides 11 and 12). The CD spectra of the β2‐ and β3‐peptides 5, 9, and 10 show the typical pattern previously assigned to an (M) 31 helical secondary structure (Fig.). The most intense CD absorption was observed with the pentadecapeptide 9 (strong broad negative Cotton effect at ca. 213 nm); compared to the analogous heptapeptide 5, this corresponds to a 2.5 fold increase in the molar ellipticity per residue!
Regioselectivity of the Base‐Induced Ring Cleavage of 1‐Oxygenated Derivatives of Cyclobutabenzene
Authors: Gokhale Abha , Schiess Peter
Published: December 2004

Oxy anions 3 generated from 1,2‐dihydrocyclobutabenzen‐1‐ones 1 through addition of a charged nucleophile or from 1‐hydroxy‐1,2‐dihydrocyclobutabenzenes 2 by deprotonation with base lead to stable products through distal and/or proximal cleavage of the strained four‐membered ring via benzyl carbanion 4 and/or aryl carbanion 5. A systematic study of this process reveals the relative stability of the two isomeric carbanions 4 and 5 as a key factor in determining the course of the ring‐cleavage reaction. While benzyl carbanions 4 can be trapped with carbon electrophiles, attempts at trapping aryl carbanions 5 with electrophiles other than H+ failed. In protic solvents, the magnesium salt of the tertiary alcohol 2 shows an increased rate of proximal cleavage as compared to its alkali salts. From this, we conclude that, in contrast to benzyl carbanions 4, free aryl carbanions 5 are of transient existence only. Proximal C,C‐bond cleavage seems to occur either through protonation of 5 from a fast, reversible equilibrium 3⇌5 in which 3 strongly predominates, or in protic solvents possibly even through a rate‐limiting protonation of 3 at the aromatic C‐atom, bypassing free anion 5 altogether. Thus, additional factors other than just the relative stability of isomeric carbanions 4 and 5 are of importance in determining the regiochemistry of the base‐induced C,C‐bond cleavage in ketones 1 and in alcohols 2.
Über Vinylchlorid und seine Polymerisationsprodukte. III. Zur Kenntnis der Polymerisation von Vinylchlorid in Lösung
Authors: Fierz‐David H. E. , Zollinger Heh.
Published: December 2004

1. Zur Lösungspolymerisation von Vinylchlorid mit Peroxydkatalysatoren eignen sich besonders jene Lösungsmittel, welche das Polymere praktisch überhaupt nicht lösen.
Etudes sur les matières végétales volatiles XXXV. Sur la constitution du soi‐disant „linaloloxyde”︁ (époxylinalol)
Authors: Naves Y. R. , Bachmann P.
Published: December 2004

L'époxylinalol est l'époxy‐2,3‐diméthyl‐2,6‐octène‐7‐ol(6). Il est hydrogéné par le sodium et l'alcool en un mélange de diméthyl‐2,6‐octène‐7‐ol‐(3,6) et d'un oxyfurane ou oxypyrane. Le spectre Raman de l'époxyde a été déterminé.
Mikrobestimmung von Alkylimid‐Gruppen
Authors: Fierz‐David H. E. , Pfanner E. , Oppliger F.
Published: December 2004

Abgeänderte Apparatur zur Bestimmung kleiner Mengen Alkoxyl, Alkylimid, Alkoxyl neben Alkylimid und Methoxyl neben Äthoxyl. An Stelle des üblichen Kupferoxydheizbades wurde ein elektrisch geheiztes Luftbad verwendet. Durch die Anbringung eines Kühlmantels, eines mit Natronasbest gefüllten Absorptionsröhrchens und durch die dadurch bedingte Verwendung von Stickstoff statt Kohlendioxyd zum Durchleiten durch die Apparatur konnte ein restloses Zurückhalten der Jodwasserstoffdämpfe erreicht werden. Dieses war bei den früher bekannten Apparaturen nicht möglich, da nur eine Waschvorrichtung angebracht war, deren Inhalt sehr leicht verbraucht wurde, was sich vor allem ungünstig bei den Alkylimid‐Bestimmungen auswirkte. Ferner wurde eine neue Absorptionsvorlage verwendet, die ein besseres Auffangen der Alkyljodide gewährleistet.
Die Bildung von Furan‐2,5‐dicarbonsäure aus d‐Glucuron und d‐Galakturonsäure beim Menschen. Ein neuer Abbauweg für Kohlenhydrate
Authors: Flaschenträger B. , Cagianut B. , Meier F.
Published: December 2004

1. Die Ausscheidung der im normalen menschlichen Harn vorkommenden Furan‐2,5‐dicarbonsäure wird nach Einnahme von 5 g d‐Glucuron und d‐Galakturonsäure um das 5–15 fache gesteigert. Da nur ein Bruchteil der gebildeten Dicarbonsäure zur Ausscheidung gelangt, muss ein grösserer Umsatz im Organismus angenommen werden. Sie lässt sich als Abbauprodukt der Zuckerreihe deuten.
Über eine neue l‐Aminosäure‐oxydase (Ophio‐l‐aminosäure‐oxydase). 3. Mitteilung
Authors: Zeller E. A. , Maritz A. , Iselin B.
Published: December 2004

1. Die Oxydation von l‐Prolin, l‐Oxyprolin, N‐Methyl‐l‐leucin, N‐Methyl‐l‐phenylalanin wird durch die l‐Aminosäure‐oxydase der Schlangengifte (Ophio‐l‐aminosäure‐oxydase) auch unter extremen Versuchsbedingungen nicht katalysiert.
Elektrochemisch‐konstitutive Beziehungen beim Haemoglobin
Authors: Pauli Wolfgang , Schwarzacher Walther
Published: December 2004

1. Krystallisiertes Oxyhämoglobin wird durch Elektrodialyse ohne jede Denaturierung bis x = 2,3–5 × 10−6 r. O. und zu der Eigenreaktion pH = 7,048–6,92 in 4–5‐proz. Lösung gereinigt. Die maximale Protonaufnahme (aus HCl) bzw. Abgabe (an Alkalilauge) wird mit 156,5 × 10−5‐n. bzw. 126 × 1−5‐n. je g Hb bestimmt. Das entspricht einer maximalen Ladungszahl (Lz) von 108 positiven bzw. 87 negativen Ladungen je Teilchen. Hb wandert auch in sehr starkem elektrischen Feld nur spurenweise kathodisch.