bluuebunny/crossref_metadata_2025 huggingface dataset:
The Eu(III) Ion as Luminescent Probe: Investigation of the Metal‐Ion Sites in a Dicyclohexyl‐18‐crown‐6 Complex
Authors: Plancherel Dominique , Jin Linpei , Massara Romano , Bünzli Jean‐Claude G.
Published: December 2004

The metal ion sites of the 3:2 complex between europium nitrate and the A‐isomer of dicyclohexyl‐18‐crown‐6, [Eu(NO3)2(DC18C6)]2[Eu(NO3)5], have been probed by high‐resolution excitation and emission spectra at 296 and 77 K. The [Eu(NO3)5]2− anion gives rise to a luminescent spectrum dominated by the 5D0→7F2 transition. The crystal‐field splitting of the 7Fj levels is close to that observed for (Phe4As)2[Eu(NO3)5], pointing to a structurally similar pentakis(nitrato) species. The 5D0←7F0 excitation spectrum of the two crystallographically independent complex cations displays five maxima. A detailed analysis of the corresponding and selectively excited emission spectra leads to the following conclusions. Well differentiated spectra are assigned to different conformations of the complex cation, in which half of the ligand atoms, including O‐atoms, Present large thermal motions. The other spectra are very similar and arise from slightly unequivalent [Eu(NO3)2(DC18C6)]+ moieties differing in the conformation of their ethylene bridges. This dimonstrates the sensitivity of the Eu(III) ion as conformational probe in the solid state.
‘Face‐to‐Face’‐Benzo‐anellierte homologe Hypostrophene. Synthesen, Röntgenstrukturanalysen und PE‐Spektren
Authors: Fessner Wolf‐Dieter , Sedelmeier Gottfried , Knothe Lothar , Prinzbach Horst , Rihs Grety , Yang Zhong‐Zhi , Kovač Branka , Heilbronner Edgar
Published: December 2004

‘Face‐to‐Face’ Benzo‐anellated Homologous Hypostrophenes. Syntheses, X‐Ray‐Structure Analyses and PE Spectra

‘Face‐to‐face’ Benzo‐anellated homologous hypostrophenes (series M), of interest as substrates for [6 + 6]‐photocycloaddition reactions, have been synthesized. From X‐ray structural analyses of 13b and 13c shortest CC distances of 2.80(2.76)/2.71 Å and interorbital angles (ω) of 129° (128°)/130° between the benzene rings have been determined. The PE spectra are discussed in the context of transannular π,π interactions.
Die Oxidation von 3‐(1‐Nitro‐2‐oxocycloalkyl)propanal
Authors: Zürcher Alois , Hesse Manfred
Published: December 2004

The Oxidation of 3‐(1‐Nitro‐2‐oxocycloalkyl)propanal

Oxidation of the title compound 1 with KMnO4 under neutral conditions led to the corresponding acid 2, 5‐(2,3,4,5‐tetrahydro‐2‐nitro‐5‐oxo‐2‐furyl)pentanoic acid (4), and 4‐oxononadioic acid (6). On the basis of experimental results the mechanism of the formation of 4 is discussed (Scheme 1). Oxidation of 1 with KMnO4 under basic conditions gave 6 which was transformed to (E)‐4,5‐dihydro‐5(2′‐oxocyclopentyliden)furan‐2(3H)‐one (12) with benzene/TsOH (Scheme 3). In contrast to this result the corresponding 4‐oxoheptandioic acid (22) yields 1,6‐dioxaspiro[4,4]nonan‐2,7‐dione (23) only (Scheme 4).
Are the known Δ2‐cephems inactive as antibiotics because of an unfavourable steric orientation of their 4α‐carboxylic group? Synthesis and biology of two Δ2‐cephem‐4β‐carboxylic acids
Authors: Cohen Nissim C. , Ernest Ivan , Scartazzini Riccardo , Wirz Peter , Fritz Hans , Fuhrer Hermann , Rihs Grety
Published: December 2004

Two representatives of the yet unknown type of Δ2‐cephem‐4β‐carboxylic acids were prepared. Contrarily to the prediction based on the activity model of Cohen, both acids proved inactive as antibiotics. Possible reasons for this discrepancy are briefly discussed.
Preparation and Odor Evaluation of Both Enantiomers of 3,4,4aα,5,6,7,8,8aβ‐Octahydro‐5,5,8aβ‐trimethyl‐2(1H)‐naphthalenone and 1,2α,3,4,4aβ,5,6,7,8,8aβ‐Decahydro‐5,5,8aβ‐trimethyl‐2β‐naphthalenyl Acetate, Four Woody Odorants
Authors: Gautier Antoine , Vial Christian , Morel Cédric , Lander Marina , Näf Ferdinand
Published: December 2004

The enantiomeric decahydro‐2‐naphthalenols (+)‐5 and (−)‐5 were prepared by enantioselective hydrolysis of the racemic chloroacetate (±)‐2 catalyzed by porcine pancreatic lipase, and converted to the corresponding acetates (+)‐1 and (−)‐1 and ketones (+)‐6 and (−)‐6. The absolute configurations of the ketones, alcohols, and acetates were established by chemical correlation with natural manool ((+)‐7) by making use of a retro‐ene cleavage reaction of the known manool degradation product 8 to (−)‐6. A distinct odour difference between the two enantiomers of each pair (+)‐1/(−)‐1 and (+)‐6/(−)‐6 has been found.
Syntheses of bile pigments. Part 15. First unequivocal assignment of the absolute configuration of an urobilinoid bile pigment by X‐ray diffraction analysis of its synthetic precursor
Authors: Pasquier Cécile , Gossauer Albert , Keller Walter , Kratky Christoph
Published: December 2004

(−)‐(4S,16S)‐8, 12‐bis[de(2‐carboxyethyl)]mesourobilin‐IIIα hydrochloride (8) has been synthesized from the enantiomerically pure 1,4,5,10‐tetrahydro‐1‐oxodipyrrin‐9‐carboxylic‐acid precursor 6a whose absolute configuration was determined by X‐ray diffraction analysis of the N‐[(S)‐1‐(1‐naphthyl)ethyl] carboxamide 7b. The present results prove unequivocally that an (S,S)‐configurated urobilin chromophore displays a negative Cotton effect in the VIS absorption range. However, the helicity of the inherently dissymmetric chromophore remains undetermined.
Enantioselektive Verseifung der Diacetate von 2‐Nitro‐1,3‐diolen mit Schweineleber‐Esterase und Herstellung enantiomerenreiner Derivate von 2‐Nitro‐allylalkoholen (chirale Verknüpfungsreagenzien)
Authors: Eberle Martin , Egli Martin , Seebach Dieter
Published: December 2004

Enantioselective Saponification of Diacetates of 2‐Nitro‐1,3‐propanediols by Pig‐Liver Esterase and Preparation of Enantiomerically Pure Derivatives of 2‐Nitro‐allylic Alcohols (Chiral Multiple‐Coupling Reagents)

The reproducible enantioselective saponification of open‐chain and cyclic diacetates of meso‐2‐nitro‐1,3‐propanediols (see 4b–13b) with pig‐liver esterase (PLE) gives monoacetates (see 4c–l3c) of > 95% enantiomeric excess. The Re enantiotopic acetate group appears to be saponified preferentially, as proved by the X‐ray crystal structure analysis of three camphanoates 4d, 6d, and 7d. Elimination of H2O or AcOH from the hydroxy acetates thus available gives derivatives of nitro‐allylic alcohols (see 20–24, 27, and 29) which are subjected to diastereoselective Michael additions or SN2′ substitutions.
Das Spermin‐Alkaloid Chaenorpin
Authors: Zhu Ji‐Ping , Guggisberg Armin , Hesse Manfred
Published: December 2004

The Spermine Alkaloid Chaenorpine

Chaenorpine (1) was isolated from Chaenorhinum minus (Scrophulariaceae). Its structure elucidation was achieved on the basis of chemical degradation and spectroscopic measurements in comparison to the known alkaloid chaenorhine (2). Structure 1 displays the absolute configuration.
Nouveaux flavonosides de Paeonia tenuifolia L
Authors: Stošić Dus̀ica , Gorunović Momčilo , Skaltsounis Alexios‐Léandros , Tillequin François , Koch Miechel
Published: December 2004

New Flavonoid Glycosides from Paeonia tenuifolia L.

Two novel flavonoid glycosides have been isolated from the stamens of Paeonia tenuifolia, sexangularetin‐3‐O‐yl β‐D‐sophoroside (1) and limocitrin‐3‐O‐yl β‐D‐sophoroside (3). Their structures have been elucidated by spectroscopic means, mainly desorption chemical ionisation mass spectrometry and ID and 2D high‐resolution 1H‐NMR spectroscopy of their acety1 derivatives.
Synthesis of D‐Erythro‐ and D‐Threo‐Sphingosine Derivatives From L‐Serine
Authors: Herold Peter
Published: December 2004

The protected serine aldehyde 10 was converted to the crystalline N‐Boc‐protected sphingosines 6–9 by a three‐step reaction sequence. Compound 10 was transformed with high diastereoselectivity (95%) either to the erythro‐ or threo‐alkynols, 17 and 18, respectively. The erythro‐isomer 17 is formed by the addition to 10 of lithium pentadecyne 16 in THF/HMPT at −78°, whereas the corresponding threo‐isomer 18 is produced in the presence of ZnBr2 in Et2O. Deprotection of the acetal moiety afforded 1,3‐diols 19 and 20. These diols were selectively reduced with Red‐Al to the (E)‐sphingosines 6 and 8, or the (Z)‐isomers 7 and 9 by partial hydrogenation over Lindlar's catalyst. Cleavage of the N‐Boc group and further transformation to ceramides were readily achieved as demonstarted by the conversion of 6 to N‐octadecanoyl‐D‐erythro‐sphingosine 5.
Circular Dichroism of Planar, Exocyclic S‐cis‐Butadienes Remotely Perturbed
Authors: Zhichen Zou , Schwager Luis , Carrupt Pierre‐Alain , Vogel Pierre
Published: December 2004

Optically pure 5,6‐dimethylidenebicyclo[2.2.1]hept‐2‐yl derivatives have been prepared. The sign of the Cotton effects associated with lowest‐energy transition of 2–(dicyanomethylidene)‐((−)‐(1S,4S)‐15), (E)‐2‐(methoxyimino)‐((+)‐(1S,4S)‐16), (Z)‐2‐(methoxyimino)‐5,6‐dimethylidenebicyclo[2.2.1]heptane ((−)(1S,4S)‐17), and 2,3,5‐trimethylidenebicyclo[2.2.1]heptane ((−)‐(1R,4S)‐18) is opposite to the chirality constituted by the coupling of the electric transition moments of the two homoconjugated π‐chromophores (Kuhn‐Kirkwood dipole‐coupling mechanism). When the substituents at C(2) are not π‐functions, no general rule can be retained for the chiroptical properties of the 5,6‐dimethylidenebicyclo[2.2.1]hept‐2‐yl systems as shown for dimethyl acetal (−)‐(1S,4S)‐19, ethylene acetal (+)‐(1R,4R)‐20, exo and endo methyl ethers (+)‐(1R,2S,4R)‐21 and (+)‐(1R,2R,4R)‐22, and for spirol[5,6‐dimethylidenebicyclo[2.2.1]heptane‐2.2'‐oxiranes](−)‐(1S,2S,4S)‐23 and (−)‐(1S,2S,4S)‐24.
New Reactions of 3‐Vinyl‐ and 3‐(2‐Propenyl)Indoles with N‐Phenylmaleimide: [4 + 2] Cycloaddition, ene reaction, and dimerization
Authors: Pfeuffer Ludwig , Pindur Ulf
Published: December 2004

Depending on the substitution pattern of the aminobutadiene subunit in the selected 3‐vinylindoles 1, 3, 6, and 9, stereospecific [4 + 2] cycloadditions (‘endo’‐preference) and dimerizations take place on reaction with N‐phenylmaleimide. In the reaction of 9 with N‐phenylmaleimide in the absence of a Lewis‐acid catalyst, a competing ene reaction occurs in addition to the Diels‐Alder reaction.
First Total Synthesis of Enantiomerically Pure(−)‐Silphiperfol‐6‐en‐5‐on
Authors: Demuth Martin , Hinsken Werner
Published: December 2004

The angular triquinane (−)‐silphiperfol‐6‐en‐5‐on ((−)‐14) has been synthesized for the first time time in enantiomerically pure form. A highly efficient triplet‐sensitized photoreaction, the oxadi‐π‐methane rearrangement of the complex β,γ‐enone(+)‐6 to (−)‐7, constitutes the key step. The know staring material, (1R, 7aR)‐3,6,7,7a‐tetrahydro‐1‐hydroxy‐7a‐methyl‐1H‐inden‐5(2H)‐one ((−)‐2), is readily accessible in > 97% enantiomeric purity. This new approach should enable access also to other angularly fused triquinanes of the silphinene type and related structures.
Synthesis of selectively trifluoromethylated pyridine derivaties as potential antihypertensives
Authors: Lang Robert W. , Wenk Paul F.
Published: December 2004

A general synthesis of selectively 6‐(trifluoromethyl)‐substitued 2(1H)‐pyridinones is described. Further transformation of one of these compounds leads to the new CF3‐containing potassium‐channel openers 2a and 2b.
A Stereoselective Synthesis of (±)‐cis‐γ‐Irone
Authors: Nussbaumer Cornelius , Fráter Georg
Published: December 2004

(±)‐cis‐γ‐Irone(1), a main constitutent of natural iris oil, has been stereoselectively synthesized from methyl (2E)‐3 ‐[(2,2,4‐trimethyl‐3‐cyclohexen‐1‐yl)methoxy]‐2‐propenoate (3) (6 steps, overall yield 14%). The cis‐configuration as the exocyclic position of the double bond of 1 were secured by the thermal ene reaction of the β‐(alkenyloxy)acrylate 3 yielding the 3‐oxabicyclo [3,3,1] nonane derivative 5.
Enantiomerically pure 7‐oxabicylo[2.2.1]hept‐5‐en‐zyl derivatives as synthetic intermediates. Part III. Total synthesis of D‐ and L‐ribose derivatives
Authors: Wagner Jürgen , Vieira Eric , Vogel Pierre
Published: December 2004

Enantiomerically pure methyl 5‐bromo‐5‐deoxy‐2,3‐O‐ isopropylidene‐β‐D‐ (D‐5b) and ‐β‐l‐ribofuranoside (l‐5b) have been derived from (−)‐(1R,2S,4R)‐2‐exo‐cyano‐7‐oxabicylo[2.2.1]hept‐5‐en‐endo,‐yl (1′S)‐camphanate (1) and (+)‐(1S,2R,4S)‐2‐exo‐cyano‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐endo‐yl(1′R)‐camphanate (2), respectively, in 5 synthetic steps and 28% overall yield. Hydrolysis of D‐5b and L‐5b afforded methyl 2,3‐O isopropylidene‐β‐D‐ribofuranoside (D‐5a) and methyl 2,3‐O‐isopropylidene β‐L‐ribofuranoside (L‐5a), respectively. The intermediate (+)‐(1R,4R,5R,6R) 5‐exo,6‐exo‐(isopropylidenedioxy)‐7‐oxabicyclo[2.2.1]heptan‐2‐one ((+)‐7) and its enantiomer(–)‐7 were also obtained enantiomerically pure by resolution of (=)‐7 by the Johnson‐Zeller method. In bothe approaches, the chiral auxiliaries ((–)‐ and (+)‐camphanic acids, or (+)‐(S)‐N,S‐dimethyl‐S‐phenylsulfoximide) were recovered at an early stage of the synthesis.
(−)‐N‐[(Cyclopropyl) methyl]‐3,4‐dimethoxy‐5‐methylmorphinan‐6‐one, an opioid agonist with preference for kappa opioid receptors
Authors: Schmidhammer Helmut , Fritsch Florian , Burkard Willy P. , Eggstein‐Aeppli Lislott , Hefti Fridolin , Holck Mark I.
Published: December 2004

N‐Allyl‐ and N‐[(Cyclopropyl)methyl]‐3,4‐dimethoxy‐5‐methylmorphinan‐6‐one (9 and 10, resp.) were synthesized from 5‐methyldih drothebainone (1). This essential intermediate was prepared from the baine via 5‐methylthebaine (5) employing a novel route. The Pharmacological studies showed 9 and 10 to be potent opioid agonists. Compound 10 was found to have preference for kappa rather than mu opioid receptors.
Transition‐metal complexes with bidentate ligands spanning trans‐position. Part XVI. X‐ray structural and 31P‐NMR solution studies of 2,11‐Bis(diethylphosphinomethyl)benzo[c]phenanthrenesilver(I) perchlorate
Authors: Camalli Mercedes , Caruso Francesco , Chaloupka Stanislav , Chaloupka Luigi , Venanzi Luigi M.
Published: December 2004

The preparation of complexes {AgX(1c)} (X  Cl, Br, I, NO3 and ClO4; 1c = 2,11‐bis(diethylphosphinomethyl)benzo[c]phenanthrene) is reported. The 31P‐NMR spectra of the above complexes were recorded and the 1J(107Ag, 31P) values are compared with the corresponding data for related complexes. The X‐ray crystal structure of [Ag(1c)](ClO4) was determined. There are two crystallographically independent molecules in the unit cell each containing two‐coordinate silver, the O‐atoms of the perchlorate anions being outside bonding range from the central atom. The two molecules, however, show different bonding parameters: Thus for ‘molecule 1’ P(1)Ag(1)P(2) = 167.6(1)°, Ag(1)P(1) = 2.389(3) and Ag(1)P(2) = 2.393(3) Å, while for ‘molecule 2’ P(3)Ag(2)P(4) = 164.8(1)°, Ag(2)P(3) = 2.377(3), and Ag(2)P(4) = 2.378(3) Å. These differences are probably due to packing forces in the crystal lattice.
A (1,5)‐Vinyl Shift
Authors: Fráter Georg , Müller Urs
Published: December 2004

The structure of the by‐product of the pyrolysis of 1 has been proved to be 3. It is proposed that a (1, 5) Shift of an (alkoxycarbonyl)vinyl group (8⇄10) is the step in formation of 3.
Metabolism of Carotenoids in Salmonids. Part 3. Metabolites of astaxanthin and canthaxanthin in the skin of atlantic salmon (salmo salar, L.)
Authors: Schiedt Katharina , Vecchi Max , Glinz Ernst , Storebakken Trond
Published: December 2004

Diets supplemented with astaxanthin and canthaxanthin, respectively, and a control diet without carotenoid additions, were fed to 1½‐year‐old Atlantic salmon (Salmo salar, L.) for one year. The integuments were investigated as to their quantitative and qualitative carotenoid composition. Astaxanthin and canthaxanthin deposited in the skin amounted to 20 and 14% of the total carotenoids only. Seventy % must be considered as metabolites of astaxanthin and canthaxanthin and 10% as basic xanthophylls also present in the control groups. Astaxanthin apparently underwent the following metabolic pathway: astaxanthin→idoxanthin→adonixanthin→zeaxanthin→zeaxanthin 5,6‐epoxides. Reduction of the 4′‐carbonyl group was stereospecific leading to the (4′R)‐idoxanthin. Canthaxanthin was obviously converted to β,β‐carotene via 4′‐hydroxyechinenone, echinenone, and 4‐hydroxy‐β,β‐carotene.
EPC syntheses from bicyclic dixoanones; (−)‐5‐epidehydrofukinone
Authors: Herradón Bernardo
Published: December 2004

(−)‐5‐Epidehydrofukinone ((−)‐15) has been synthesized from (2S,4aS,5S,8aS)‐4a,5‐dimethyl‐2‐(tert‐butyl)‐perhydro‐4H‐1,3‐benzodioxan‐4‐one (4a), a counpound readily available by yeast reduction of ethyl 2‐oxocyclohexanecarboxylate.
Thermal and Photochemical Oxetane Formation. A Contribution to the Synthesis of Branched‐Chain Aldonolactone
Authors: Mattay Jochen , Buchkremer Karl
Published: December 2004

Derivatives of 2‐C‐branched‐chain erythrono‐1,4‐lactones of the types 1 have been synthesized under reductive conditions using DIBAL from the oxetane 2, which is easily accessible from diethyl mesoxalate (4) and 2,2‐diisopropyl‐1,3‐dioxole (3) in high yield by means of a catalytic cycloaddition. Similarly, 2 rearranges in presences of AlMe3 under formation of an erythronolactone with an additional branching at C(4). The corresponding oxetanes 7–9 from ethyl pyruvate (5) and ethyl trimethylpyruvate (6), respectively, have been studied with regard to their reductions yielding building blocks of branched‐chain sugars.
A Vibrational Study of Some 1,2,4‐Trioxanes
Authors: Mohnhaupt Martin , Hagemann Hans , Perler Jean‐Pascal , Bill Hans , Boukouvalas John , Rossier Jean‐Claude , Jefford Charles W.
Published: December 2004

The vibrational spectra of some 1,2,4‐trioxanes present two characteristic bands at 790 and 880 cm−1. On the basis of 18O‐isotopic substitution and comparison with analogous compounds, these bands have been assigned to coupled CO and OO stretching modes of the COO element.
Singlet‐Oxygen Quenching by Carotenoids: Steady‐state luminescence experiments
Authors: Murasecco‐Suardi Patricia , Oliveros Esther , Braun André M. , Hansen Hans‐Jürgen
Published: December 2004

The near‐infrared luminescence of singlet oxygen (1O2) has been measured in order to determine the efficiency of 1O2 quenching by two carotenoid compounds, β‐carotene and canthaxanthin. 1H‐Phenalen‐1‐one and rose bengal have been used as photosensitizers in those steady‐state luminescence experiments. Stern‐Volmer analysis of the 1O2 luminescence in solutions of CCl4 and CD3OD, containing different concentrations of the carotenoids, has shown a very efficient quenching by canthaxanthin. The rate constants are about a factor of 2 below the diffusion limited values for the given solvents, confirming earlier results in benzene. In comparison, the efficiency of 1O2 quenching by β‐carotene is slightly lower than that by canthaxanthin in non‐polar solvents and is reduced by an order of magnitude in CD3OD, due to the aggregation of this quencher.
Synthesis and Characterisation of the Sodium and Lithium Cryptates of Macrobicyclic Ligands incorporating pyridine, bipyridine, and biisoquinoline units
Authors: Alpha Béatrice , Anklam Elke , Deschenaux Robert , Lehn Jean‐Marie , Pietraskiewiez Marek
Published: December 2004

Sythetic procedures have been deweloped for the preparation of sodium and lithium cryptates of the macrabicyclic ligands 1–11 containing pyridine, bipyridine, and biisoquinoline groups. They involve stepwise construction of the bicyclic system as will as direct macrobicyclisation procedures (Scheme 1) and give access to both symmetrical and dissymmetrical structures. Marked cation template effects have been found that facilitate the cyclisation processes. The ligands 1–11 were isolated as their cryptates with Na+ or Li+ cations.
Absorption Spectra and Luminescence Properties of Isomeric Platinum (II) and Palladium (II) Complexes containing 1,1′‐biphenyldiyl, 2‐phenylpyridine, and 2,2′‐bijpyridine as ligands
Authors: Maestri Mauro , Sandrini Diana , Balzani Vincenzo , von Zelewsky Alex , Deuschel‐Cornioley Christine , Jolliet Philippe
Published: December 2004

The absorption spectra, luminescence spectra, and luminescence lifetimes of the isomeric [M(bph)(bpy)] and [M(phpy)2] complexes M = Pt(II) or Pd(II), bph2− = 1,1′‐biphenyl‐2,2′‐diyl dianion, phpy− = 2‐phenylpyridine‐2′‐yl anion, and bpy = 2,2′‐bipyridine have been investigated and compared with those of [M(bpy)2]2+ complexes and of the free protonated ligands H2bph, Hbpy+, and Hphpy. In the absorption spectra, the region below 320 mm is dominated by ligand‐centered (LC) transitions, whereas metal‐to‐ligand charge transfer (MLCT) transitions are responsible for the bands present in the near UV/VIS region. The MLCT bands move to higher energies on replacing Pt with Pd and in going from [M(bph)(bpy)] to the [M(phpy)2] isomer. For the mixed‐ligand complexes, evidence for both M → bph2− (at higher energies) and M → bpy bands is found. The structured luminescence observed at 77 K shows lifetimes of 4.0 and 1.1 μs for [Pt(phpy)2] and [Pt(bph)(bpy)], respectively, and 480 and 250 μs for the analogous Pd complexes. On the basis of the energy and lifetime data, the luminescence of the Pt(II) complexes is assigned to the lowest triplet MLCT excited state, whereas for the Pd complexes the luminescent state is thought to result from a mixture of MLCT and LC triplet levels.
First Synthesis of 2‐Vinylindole and its diels‐Alder Reactions with CC‐Dienophiles
Authors: Pindur Ulf , Eitel Manfred
Published: December 2004

By means of an intramolecular Wittig process, 2‐vinylindole (2) was prepared. The indole 2 functions as a heterocyclic, donor‐activated 1,3‐diene and undergoes [4+2] cycloaddition reactions with dimethyl acetylenedicarboxylate, N‐phenylmaleimide, and p‐benzoquinone leading to the novel carbazole dervatives 3, 4, 5c, 6 and 7 respectively. The reaction of 2 with acceptor (A)‐Substituted dienophiles (e.g.) ACHCH2, AC≡(CH) does not yield products that can be isolated.
Design and Synthesis of 5‐Lipoxygenase Inhibitors
Authors: Strasser Michael , Cooper Philip , Dewald Beatrice , Payne Trevor
Published: December 2004

Based on the substrate specificity for 5‐lipoxygenase and the known stereochemical course of the reaction, a hypothetical model of the enzyme active site was developed and used to design 2 types of selective inhibitors of 5‐lipoxygenase. Both inhibitor types used aromatic rings in place of (Z)‐olefins of the substrate and were designed to mimic the nonpolar end of arachidonic acid. One inhibitor type used a carboxylic‐acid interaction with the O‐binding centre of the enzyme in analogy with known cyclooxygenase inhibitors, whereas a second type employed a hydroxylamine function to interact with a presumed tyrosine or cysteinyl radical predicted to be in the enzyme active site. Selective 5‐lipoxygenase inhibitors were 7‐(hexyloxy) naphthalene‐2‐acetic acid (1) and N‐methyl;‐N(7‐propoxynaphthalene‐2‐ethyl)hydroxylamine (2). Structure‐activity relationships for both types of inhibitors are discussed.
Colchicine Models: Synthesis and Binding to Tubulin of Tertamethoxybiphenyls
Authors: Itoh Yoshikuni , Brossi Arnold , Hamel Ernest , Lin Chii M.
Published: December 2004

Syntheis of tetramethoxybiphenyl 21 was accomplished from 4‐phenylcylohexane‐1,3‐dione 13 by aromatization to biphenyl 19 and reductive removal of the phenolic OH group as phenyltetrazolyl ether. Tertramethoxybiphenyls 34 and 40 were obtained from 4‐phenylcyclohexenone 26 via ester 27. The tetramethoxybiphenyls 21, 34, and 40, and analogs 28, 29, and 31 were evaluated for antitubulin activity and as antimitotic agents with L1210 murine leukemia cells. Compounds 31 and 34 had significant effects on the in‐vitro polymerization of tubulin. Compound 31 was the most cytotoxic of the six new biphenyls studied (IC50 for cell growth, 0.6M) and caused the accumulation of cells in metaphase arrest.
Antifungal Polyphenols from Cordia goetzeiGürke
Authors: Marston Andrew , Zagorski Michael G. , Hostettmann Kurt
Published: December 2004

Four highly oxygenated polyphenols 1–4, have been isolated from the stem bark of Cordia goetzei Gürke (Boraginaceae) and their structures elucidated by a combination of one‐ and two‐dimensional (including COLOC) NMR spectroscopic techniques, mass spectroscopy, and chemical methods. The first new compound, cordigone (1), is a tetrahydrofuran derivative and the second one, cordigol (2), a furobenzopyran derivative. The benzofurans 3 and 4 are orange pigments, responsible for the coloration of the stem bark of the tree. All four polyphenols are fungicidal against cladosporium cucumerinum.
Synthese neuer schwefel‐ und selen‐haltiger ‘Donor‐Akzeptor‐stabilisierter’ Molekülsysteme mit zentraler bicyclo[4.4.1]undeca‐4,6,8,10‐tetraen‐2,3‐diyliden‐ oder Bicyclo[4.4.1]undeca‐3,6,8,10‐tetraen‐2,5‐diyliden‐Gruppe
Authors: Neidlein Richard , Lucchesini Francesco
Published: December 2004

Synthesis of New Sulfur‐ and Selenium‐Containing ‘Donor‐Acceptor‐Stabilized’ Systems with Central Bicyclo‐[4.4.1]undeca‐4,6,8,10‐tetraene‐2,3‐diylidene‐ or Bicyclo[4.4.1]undeca‐3,6,8,10‐tetraene‐2,5‐diylidene Groups

Syntheses of starting materials 3–55 and 8 and of the S‐ and containing 1,6‐methano[10]annulene (=1,6‐methanobicyclo[4.4.1]undeca‐1,3,5,7,9‐pentaene) derivatives 12, 13, 15 and 16 are described.
Conformational Flexibility of the Acetoxyphenyl Group Studied by Statistical Analysis of Crystal Structure Data
Authors: Hummel Wolfgang , Roszak Aleksander , Bürgi Hans‐Beat
Published: December 2004

The preferred conformation of the acetoxyphenyl fragment shows a planar acctoxy (AcO) group perpendicular to the Ph ring. Steric hindrance strongly limits and affects rotation about the COCOCH3 bond: if the AcO group twists away from its perpendicular conformation, the carbonyl oxygen moves to keep the nonbonded distance to the atoms in ortho‐position maximal. This is achieved by some twisting about the OCOCH3 bond correlated with angle bending at the ipso‐C‐atom and ester O‐atom. The maximum observed deviation away from the perpendicular conformation is ∼ 47°. In the case of one or two ortho‐hydrogens, deviations of the AcO group from the perpendicular conformation tend to be larger than in the case of two substituents.
Conformational Flexibility of the Methoxyphenyl Group Studied by Statistical Analysis of Crystal Structure Data
Authors: Hummel Wolfgang , Huml Karel , Bürgi Hans‐Beat
Published: December 2004

In a large sample of observed methoxyphenyl groups, the twist angle τ about the MeO‐CPh bond measuring internal rotation of the MeO group shows a continuous distribution with maxima at (0°) (coplanar conformation) and (∼90°) (perpendicular conformation). The preferred conformation of methoxyphenyl depends on the nature of the ortho‐‐substituents: In general, it is coplanar in the case of one or two ortho‐hydrogens, and perpendicular in the case of two substituents. The internal rotation of the MeO group is accompained by systematic variations in bond angles and bond distances: 1 if MeO is twisted out of plane, the bond angle CH3OCPh decreases from 117.7°, until it reaches a minimum of 114.9° at τ = ±90°. The OCC angle which is syn to CH3 for τ = 0° decreases from 124.6° to a minimum of 115.4° at τ = ±180°. These angles changes keep the nonbonded distance CH3 …︁ ortho substituent maximal during internal rotation of MeO and tend to minimize the corresponding strain energy. (2) In the perpendicular conformation, the O‐atom is ∼ 0. 06 Å displaced from the Ph plane, O and CH3 and being on opposite sides of this plane. In addition, small but systematic increases of bond lengths MeOCPh and CH3O are observed. These variations indicate a decrease in conjugation with increasing twist angle. Their interdependence during twisting and the magnitudes of the changes are close values obtained by ab initio calculations.
The Reaction of Water with Iron‐ and Rutheniuncarbonyl Complexes of Polyolefins: 1,2‐ and 1,4‐hydrogenation of 1,3‐dienes. hydrogenolysis of allylic ethereal bonds and deoxygenation of 7‐oxabicyclo[2.2.1]hept‐2‐enes
Authors: Araki Shuki , Bonfantini Edia , Vogel Pierre
Published: December 2004

Under basic conditions, H2O reacts with tricarbonyl[(1R,2R,3S,4S,5R,6S)‐C,5,6,C‐η‐(2‐exo,3‐exo‐bis‐(chloromethyl)‐5,6‐dimethylidene‐7‐oxabicyclo[2.2.1]heptane)]iron) (1), and ‐ruthenium (4), with tricarbonyl‐[(1R,2R,3S,4S)‐C,2,3,C‐η‐(2,3,5,6‐teramethylidene)‐7‐oxabicyclo[2.2.1]heptane)]iron (6) and ‐ruthenium (7), and with cis‐η‐[1S,2S,3R,4S,5S,6R)‐C,2,3,C‐η : C‐η‐(2,3,5,6‐tetramethylidene‐7‐oxabicyclo)[2.2.1]heptane)bis‐(tricarbonyliron) (11)] to give products of demetallation and 1,2‐ or/and 1,4‐hydrogenation. Reductive demetallation of tricarbonyl[C,5,6,C‐η‐(1‐(dimethoxymethyl)‐5,6‐dimethylidenecylohexa‐1,3‐diene]iron (14) required heating under acidic conditions, giving 2,3‐dimethylbenzaldehyde (16). H2O reacted under neutral conditions with cis‐heptacarbonyl‐μ‐[(1RS,2SR,3RS,4SR,5RS,6SR)‐2,3‐η : C,5,6,C‐η‐(1‐(dimethyoxymethyl)‐5,6,‐(dimethylidene‐7‐oxabicyclo[2.2.1]hept‐2‐ene]diiron (17) and with tricaboyl[(1RS,2SR,3RS,4SR,5RS,6SR)‐C‐η5,6,C‐η‐(1‐(dimethyoxymethyl)‐5,6‐dimethyldidene‐7‐oxabicyclo[2.2.1]hept‐2‐ene)]iron (18) to give the orthoquinodimethane complex 14 as major product. This reaction was accompanied by hydrogenolysis of the allylic ethereal C(4)O(7) bond in 17 and 18 and gave tricarbonyl[(1RS,5RS,6SR)‐C,5,6,C‐η‐(1‐(dimethoxymethyl)‐5,6‐dimethylidenecylohex‐2‐en‐1‐ol)]iron (21) as minor product. The latter was not an intermediated of reaction 17 → 14. Reactions with D2O allowed one to discuss the possible mechanism of this deoxygenation process. With Trans‐heptacarbonyl‐μ‐[(1RS,2SR,3RS,4SR,5RS,6SR)‐2,3‐η : C,5,6,C‐η‐(1‐(dimethoxymethyl‐5,6‐dimethylidene‐7‐oxabicyclo[2.2.1]‐hept‐2‐ene)diiron (38)], the reaction with THF/H2O gave 14 nearly quantitatively, with no D‐incorporation in the presence of D2O.
Pteridines. Part LXXXVII. Synthesis and Properties of 8‐Substituted 2‐Thiolumazines
Authors: Hübsch Walter , Pfleiderer Wolfgang
Published: December 2004

Various 8‐substituted 2,8‐dihydro‐2‐thioxopteridin‐4(3H)‐ones (14–21) and 2‐(methylthio)pteridin‐4(8H)‐ones (27–32) have been synthesized by condensation of the appropriate 5‐amino‐6‐(substituted amino)‐1,2‐dihydro‐2‐thioxopyrimidin‐4(3H)‐ones (22–34) and 5‐amino‐6‐(substituted amino)‐2‐(methylthio)pyrimidin‐4(3H)‐ones (25, 26), respectively, with glyoxal, biacetyl, and benzil. The presence of a quinonoid cross‐conjugated π‐electron system makes this type of compounds susceptible to nucleophilic additions in position 7, which leads to intramolecular (43, 45) and intermolecular (44) covalent adducts. The newly synthesized compounds have been characterized by elemental analyses, pKa determinations, 1H‐NMR and UV spectra. UV‐Spectral changes in dependence of the pH are associated with the most appropriate molecular species including the monocations, neutral forms, covalent adducts, mono‐ and dianions.
Transition‐Metal Complexes with Bidentate Ligands Spanning trans‐Positions. Part XVII. Some platinum(II) complexes with anionic ligands such as methoxide, formate, carboxylate, hydride, and borohydride, and the X‐ray crystal structure of [PtHCl()] (PP = 2,11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene)
Authors: Bracher Gustav , Kellenberger Bruno , Venanzi Luigi M. , Bachechi Fiorella , Zambonelli Luigi
Published: December 2004

The complexes trans‐[PtXY(2] (X = H or Me; Y = OMe, OCHO, CO2H, and BH4; 2 = 2,11‐bis{bis[3‐(trifluoromethyl)phenyl]phosphinomethyl}benzo[c]phenanthrene) were prepared, and their decompositions to trans[PtHX(2)] were studied. Some binuclear hydrido‐bridged complexes, e.g.[(2)HPt(μ‐H)PtH(2)]+, were also obtained. The preparation of complexes trans‐[PtHX(28)2] (X = H or Me, 28 = bis[3‐(trifluoromethyl)phenyl]benzylphosphine) is also reported. The X‐ray crystal structure of trans‐[PtHCl1)] (1 = 2,11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene) was carried out.
Applications of ENDOR spectroscopy to radical cations in freon matrices. Part 2. The radical cation of 2,3‐diazabicyclo[2.2.2]oct‐2‐ene
Authors: Gerson Fabian , Qin Xue‐Zhi
Published: December 2004

The radical cation of 2,3‐diazabicyclo[2.2.2]oct‐2‐ene (1), generated by γ‐rays in a CF2ClCFCl2 matrix, has been fully characterized by its hyperfine data with the use of ESR, ENDOR, and TRIPLE resonance spectroscopy. The isotropic coupling constants for \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }}$\end{document} are +3.14 mT for the two 14N Nuclei in the azo group, −0.336 mT for the two protons at the bridgehead C atoms, and +151 and +0.135 mT for the sets of four exo‐ and four endo‐protons, respectively. MO calculations indicate that these values are consistent with an electron removal from an orbital represented by the antibonding combination (n_) of the lone‐pair atomic orbitals at the two N atoms. The corresponding radical anion \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }}$\end{document} is persistent in fluid solution and its hyperfine data, combined with MO calculations, point to an electron uptake into the antibonding π orbital (π*) of the azo group. It is, thus, reasonable to classify \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{+}\kern-4pt {.} }}$\end{document} as a σ and \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }}$\end{document} as a π radical.
β‐Cleavage of Bis(homoallylic) Potassium Alkoxides. Synthesis of γ‐damascone
Authors: Snowden Roger L. , Linder Simon M.
Published: December 2004

Starting from the γ‐lactone cis‐1, two new syntheses of γ‐damascone ((E)‐4) are described. In both syntheses, the key step involves the β‐cleavage of a bis(homoallylic) potassium alkoxide, viz. the transformation of 3a to 20 and (E/Z)‐4, and the conversion of 21a to 23 and (E/Z)‐24.
Diastereoselektive Alkylierung von 3‐Aminobutansäure in der 2‐Stellung
Authors: Estermann Heinrich , Seebach Dieter
Published: December 2004

Diastereoselective Alkylation 3‐Aminobutanoic Acid in the 2‐Position

The enantiomerically pure 3‐aminobutanoic acids (R)‐ and (S)‐6 are readily available by preparative HPLC separation of the two diastereoisomers 5 obtained from addition of (S)‐phenethylamine to methyl crotonate and subsequent hydrogenolysis (Scheme 2). (S)‐Methyl 3‐(benzoylamino) butanoate ((S)‐3) is also available by enzymatic kinetic resolution with pig‐liver esterase. The N‐benzyl‐ and N‐ benzyloxycarbonyl derivatives rac3,8, and 9 of 3‐aminobutanoates are doubly deprotonated with LDA and alkylated or aminated in high selectivity (17 examples, relative topicity like; see Tables 1 and 2). The configuration of three of the products is assigned (Schemes 4–6), and in four cases, the free α‐substituted β‐amino acid is prepared by acidic hydrolysis (see Table 3). It is shown that the doubly lithiated β‐amino‐acid derivative is solubilized, and its reactivity may be strongly influenced by the presence of 3 equiv. of LiCl.
Synthesis of New, Unnatural Macrocyclic Trichothecenes: 3‐isoverrucarin A ((1″‐O)(3→4)abeo‐verrucarin A), verrucinol, and verrucene. 46th Communication on verrucarins and roridins
Authors: Jeker Nicolas , Tamm Christoph
Published: December 2004

A new unnatural macrocyclic trichothecene, an analogue of verrucarine A (1), which was named 3‐Isoverrucarin A ((1″‐O)(3→4)abeo‐verrucarin A; 3) was synthesized starting from anguidine (5). The two key reactions were the removal of the 4β‐acetoxy group of anguidine (5) by a Barton deoxygenation and the final macrolactonization. During the cyclization procedure, two unexpected new macrocyclic by‐products, which were named verrucinol (19) and verrucene (20), were formed. They represent novel types of macrocyclic trichothecenes, the macrolidic moiety of verrucene (20) consisting only of the (Z,E)‐muconic‐acid residue. The formation of the analogous macrolide 26 of verrucene (20) was not possible, probably because the ring strain is too strong.
Synthese von Triafulven‐Vorstufen aus trisubstituierten Cyclopropanen
Authors: Weber Andreas , Sabbioni Gabriele , Galli Roberto , Stämpfli Urs , Neuenschwander Markus
Published: December 2004

Synthesis of Triafulvene‐Precursors from Trisubstituted Cyclopropanes

Trisubstituted cyclopropanes 5a–f are prepared by carbene addition to the appropriate olefins. While 5a (Y = OAc) and 5c (Y = Cl) rearrange in the presence of BuLi, 5d (Y = SPh) is stable enough to allow the envisaged sequence for triafulvene (Scheme 2) : halogen‐Li exchange, followed by methylation of 6d, gives 7d in a 93% yield; after base‐induced elimination of HBr from 7d, the key precursor 1‐methylene‐2‐(phenylthio)cyclopropane (9, 70% yield) is isolated. Compound 9 is transformed into the corresponding sulfoxide 10 (83%), sulfone 11 (80%), and sulfonium fluoroborate 12 (95% yield) by subsequent oxidation and methylation, respectively. Some 1H‐NMR results of cyclopropanes 5a–f and 7d as well as of methylidene‐cyclopropanes 9–11 are discussed.
Mechanistic and Synthetic Studies on the Formation of 1,2,4‐Trioxanes Related to Arteannuin. Photooxygenation of a bicyclic dihydropyran
Authors: Jefford Charles W. , Wang Ying , Bernardinelli Gérald
Published: December 2004

The photooxygenation of (4R,4aS,7R)‐4,4a,5,6,7,8‐hexahydro‐4,7‐dimethyl‐3H‐2‐benzopyran (16) was performed in (i) MeOH, (ii) acetaldehyde, and (iii) acetone at −78°. The products obtained respectively were (i) (2R)‐2‐[(1S,4R)‐4‐methyl‐2‐oxocyclohexyl]propyl formate (17; 72% yield), (ii) 17 (54.5%), (1R,4R,4aS,7R)‐3,4,4a,5,6,7‐hexahydro‐4,7‐dimethyl‐1H‐2‐benzopyran‐2‐yl hydroperoxide (19; 16.7%), a 12:1 ratio of (3R,4aR,7R,7aS,10R,11aR)‐7,7a,8,9,10,11‐hexahydro‐3,7,10‐trimethyl‐6H‐[2]benzopyrano[1,8a‐e]‐1,2,4‐trioxane (20) and its C(3)‐epimer 21 (17%), together with evidence for the 1,2‐dioxetane (22) originating from the addition of dioxygen to the re‐re face of the double bond of 16, and iii) unidentified products and traces of 22. Addition of trimethylsilyl trifluoromethanesulfonate (Me3SiOTf) to the acetone solution of 16 after photooxygenation afforded (4aR,7R,7aS,10R,11aR)‐7,7a,8,9,10,11‐hexahydro‐3,3,7,10‐tetramethyl‐6H‐[2]benzopyrano[1,8a‐e]‐1,2,4,‐trioxane (23, 40%). The photooxygenation of 16 in CH2Cl2 at −78° followed by addition of acetone and Me3SiOTf afforded 17 (11%), 23 (59%), and (4aR,7R,7aS,10R,11aR)‐7,7a,8,9,10,11‐hexahydro‐3,3,7,10‐tetramethyl‐6H‐[2]benzopyrano[8a,1‐e]‐1,2,4‐trioxane (24; 5%. Repetition of the last experiment, but replacing acetone by cyclopentanone, gave 17 (16%), (4′aR,7′R,7′aS,10′R,11′aR)‐7′,7′a,8′,9′,10′,11′‐hexahydro‐7′,10′‐dimethylspiro[cyclopentane‐1,3′‐6′H‐[2]benzopyrano[1,8a‐e]‐1,2,4‐trixane] (25; 61%), and (4′aR,7′R,7′aS,10′R,11′aR)‐7′,7′a,8′,9′,10′,11′‐hexahydro‐7′,10′‐dimethylspiro[cyclopentane‐1,3′‐6′H‐[2]benzopyrano[8a,1‐e]‐1,2,4‐trixane] (26, 4%). The X‐ray analysis of 23 was performed, which together with the NMR data, established the structure of the trioxanes 20, 21, 24, 25, and 26. Mechanistic and synthesis aspects of these reactions were discussed in relation to the construction of the 1,2,4‐trioxane ring in arteannuin and similar molecules.
The Conformation of Cycloartenol Investigated by NMR and Molecular Mechanics
Authors: Milon Alain , Nakatani Yoichi , Kintzinger Jean‐Pierre , Ourisson Guy
Published: December 2004

Cycloartenol (4), a natural plant sterol, was shown to be an effective membrane reinforcer; this was attributed to its conformation. We now present a conformational analysis of 4 by molecular modeling and NMR. Molecular modeling suggests that two conformations I and II coexist, differing mainly at the level of ring C, and of nearly equal energy, I and II each having ring A and B in a chair and half‐chair conformation, respectively, with ring C 1,3‐diplanar in I (solid‐state structure as determined by X‐ray crystallography) and in chair conformation in II. A complete assignment of the 1H‐ and 13C‐NMR spectra of 4 and the entire coupling network in rings A and B is determined by various modern NMR techniques. The conformation of rings A and B thus determined is in agreement with conformations I and II. Low‐temperature NMR experiments show a fast equilibrium between two conformations, presumably I and II. It is concluded, therefore, that the cyclopropane ring of 4 produces a flexibility at the level of ring C which may be important for the membrane properties.
A Nonconcerted Intramolecular Diels‐Alder Reaction of Chiral Allenic‐Acid Derivatives
Authors: Trifonov Latchezar S. , Orahovats Alexander S.
Published: December 2004

The reaction between the chiral allenic acid (+)‐(S)‐1 and the carbodiimides 2a–d and the keten‐imine 6 gives, under mild conditions, the tricyclic compounds 3–5, 7, and 8. Low diastereoselectivity and a partial loss of optical activity are observed. A stepwise mechanistic pathway via a biradical intermediate is postulated.
6‐Thia‐1‐aza‐5λ5‐phosphabicyclo[3.2.0]hept‐3‐ene und Isothiocyanatophosphin‐sulfide aus (Methylidenamino)phosphinen, Schwefelkohlenstoff und Acetylen‐ oder Ethylen‐Derivaten
Authors: Fulde Maria , Ried Walter , Bats Jan W.
Published: December 2004

6‐Thia‐l‐aza‐5λ5‐phosphabicyclo[3.2.0]hept‐3‐enes and Isothiocyanatophosphine‐sulfides from (Methylidenamino)phosphines, Carbon Disulfide, and Acetylene‐ or Ethylene Derivatives

(Methylidenamino)phosphines react with carbon disulfide to 1,3,2‐thiazaphosphete derivatives 2. Acetylenedicarboxylates give with 2 6‐thia‐l‐aza‐5λ5‐phosphabicyclo[3.2.0]hept‐3‐enes 4a, b, and acrylates yield isothio‐cyanatophosphin‐sulfides 5a–c. The structures of 4a and 5a are proven by an X‐ray diffraction analysis.
Formation of the First Trimeric Monoterpenoid Indole Alkaloids
Authors: Schübel Helmut , Fahn Walter , Stöckigt Joachim
Published: December 2004

Under O2, the Aspidosperma alkaloid tabersonine (1) was converted by a crude enzyme preparation from leaves of mature plants of Catharanthus roseus G DON into the trimeric 3‐hydroxy‐14′‐(3α″‐tabersonyl)voafrine B (4) which was easily reduced by NaBH4 to 14′‐(3α″‐tabersonyl)voafrine B ( = tertabersonine; 5). Compounds such as 4 and 5 are the first trimeric alkaloids in the series of monoterpenoid indole alkaloids.
Eine neue Aminoazirin‐Reaktion. Bildung von 3,6‐Dihydropyrazin‐2(1H)‐onen
Authors: Hugener Martin , Heimgartner Heinz
Published: December 2004

A New Aminoazirine Reaction. Formation of 3,6‐Dihydropyrazin‐2(1H)‐ones

The reaction of 3‐(dimethylamino)‐2H‐azirines 1 and 2‐(trifluoromethyl)‐1,3‐oxazol‐5(2H)‐ones 5 in MeCN or THF at 50–80° leads to 5‐(dimethylamino)‐3,6‐dihydropyrazin‐2(1H)‐ones 6 (Scheme 3). Reaction mechanisms for the formation of 6 are discussed: either the oxazolones 5 react as CH‐acidic heterocycles with 1 (Scheme 4), or the azirines 1 undergo a nucleophilic attack onto the carbonyl group of 5 (Scheme 6). The reaction via intermediate formation of N‐(trifluoroacetyl)dipeptide amide 8 (Scheme 5) is excluded.
Colchicine models: Synthesis and Antitubulin Activity of 2′‐Monosubstituted and 2′, 5‐Disubstituted 2,3,4,4′‐Tetramethoxy‐1,1′‐biphenyls. Synthesis of 4,4′, 5′, 6′‐tetramethoxy‐1,1′‐biphenyl‐2,3′‐dicarboxylic acid
Authors: Itoh Yoshikuni , Brossi Arnold , Hamel Ernest , Flippen‐Anderson Judith L. , George Clifford
Published: December 2004

Reductive amination of 2,3,4,4′‐tetramethoxtybiphenyl‐2‐carbaldehyde (4) with MeNH2 afforded methylamine 5 (Scheme 1), Hydroxymethylation of amine 8, prepared similarly from 4 by reductive amination with benzylamine followed by N‐methylation, afforded alcohol 12 which was converted the 5‐methyl‐substituted methylamine 14 by conventional chemical reactions (Scheme 2), Methylamine 14 was also obtained from ester 16 after hydroxymethylation to alcohol 17 and conventional manipulation of alcohol and ester functions (Scheme 2). Both amines 5 and 14 as well as the 2′, 5‐dimethyl‐substituted biphenyl 26 prepared from the dialdehyde 25 by a Wolff‐Kishner reduction, did not show noteworthy activity in the tubulin binding assay or as inhibitors of tubulin polymerization (Table). However, the 2′ethyl‐substituted biphebyl 11 prepared from 4 by reaction with MeLi followed by dehyderation and catalytic reduction of styrene 10 (Scheme 1) showed appreciable activity in both assays, coming close to that of known phenyltropolone models. The X‐ray analysis of 14·HCl and 11 showed significant difference in the orientation of the rings with respect to one another (Fig.).
Synthesis of Aristotelia‐Type Alkaloids.. Part IV. Synthesis of (±)‐aristoserratine
Authors: Burkard Stefan , Borschberg Hans‐Jürg
Published: December 2004

A convergent diastereoselective synthesis of racemic aristoserratine ((±)‐24) via an intramolecular iminium‐ion cyclization is described. The pivotal imine (±)‐19 was prepared by condensation of the two building blocks (± )‐trans‐8‐amino‐3‐(2,6‐difluorobenzyloxy)‐1‐p‐menthene ((±)‐11) and N‐(p‐methoxybenzenesulfonyl)‐3‐indo‐leacetaldehyde (18) which were synthesized from (±)‐trans‐1‐p‐menthene‐3,8‐diol ((±)‐7) and 3‐indoleacetic acid, respectively. On the route to the target (±)‐24, two previously unknown indole alkaloids have been characterized, namely (±)‐‘anti’‐hobartin‐15‐ol ((±)‐22) and (±)‐‘anti’‐aristotelin‐15‐ol ((±)‐23).
Syntheses of α, β‐Epoxy Silyl Ketones
Authors: Scheller Markus E. , Bernd Schweizer W. , Frei Bruno
Published: December 2004

The synthesis of the α, β‐epoxy‐acylsilanes 1 and 2 starting from the allylic silyl alcohols (E)‐ and (Z)‐3, respectively, by epoxidation with t‐BuOOH/VO(acac)2 followed by oxidation with Collins reagent (CrO3/pyridine) in up to 70% overall yields, is described. The acid‐catalyzed rearrangement of the epoxy‐silyl alcohols 4A + B und 5A + B led to the novel unstable diastereoisomeric α‐silyl‐β‐hydroxy‐aldehydes 9 and 10, respectively. The structure of 10 was established by X‐ray crystal‐structure analysis of the corresponding alcohol 11.
Synthesis of (−)‐Conduritol C (1L‐Cyclohex‐5‐ene‐1,2,3/4‐tetrol)
Authors: Le Drian Claude , Vieira Eric , Vogel Pierre
Published: December 2004

(1R, 2R, 4R)‐2‐endo‐Cyano‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐yl acetate ((−)‐7) has been transformed into the all‐cis‐configurated 4L‐4,5,6/0‐trihydroxycyclohex‐2‐en‐1‐one derivatives (−)‐12 and (−)‐19. (−)‐Conduritol C ((−)‐3) was derived in a stereospecific manner from (−)‐12.
Synthesis of Gossypol Analogues
Authors: Ognyanov Vassil I. , Petrov Orlin S. , Tiholov Emil P. , Mollov Nikola M.
Published: December 2004

Two gossypol analogues 2a and 2b were synthesized for biological evaluation as male contraceptive agents. The naphthol 8c was prepared by analogy with a known procedure starling from 3‐isopropylcatechol (3). (t‐Bu)2O2‐Mediated phenolic coupling of 8c furnished the binaphthol 9c which, after pyrane ring closure, deprotection. and selective bisformylation with SnCl4/Cl2CHOCH3, gave the target compound 2a. The corresponding tetrahydroxy analogue 2b was prepared in a similar way.
Synthese von (+)‐Abscisinsäure
Authors: Soukup Milan , Lukáč Teodor , Lohri Bruno , Widmer Erich
Published: December 2004

Synthesis of (+)‐Abscisic Acid.

Starting from (4S)‐4‐hydroxy‐2,6,6‐trimethylcyclohex‐2‐enone (2), a short synthesis of the natural (+)‐abscisic acid ((+)‐1) has been accomplished.
Cyclometalated Compounds of Platinum(II) with two different C, N‐aromatic ligands
Authors: Deuschel‐Cornioley Christine , Lüönd Rainer , von Zelewsky Alex
Published: December 2004

A synthetic route leading to bis‐heteroleptic cyclometalated complexes magnified image is described. The complexes [2‐(2′‐thienyl)pyridinato‐N, C‐3′]{2‐[3′‐(trimethylsilyl)2′‐thienyl]pyridinato‐N, C3′}platinum(II) ([Pt(thpy) (TMS‐thpy)]; I) and (l‐phenylpyrazolato‐N2, C2′)[2‐(2′‐thienyl)pyridinato‐N, C3′]platinum ([Pt(Phpz)(thpy)]; II) are characterized by UV/VIS, NMR, and mass spectroscopy. Thermal and photochemical oxidative addition reactions yield two out of the 10 possible pairs of enantiomers of octahedral Pt(IV) compounds.
Stereoselectivity in Reactions of Metal Complexes. Part XI. 2,6‐Bis(pyrrolidin‐2‐yl)pyridine: Synthesis and resolution of the meso and the optically active isomers. Complex formation with copper(II) ion in aqueous solution
Authors: Bernauer Klaus , Gretillat François
Published: December 2004

The new linear triamine 2,6‐bis(pyrrolidin‐2‐yl)pyridine (II) has been synthesized, and the (R, S)‐, (R, R)‐, and (S, S)‐isomers have been separated. Compared to other triamines showing a similar structure, these new ligands form very stable Cu2+ complexes. No significant difference is observed between the meso and the racemic forms for their binary or ternary mixed‐ligand complexes with the amino acids alanine and proline.