bluuebunny/crossref_metadata_2025 huggingface dataset:
Dissimilar behaviour of 3β, 16α‐dihydroxy‐5α‐androstan‐17‐one Diacetate under Basic and Acidic Conditions
Authors: Doller Darío , Gros Eduardo G.
Published: December 2004

The base‐catalysed rearrangement of 3β, 16α‐dihydroxy‐5α‐androstan‐17‐one diacetate (1) in (D6)benzene/CD3OD to 3β, 17β‐dihydroxy‐5α‐androstan‐16‐one (3) is followed by 13C‐NMR spectroscopy. By the same procedure, it is determined that in (D6)benzene/CD3OD, but under acid catalysis, 1 does not rearrange to 3 but yields the intermediate product 3β, 16α‐dihydroxy‐5α ‐androstan‐17‐one 17α ‐methyl hemiacetal (5).
Metal Complexes with Macrocyclic Ligands Part XXX. Synthesis and structure of halocuprates of tetraprotonated 1,4,8,11‐tetraazacyclotetradecane and its Cu2+ complex
Authors: Studer Martin , Riesen Andreas , Kaden Thomas A.
Published: December 2004

By mixing acidic solutions of 1,4,8,11‐tetraazacyclotetradecane (Cy) with CuX2 (X = Cl−, Br−), either the hexahalocuprates of the tetraprotonated form of the macrocycle ([CyH4] [CuX6]) or the tetrahalocuprates of its Cu2+ complex ([CuCy] [CuX4]) are obtained. The structures of the chloro derivatives are established by X‐ray diffraction analysis. In [CyH4] [CuCl6], the Cu2+ is in a tetragonally distorted octahedral geometry with four short and two long CuCl bonds. The tetraprotonated macrocycle is centrosymmetric, and its conformation is exodentate, so that the four ammonium groups are as far as possible from each other to minimize the electrostatic repulsion. In [CuCy] [CuCl4], the Cu2+ ion complexed by the macrocycle is surrounded by four N‐atoms in a square‐planar arrangement. In addition, the axial positions are occupied by two Cl− ions of two CuCl units, which act as bridges. The macrocycle is in the trans‐III‐configuration. The other Cu2+ ion is coordinated by four Cl− ions in a distorted tetrahedral geometry. IR and VIS spectra of the chloro and bromo derivatives are used to discuss the structure of the bromo species.
Synthèse énantiospécifique de la (+)‐(R)‐éthyl‐6‐dihydro‐2,3‐méthyl‐2‐4H‐pyranone‐4, phéromone de la mite Hepialus hecta L
Authors: Deschenaux Pierre‐François , Kallimopoulos Thomas , Jacot‐Guillarmod André
Published: December 2004

Enantiospecific Synthesis of (+)‐(R)‐6‐Ethyl‐2,3‐dihydro‐2‐methyl‐4H‐pyran‐4‐one, Sex‐pheromonal Component of the Male Swift Moth Hepialus hecta L.

A new synthesis of (+)−(R)‐6‐ethyl‐2,3‐dihydro‐2‐methyl‐4H‐pyran‐4‐one ((R)‐8), sex‐pheromonal component of the male swift moth Hepialus hecta L., has been performed from (−)‐(R)‐1‐(1,3‐dithian‐2‐yl)propan‐2‐ol with an enantiomeric excess of ⩾ 97%.
Transition‐metal complexes with bidentate ligands spanning trans‐positions. Part XVIII. Crystal and molecular structure of the ligands 2,11‐bis(di‐R‐phosphinomethyl)benzo[c]phenanthrene (R = Phenyl, tert‐Butyl) and a comparison of their conformation in a variety of complexes
Authors: Bürgi Hans‐Beat , Murray‐Rust Judith , Camalli Mercedes , Caruso Francesco , Venanzi Luigi M.
Published: December 2004

The X‐ray crystal structures of 2,11‐bis(di‐R‐phosphinomethyl)benzo[c]phenanthrenes (R = Ph, t‐Bu) are reported. Both ligands have the same conformation and the substitution of a Ph by a t‐Bu group does not cause significant changes in the tetracyclic aromatic unit which shows the same distortions as the parent hydrocarbon. The conformations and structural features of the two ligands and 18 complexes containing these ligands as well as of one compound with a ligand with Et substituents are compared. It is pointed out that (1) the conformations of the free ligands differ significantly from those of their complexes, (2) in all the complexes characterized to date, these ligands act as chelating agents, and (3) the ligands adopt two different conformations in the complexes, one of them appearing to be more flexible than the other.
Glycosylidene Carbenes a new approach to glycoside synthesis. Part 1. Preparation of glycosylidene‐derived diaziridines and diazirines
Authors: Briner Karin , Vasella Andrea
Published: December 2004

A new approach towards the synthesis of glycosides based upon a (formal) insertion of glycosylidene carbenes into OH bonds is presented. The synthesis and characterization of the glycosylidene‐derived diazirines 25–28, precursors of glycosylidene carbenes, are described. The diazirines were prepared by the rapid, high‐yielding oxidation of the diaziridines 20 and 22–24 with I2/Et3N. The diaziridines, the first examples of C‐ alkoxy‐diaziridines, were formed in high yields by the reaction of the [(glycosylidene)‐amino]methanesulfonates 14 and 17–19 with a saturated solution of NH3 in MeOH. The diazirines are highly reactive compounds, losing N2 at room temperature or below. The reaction of the gluco‐configurated diazirine 25 with i‐PrOH yielding a mixture of the α‐ and β‐D‐glucosides 29 and 30 illustrates the potential of glycosylidene‐derived diazirines as a new type of glycosyl donors.
Corallistin A, a second example of a free porphyrin from a living organism. Isolation from the demosponge Corallistes sp. of the coral see and inhibition of abnormal cells
Authors: D'Ambrosio Michele , Guerriero Antonio , Debitus Cécile , Ribes Olivier , Richer De Forges Bertrand , Pietra Francesco
Published: December 2004

It is shown that the demosponge Corallistes sp. (Tetractinomorpha, Lithistida, Corallistidae) collected in the Coral Sea, contains corallistin A (1), the second example, of a free porphyrin from a living organism. The compound proved to be active against the Kb cell line. In contrast with the geoporphyrins which do not bear any O‐atom corallistin A (1) carries two carboxylic groups.
Synthesis of hydroxy‐ and methoxy‐substituted octahydrobenzo[g]isoquinolines as potential ligands for serotonin receptors
Authors: Papageorgiou Christos , Petcher Trevor J. , Waldvogel Erwin
Published: December 2004

In 7 steps, 6‐ or 9‐hydroxylated or ‐methoxylated trans‐octahydrobenzo[g]isoquinolines were efficiently synthesized starling from dimethoxynaphtbalenes (Scheme), as potential new selective ligands for serotonin receptors. The 6‐substituted compounds had very little affinity to common neurotransmitter receptors, with the exception of adrenergic α2. The 9‐substituted compounds, while showing interesting affinity for 5HT1a receptors, had comparable affinities for adrenergic α1 and β2, and in one case for dopamine D2 receptors.
Synthesis of macrocyclic imides by one‐step ring enlargement
Authors: Ognyanov Vassil I. , Hesse Manfred
Published: December 2004

By one‐step ring‐enlargement reaction with isocyanates, 2‐cyano‐ and 2‐(ethoxycarbonyl)‐substituted cycloalkanones are converted into macrocyclic imides.
Strukturaufklärung von N6‐, 9‐ und 7‐Acyladeninen durch 1H‐und 13C‐NMR‐Spektroskopie von Festkörpern und in Lösung
Authors: Ried Walter , Woithe Heinz , Müller Arndt
Published: December 2004

Structure Determination of N6‐, 9‐and 7‐Acyladenines by 1H‐ and 13C‐NMR Spectroscopy of Solids and in Solution.

Adenine (1) reacts with carboxylic acid anhydrides or chlorides 2 to yield the acyladenine isomers 3–5. The isomeric structures were determined by 33C‐ and 1H‐NMR spectroscopy in solution and by solid‐state 13C‐NMR spectroscopy.
On the Macrolactonization of β‐Hydroxy Acids. Crystal structures of the pentolide and the hexolide from (R)‐3‐hydroxybutanoic acid. Molecular modeling studies of the tetrolide
Authors: Seebach Dieter , Brändli Urs , Müller Hans‐Martin , Dobler Max , Egli Martin , Przybylski Michael , Schneider Klaus
Published: December 2004

The temperature and concentration dependence of the previously reported formation of oligolides from (R)‐ or (S)‐3‐hydroxybutanoic acid under Yamaguchi's macrolactonization conditions (2,4,6‐trichlorobenzoyl chloride/base) was studied. While the content of hexolide 2 in the product mixture is almost invariably ca. 35%, the amounts of pentolide 1 and of the larger rings strongly depend upon the temperature employed (Fig.1). Cyclic oligomers (5,6) are also obtained from 3‐hydroxypentanoic acid. Enantiomerically pure β‐butyrolactone can be used for the preparation of pento‐, hexo‐, and heptolide under Shanzer's macrolactonization conditions (tetra‐oxadistannacyclodecane ‘template’). The X‐ray crystal structures of the pentolide 1 and of two modifications (space groups C 2 and P 21) of the hexolide 2 were determined (Figs. 2–6 and Tables 1 and 5). No close contacts between substituent atoms and atoms in the rings or between ring atoms are observed in these structures. The hexolide C 2 modification is ‘just a large ring’, while the crystals of the P 21 modification contain folded rings the backbones of which resemble the seam of a tennis ball. A comparison of the torsion angles in the folded hexolide ring of the P 21 modification with those in the helical poly‐(R)‐3‐hydroxybutanoate (PHB) suggests (Table 2) that the same interactions might be responsible for folding in the first and helix formation in the second case. Molecular modeling with force‐field energy minimization of the tetrolide from four homochiral β‐hydroxybutanoic acid units was undertaken, in order to find possible reasons for the fact that we failed to detect the tetrolide in the reaction mixtures. The calculated conformational energies (per monomer) for some of the tetrolide models (Figs. 7–9 and Tables 3 and 4) are not significantly higher than for the pentolide and hexolide crystal structures. We conclude that thermodynamic instability is an unlikely reason for the lack of tetrolide isolation. This result and failure to observe equilibration of pentolide 1 to a mixture of oligomers under the reaction conditions suggest that product distribution is governed by kinetic control.
Variable‐Temperature and Variable‐Pressure Kinetic and Equilibrium studies of formation and dissociation of [V(H2O)5NCS]2+
Authors: Sauvageat Pierre‐Yves , Ducommun Yves , Merbach André E.
Published: December 2004

The kinetics of formation and dissociation of [V(H2O)5NCS]2+ have been studied, as a function of excess metal‐ion concentration, temperature, and pressure, by the stopped‐flow technique. The thermodynamic stability of the complex was also determined spectrophotometrically. The kinetic and equilibrium data were submitted to a combined analysis. The rate constants and activation parameters for the formation (f) and dissociation (r) of the complex are: k/M−1 · S−1 = 126.4, k/s−1 = 0.82; ΔH /kJ · mol−1 = 49.1, ΔH/kJ · mol−1 = 60.6; ΔS/ J·K−1·mol−1= −39.8, ΔSJ·K−1·mol−1 = −43.4; ΔV/cm3·mol−1 = −9.4, and ΔV/cm3 · mol−1 =−17.9. The equilibrium constant for the formation of the monoisothiocynato complex is K298/M−1 = 152.9, and the enthalpy and entropy of reaction are ΔH0/kJ · mol−1 = − 11.4 and ΔS0/J. K−1mol−1 = +3.6. The reaction volume is ΔV0/cm3· mol−1 = +8.5. The activation parameters for the complex‐formation step are similar to those for the water exchange on [V(H2O)6]3+ obtained previously by NMR techniques. The activation volumes for the two processes are consistent with an associative interchange, Ia, mechanism.
Synthetic Studies Directed toward the Pseurotins. Part I. Synthesis of Related Furan‐3(2H)‐ones
Authors: Dolder Matthys , Shao Xie , Tamm Christoph
Published: December 2004

According to a general concept for the total synthesis of pseurotin A (1), a secondary metabolite of Pseudeurotium ovalis STOLK, 5‐[(1S,2S,Z)‐1,2‐dihydroxyhex‐3‐enyl]‐2,2,4‐trimethylfuran‐3(2H)‐one (17) was prepared. It is a model substance for the substituted furan‐3(2H)‐one moiety of 1. The aldol condensation of the aldehyde 26, derived from D‐glucose, and the enolate of ketone 29 served as key reaction.
Intramolecular Dynamics of Tetranuclear Iridium Carbonyl Cluster Compounds. Part III. Crystallographic and dynamic evidence for the intermediate of the ‘merry‐go‐round’ process in nonacarbonyl‐μ3‐(1,3,5‐trithiane)‐tetrairidium
Authors: Suardi Gianfranco , Strawczynski Andres , Ros Renzo , Roulet Raymond , Grepioni Fabrizia , Braga Dario
Published: December 2004

The title complex crystallises in two C3v, isomeric forms differing in carbonyl‐ligand arrangement. In solution, the isomer 1b with three edge‐bridging carbonyls on a common face of the metal tetrahedron converts via an endothermic equilibrium into the isomer 1u with no bridging carbonyls. The latter was shown by 13C‐NMR to be the intermediate of the ‘merry‐go‐round’ process which exchanges the sites of the basal CO's.
The Bioconversion of (3RS,E)‐ and (3RS,Z)‐Nerolidol into Oxygenated Products by Streptomyces cinnamonensis. Possible Implications for the Biosynthesis of the Polyether Antibiotic Monensin A??
Authors: Holmes Duncan S. , Ashworth Doreen M. , Robinson John A.
Published: December 2004

The ability of the monensin‐producing organism Streptomyces cinnamonensis to bioconvert the (E)‐and (Z)‐isomers of nerolidol (= 3,7,1 1‐trimethyldodeca‐1,6,10‐trien‐3‐ol) into new oxygenated products has been investigated. When a 3H‐labelled racemic form of each sesquiterpene was added to fermentations of S. cinnamonensis, several new 3H‐labelled products could be detected. Two products were isolated from bioconversion of (E)‐nerolidol, the amide 8 and the 9 (Scheme 2), whereas four products were isolated from the bioconversion of (Z)‐nerolidol, the epoxydiol 10, triols 11 and 12, and the tetrahydrofuryl alcohol 13 (Scheme 4). Products 9–13 were obtained as a 1 : 1 mixture of diastereoisomers, and 12 was shown to arise by the overall anti addition of two OH groups to the trisubstituted (Z)‐double bond of (Z)‐nerolidol. Both isomers of nerolidol as well as the acetylene 7 are inhibitors of monensin production in shake cultures of S. cinnamonensis.
Synthese von 2‐Oxo‐2H‐pyran‐5‐Carboxylat‐Derivaten
Authors: Kvitu Vratislav
Published: December 2004

Synthesis of 2‐Oxo‐2H‐pyran‐5‐carboxylate Derivatives

3‐Substituted diethyl pent‐2‐enedioates are easily formylated by means of ethyl formate/TiCl4/4‐methylmorpholine to produce the ethoxymethylene derivatives, which are smoothly cyclized either with HCOOH or PPA to corresponding 2‐oxo‐2H‐pyran‐5‐carboxylate derivatives.
Diastereoselective Spirocyclization of C‐(Alkyloxycarbonyl)formimines of 2‐Substituted 1HIndole‐3‐ethanamines (= Tryptamines): Basic Studies. 5th Communication on Indoles, Indolenines, and Indolines
Authors: Freund Ralf , Mahboobi Siavosh , Noack Klaus , Schonhölzer Peter , Bernauer Karl
Published: December 2004

C‐(Alkoxycarbonyl)formimines of type 15–18 were derived from the 2‐substituted tryptamines 2, 9, 10, and 11 and transformed with tosyl chloride into tricyclic 3‐spiroindoles of types 19–22 (Scheme 3). The influence of the homochiral alkoxy moieties A–D on the stereochemical outcome of this reaction was studied. Good‐to‐excellent diastereoselectivities were observed with the (−)‐8‐(phenylmenth‐3‐yl)oxy group (B) as homochiral auxiliary. The structures of the tricycles 4, (2′R,3S)‐19B, and (2′S,3R)20C were established by X‐ray analysis, the structures of the others by NOE and CD studies, and by chemical correlation. Possibilities to explain the steric course of the spirocyclizations are discussed.
Struktur der Valenciaxanthine und Valenciachrome
Authors: Märki‐Fischer Edith , Eugster Conrad Hans
Published: December 2004

Structure of the Valenciaxanthins and Valenciachromes

Valenciaxanthin, a carotenoid first isolated from Californian Valencia orange juice in 1952/1954 by American scientists, was re‐isolated from fresh Spanish ‘Navelinas’ and shown, by spectroscopical and chiroptical examination, to have the unexpected (9Z)‐10′‐apo‐11′,12′‐dihydroviolaxantin‐10′‐ol structure 6. A further, very minor component represents the (all‐E)‐structure 7. Therefore, the Valenciachromes are the furanoid rearrangement products of 6 and 7 and, thus, stereoisomers of the 10′‐apo‐11′,12′‐dihydroauroxanthiiv 10′‐ols 8. Valenciaxanthin represents a modification of the common cleavage of carotenoids in higher plants according to the scheme C40 → C27 + C13, insofar as the reduction step not only includes the aldehyde function but also the subsequent conjugated double bond.
Synthetic studies directed toward the pseurotins. Part II. Synthesis of related highly functionalized furan‐3(2H)‐ones
Authors: Dolder Xie Shao Matthys , Tamm Christoph
Published: December 2004

The synthesis of 2,2‐bis(hydroxymethyl)‐4‐methyl‐5‐phenylfuran‐3(2H)‐one (9), 5‐[(1S,2S,Z)‐1,2‐(ethylidenedioxy)hex‐3‐enyl]‐2,2‐bis(hydroxymethyl)‐4‐methylfuran‐3(2H)‐one (24), and 5‐[(1S,2S,Z)‐1,2‐(ethylidenedioxy)hex‐3‐enyl]‐2‐(hydroxymethyl)‐4‐methylfuran‐3(2H)‐one (28), which represent more advanced, suitably functionalized intermediates for the synthesis of pseurotin A (1), a secondary metabolite of Pseudeurotium ovalis STOLK, is described.
Optical Absorption Spectra for the Solvated Electron Observed in the Pulse Radiolysis of cis‐ and trans‐ Isomers of 3‐ and 4‐Methylcyclohexanols
Authors: Fujisaki Noboru , Comte Pascal , Infelta Pierre P. , Gäumann Tino
Published: December 2004

The absorption band maximum of solvated electrons, λmax(e−s), in 3‐ or 4‐methylcyclohexanols is observed at longer wavelengths (818–837 nm), if the OH group is axial, and at shorter wavelengths (721–723 nm), if it is equatorial. It is surmised that the size of cavity for the solvated electron is larger in the former case and smaller in the latter.
How good are quartic functions to describe double‐minimum energy profiles? Nitrogen inversion as example
Authors: Ha Tae‐Kyu , Dunitz Jack D.
Published: December 2004

Energy profiles for nitrogen inversion in ammonia (1), aziridine (2), 1 H‐azirine (3), trans‐2,3‐difluoro‐aziridine (4), cis‐2,3‐difluoroaziridine (5), 2,3‐difluoro‐1H‐azirine (6), methanimine (7), and 2,2‐difluoro‐methammine (8) have been calculated at the 6–31 G** and 4‐21G* levels. If the reaction coordinate is chosen as the angle τ between the NH bond and the CNC plane (or the NC line for the imines 7 and 8), the energy is reproduced quite well by a quartic function V(τ) = aτ4 – bτ2 in all cases. Moreover, for this series of molecules the ratio a/b is approximately constant, which means that the inversion barrier is directly proportional to the quadratic force constant of the equilibrium structure along the reaction coordinate. The use of this and other simple relationships for automerization reactions is discussed. Some of the molecules studied show features that can be nicely interpreted in terms of stereoelectronic factors.
Synthese von enantiomerenreinen ‘Grasshopper’‐Ketonen und verwandten Verbindungen
Authors: Baumeler Andreas , Brade Walter , Haag Andreas , Eugster Conrad Hans
Published: December 2004

Synthesis of Optically Pure Grasshopper Ketone and of Its Diastereoisomers and Related Compounds

Starting from our previously described synthon 1, the synthesis of four enantiomerically pure grasshopper ketons (diastereoisomeric 4‐(2′,4′‐dihydroxy‐2′,6′,6′‐trimethylcyclohexylidene)but‐3‐en‐2‐ons) and of their oxo derivatives was performed. Spectral and chiroptical data are presented.
Enantiomeric 3,7‐Dimethylocta‐1,7‐dienes as Useful Chiral Building Blocks. A New Access to Both Optical Antipodes of Natural (E)‐3,7‐Dimethyloct‐2‐ene‐1,8‐diol and (E)‐3,7‐Dimethyloct‐2‐ene‐1,8‐dicarboxylic Acid
Authors: Giersch Wolfgang , Schulte‐Elte Karl H.
Published: December 2004

Ozonolysis of the easily available monoterpenoids (−)‐1 and (+)‐1 leads in high yield to the ketoaldehydes (−)‐4 and (+)‐4, which serve as convenient intermediates for efficient new routes to both optical antipodes of the naturally occurring octenediol (E)‐2 (Monarch butterfly secretion product) and octene‐dicarboxylic acid (E)‐3 (Callosobruchus chinensis sex pheromone). All steps proceed with almost complete retention of configuration, ensuring the synthesis of the target compounds with high optical purity.
Ein neuer synthetischer Zugang zu Ubichinonen
Authors: Rüttimann August , Lorenz Peter
Published: December 2004

A New Synthetic Route to Ubiquinones

Ubiquinones 11 have been prepared employing a new strategy: as key step, the Diels‐Alder reaction of 1,1,2‐trichloroethene 3 with 2,5‐bis[(trimethylsilyl)oxy]‐3‐methylfuran (2) has been used for the construction of the quinone part. After methanolysis of the [4 + 2] adducts 4a/4b, further reaction with cyclopentadiene and substitution of the Cl‐atoms by MeO groups, the intermediate 7 is obtained. Diketone 7 can easily be alkylated with the desired polyprenyl side chain 9 (X = Br) using a strong base to yield, after a retro‐Diels‐Alder reaction, the corresponding ubiquinones 11 in high yields.
Synthese von 2,4‐Diamino‐thieno[2,3‐d]pyrimidin‐Derivaten
Authors: Link Helmut
Published: December 2004

Synthesis of 2,4‐Diamino‐thieno[2,3‐d]pyrimidines

Condensation of 2‐aminothiophene‐3‐carbonitrile (4) with guanidine or sequential addition of CS2 and NH3 to 4 provides 2,4‐diaminothieno[2,3‐d]pyrimidine (7). This compound yields, after sequential addition of sec‐BuLi and either [3‐(trifluoromethyl)benzene]sulfenyl chloride (8) or the corresponding disulfide 9, followed by acidic work up, 2,4‐diamino‐6‐{[3‐(trifluoromethyl)phenyl]thio}thieno[2,3‐d]pyrimidine (10). In another approach, 2‐amino‐5‐{[3‐(trifluoromethyl)phenyl]thio}thiophene‐3‐carbonitrile (11) obtained from 4 and 8 is transformed to 10 by condensation with guanidine. Corresponding to the second route, 2,4‐diamino‐6‐[(naphth‐2‐yl)thio]thieno‐[2,3‐d]pyrimidine (16) is synthesized. Oxidation of 10 with m‐chloroperbenzoic acid gives 2,4‐diamino‐6‐{[3‐(tri‐fluoromethyl)phenyl]sulfinyl}thieno[2,3‐d]pyrimidine (13).
Thermal 1,6‐Electrocyclization Reactions of Acceptor‐Substituted 2,3‐Divinyl‐1H‐indoles Yielding Functionalized Carbazoles
Authors: Pindur Ulf , Adam Reinhard
Published: December 2004

Three new synthetic procedures for and thermal 1,6‐electrocyclizations of acceptor‐substituted 2,3‐divinyl‐1H‐indoles leading to functionalizing carbazoles are described. The scope and limitations as well as some mechanistic aspects of the methodologies are discussed. The key strategies employed include Pd(II)‐catalyzed coupling and Wittig procedures.
Synthese von einigen 2H‐Pyran‐2‐on‐Derivaten
Authors: Kvita Vratislav , Sauter Hanspeter
Published: December 2004

The Synthesis of Some 2H‐Pyran‐2‐one Derivatives

Derivatives of 6‐unsubstituted 2H‐pyran‐2‐one have been synthesized by several different methods. The 4‐chloro‐2H‐pyran‐2‐one (9) is the most important, since it serves as starting material for the synthesis of different 4‐substituted 2H‐pyran‐2‐ones (Scheme 2). Also described are simple transformations of cumalic‐acid derivatives producing 5‐(2,2‐dichlorovinyl)‐2H‐pyran‐2‐one (23), 2‐oxo‐2H‐pyran‐2‐carbonitrile (26), and 4,5‐bis(trifluoromethyl)‐2H‐pyran‐2‐one (32) (Scheme 3 and 4).
Tetrahydrolipstatin: Thermal and Hydrolytic Degradation
Authors: Stalder Henri , Schneider Pierre R. , Oesterhelt Gottfried
Published: December 2004

The thermal and hydrolytic degradation of tetrahydrolipstatin (THL, 1) was investigated. All main degradation products were isolated, characterized, and synthesized. Labile intermediates unavailable to isolation were detected and identified by GC/MS analysis of their silylated derivatives, and whenever possible, compared with independently prepared reference compounds. The identified degradation products represent at least 97% of the total degradation mixture. Two main reaction pathways arc proposed. Pharmacological data are reported for the degradation mixture and the main degradation products.
Neoflor und 6‐Epineoflor aus Blüten von Trollius europaeus; Hochfeld‐1H‐NMR‐Spektren von Neoxanthin und (9′Z)‐Neoxanthin
Authors: Märki‐Fischer Edith , Eugster Conrad Hans
Published: December 2004

Neoflor and 6‐Epineoflor from Flowers of Trollius europaeus; Highfield 1H‐NMR Spectra of (all‐E)‐Neoxanthin and (9′Z)‐Neoxanthin

Re‐isolation of the very polar carotenoids from flowers of the title plant furnished two epimeric pentahydroxy compounds. Based on spectroscopical and chiroptical arguments and by chemical correlation with neoxanthin, their structures were established as 11 (proposed name neoflor) and 12 (6‐epineoflor), Decoupling experiments and COSY‐2D‐1H‐NMR spectra allowed a complete assignement of the vinyl protons of the two isomers, and furthermore, for the first time, also of those of (all‐E)‐neoxanthin and (9′Z)‐neoxanthin.
Carbonyliron Complexes of Allenic Acids, Esters, Amides, and Imides
Authors: Trifonov Latchezar S. , Orahovats Alexander S. , Heimgartner Heinz
Published: December 2004

On irradiation in the presence of Fe(CO)5, the allenic amides and imides showed a similar course of complexation to that of esters and lactones, respectively, e.g. the amides of type 10 led to diiron complexes of type 11 (Scheme 3), whereas the imide 12 yielded a mixture of a dinuclear and two mononuclear complexes (13–15, Scheme 4). The racemic ester 6 also gave mononuclear (7a, 7b, and 9) and dinuclear complexes (8a and 8b; Scheme 2). In case of the allenic acid 4, only complexation of type 5 was observed (Scheme 1).
Synthesis and Biological Evaluation of 14‐Alkoxymorphinans. Part 8. 14‐methoxymetopon, an extremely potent opioid agonist
Authors: Schmidhammer Helmut , Schratz Andrea , Mitterdorfer Jörg
Published: December 2004

14‐Methoxymetopon (= 5,14‐O‐dimethyloxymorphone; 4)and 14‐ethoxymetopon (5) were synthesized from 14‐hydroxy‐5‐methylcodeinone (6). In the AcOH‐writhing test in mice, compound 4 was found to be ca. 20000 times more potent than morphine.
2H/1H Isotope Shifts for 6Li‐NMR: First Experimental Detection and Applications to Structural Problems in the Field of Organolithium Compounds
Authors: Eppers Oswald , Günther Harald
Published: December 2004

Deuterium‐induced isotope effects on 6Li chemical shifts, transmitted over two bonds, 2Δ(6Li)(2H/1H), have been measured for the first time for methyllithium and the system methyllithium/lithium iodide. The observed shifts are to low field and range from 15 to 20 ppb per CD3 group. The multiplicity and intensity distribution of the 6Li signals resulting for mixtures of CH3‐ and CD3‐containing samples in the limit of slow inter‐ as well as intra‐aggregate exchange yield information about the size of the various clusters present in diethylether solution. It is expected that these isotope shifts can facilitate structural investigations of organolithium compounds. In some cases, the results of such measurements are expected to be less ambiguous then the conclusions based on multiplets that arise from scalar 13C,6Li spin‐spin coupling.
The Gas‐Phase Ion/Molecule Reactions of C3H5X (X = C1, Br, I)
Authors: Gäumann Tino , Zhu Zhiqing , Kida Marcia C. , Riveros José M.
Published: December 2004

The ion/molecule reactions of the molecular ion, the C3H ion, and the C3H ion obtained from 3‐chloropropene. 1‐bromopropene, 2‐bromopropene, 3‐bromopropene, bromocyclopropane. and 3‐iodopropene have been studied with their neutral precursor in a Fourier‐transform mass spectrometer (FT/ICR). The molecular ions react to yield primarily C6H except for the ion derived from 1‐bromopropene that is unreactive. The kinetics of the 3‐bromopropene molecular ion reveals that 18% of these ions must possess a different structure which is unreactive. The fact that C3H ions obtained from 2‐bromopropene are the only ones to undergo proton transfer is taken as evidence that only this parent compound gives rise to 2‐propenyl cations by low‐energy electron impact. The C3H ions generated in these systems are shown to be roughly an equal mixture of propargylium ions that react to yield C6H and unreactive cyclopropenium ions.
A New General Synthesis of 2,2‐Dialkyl‐2,3‐dihydro‐4H‐pyran‐4‐ones and Their Application for the in situ Preparation of Electron‐Rich Dienes in Carbonyl‐Alkyne Exchange Reactions with Acetylenes
Authors: Obrecht Daniel
Published: December 2004

The substituted 2,2‐dialkyl‐2,3‐dihydro‐4H‐pyran‐4‐ones of type II and III have been prepared by acid‐catalyzed cyclization of the corresponding substituted acetylenic ketones I in good to excellent yields (Scheme 1). These 2,2‐dialkyl‐2,3‐dihydro‐4H‐pyran‐4‐ones II and III have been used for the in situ preparation of highly reactive dienes of type IV–VI (Scheme 2) in carbonyl‐alkyne exchange reactions with electron‐poor alkynes VII to yield the highly substituted aromatic compounds VIII and IX. These reactions proceed in good yields and with excellent degree of regioselectivity. Aryl‐substituted 2,2‐dialkyl‐2,3‐dihydro‐4H‐pyran‐4‐ones III (R1 = Ar) subsequently yield highly substituted biaryls. Reaction mechanisms are presented for the formation of the 2,2‐dialkyl‐2,3‐dihydro‐4H‐pyran‐4‐ones as well as for the carbonyl‐alkyne exchange reactions with electron‐poor acetylenes.
Structural and Luminescence Study of the 3:2 Complex between Europium Nitrate and the B Isomer of Dicyclohexyl‐18‐crown‐6
Authors: Moret Emmanuel , Nicolò Francesco , Plancherel Dominique , Froidevaux Pascal , Bünzli Jean‐Claude G. , Chapuis Gervais
Published: December 2004

The crystal and molecular structure of bis[dinitrato‐(2,4,8,15,18,21‐hexaoxatricyclo[20.4.0.09,14]hexacosane)europium(III)]pentakis(nitrato)europiate(III) [Eu(NO3)2LB]2([Eu(NO3)5]), has been determined at 170 K from single‐crystal X‐ray diffraction. The complex crystallizes in the monoclinic space group P21/n (ITC No. 14): a = 16.338(3) Å, b = 15.704(3) Å, c = 24.474(4) Å, β = 97.73(1)°, Z = 4. The structure was refined to a final R value of 0.058 (Rw = 0.060). The asymmetric unit contains three independent ions lying on general positions: [Eu(NO3)5]2− and two distinct [Eu(NO3)2LB]+ cations with the macrocyclic ligand in the cis‐anti‐cis conformation (B‐isomer). The EuIIIions are 10‐coordinate with the following mean bond lengths: Eu–O(nitrate) = 2.48(2) Å in the anion and 2.45(2) Å in the two cations, Eu–O(ether) = 2.56(8) and 2.55(5) Å. Small but significant differences are observed between the two complex cations, especially with respect to the positions of the cyclohexyl substituent. A conformational analysis performed on the six O‐atoms of the complex cations confirms the predictions of a simple model. The metal ion sites of the complex have been probed by high‐resolution excitation and emission spectra at 296 and 77 K. The 5D0←7F0 excitation spectrum displays two main bands along with several other minor components. A detailed analysis of the corresponding and selectively excited emission spectra leads to the observation of three types of spectra corresponding to the three crystallographically different EuIII ions. Moreover, three minor sites are identified, one anionic and two cationic, with a population equal to ca. 10% of the population of the main sites. We interpret this finding as reflecting the presence of molecules with slightly different conformations.
Michael Reactions of α‐Unsubstituted Trisubstituted 1H‐Pyrroles
Authors: Lüönd Rainer , Neier Reinhard
Published: December 2004

To obtain stable derivatives of α‐unsubstituted pyrroles, the reaction of the test pyrrole 9 with a series of chalcones 14a–h were studied. Michael adducts 16b–h could be isolated. In order to synthesize coloured derivatives, the reaction of different pyrroles 9, 21, 23, and 25 with diphenylpropynone 19 was investigated. In these cases, too, Michael‐addition products were formed. The intense absorption band around 400 nm makes the identification of these derivatives easy.
2,3‐ and 4,5‐Secodopa, the Biosynthetic Intermediates Generated from L‐Dopa by an Enzyme System Extracted from the Fly Agaric, Amanita muscaria L., and Their Spontaneous Conversion to Muscaflavin and Betalamic Acid, Respectively, and Betalains
Authors: Terradas Fernand , Wyler Hugo
Published: December 2004

An enzyme is extracted from the red peel of Amanita muscaria which cleaves the C(2)–C(3) and the C(4)–C(5) bond of the aromatic ring of L‐dopa (1) to form a mixture of 4,5‐secodopa (= salt of 6‐amino‐2‐hydroxy‐4‐(2′‐oxoethylidene)hept‐2‐enedioic acid; 2) and 2,3‐secodopa ( = salt of 7‐amino‐5‐formyl‐2‐hydroxyocta‐2,4‐dienedioic acid; 3), two hitherto hypothetical biosynthetic intermediates (see Scheme). Though isolation of these products has not been possible, structural evidence is inferred from reaction products, kinetics, and spectroscopical characteristics in comparison with known compounds. Secodopas 2 and 3 are characterized in dilute solution by HPLC and UV/VIS spectroscopy (anions; λmax 424 and 414 nm, resp., ϵ420 = 25500; on acidification, shift to 380 and 372 nm, resp.). They cyclize without enzyme catalysis, optimally at pH 4.5–5; 3 produces muscaflavin (5) and 2 betalamic acid (4). The products arc identified by direct comparison with authentic samples in HPLC, by 1H‐NMR of 5, and by condensation of 4 with L‐proline to form the well known betalain indicaxanthin (7). The enzymatic conversion of L‐dopa (1) via 2 to betalamic acid (4; (S)) and its condensation with L‐proline leads to pure natural indicaxanthin (7; (2S,115)); correspondingly, the enzymatic conversion of D‐dopa to (R)‐betalamic acid and its condensation with L‐proline produces isoindicaxanthin ((2S,11R)) which is unknown in nature. Particularly relevant is the fact that the same enzyme cleaves pyrocatechol to produce a solution of the enolate form of the known 2‐hydroxy‐6‐oxohexa‐2,4‐dienoate (secopyrocatechol; 9; see Fig. 5). Dissociation constants of the corresponding enolic functions in the cleavage products are determined by spectrometric titration and compared to those of known systems.
C‐Alkylation of Peptides through Polylithiated and LiCl‐Solvated Derivatives Containing Sarcosine Li‐Enolate Units
Authors: Seebach Dieter , Bossler Hans , Gründler Hansjörg , Shoda Shin‐Ichiro , Wenger Roland
Published: December 2004

The tripeptide and hexapeptide derivatives Boc‐Gly‐Sar‐MeLeu‐OH (5b), Boc‐Ala‐Sar‐Sar‐OH (6b), Boc‐Ala‐Sar‐MeLeu‐OH (7b), and Boc‐Abu‐Sar‐MeLeu‐Val‐MeLeu‐Ala‐OH (12b) can be poly‐deprotonated (tri‐ and pentalithio derivatives K and P, respectively), and thus C‐alkylated on sarcosine (Sar) moieties with MeI and allyl or PhCH2Br. The polylithiated species are solubilized in THF, and their reactivity modified by excess base (lithium diisopropylamide (LDA)), by added LiCl, and/or the cosolvent N,N′‐dimethylpropyleneurea (DMPU). Optimization of the reaction conditions for methylation in the cases of 7b (Table 3) and 12b (Scheme 8) gave products in which the Sar residue of the educt has been transformed into a Me‐D‐Ala unit in yields of 80 (9c/8c) and 67% (14c/13c), respectively, and with a diastereoselectivity of ca. 4:1. Less selective methylations and benzylations were observed with the tripeptides 5b and 6b containing only one stereogenic center; also, excess base and alkyl halide may lead to double alkylations in those latter two cases (Tables 1 and 2). No epimerization of stereogenic centers was detected under the strong‐base conditions. The analysis of the products was accomplished by a combination of NMR and FAB‐MS spectroscopy, as well as by hydrolysis to the parent amino acids, subsequent formation of derivatives with isopropyl isocyanate, and GC analysis on the chiral column Chirasil‐Val®.
Quantitative Structure‐Affinity Relationships of Dopamine D2 Receptor Antagonists: A Comparison between Orthopramides and 6‐Methoxysalicylamides
Authors: de Paulis Tomas , El Tayar Nabil , Carrupt Pierre‐Alain , Testa Bernard , van de Waterbeemd Han
Published: December 2004

A large series of orthopramides (= 2‐methoxybenzamides), 6‐methoxysalicylamides, and 2,6‐dimethoxy‐benzamides were examined for their affinity to the dopamine D2 receptor. The binding data were correlated with physicochemical parameters and 13C‐NMR chemical shifts using the cross‐validated partial least‐squares method and multiple linear regression analysis. The results quantitate the influence of electronic factors and lipophilicity to D2 receptor binding. They also show that the N‐[(1‐ethylpyrroIidin‐2‐yl)methyl] and N‐(1‐benzylpiperidin‐4‐yl) side‐chains affect the mode of binding of these compounds.
Synthesis of Aristotelia‐type alkaloids. Part VII. Syntheses of (±)‐sorelline, (±)‐serratenone, and (±)‐aristotelin‐19‐one
Authors: Burkard Stefan , Borschberg Hans‐Jürg
Published: December 2004

The imine obtained by condensing indole‐protected 2‐(indol‐3‐yl)acetaldehyde (5) with the terpinylamine derivative (±)‐4 was cyclized in 51% yield to the 19‐substituted hobartine derivative (±)‐20 upon exposure to anhydrous HCOOH. This pivotal intermediate was further elaborated into the indole alkaloids (±)‐serratenone ((±)‐22) and (±)‐sorelline ((±)‐29). In the course of these investigations, a novel rearrangement was uncovered; a Lewis acid‐catalyzed 1,3‐migration of an arylsulfonyl group from the indole N‐atom into the benzene ring. The discovery that synthetic (±)‐aristotelin‐19‐one ((±)‐34) has decidedly different spectroscopic properties than aristolasicone, a metabolite for which the structure has been recently proposed, led to a revision of the structure of the latter.
Axially Dissymmetric Diphosphines in the Biphenyl Series: Synthesis of (6,6′‐Dimethoxybiphenyl‐2,2′‐diyl)bis(diphenylphosphine)(‘MeO‐BIPHEP’) and Analogues via an ortho‐Lithiation/Iodination Ullmann‐Reaction Approach
Authors: Schmid Rudolf , Foricher Joseph , Cereghetti Marco , Schönholzer Peter
Published: December 2004

The new axially dissymmetric diphosphines (R)‐ and (S)‐(6,6′‐dimethoxybiphenyl‐2,2′‐diyl)bis(diphenyl phosphine) ((R)‐ and (S)‐5a; ‘MeO‐BIPHEP’) and the analogues (R)‐ and (S)‐5b and 5c have been synthesized in enantiomerically pure form. These ligands have become readily available by a synthetic scheme which employs, as key steps, an ortho‐lithiation/iodination reaction of the (m‐methoxyphenyl)diprienylphosphine oxides 8 and a subsequent Ullmann reaction of the resulting iodides 9 to provide the racemic bis(phosphine oxides) 10. The bis(phosphine oxides) 10 subsequently are resolved with (−)‐(2R,3R)‐ and (+)‐(2S,3S)‐O‐2,3‐dibenzoyltartaric acid and reduced to diphosphines 5. The Ullmann reaction constitutes a new and efficient route to 2,2′‐bis(phosphinoyl)‐substituted biphenyl systems. Absolute configurations were established for (R)‐5a by X‐ray analysis of the derived Pd complex (R,R)‐17a, and for 5b and 5c by means of 1H‐NMR comparisons of the derived Pd complexes 16 or 17, respectively, and by means of CD comparisons. The MeO‐BIPHEP diphosphine 5a proved to be as efficient as the previously described BIPHEMP diphosphine ((6,6′‐dimethylbiphenyl‐2,2′‐diyl)bis(diphenylphosphine)) in enantioselective isomerizations and hydrogenations.
A Direct Route to 3‐(D‐Ribofuranosyl)pyridine Nucleosides
Authors: Piccirilli Joseph A. , Krauch Tilman , MacPherson Lawrence J. , Benner Steven A.
Published: December 2004

A route for synthesizing C‐nucleosides with 2,6‐substituted pyridines as heterocyclic aglycones is described. Condensation of appropriately substituted lithiated pyridines with ribono‐1,4‐lactone derivatives yields hemiacetal 4a–g (Table 1), which can be reduced by Et3SiH and BF3·Et2O to the corresponding C‐nucleoside (see Scheme 1 for 4d → β‐D‐5). Conditions are presented that optimize the amount of the 2,6‐dichloropyridine‐derived β‐D‐anomer β‐D‐5 formed (Table 3). Aminolysis of β‐D‐5 yields the diaminonucleoside 14 (Scheme 3).
Über die Reaktion einiger 2H‐Pyran‐2‐on‐Derivate mit primären Aminen
Authors: Kvita Vratislav , Sauter Hanspeter , Rihs Grety
Published: December 2004

On the Reaction of Some 2H‐Pyran‐2‐one Derivatives with Primary Amines

The versatile reactivity of 6‐unsubstituted 2H‐pyran‐2‐ones towards aliphatic and aromatic amines has been studied. It was found that the result of the reaction depends not only on the substitution of 2H‐pyran‐2‐ones and on the structure of amines, but also on the stoichiometric ratio of reacting compounds.
Katalytische Carbonylierung von Aceton‐oxim an Bisoximato‐diruthenium‐Komplexen: Ein einfacher Zugang zu wasserfreiem Acetonin. Isolierung und Molekülstruktur von [Ru2(CO)5(Me2CNO)2(Me2CNOH)]
Authors: Langenbahn Meinhard , Stoeckli‐Evans Helen , Süss‐Fink Georg
Published: December 2004

Catalytic Carbonylation of Acetone Oxime at Bisoximatodiruthenium Complexes: A Simple Access to Anhydrous Acetonine. Isolation and Molecular Structure of [Ru2(CO)5(Me2CNO)2(Me2CNOH)]

In the presence of catalytic amounts of [Ru2(CO)4(Me2CNO)2(Me2CNOH)2] (1), acetone oxime reacts with carbon monoxide to give 2,3,4,5‐tetrahydro‐2,2,4,4,6‐pentamethylpyrimidine (‘acetonine’). CO2, and NH3. The reaction proceeds presumablyviacarbonylation of Me2CNOH to the unstable intermediate Me2CNOCHO which undergoes decarboxylation to give the corresponding imine Me2CNH. The final product is assumed to result from the cyclotrimerisation of Me2CNH with elimination of NH3. Evidence for the intermediacy of the imine comes from the analogous reaction of acetophenone oxime, PhMeCNOH, which gives the corresponding imine PhMeCNH as a stable product. The isolation of the complex [Ru2(CO)5(Me2CNO)2(Me2CNOH)] (2) suggests the carbonylation to take place at the bridging oximato ligand of1.
Synthesis and Properties of Sodium and Europium(III) Cryptates Incorporating the 2,2′‐Bipyridine 1,1′‐Dioxide and 3,3′‐Biisoquinoline 2,2′‐Dioxide Units
Authors: Lehn Jean‐Marie , Roth Christine O.
Published: December 2004

The sodium and europium cryptates of the new macrobicyclic ligands 2 and 3 incorporating the 2,2′‐bipyri dine 1,1′‐dioxide and 3,3′‐biisoquinoline 2,2′‐dioxide units, respectively, have been prepared. The EuIII complexes present characteristic 1H‐NMR spectra, showing large shifts, and are strongly luminescent in aqueous solution. These markedly improved luminescent properties, compared to the europium cryptate of the parent macrobicyclic ligand 1, may be ascribed at least in part to a better shielding of the bound cation by the N‐oxide sites.
Lithium‐Salt Effects in Peptide Synthesis. Part II. Improvement of Degree of Resin Swelling and of Efficiency of Coupling in Solid‐Phase Synthesis
Authors: Thaler Adrian , Seebach Dieter , Cardinaux Francis
Published: December 2004

The course of solid‐phase peptide‐coupling reactions as well as the swelling properties of a peptide‐resin are influenced by the addition of inorganic salts (LiCl, LiBr, LiClO4, KSCN). Used as additives, these salts can (i) improve coupling yields (e.g., for Fmoc‐(Ala)5‐Phe‐resin → Fmoc‐(AIa)6‐Phe‐resin in DMF/CH2Cl2 1:1 from 89.4 to 97.1% (for polyethylene oxide) on polystyrene ( PEO‐PS) resin) or from 77.5 to 93.8% (for poly‐(N,N′‐dimethylacrylamide) on ‘Kieselgur’ (PDMAA‐KG) resin) without and with 0.4M LiCl, respectively), (ii) increase resin swelling (e.g. for Fmoc‐(Ala)5‐Phe‐(polystyrene resin) from 2.42‐ to 5.73‐fold in 1‐methylpyrrolidin‐2‐one (NMP) without and with LiCl, (respectively), and (iii) change coupling rates. Example;; of coupling reactions and swelling behaviour (degree and rate) in different solvents (DMF, DMF/CH2Cl2 1:1, THF, NMP, N,N‐dimethylpropyleneurea ( DMPU) with and without salts) using different resins (polystyrene (PS); PEO–PS, and PDMAA‐KG) and an improved analysis of alanine oligomers up to Ala12‐Phe by HPLC and FAB‐MS are reported.
[5‐Leucin]enkephalin‐Related Glycoconjugates: Structurally Novel Agents Effective against HIV‐1
Authors: Horvat Štefica , Varga Lidija , Horvat Jaroslav , Pfützner Andreas , Suhartono Haryadi , Rübsamen‐Waigmann Helga
Published: December 2004

A series of [Leu5]enkephalin‐related glycoconjugates with an ester‐, ether‐, or amide‐type linkage were synthesized and evaluated for antiviral activity against HIV‐1 in a cell‐culture system using peripheral blood lymphocytes. All tested glycoconjugates exhibited a certain antiviral activity which was significantly higher than the activity of the parent peptide compound itself. These results indicate that synthetic glycoconjugates of opioid peptides are good candidates for the development of anti‐HIV agents.
Photo‐induced molecular transformations. Part 123. One‐step synthesis of 1H‐benz[f]indole‐4,9‐diones by a new regioselective photoaddition of 2‐amino‐1,4‐naphthoquinone with various alkenes and its application to one‐step synthesis of kinamycin skeleton
Authors: Kobayashi Kazuhiro , Takeuchi Hiroyasu , Seko Shinzo , Suginome Hiroshi
Published: December 2004

2,3‐Dihydro‐1H‐benz[f]indole‐4,9‐diones are formed in one‐step in 45–82% yields by an unprecedented [2+3]‐type regioselective photoaddition of 2‐amino‐1,4‐naphthoquinone with various electron‐rich alkenes and the [2+3] adducts derived from ammonaphthoquinone with vinyl ethers and vinyl acetate to give 1H‐benz[f]indole‐4,9‐diones including a benzindole‐dione with a kinamycin skeleton in 33–72% yields. A probable pathway leading to the formation of the dihydroindole‐dione involving air oxidation of an intermediary hydroquinone is proposed.
Biphenyltetrols and Dibenzofuranones from Oxidative Coupling of Resorcinols with 4‐Alkylpyrocatechols: New Ciues to the Mechanism of Insect Cuticle Sclerotization
Authors: Miessner Merle , Crescenzi Orlando , Napolitano Alessandra , Prota Giuseppe , Andersen Svend Olav , Peter Martin G.
Published: December 2004

Oxidation of 4‐alkylpyrocatechols 2 by means of an insect diphenoloxidase (laccase) or K3 [Fe(CN)6] yields, in the presence of resorcinols 1 (R2  H), complex mixtures of products from which biphenyltetrols 3 (R3  H) and dibenzofuranones 5 and 6 were isolated. It is suggested that similar homo‐coupling products are formed from pyrocatechols 2b and 2c in insects during cuticle sclerotization.
Synthèse énantiospécifique du (—)‐(1S,3R,5R)‐1,8‐diméthyl‐3‐éthyl‐2,9‐dioxabicyclo[3.3.1]non‐7‐ène
Authors: Kallimopoulos Thomas , Deschenaux Pierre‐François , Jacot‐Guillarmod André
Published: December 2004

Enantiospecific Synthesis of (—)‐(1S,3R,5R)‐1,8‐Dimethyl‐3‐ethyl‐2,9‐dioxabicyclo[3.3.1]non‐7‐ene

The isomer (—)‐(1S,3R,5R)‐1,8‐dimethyl‐3‐ethyl‐2,9‐dioxabicyclo[3.3.1]non‐7‐ene ((1S,3R,5R)‐8) was synthesized from (—)‐(3R)‐methyl 3‐hydroxypentanoate with an enantiomeric excess ≥ 96%.
3:1 Molecular Complex of Hydroquinone and C60
Authors: Ermer Otto
Published: December 2004

The preparation of a 3:1 complex of hydroquinone (HQ) and C60, (HQ)3C60, is reported and its X‐ray crystal structure described. The HQ host builds up a single H‐bonded super‐polonium network with super‐cubes as building blocks, which accommodate the large C60 guest molecules. The enclathration of C60 is rather tight (high density of the complex) owing, in part, to favorable charge‐transfer host‐guest interactions (π‐donor‐acceptor complex). Nonetheless, the C60 molecules arc orientationally disordered, and no individual bond lengths could be measured. In contrast, the HQ host network is essentially ordered and well‐defined with normal intramolecular geometry. No appreciable (powder) conductivity could be observed for (HQ)3C60, yet ESR spectra of single crystals showed interesting narrow signals.
3‐Deazaguanine N7‐ and N9‐(2′‐Deoxy‐β‐D‐ribofuranosides): Building Blocks for Solid‐Phase Synthesis and Incorporation into Oligodeoxyribonucleotides
Authors: Seela Frank , Lampe Sigrid
Published: December 2004

Oligonucleotides continuing 3‐deaza‐2′‐deoxyguanosine (I) or its N7‐regioisomer 2 were prepared by solid‐phase synthesis using P111 chemistry. Protection of 1 or 2 with N,N V‐dimethylformamide diethyl acetal followed by 4,4′‐dimethoxytritylation afforded imidazo[4,5‐c]pyridines 10b and 11b, respectively. The latter were converted into the 3′‐phosphonates 10c or lie, respectively; the cyanoethyl N,N‐diisopropylphosphoramidite 10d was also prepared. The oligonucleotide building blocks were employed in automated solid‐phase synthesis. 1 he self‐complementary oligomers 13, 15, and 17 were prepared and characterized by enzymatic hydrolysis with snake‐venom phosphodiesterase followed by alkaline phosphatase. There CD spectra exhibited the general structure of a B‐DNA.
New Dolabellane Derivatives from the Brown Alga Dictyota pardalis
Authors: Wright Anthony D. , König Gabriele M. , Sticher Otto , Lubini Paolo , Hofmann Patrick , Dobler Max
Published: December 2004

Reinvestigation of the brown alga Dictyota pardalis f. pseudohamata CRIBB led to the crystallization of 1 and to the isolation of the two new dolabellane derivatives 2 and 3. X‐Ray analysis of 1 and 2, together with detailed 1D‐and 2D‐NMR studies on 2 and 3, allowed their structures to be elucidated as (1R*,3S*,7S*,11R*,4Z)‐dolabella‐4,8(17), 12(18)‐triene‐3,7‐diol (1), (1R*,3S*,4S*,7S*,8S*,11R*,14R*,12E)‐3,4:7,8‐diepoxydolabe11‐12‐ene‐14, 18‐diol (2), and (1R*,3S*,4S*,7S*,8S*,11R*,14R*)‐3,4:7,8‐diepoxy‐l,4,8,12,12‐pentamethylbicyclo[9. 3. 0]tetra‐decan‐14‐ol(3).