bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthese von natürlichen Haloindolen via Hetero‐Cope‐Umlagerung von Vinyl‐N‐phenylhydroxamaten
Authors: Martin Pierre
Published: December 2004

Synthesis of Natural, Halogenated Indoles via Hetero‐Cope Rearrangement of Vinyl N‐Phenylhydroxamates

An efficient method for the synthesis of natural 4‐chloro‐6‐methoxyindole (the promutagen from fava beans) and of the two 4,6‐ dibromo‐ and 3,4,6‐tribromoindoles (produced by acorn worms, Enteropneusta) is presented. The key step is a hetero‐Cope rearrangement of the intermediate N‐phenyl‐O‐vinylhydroxylamine derivatives.
Photochemistry of 2,2‐Dimethyl‐2H‐Furo[3,4‐b]Pyran‐4,7(3H, 5H)‐Dione
Authors: Lau Sabine , Margaretha Paul
Published: December 2004

Irradiation (λ > 340 nm) of the title compound 2a in t‐BuOH affords 3,3,10,10‐tetramethyl‐2,8‐dioxatricyclo‐[4.3.2.01,6]undecane‐5,9‐dione (3) via photoextrusion of 2‐methylpropene and subsequent photocycloaddition of 2a to the alkene. The same regioisomer 3 is formed selectively and in much higher yields on irradiating 2a in the presence of excess 2‐methylpropene. Irradiation of 3 (λ = 300 nm) in t‐BuOH in the presence of the same alkene gives a 6:1 mixture of spirooxetanes 7a and 7b but not α‐cleavage products. In 2‐propanol, 2a is photoreduced to a 2:1 mixture of diastereoisomeric hydrodimers 9.
Fredericone, neue hochfunktionalisierte Abietanoide aus Blattdrüsen von Coleus fredericii G. TAYL
Authors: Zhu Zhen‐Yan , Nayeshiro Hidekazu , Prewo Roland , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Fredericon A, B, C, and D, Novel and Highly Functionalized Abietanoids from Leaf‐Glands of Coleus fredericii

From the leaf‐glands of the title plant (fam. Labiatae) two novel, genuie spirocycloopropyl‐coleons have been isolated and structurally characterized. Fredericon A (1) bears the unusal 1,1,2‐tricarbonylcyclopropane substructure that renders the molecule very suseptible to nucleophile‐promoted rearrangements. Biogenetically intriguing is the presence of a 3‐acetoxypropyl side‐chain in fredericon B (3). Its formation from the well known isopropyl group is explained by transformation of the latter into a spirocyclopropane, followed by a reductive opening of the cyclopropane and reducation of the aldehyde, MeOH addition to 1, yields fredericon C (5), a derivative of 1H‐phenanthro[3,2‐b]pyran‐7,12(2H,8H)‐dione by two consecutive introlecular nucleophilic openings of the cyclopropane ring and the derived methoxy‐oxirane. Similar methanolysis of a crude fraction of 1, produced, in addition to 5, the fredericon D, a novel derivative of 3H‐phenanthro[3,2‐b]pyran‐2‐(4H)‐one(6).
Mécanisme de solvolyse des cis ‐ et trans‐(p‐toluénesulfonates) d'aryl1‐2‐cyclopentyle II. Etude des étapes ultérieures à l'ionisation lors de la solvolyse des cis‐(p‐toluénesulfonates) d'aryl‐2‐cyclopentyle
Authors: Ronco G. , Guyon R. , Villa P.
Published: December 2004

Solvolysis Mechanism of cis‐ and trans‐2‐Arylylopentylp‐ Toluenesulfonates, Subsequent Step in cis‐2‐Arylcyclopentyl p‐Toluenesulfonate Solvolysis

The solvolysis of a series of 1‐deuteriated, 2‐deuteriated, and undeuteriated cis‐2‐arylcyclopentyl p‐toluenesulfonates in HCOOH, AcOH, and EtOH has been studied. We have shown that classical secondary carbocation arising from substrate ionisation undergoes two concurrent processes, namely kc (direct products formation) and kip (hydrogenium bridged ion formation as tertiary carbocation or products precursor). The intrinsic properties of solvent and the aryl substitutant electronic effects the total solvolysis rate and the respective contributions of k c and k ip processes. Comparing the observed and calculated kinetic isotope of D–C(2) allows one to conclude that no step can called ‘rate‐determining step’ but that the steps following ionisation have a preponderent effect on the total solovolysis rate.
Anion‐receptor molecules: Synthesis of a chiral and functionalized binding subunit, a bicyclic guanidinium group derived from L‐ or D‐ asparagine
Authors: Echavarren Antonio , Galán Amalia , de Mendoza Javier , Salmerón Armando , Lehn Jean‐Marie
Published: December 2004

The optically active (4S,8S)‐4, 8‐bis(hydroxymethyl)‐1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene ((S,S)‐1) has been synthesized in nine steps from L‐asparagine with a total yield of 5.1%. Similarly, the enantiomer (R,R)‐1 has been prepared from D‐asparagine. (S,S)‐ and (S,S)‐1 are representative examples of rigid and functionalized bicyclic guanidine systems and constitute useful intermediates in the construction of chiral selective anion‐receptor molecules.
Photooxygenation of 5‐aryl‐2,4‐diaminopyrimidines leading to 4‐amino‐1,3,5‐triazin‐2‐yl ketones and, in the presence of sodium borohydride, to 5,6‐dihyro‐4(3H)‐pyrimidinones
Authors: Oppenländer Thomas , Pfoertner Karl‐Heniz , Schönholzer Peter
Published: December 2004

The photosensitized oxygenation of 5‐aryl‐2,4‐diaminopyrimidines 1 in protic solvent led to the formation of the new 4‐amino‐1,3‐5‐triazin‐2‐yl ketones 2 in high yields. The structures of 2 were elucidated by spectroscopical means, especially by 13C‐NMR and UV data. Photooxygenation of 2,4‐diamino‐5‐(p‐chlorophenyl)‐6‐ethylpyrimidine 1a under reductive conditions, e.g. In the presence of excess NaBH4, gave 2‐amino‐5‐(p‐chlorophenyl)‐t‐6‐ethyl‐5,6‐dihydro‐r‐5‐hydroxy‐4(3H)‐pyrimidinone (4a), the structure of which was determined by X‐ray analysis. In the proposed mechanisms for both types of reactions, the dipolar ion 5 is assumed to be a common intermediate. For the new efficient synthesis of 1,3,5‐triazines from 2,4‐diaminopyrimidines, a 5‐aryl substituent seems to be essential.
Studies on Antifungal Agents. Part 22. 3‐aryl‐5‐[(aryloxy)alkyl]‐3‐[(1H‐imidazol‐1‐yl)methyl]‐2‐methylisoxazolidines and related derivatives
Authors: Mullen George B. , Swift Patricia A. , Marinyak David M. , Allen Stanley D. , Mitchell Jeffrey T. , Kinsolving C. Richard , Georgiev Vassil St.
Published: December 2004

The synthesis and antifungal activity of a novel series of 3‐aryl‐5‐[(aryloxy)alkyl]‐3‐[(1H‐imidazol‐1‐yl)‐methyl]‐2‐methylisoxazolidines and related compounds, are discussed. The synthesis of the title compounds was accomplished via a 1,3‐dipolar cycloaddition of α‐substituted ketonitrones with l‐alkenyl phenyl ethers (Scheme 2 and 3). The compounds were evaluated for in vitro antifungal activity in solid agar cultures against a broad variety of yeast and systemic mycoses and dermatophytes. While antifungal activity was evident throughout the series, in general, derivatives having halogen atom(s) in either or both aryl rings demonstrated the highest potency, especially against Trichophyton rubrum and Candida albicans. The dichloro analog 20 (PR 967‐248) was found to possess the most useful activity. Its minimum inhibitory concentration (MIC) values ranged between 0.2 and 2.0 μg/ml, as compared to 0.2–20.0 μg/ml for the standard drug ketoconazole (4).
Captodative olefins in normal and inverseDiels‐AlderReactions
Authors: Mertes Jürgen , Mattay Jochen
Published: December 2004

Olefins with captodative substitution are reactive dienophiles inDiels‐Alderreactions with normal and inverse electron demand. This is shown for reactions of 2‐(tert‐butylthio)acrylonitrile (1) with various dienes and heterodienes,e.g.1,3‐cyclohexadiene, hexachloro‐1, 3‐cyclopentadiene, acrolein, methacrolein, and methyl vinyl ketone (Schemes 2and3). In case of the hetrodienes, 3,4‐dihydro‐2H‐pyrans are formed beside small amounts of tetrahydrothiophenes; however, with methyl vinyl ketone, both reaction pathways are equally followed. The high reactivity of captodative olefins inDiels‐Alderreactions are rationalized on the basis ofSustmann's FMO model under consideration of Viehe's concept of captodative substitution of alkenes.
Anion‐receptor molecules: Macrocyclic and macrobicyclic effects on anion binding by polyammonium receptor molecules
Authors: Hosseini Mir Wais , Lehn Jean‐Marie
Published: December 2004

The stability constants for anion binding by the acyclic hexaamine 1, its macrocyclic analogue 2, and the bicyclic compound 3 in their protonated forms are reported. Compound 3 forms stable and selective complexes with halide ions, the stability sequence being I− > Br− > Cl−. Compound 2 forms more stable complexes with sulfate, oxalate, and malonate dianions than its acyclic analogue 1 and shows a better selectivity pattern. Compound 3 forms stronger complexes with oxalate2− than 2 and shows a remarkably high binding selectivity between oxalate2− and malonate2−. The comparison of the ability of 1–3 to complex anions demonstrates the macrocyclic and macrobicyclic effects on anion binding stability and selectivity.
Synthèses et caractérisation d'une nouvelle classe de sels de flavylium; voie d'accès aux composés du type (acétoxy‐2‐phényl)2‐méthylidène‐4‐4H‐benzopyranne‐1. Structure radiocristallographique de l'(acétoxy‐2‐méthyl‐5‐phényl)‐2‐diméthyl‐4, 6‐benzopyranne‐1‐ylium pentachlorostannate: mise en évidence de ponts chlore dans l'uniteé decachlorodistannate(2–)
Authors: Jolibois Henri , Vebrel Joél , Guyetant René , Theobald François
Published: December 2004

Synthesis and Characterization of a New Class of Flavylium Salts; a Facile Route to the 2‐(2‐Acetoxyphenyl)‐4‐methylidene‐4H‐1‐benzopyran Derivatives. X‐Ray Crystal Structure of 2‐(2‐Acetoxy‐5‐methylphenyl)‐4,6‐dimethyl‐1‐benzopyranylium Pentachlorostannate: Supporting evidence of Chlorine Bridging in the Decachlorodistannate(2–) Unit

Several mixtures of compounds 1 and 2 were synthesized from SnCl4 and p‐substituted aryl acetates. Separation of 1/2 was achieved either by treatment of the mixture with MeCN providing the pure complex 1 or by reaction with MeCOCl leading selectively to a new class of flavylium salts 3 or 4. The structure of 2‐(2‐acetoxy‐5‐methylphenyl)‐4,6‐dimethyl‐l‐benzopyranylium pentachlorostannate (3a) was determined by single‐crystal X‐ray diffraction. The Sn‐atoms are hexacoordinated in the dimeric unit Sn2Cl through Cl bridging. Furthermore, we report the easy preparation of 1‐benzopyran derivatives starting from the salts 3.
A Total Synthesis of (±)‐ Aphidicolin: Regio‐ and stereoselective conversion of 3α,18‐Di‐O‐benzyl‐17‐nor‐14‐aphidicolen‐16‐one into (±)‐aphidicolin
Authors: Lupi Alessandro , Patamia Maria , Bettole Rinaldo Marini
Published: December 2004

A regio‐ and steroselective conversion of the totally synthetic 3α, 18‐di‐O‐benzyl‐17‐nor‐14‐aphidicolen‐16‐one (5), into (±)‐aphidicolin 1, by hydroxylation of the 2‐methylidenebicyclo[3.2.1] oct‐3‐ene derivative 6 is described. Compound 5 was a key intermediate in our previously described total synthesis of 2, which represented a formal synthesis of 1.
The Radical Cation of Cyclobutene and its Photoproduct. Preliminary communication
Authors: Gerson Fabian , Qin Xue‐Zhi , Bally Thomas , Aebischer Jean‐Nicolas
Published: December 2004

The hitherto unknown radical cation of cyclobutene (2) has been generated in a CFCl3 matrix by γ rays at 77 K. The coupling constants, as determined from the ESR spectrum of 2+, are 2.80 and 1.11 mT for the four CH2 and the two CH = protons, respectively. Photo‐induced ring opening of 2+ yields a radical cation which exhibits the same ESR and ENDOR spectra as those observed upon direct ionization of s‐trans‐buta‐1, 3‐diene (s‐trans‐1). The radical cation s‐trans‐1+, should, therefore, be the final product of this conversion.
Asymmetric Catalysis by Vitamin B12. The isomerization of achiral epoxides to optically active allylic alcohols
Authors: Su Heng , Walder Lorenz , Zhang Zhong‐da , Scheffold Rolf
Published: December 2004

Achiral epoxides are isomerized to optically active allylic alcohols under the influence of catalytical amounts of cob(I) alamin in protic polar solvents.
Dreifach‐Diamantstruktur von. 2,6‐Dioxoadamantan‐1,3,5,7‐tetracarbonsäure (Hydrat) als Wirtsgitter für Essigsäure
Authors: Ermer Otto , Lindenberg Lorenz
Published: December 2004

Triple‐Diamond Structure of 2,6‐Dioxoadamantane‐1,3,5,7‐tetracarboxylic Acid (Hydrate) as Host Lattice for Acetic Acid

A novel solid‐state channel‐inclusion compound characterized by X‐ray methods is based on three interpenetrating, translationally equivalent super‐diamond network as host structure and AcOH as guest. The diamondoid host network are fromed by the 2,6‐dioxoadamantane‐1,3,5,7‐tetracarboxylic acid tied together via pairwise H‐bonds. The channels embedding the AcOH molecules may be viewed as symmetric triple helices winding about the guest species. Prospects regarding design and potentialities of diamondoid inclusion compounds are exemplified and appear promising.
Ruthenium(II) Complexes with Three Different Diimine Ligands
Authors: von Zelewsky Alex , Gremaud Gabriel
Published: December 2004

The synthesis of tri‐heteroleptic complex of Ru(II) with diimine ligands is describe. Ten compounds [Ru(R2bpy) (biq) (L)][PF6]2(R = H, CH3); L = 2,2′‐bipyridine (bpy), 4,4′‐dimethyl‐2,2′‐bipyridine (Me2bpy), 2,2′‐bipyrimidine (bpm), 2,2′‐biisoquinoline (biiq), 1,10‐phenanthroline (phen), dipyrido[3,2‐c:2′,3′‐e]pyridazine (taphen), 2,2′‐biquinoline (biq), 6,7‐dihydrodipyrido[2,3‐b:3,2‐j][1,10]‐phenanthroline (dinapy), 2‐(2[pyridyl)quinoline (pq), 1‐(2‐pyrimidyl)pyrazole] (pzpm), 2,2′‐biimidazole (H2biim) are characterized by elemental analysis, electronic and1H‐NMR spectroscopy. The relative photosustitution rates of biq in MeCN are given at three temperatures.
Synthesis of Optically Pure Tricarbonyliron Complexes of 5,6‐Dimethylidenebicyclo[2.2.2.]oct‐2‐yl derivatives. Crystal structure and absolute configuration of (+)‐tricarbonyl(1S,2S,4R,5R,6S)‐C,5,6,C,‐η‐(5,6‐dimethylidenebicyclo[2.2.2]oct‐2‐yl p‐bromobenzoate)iron
Authors: Carrupt Pierre‐Alain , Berchier Fabienne , Vogel Pierre , Pinkerton Alan A. , Schwarzenbach Dieter
Published: December 2004

The title complexes have been derived from tricarbonyl [(1R,4S,5S,6R,)‐C,5,6,C‐η‐(5,6‐dimethylidenebicyclo[2.2.2]oct‐2‐ene)]iron (1.). The crystal structure and absoulte configuration of (+)‐tricarbonyl (1S,2S,4R,5R,6S)‐C,5,6,C,‐η‐(5,6‐dimethylidenebicyclo[2.2.2]oct‐2‐yl p,‐bromobenzoate)]iron ((+)−6) determined by X‐ray diffrac‐tion studies proved earlier attribution of the relative configuration (endo us. exo,) of the tricarbonyliron moieties in complexes 1 and 2 of 5,6‐dimethylidenebicyclo[oct‐2‐ene. The structure of (+)‐6 confirms the absolute configuration derived earlier from circular‐dichroism spectra of 5,6‐dimethylidenebicyclo[2.2.2]oct‐2‐yl esters and 5,6‐dimethylidenebicyclo[2.2.2]octan‐2‐one.
Synthesis and Steroidogenic Activity of Covalently Dimerized Corticotropin (ACTH) Fragments
Authors: Stolz Monica B. , Fauchère Jean‐Luc
Published: December 2004

The chemical synthesis by classical methods in solution of a dimer of the sequence 1 to 24 of adrenocorticotropin(ACTH) is described. The two monomers were covalently linked through their C‐termini, using lysine amide as spacer. Dimerization did not improve significantly the potency of the agonist ACTH‐(1–24), while it strongly potentiated the antagonistic effect of the fragments ACTH‐(11–24) and ACTH‐(7–24) in the stimulation of steroidogenesis in isolated adrenal cells. The results seem to imply a microaggregation of the receptors at the adrenal cell surface.
Stoffwechselprodukte von Mikroorganismen. 250. Mitteilung. Maduraferrin, ein neuartiger Siderophor aus Actinomadura madurae
Authors: Keller‐Schierlein Walter , Hagmann Leonhard , Zähner Hans , Huhn Wolfgang
Published: December 2004

Maduraferrin, a Novel Siderophore from Actinomadura madurae

From a strain of Actinomadura madurae, a new siderophore was isolated. Maduraferrin is the Fe complex of an oligopeptide composed of salicylic acid, β‐alanine, glycine, L‐serine, Nδ‐hydroxy‐Nα‐methyl‐L‐ornithine, and L‐hexahydropyridazine‐3‐carboxylic acid. The complexing centers are a salicylamide moiety, a hydroxamic‐acid group and an acid hydrazide group.
Synthesis and Characterization of Crown‐Ether‐Containing Phthalocyanines with Group‐IV‐A Elements
Authors: Ahsen Vefa , Yilmazer Emel , Gürek Ayşegül , Gül Ahmet , Bekâroǧlu Özer
Published: December 2004

Group‐IV‐A phthalocyanines with four crown ether substituents have been prepared from 4′,5′‐dicyanobenzo(15‐crown‐5), 4′,5′‐diiminoisoindolino(15‐crown‐5), or metal‐free phthalocyanine and the corresponding metal salts. The axial ligands of dichloro[tetra(15‐crown‐5)phthalocyaninato]silicon or ‐tin have been converted into dihydroxy derivatives by hydrolysis in aqueous Et3N. The catalytic effect of H2O‐free CaC12 in quinoline is used for the polycondensation of dihydroxysilicon‐phthalocyanine to cofacially arrayed polymers. The thermal stability of group‐IV‐A‐metal phthalocyanines is confirmed by the higher initial decomposition points (290–440°) compared to those of the corresponding transition‐metal phthalocyanines.
Diazotisations in Highly Concentrated Mineral Acids: The nitrosation mechanism of anilinium and hydroxylammonium ions through proton loss from the ammonio group
Authors: Zollinger Heinrich
Published: December 2004

It is shown that the acidity dependence of the rate of nitrosation of aromatic amines and of hydroxylamine in strongly acidic aqueous solutions does not necessarily involve the rearrangement of a charge transfer complex (consisting of the NO+ ion and the substrate with an NH group) in concert with a proton loss at the NH group. More likely, proton loss of the charge complex preceeds the π → N rearrangement of the NO+ ion.
Design and Synthesis of a Potential Dopamine D‐1 Antagonist
Authors: Revesz Laszlo , Meigel Harald
Published: December 2004

The diastereoselective synthesis of (±)‐trans‐transoid‐7‐bromo‐8‐hydroxy‐1‐methyl‐1,2,3,4,4a,5,10,10a‐octahydro‐10‐phenylbenzo[g]quinoline (8) is described, using an intramolecular Diels‐Alder reaction and a reductive cyclisation for piperidine ring‐formation as key steps. Compound 8 was prepared as a putative D‐1 receptor antagonist which contains (2,2‐diphenylethyl)amine as a partial structure.
Synthesis of New 1,2,4‐Trioxanes and their Antimalarial Activity
Authors: Jefford Charles W. , McGoran Ernest C. , Boukouvalas John , Richardson Geoffrey , Robinson Brian L. , Peters Wallace
Published: December 2004

The three dihydronaphtho[1,2,4]trioxines 9–11 have been synthesized and two of them converted to the five carbamate and ester derivatives 12–16 (Schemes 1 and 2). The resulting new trioxanes together with two already known and ascaridole (7) were tested for antimalarial activity against the sensitive N strain of Plasmodium berghei in mice. On comparison with artemisinin (1) and dihydroartemisinin (2), modest activity was found. The four most active compounds were some 12–18 times less potent than 1.
The Allyl Ester as Carboxy‐Protecting Group in the Stereoselective Construction of Neuraminic‐Acid Glycosides
Authors: Kunz Horst , Waldmann Herbert , Klinkhammer Uwe
Published: December 2004

The application of the allyl‐ester moiety as protecting principle for the carboxy group of N‐acetylneuraminic acid is described. Peracetylated allyl neuraminate 2 is synthesized by reacting the caesium salt of the acid 1 with allyl bromide. Treatment of 2 with HCl in AcCl or with HF/pyridine gives the corresponding 2‐chloro or 2‐fluoro derivatives 3 and 4, respectively (Scheme 1). In the presence of Ag2CO3, the 2‐chloro carbohydrate 3 reacts with di‐O‐isopropylidene‐protected galactose 5 to give the 2–6 linked disaccharide with the α‐D‐anomer 6a predominating (α‐D/β‐D = 6:1; Scheme 2). Upon activation of the 2‐fluoro derivative 4 with BF3 · Et2O, the β‐D‐anomer 6b is formed preferentially (α‐D/β‐D = 1:5). In further glycosylations of 4 with long‐chain alcohols, the β‐D‐anomers are formed exclusively (see 10 and 11; Scheme 4). The allyl‐ester moiety can be removed selectively and quantitatively from the neuraminyl derivatives and the neuraminyl disaccharides by Pd(0)‐catalyzed allyl transfer to morpholine as the accepting nucleophile (see Scheme 5).
Chaetoglobosin M, a New Metabolite of a Mutant of Diplodia macrospora, belonging to the family of (1H‐indol‐3‐yl)‐substituted 10,11‐diethyl‐10,11‐dinorcytochalasans
Authors: Spöndlin Christoph , Tamm Christoph
Published: December 2004

From a mutant of Diplodia macrospora, chaetoglobosin M (5), ergosterol, β‐sitosterol, and a third sterol, most likely stigma‐5,7,22‐trien‐3β‐ol, were isolated. Metabolite 5 is a new member of the (1H‐indol‐3‐yl)‐substituted 10,11‐diethyl‐10,11‐dinorcytochalasans. Its structure was determined by 1H‐ and 13C‐NMR and mass spectrometry.
Synthesis of New unnatural Macrocyclic Trichothecenes: 4‐epiverrucarin A. 47th Communication on verrucarins and roridins
Authors: Jeker Nicolas , Tamm Christoph
Published: December 2004

The 4‐epiverrucarin A (24), a new unnatural macrocyclic trichothecene, was synthesized starting from 4‐epiverrucarol (20). The latter was obtained by metal‐hydride reduction of the 4‐oxo derivative 19. Subsequent conversion of 20 into the monoester 30 and then the diester 32 followed by macrolactonization of the latter yielded 4‐epiverrucarin A (24). Attempts to invert the configuration of the naturally occuring 3α‐OH group of a trichothecene were unsuccessful. The cytostatic (P‐815) and immunosuppressive (MLR) activity of several natural and unnatural trichothecenes was determined in vitro.
Synthese, 13C‐NMR‐Spektren und räumliche Struktur von ‘Push‐Pull’‐Diacetylenen
Authors: Galli Roberto , Neuenschwander Markus , Engel Peter
Published: December 2004

Synthesis, 13C‐NMR Spectra, and X‐Ray Investigation of ‘Push‐Pull’ Diacetylenes

Phenyl‐substituted ‘push‐pull’ diacetylenes 1f and 1g have been prepared by acetylation and benzoylation of the appropriate lithiodiynylamines 4 (Scheme 2). 13C‐NMR spectra of diacetylenes 1a–g (Table 1) are discussed with respect to the expected polarisation of the diacetylene unit by ‘push’ and ‘pull’ substituents. X‐Ray investigations of 1c, 1e, and 1f have been performed in view of the planned solid‐state polymerisation of ‘push‐pull’ diacetylenes. In the crystalline state, diacetylenes 1c and 1f are stacked, however, the stacking parameters do not allow a solid‐state polymerisation.
The Azo(Azoxy) Functionality as a π2 Component in Photo [2+2] cycloadditions ‘syn’‐ and ‘anti’‐3,4‐diazatricyclo[4.2.2.22,5]dodeca‐3,7‐diene, syntheses, photolyses, X‐ray‐structure analysis, and PE spectra
Authors: Marterer Wolfgang , Prinzbach Horst , Rihs Grety , Wirz Jakob , Lecoultre Jaques , Heilbronner Edgar
Published: December 2004

The propensity of the NN bond to undergo photo [2 + 2] cycloadditions has been further explored. In the specifically designed 1,5‐azo/enes 1–3, no [2 + 2] cycloaddition has been observed upon either direct or sensitized excitation with light of various wave lengths at temperatures down to 77 K, in line with expectations based on X‐ray (1: d = 2.71 Å, ω = 129°) and PE measurements (1: I1 = 8.00, I2 = 9.05 eV; 2; I1 = 8.00, I2 = 9.25eV). The steric/stereoelectronic demands for the participation of the NN bond in pericyclic reactions are clearly more stringent than those for the CC bond.
Stoffwechselprodukte von Mikroorganismen. 251. Mitteilung. Die Esmeraldine A und B, tief grüne Farbstoffe aus Streptomyces antibioticus, Stamm Tü 2706
Authors: Keller‐Schierlein Walter , Geiger Adrian , Zähner Hans , Brandl Matthias
Published: December 2004

The Esmeraldines A and B, Green Pigments from Streptomyces antibioticus, Strain Tü 2706

From a strain of Sterptomyces antibioticus, Tü 2706, two dark green substances, the esmeraldines A and B, 4 and 3, respectively, were isolated. The structural elucidation was carried out by spectroscopic comparison with some simpler phenazines obtained from the same organism, saphenamycin (1) and related compounds, and by a series of chemical transformations. Esmeraldin B (3) is the 6‐methylsalicylic acid ester, and esmeraldin A (4) a mixture of higher saturated and unsaturated fatty acid esters of esmeraldic acid. The latter is a heterocyclic compound with seven rings and four N‐atoms, formally derived by condensation of two phenazine residues of the saphenic acid family. The esmeraldins are mixtures are of diastereoisomers.
Hetero‐Diels‐Alder‐Reaktion mit 1,3‐Thiazol‐5(4H)‐thionen
Authors: Tromm Peter , Heimgartner Heinz
Published: December 2004

Hetro‐Diels‐Alder Reaction with 1,3‐Thiazol‐5(4H)‐thiones

On heating in toluene to 180° and on treatment with BF3·Et2O in CH2Cl2 room temperature, 1,3‐dienes react with the CS group of 1,3‐thiazol‐5(4H)‐thiones 1 in a reversible Diels‐Alder reaction to give spiro[4.5]‐heterocycles of type 6. A 1:1 mixture of two regioisomeric cycloadducts is formed in the thermal reaction with 2‐methylbuta‐1,3‐diene (isoprene, 5b). In contrast, the formation of one regioisomer is strongly preferred in the BF3‐catalyzed reaction. Frontier‐orbital control as well as steric factors seem to be responsible for the observed regioselectivity. BF3‐Catalyzed, cyclic 1,3‐dienes and 1 also undergo a smooth Diels‐Alder reaction. Whereas cyclohexa‐1,3‐diene (5c) reacts with 1a and 1b to give a single isomer (presumably the ‘exo’‐adduct), cyclopenta‐1,3‐diene (5d) leads to a ca. 3:1 mixture of ‘exo’‐and ‘endo’‐isomer.
Palladium(0)‐Catalyzed Cyclizations of Simple 1‐Aryl‐1,7‐octadien‐3‐yl Acetates. Preliminary communication
Authors: Oppolzer Wolfgang , Swenson Rolf E. , Pachinger Werner
Published: December 2004

Dienyl acetates 2 lacking a geminal disulfone or a malonate group cyclize selectively to (E)‐l‐methylidene‐2‐styrylcyclopentanes 4 in the presence of 7 mol‐% of [Pd(PPh3)4].
Konkurrenz von Endoperoxid‐ und Hydroperoxid‐Bildung bei der Umsetzung von Singulett‐Sauerstoff mit cyclischen, konjugierten Dienen. Teil I
Authors: Matusch Rudolf , Schmidt Gerhard
Published: December 2004

Competition of Endoperoxide and Hydroperoxide Formation in the Reaction of Singlet Oxygen with Cyclic, Conjugated Dienes

Rose‐bengal‐sensitized photooxygenation of (−)‐(R)‐α‐phellandrene (1) in MeOH at room temperature yielded a complex mixture of products, contrary to previous reports describing cis‐(3S, 6R)‐epidioxy‐p‐menthene (2) and trans‐(3R, 6S)‐epidioxy‐p‐menthene (3) as the only products. The mixture was separated by prep. HPLC (silica gel, pentane/Et2O 9:1). Besides the known endoperoxides 2 (yield 39%) and 3 (26%), all those hydroper‐oxides, which can be deduced from an ene reaction of 1O2 with 1, were isolated, i.e. 4β‐p‐mentha‐2,5‐dien‐1β‐yl hydroperoxide (4) (14%), 4β‐p‐mentha‐2,5‐dien‐1α‐yl hydroperoxide (5) (9%), (2R, 4R)‐p‐mentha‐1(7), 5‐dien‐2‐yl hydroperoxide (6) (2,1%), (2S, 4R)‐p‐mentha‐1(7),5‐dien‐2‐yl hydroperoxide (7) (1,5%) and (1R)‐p‐mentha‐3,6‐dien‐yl hydroperoxide (8; 1,5%; Scheme 1). Furthermore, the constant cis/trans ratio for all diastereoisomeric pairs (2/2, 4/2, 6/2) was striking. With the help of the two possible conformers 1a and 1b of the starting material a model of a common first step for endoperoxide as well as for hydroperoxide formation is developed. A photooxygenation at −50° supports this model. The absolute value of the cis/trans ratio changes in the same way for the endoperoxides and the hydroperoxides.
Electronic and Molecular Structure of the C8H Valence Isomers 1,3,5‐Cyclooctatriene+· and Bicyclo[4.2.0]octa‐2,4‐diene+· from their Electronic absorption Spectra in Freon
Authors: Bally Thomas , Roth Kuno , Straub Rolf
Published: December 2004

The molecular cations of 1,3,5‐cyclooctatriene (COT+·) and bicyclo[4.2.0]octa‐2,4‐diene (BCO+·) can be observed intact in γ‐irradiated Freon glasses, as opposed to Ar matrices where ionization is accompanied by extensive rearrangements. This proves the superiority of the Freon‐glass method for the generation of metastable primary cations. The electronic absorption (EA) spectra reveal a) that a previous analysis of the BCO+· electronic structure on the basis of the ultraviolet photoelectron (UP( spectrum of BCO was incomplete, and b) that COT undergoes planarization upon ionization, in accord with qualitative expectations and MNDO calculations. A previously proposed LCBO model was used to assess the influence of the above geometry change on the electronic structure of COT+·.
Stereoselektive Synthesen von Taxan‐Derivaten
Authors: Neh Harribert , Kühling Andrea , Blechert Siegfried
Published: December 2004

Stereoselective Synthesis of Taxane Derivatives

Substituted racemic 4,8,12‐trinortaxanes were prepared stereoselectively in several steps from the dienone 10. A variant of the de Mayo reaction with bicyclononenones 4 and cyclohexen produced the desired configuration at C(8) of the taxane framework. Retro‐aldol cleavage of the tetracycle 5 led to the taxane skeleton 6. Stereoselective reduction followed by treatment with base afforded 7b. Hydrolysis of the acetal group and further reduction yielded 9 in which the relative configuration corresponds to the one of the natural products.
Template‐Dependent Incorporation of Spin‐Labeled Thymidine Analogs into Viral DNA
Authors: Pauly Gary T. , Bobst Elisabeth V. , Bruckman David , Bobst Albert M.
Published: December 2004

The synthesis of novel pppUd analogs substituted at position C(5) with tethered nitroxide radicals is reported. It is shown that these analogs can serve as good substrates for E. coli DNA polymerase (Pol I) and T‐4 DNA polymerase using lambda‐phage DNA as template. The template‐dependent incorporation of the substrates was established by radio‐labeling and ESR experiments.
Synthesis of the Oviposition‐Deterring Pheromone (ODP) in Rhagoletis cerasi L. Preliminary communication
Authors: Ernst Beat , Wagner Beatrice
Published: December 2004

For the assignment of the configuration at C(8) and C(15) of the natural oviposition‐deterring pheromone 1 in Rhagoletis cerasi L., the four possible stereoisomers of 1 are synthesized. By condensing the C6 building blocks (5R)‐4 and (5S)‐4 with the boron enolates of the C10 building blocks (4S)‐13 and (4R)‐13, followed by decarboxylative dehydration, all stereoisomers of 16 are available (Scheme 5). Glucosylation of 16 followed by formation of the taurin amide gives, after deprotection, the four stereoisomers (8R,15S)‐1, (8R,15R)‐1, (8R,15S)‐1, and (8S,15S)‐1 (Scheme 6).
The Chemistry of Thujone. Part XIV.. Synthesis of biologically active aryl terpenoid analogues
Authors: Carvalho Chris , Cullen William R. , Fryzuk Michael D. , Jacobs Helen , James Brian R. , Kutney James P. , Piotrowska Krystyna , Singh Vinod K.
Published: December 2004

Employing thujone‐derived intermediates, a series of achiral (9a–d; Scheme 1) and chiral (11b and 11d; Scheme 2) terpene analogues related to the biologically active ‘terpenoid’ hybrids have been prepared. The stereochemistry of the key epoxidation reaction was established by correlation of the product 11b with the previously reported alcohol (R)‐20 of known absolute configuration (Scheme 3).
Vinyl Carbanions. Part 36.. Synthesis of 3‐deoxy‐D‐manno‐2‐octulosonic acid (KDO) and derivatives
Authors: Esswein Angelika , Betz Rainer , Schmidt Richard R.
Published: December 2004

The β‐C‐lithiated acrylamide 3A has been proven to be an ideal pyruvate β‐carbanion equivalent useful in a highly diastereoselective KDO synthesis. The starting material 3 was prepared from pyruvate diethyl acetal in four convenient steps. Direct lithiation with 2 equiv. of LDA generated the dilithiated species 3A quantitatively. Reaction with 2,3:4,5‐di‐O‐isopropylidene‐D‐arabinose (11) was highly D‐manno‐selective. The product 12 was obtained readily from the reaction mixture via crystallization. Ring closure to the butenolide 13, subsequent PhS‐group removal with Bu3SnH and pyridinium bromide, and hydrogenolytic debenzylation afforded the known butenolide 19; this KDO precursor gives KDO in two convenient steps. Butenolide 19 was also transformed via two high‐yielding steps into the 4,5:7,8‐di‐O‐cyclohexylidene‐KDO derivative 22, a valuable starting material for KDO α‐glycoside syntheses.
Highly Stereoselective Total Syntheses of 2,5‐Anhydro‐4‐deoxy‐D‐ribo‐hexonic Acid and of (1S)‐1‐C‐(6‐amino‐7H‐purin‐8‐yl)‐1,4‐anhydro‐3‐deoxy‐D‐erythro‐pentitol (= cordycepin C)
Authors: Gasparini Fabrizio , Vogel Pierre
Published: December 2004

Highly regio‐ and stereoselective monohydroxylation of the CC bond of (+)‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐one (8) was achieved via LiAlH4 reduction of the corresponding 5,6‐exo‐epoxy dimethyl acetal 9. The reaction gave exclusively (–)‐(1R, 2R, 4S)‐6,6‐dimethoxy‐7‐oxabicyclo[2.2.1]heptan‐2‐exo‐ol (10) which was transformed into 2,5‐anhydro‐3‐O‐benzyl‐4‐deoxy‐D‐ribo‐hexonic acid (15) and 2,5‐anhydro‐4‐deoxy‐D‐ribo‐hexonic acid (6) via ozonolysis of (–)‐(1R, 4S, 6R)‐6‐exo‐benzyloxy‐2‐{[(tert‐butyl)dimethylsilyl]oxy}‐7‐oxabicyclo[2.2.1]hept‐2‐ene (14). Cordycepin C (5) was derived from 6 and 4,5,6‐triaminopyrimidine using CsF/DMF to generate the adenine heterocycle.
Die absolute Konfiguration der Iridale und Cycloiridale unterschiedlicher Herkunft
Authors: Marner Franz‐Josef , Jaenicke Lothar
Published: December 2004

The Absolute Configuration of Iridals and Cycloiridals of Different Origin

Natural irones are known to occur in enantiomeric forms within Iris oils of different origin. They are formed by oxidative degradation of the cycloiridals (C31‐triterpenoids) found in rhizomes of various Iris species. The absolute configuration of iridals from different varieties is determined by ozonolysis of the triterpenoids and comparison of their degradation products with authentic samples of known configuration. It is shown that the initial cyclization of squalene resulting in the formation of a monocyclic seco‐ring‐A iridal has the same stereo‐chemical course throughout all Iris species studied. The subsequent cyclization of the homofarnesyl side chain of the iridals, however, produces cycloiridals with enantiomeric irone moieties within different subspecies of the sword lilies.
Neue Dimethinmerocyanin‐Farbstoffe mit der (Sulfobutyl)benzothiazol‐Gruppe als Donor‐Teilchromophor und deren Aggregationsverhalten in wässriger Lösung
Authors: Kussler Manfred , Balli Heinz
Published: December 2004

Novel Dimethinemerocyanine Dyes with the (Sulfobutyl)benzothiazole Group as Donor Part of the Chromophor and their Aggregation Tendency in Aqueous Solution

A series of novel dimethinemerocyanine dyes with the (sulfobutyl)benzothiazole group as the donor part of the chromophor is synthesized in good yield and their aggregation tendency in H2O without addition of salt investigated. The merocyanine dye 2b only gives J‐aggregation in H2O. The dyes 1a–f and 2a exhibit an intense, red‐shifted absorption band due to J‐aggregation in H2O in the presence of Me4NCl. In contrast, the dyes 1g and 2c–f show a slightly red‐shifted absorption band. The degree of aggregation in H2O is investigated by ultracentrifugation of the representative 2e. Indeed, the slightly red‐shifted absorption band in H2O is due to aggregation of ‘oligomers’ of the dye. Contrary to the aggregation of ‘polymers’ of dyes (J‐aggregation), we suggest the term ‘K’ band for the slightly red‐shifted absorption band. The hemicyanine dye 5 gives the same absorption band in MeOH and in MeOH/H2O 1:3. The dye 11 shows an absorption band in H2O that is probably blue‐shifted because of negative solvatochromism. The merocyanine dye 13 gives H‐aggregation in H2O.
Models for Copper‐Dioxygen Complexes: The chemistry of copper(II) with some planar tridentate nitrogen ligands
Authors: Piguet Claude , Bocquet Bernard , Müller Edgar , Williams Alan F.
Published: December 2004

The solution chemistry of Cu(II) with a series of five planar tridentate nitrogen ligands, 2,6‐bis(benzimidazol‐2‐yl)pyridine (bzimpy, 1), 2,6‐bis(l‐methylbenzimidazol‐2‐yl)pyridine (mbzimpy, 2) 2,6‐bis(benzothiazol‐2‐yl) pyridine (bzthpy, 3), 2,6‐bis(benzoxazol‐2‐yl)pyridine (bzoxpy, 4), and 2,2′, 6′, 2″‐terpyridyl (terpy, 5) is reported. Electronic and EPR spectra are consistent with the complexes [CuL]2+ having essentially tetragonal structure in solution, with the fourth coordination site in the plane of the ligand occupied by solvent. bzthpy and bzoxpy show smaller ligand‐field splittings than bzimpy, mbzimpy, and terpy, and are easily decomplexed from the copper. Substitution of the coordinated solvent molecule in the plane of the ligand is observed with Cl− and OH− (provided that the ligand has no acidic protons) for all ligands except terpy. The reaction between [Cu(mbzimpy)]2+ and imidazole has been studied by potentiometric titration in MeCN/H2O 1:1 and shows strong binding of the imidazole in the plane (log K = 4.5 at 25°), and also the formation of an imidazolate‐bridged dinuclear species.
Stoffwechselprodukte von Mikroorganismen. 253. Mitteilung. Hormaomycin, ein neues Peptid‐lacton mit morphogener Aktivität auf Streptomyceten
Authors: Andres Nikolaus , Wolf Heinz , Zähner Hans , Rössner Ellen , Zeeck Axel , König Wilfried A. , Sinnwell Volker
Published: December 2004

Hormaomycin, a Novel Peptide Lactone with Morphogenetic Activity on Streptomyces

A culture identified as Streptomyces griseoflavus (strain W‐384) has been found to produce a novel peptide‐lactone antibiotic designated hormaomycin (6). The empirical molecular formula of the compound is established to be C55H69ClN10O14. The constituent amino acids of the antibiotic are suggested to be allothreonine (1; 1), isoleucine (2; 1), 3‐methyl‐phenylalanine (3; 2), and, for the first time identified from a natural source, 4‐[(Z)‐prop‐1‐enyl]‐proline (4; 1) and 3‐(2‐nitrocyclopropyl)‐alanine (5; 2). The amino acids were delivered by acidic hydrolysis and assigned by high‐resolution‐ GC/MS analysis (after transformation to derivatives) in combination with extended 2D‐NMR experiments of the antibiotic itself. From the latter, it became plausible that the N‐terminus of the peptide chain is acylated by a Cl‐containing derivative of 1H‐pyrrol‐2‐carboxylic acid. Hormaomycin is active against some Gram‐positive bacteria. In addition, the antibiotic exhibits potent aerial mycelium‐inducing activity and effects the production of antibiotics.
Novel Trinor‐eremophilanes (Dendryphiellin B, C, and D), Eremophilanes (Dendryphiellin E, F, and G), and Branched C9‐Carboxylic Acids (Dendryphiellic Acid A and B) from the Marine Deuteromycete Dendryphiella salina (SUTHERLAND) PUGHet NICOT
Authors: Guerriero Antonio , D'Ambrosio Michele , Cuomo Vincenzo , Vanzanella Fortunato , Pietra Francesco
Published: December 2004

Further investigation of global extracts from cultures of the marine deuteromycete Dendryphiella salina leads to the isolation of three novel trinor‐eremophilanes esterified by branched C9‐carboxylic acids, dendryphiellin B(= (+)‐(1R*,2S*,7R*,8aR*)‐1,2,6,7,8,8a‐hexahydro‐7‐hydroxy‐1,8a‐dimethyl‐6‐oxonaphthalen‐2‐yl (6R*, 2E, 4E)‐6‐hydroxy‐6‐methylocta‐2,4‐dienoate; (+)‐2), dendryphiellin C (=(+)‐(1R*, 2S*, 7R*, 8aR*)‐1,2,6,7,8,8a‐hexa‐hydro‐7‐hydroxy‐1,8a‐dimethyl‐6‐oxonaphthalen‐2‐yl (6S, 2E, 4E)‐6‐methylocta‐2,4‐dienoate; (+)‐3)), and dendryphiellin D (=(+)‐(1R*, 2S*, 7R*, 8aR*)‐1,2,6,7(8,8a‐hexahydro‐7‐hydroxy‐1,8a‐dimethyl‐6‐oxonaphthalen‐2‐yl (6R*,2E,4E)‐6‐(hydroxymethyl)octa‐2,4‐dienoate; (+)‐4). An intact eremophilane, dendryphiellin E (5), and its ethanolysis product dendryphiellin F whose absolute configuration is represented by structural formula (+)‐6 are also isolated from the above extracts. Dendryphiellin E exists as an open form 5a in equilibrium with a closed form 5b. A similar equilibrium exists between the open form 8a and the closed form 8b of a non‐esterified eremophilane, dendryphiellin G (8), which is isolated too from the above extracts and proves structurally related to the cyclic portion of 5. Finally, the free, branched C9‐carboxylic acids dendryphiellic acid A ((+)‐9) and B ((+)‐10) which correspond to side chains of the above esterified terpenes are also isolated from the above extracts.
Acid‐Catalyzed Cyclization Reactions of Substituted Acetylenic Ketones: A new Approach for the Synthesis of 3‐Halofurans, Flavones, and Styrylchromones
Authors: Obrecht Daniel
Published: December 2004

Acetylenic acetals of type I (Scheme 1) and acetylenic ketones of type III (Scheme 1), 37 and 38 (Scheme 7) are versatile synthetic precursors for the synthesis of various heterocycles by acid‐catalyzed cyclization reactions. By this way, substituted 3‐halofurans of type II and IV (Scheme 1) and flavones and styrylchromones (Scheme 7) can be synthesized in good‐to‐excellent yields. The high degree of regioselectivity in the synthesis of the 3‐halofurans (Scheme 4) is the result of the regioselective β‐addition of HX (X = Cl, Br, I) to the acetylenic aldehyde and acetylenic ketone moieties. A possible mechanism is depicted in Scheme 5. Since 3‐halofurans can easily be metalated and substituted, this approach constitutes a new synthesis of highly substituted furans.
Neue Sulfobutyl‐haltige Bis(dimethinmerocyanin)‐Farbstoffe mit isolierten Chromophoren im Molekül und deren Aggregationsverhalten in wässeriger Lösung
Authors: Kussler Manfred , Balli Heinz
Published: December 2004

Novel Bis(dimethinemerocyanine) Dyes with Isolated Chromophores in the Molecule Containing the Sulfobutyl Group and their Aggregation Tendency in Aqueous Solution

The bis(dimethinemerocyanine) dyes 7a–c with Chromophores separated by a polymethylene chain as ‘isolator’ are synthesized in good yield. Their aggregation tendency in organic solvents, organic solvents/H2O mixtures, and in H2O is investigated. In organic solvents, the dyes 7a–b show a splitted absorption band, due to interaction of the two Chromophores of the dye. In H2O, 7a exhibits an intense absorption band at 496 nm (ϵ = 224 300 1·mol−1·cm−1) with a small width \documentclass{article}\pagestyle{empty}\begin{document}$ (\tilde v_{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}} = 1000\;{\rm cm}^{ - 1}) $\end{document} and shoulders at 552 and 580 nm. In presence of starch, this absorption band shifts to 617 nm, probably due to J‐aggregation. The dye 7b shows the same spectral behaviour as 7a. In contrast, 7c exhibits an absorption band without splitting in organic solvents; the interaction of the Chromophores has disappeared. In H2O and in H2O containing starch, 7c shows a wide absorption band, due to interaction of the Chromophores of the dye.
A Simple and Efficient Method for the Preparation of Binaltrorphimine and Derivatives and determination of their K opioid antagonist selectivity
Authors: Schmidhammer Helmut , Smith Colin F. C.
Published: December 2004

The bimorphinans 1 (binaltrorphimine), 3, and 7 have been prepared by treatment of the parent morphinan‐6‐ones naltrexone (5), naloxone (4), and dihydrocodeinone (6), respectively, with N‐methylhydrazine sulfate in AcOH at room temperature. Compound 3 showed opioid antagonist potency and selectivity for K receptors which were somewhat lower in comparison to 1.
New Spirostaphylotrichins from Staphylotrichum coccosporum
Authors: Sandmeier Peter , Tamm Christoph
Published: December 2004

The isolation and structure elucidation of the new spirostaphylotrichins B (2), C and D (3/4), F (5), Q (6), and R (7) are described. Compounds 2 and 3 are artefacts formed during the isolation of the metabolites from the cultures. The absolute configuration of spirostaphylotrichin A (1) has been determined by CD spectroscopy.
Stereoselektive Synthese von 3,5‐disubstituierten Octahydroindolizinen
Authors: Vavrecka Mojmir , Hesse Manfred
Published: December 2004

A Stereoselective Synthesis of 3,5‐Disubstituted Octahydroindolizines

On catalytic hydrogenation, methyl 6‐nitro‐9‐oxodecanoate (1) underwent cyclization to 2 which, after hydrolysis, gave the bicyclic product 4. By another series of reactions, 2 was transformed to methyl 3‐methyloctahydroindolizine‐5‐carboxylate (7), Conversions of 7a to its C(5)‐epimer 7b and vice versa were accomplished and the configurations of 7a and 7b determined. Finally, 7b was reduced in three steps to 11 (overall yield from 1, 24%), which is an analog of several natural products.
Modelling the Metabolic Epimerization of Anti‐inflammatory 2‐Arylpropanoyl‐coenzyme‐A Conjugates: Solvent effects on the 1H/2H exchange in S‐[2‐(dimethylamino)ethyl] 2‐phenylpropanethioate
Authors: Mayer Joachim M. , Young Malcolm , Testa Bernard , Etter Jean‐Claude
Published: December 2004

The 1H/2H exchange at the methine position of S‐[2‐(dimethylamino)ethyl] 2‐phenylpropanethioate (DEPP) in solvent/D2O mixtures was taken as a model reaction for the metabolic epimerization of 2‐arylpropanoyl‐coenzyme‐A thioesters and was monitored by 1H‐NMR spectroscopy at 37°. The solvents used were (D6)acetone, (D3)acetonitrile, (D6)dimethylsulfoxide, and (D5)pyridine. In the investigated range of D2O percentage (10–50%), the exchange reaction was found to increase linearily with D2O content and with the basicity of the organic solvent, the fastest rates being close to 0.09 h−1 (t½ ca. 8 h). These rates are slower than those observed in vivo for the configurational inversion of profens, and they are elicited in totally unphysiological concentrations of bases. The hypothesis thus formulated is that the metabolic epimerization of 2‐arylpropanoyl‐coenzyme‐A thioesters cannot occur nonenzymatically.
Synthesis of an N‐Acetylated Heparin Pentasaccharide and its anticoagulant activity in comparison with the heparin pentasaccharide with high anti‐factor‐Xa activity
Authors: Peter Wessel Hans , Labler Ludvik , Tschopp Thomas B.
Published: December 2004

The synthesis of tri‐N‐acetylated heparin pentasaccharide 2 is described. It was assembled from five suitably blocked monosaccharide units (3–7). Glucuronic‐acid building block 4 was prepared from glucose by direct Jones oxidation of the 6‐O‐trityl derivative 18. The resulting acid 16 was esterified to 17 in large mounts using methyl chloroformate/base. Trimethylsilyl bromide proved to be an excellent reagent for the hydrolysis of a prop‐1‐enyl glycoside (19 →21). The pentasaccharide 29 was obtained by a [2 + 2] + 1 synthesis, the glycosylation reactions furnished good to very good yields. The identity of protected oligosaccharides was confirmed by 1H‐NMR spectroscopy. Sequential deblocking of the pentasaccharide, O‐sulfation, and N‐acetylation gave 2 which was shown to exhibit ca. 600 times lower anticoagulant activity than pentasaccharide 1.
Separation of enantiomeric algal pheromones and related hydrocarbons by gas‐liquid Chromatography on Modified Cyclodextrins as Chiral Stationary Phases. Biosynthetic relevance of racemic by‐products
Authors: Boland Wilhelm , König Wilfried A. , Krebber Ralph , Müller Dieter G.
Published: December 2004

The separation of the enantiomers of the olefinic hydrocarbons multifidene 3 and aucantene 5 from the pheromone blend of the two seaweeds Cutleria multifida and Chorda tomentosa is achieved by gas chromatography on modified cyclodextrins as chiral stationary phases. The method is also applicable for the separation of enantiomeric alkyl‐, alkenyl‐ or alkynyl‐substituted cyclooctadienes and cyclopentenes. A plausible rational is presented for the biosynthesis of racemic by‐products of algal pheromone blends.
Nucleotides part XXX Chemical synthesis of adenylyl‐(2′ → 5′)‐adenylyl‐(2′ → 5′)‐8‐azidoadenosine, and activation and photoaffinity labelling of RNase L by [32P]p5′A2′p5′A2′p5′N38A
Authors: Charubala Ramamurthy , Pfleiderer Wolfgang , Sobol Robert W. , Wu Li Shi , Suhadolnik Robert J.
Published: December 2004

The chemical synthesis of adenylyl‐(2′–5′)‐adenylyl‐(2′–5′)‐8‐azidoadenosine (15) was performed by the phosphotriester approach. Enzymatic phosphorylation of 15 by [γ‐32P]ATP led to the corresponding labelled 5′‐monophosphate 16. Photoinsertion of 16 took place on UV irradiation by covalent cross linking to a protein of Mr 80 K known to be RNase L. Radiobinding and core‐cellulose assays as well as photoaffinity labelling experiments with 16 are described.