bluuebunny/crossref_metadata_2025_split huggingface dataset:
Melanotropin Receptors II. Synthesis and Biological Activity of α‐Melanotropin/Tobacco Mosaic Virus Disulfide Conjugates
Authors: Wunderlin Rudolf , Sharma Shub Dev , Minakakis Panagiota , Schwyzer Robert 
Published: December 2004

AbstractAsymmetric disulfide conjugates of mercaptosuccinyl tobacco mosaic virus (TMV ∼ SH) with Nα‐desacetyl‐Nα‐5‐(mercaptovaleryl)‐α‐melanotropin were prepared via the S‐sulfoderivative of the peptide. The conjugates, TMV ∼ SS ∼ α‐MSH(n), contained up to n = 330 disulfide‐linked peptide molecules/virion. Similarly, fluorescent conjugates, Rh(m) ∼ TMV ∼ SS ∼ α‐MSH(n) were prepared, containing m ≈︁ 200 rhodamine molecules linked to the virions by thiourea bridges. Such conjugates were designed to study α‐MSH receptor localization and dynamics (mainly internalization), because the carrier virions which served to enhance specific receptor binding and as fluorescent or radioactive markers may be detached from the neuropeptides at will by reduction. Reduction occurred in solution and on the cell surface, but not in the cytoplasm, thus allowing detection of internalized agonist‐receptor complexes. The conjugates were superpotent agonists for tyrosinase stimulation in Cloudman S‐91 melanoma cell cultures, but were inactive for cyclic AMP accumulation. Their rather rapid internalization and the influence of reducing agents and other agonists on their biologic activity suggest a close connection between receptor location and biologic response as well as the presence of essential receptor HS‐groups.
Sesquiterpenoids of the Sponge Dysidea fragilis of the North‐Brittany Sea
Authors: Guella Graziano , Guerriero Antonio , Pietra Francesco 
Published: December 2004

AbstractThe title sponge is shown to contain eight new sesquiterpenoids for which a common, unusual biogenetic origin is postulated. The compounds are shown to be: (–)‐(1R*,4R*)‐3‐(3′‐furyl)methyl‐2‐p‐menthen‐7‐yl acetate ((–)‐8b); two diols separated as the monoacetates (–)‐(1S*,4R*)‐3‐(3′‐furyl)methyl‐l‐hydroxy‐2‐p‐menthen‐7‐yl acetate ((–)‐13a) and the (–)‐(1R*,4R*)‐epimer (–)‐13b, the two C(4)‐epimeric 4‐ethoxy‐3‐(1′(7′),2′‐p‐menthadien‐3′‐yl)methyl‐2‐buten‐4‐olides ((+)‐14a and (–)‐14b), (–)‐3‐(3′‐furyl)methyl‐7‐nor‐2‐p‐menthen‐l‐one ((–)‐11), (–)‐(3Z)‐1‐(3′‐furyl)‐4,8‐dimethylnona‐3, 7‐dien‐2‐yl acetate ((–)‐17), and (+)‐3‐(5′,7′‐seco‐2′(10′)‐pinen‐7′‐yl)methylfuran ((+)‐15).
Stoffwechselprodukte von Mikroorganismen. 231. Mitteilung. Bafilomycin‐A1‐21‐O‐(α‐L‐rhamnopyranosid): Strukturaufklärung durch chemische Verknüpfung mit Bafilomycin A1 und Leucanicidin
Authors: Meyer Michael , Keller‐Schierlein Walter , Drautz Hannelore , Blank Wolfgang , Zähner Hans 
Published: December 2004

Isolation of Bafilomycin‐A1‐21‐O‐(α‐L‐rhamnopyranoside). Structural Determination by Chemical Correlation with Bafilomycin A1 and LeucanicidinFrom cultures of an actinomycete strain, the known antifungal and insecticidal antibiotic leucanicidin (1) and a hitherto unknown antifungal antibiotic, bafilomycin‐A1‐21‐O‐(α‐L‐rhamnopyranoside) (2), were isolated. The latter is spectroscopically closely related to 1 and bafilomycin A1 (3) and gave degradation products identical with compounds obtained by analogous degradation of 1 and 3.
α‐Alkylation of Amino Acids without Racemization. Preparation of Either (S)‐ or (R)‐α‐Methyldopa from (S)‐Alanine
Authors: Seebach Dieter , Aebi Johannes D. , Naef Reto , Weber Theodor 
Published: December 2004

AbstractEnantiomerically pure cis‐ and trans‐5‐alkyl‐1‐benzoyl‐2‐(tert‐butyl)‐3‐methylimidazolidin‐4‐ones (1, 2, 11, 15, 16) and trans‐2‐(tert‐butyl)‐3‐methyl‐5‐phenylimidazolidin‐4‐one (20), readily available from (S)‐alanine, (S)‐valine, (S)‐methionine, and (R)‐phenylglycine are deprotonated to chiral enolates (cf. 3, 4, 12, 21). Diastereoselective alkylation of these enolates to 5,5‐dialkyl‐ or 5‐alkyl‐5‐arylimidazolidinones (5, 6, 9, 10, 13a‐d, 17, 18, 22) and hydrolysis give α‐alkyl‐α‐amino acids such as (R)‐ and (S)‐α‐methyldopa (7 and 8a, resp.), (S)‐α‐methylvaline (14), and (R)‐α‐methyl‐methionine (19). The configuration of the products is proved by chemical correlation and by NOE 1H‐NMR measurements (see 23, 24). In the overall process, a simple, enantiomerically pure α‐amino acid can be α‐alkylated with retention or with inversion of configuration through pivaladehyde acetal derivatives. Since no chiral auxiliary is required, the process is coined ‘self‐reproduction of a center of chirality’. The method is compared with other α‐alkylations of amino acids occurring without racemization. The importance of enantiomerically pure, α‐branched α‐amino acids as synthetic intermediates and for the preparation of biologically active compounds is discussed.
Nucleophilic 1,2‐Shifts of Alkoxycarbonyl and Carboxylate Groups in the Benzilic‐Acid Type Rearrangement of α,β‐Dioxobutyric Esters
Authors: Gowal Heike , Dao Lê H. , Dahn Hans 
Published: December 2004

Abstracttert‐Butyl α,β‐dioxobutyrate (hydrate; 1d) undergoes, at medium or high pH, the benzilic‐acid rearrangement with exclusive 1,2‐shift of the COO(t‐Bu) group; the same is true for the corresponding isopropyl ester 1c and ethyl ester 1b at high pH, whereas at lower pH, the overall picture of these reactions is complicated by concurrent hydrolysis of the ester, followed by a 1,2‐shift of the COO− group. Consequently, the shift of these electron‐attracting groups cannot be considered to be systematically disfavoured (compared, e.g., with alkyl‐group shifts). Kinetic measurements of the rearrangement show for both esters (as well as for the analogous ethyl ester 1b, and also for ethyl 3‐cyclopropyl‐α,β‐dioxopropionate (4)) a characteristic rate profile: at relatively low pH, k is proportional to [HO−], approaching saturation with increasing [HO−] (interpreted as complete transformation of the substrate into the hydrate monoanion), which is followed at higher pH by another rate increase with k proportional to [HO−] (probably due to the reaction of the hydrate dianion). The similarity of k values for 1b‐d shows that in the shift of COOR steric hindrance caused by R is negligible.
Photochemical reactions. 142nd communication. Photochemistry of a 6,7‐epoxy‐1,3‐diene of the ionone series
Authors: Mathies Peter , Frei Bruno , Jeger Oskar 
Published: December 2004

AbstractOn singlet excitation (λ = 254 nm), the epoxydiene (E)‐3 underwent (E)/(Z)‐isomerization, electrocyclic ring closure of the diene side chain leading to the cyclobutenes 4A + B, and rearrangement to the cyclohexanones 5A + B. Compounds 5A + B were presumably formed in a series of processes including a 1,3‐acyl shift of the homoconjugated ketone 8, arising from (Z)‐3 by a 1,5‐H‐shift accompanied by cleavage of the C,O‐bond of the oxirane.
Synthese und Reaktionen von Bicyclo[6.4.0]dodecan‐3‐carbonsäure‐Derivaten
Authors: Buchbauer Gerhard , Gabmeier Johanna , Haslinger Ernst , Robien Wolfgang , Steindl Harald 
Published: December 2004

Synthesis and Reactions of the Bicyclo[6.4.0]dodecane‐3‐carboxylic Acid DerivativesThe synthesis and some consecutive reactions of the compounds 5‐8, derivatives of bicyclo[6.4.0]dodecane‐3‐carboxylic acid (1), are described. The esters 7 and 8 can be obtained by Baeyer‐Villiger oxidation of 2‐hydroxy‐8‐methyltricyclo[7.3.1.02,7]tridecan‐13‐one (4) and subsequent hydrolysis of the lactone 5. The structure and configuration of these compounds has been evaluated by spectroscopic techniques (mainly 2D‐NMR methods). The formation of 7 via 1,2‐H shift and subsequent isomerization to 8 has been studied. The esters 11 and 13 are formed stereospecifically from 7 and 8.
Synthesen von stellungsisomeren Alkoxyformylderivaten des 1,6‐Methano[10]annulens
Authors: Neidlein Richard , Hartz Georg 
Published: December 2004

Syntheses of Positionisomeric Alkoxyformylderivatives of 1,6‐Methano[10]annulenesDifferent aldehydes of 1,6‐methano[10]annulene – namely 3–6, 11, 12, 15, and 19 – were synthesized. They can be used as starting materials for synthetic reactions of other new bridged systems; the results of 1H‐NMR‐ and 13C‐NMR measurements are included.
The Radical Anions of syn‐1,6:8,13‐Bridged [14] Annulenes. A Compilation of Hyperfine Data
Authors: Gerson Fabian , Knöbel Jürgen , Lopez Javier , Vogel Emmanuel 
Published: December 2004

AbstractHyperfine coupling constants and g‐factors determined by ESR and ENDOR spectroscopy are given for the radical anions of 21 syn‐1,6:8,13‐bridged [14]annulenes. The great majority of these values is reported for the first time. The hyperfine data are consistent with the single occupancy of an orbital which resembles a π‐perimeter‐LUMO of the same nodal properties. The sum of the coupling constants of the protons attached to the π‐perimeter can be used as a planarity criterion for this perimeter.
Synthese von 3,3‐Dimethylperhydro‐1,4‐diazepin‐2,5,7‐trionen aus 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirin und Malonsäuremonoamiden
Authors: Obrecht Daniel , Scholl Bernhard , Heimgartner Heinz 
Published: December 2004

Synthesis of 3,3‐Dimethylperhydro‐1,4‐diazepin‐2,5,7‐triones from 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirine and Malonic Acid MonoamidesReaction of the aminoazirine 1 and malonic acid monoamides 5 in CH3CN yielded triamides of type 6 (Scheme 2), which were transformed to the corresponding phenylthioates 9 by treatment of a solution of 6 and thiophenol in CH3CN with HCl (Scheme 4). Cyclization of 9 to give the 1,4‐diazepin‐2,5,7‐trione of type 10 was achieved with NaH in toluene at about 90°. It has been shown that 2‐oxazolin‐5‐ones are intermediates in the selective cleavage of the therminal amide function of 6 (Scheme 3).
The Crystal Structure of trans‐2,2′‐Azoquinoxaline
Authors: Krieger Claus , Koçak Ahmet , Bekâroǧlu Özer 
Published: December 2004

AbstractThe structure of the title compound obtained from 2(1H)‐quinoxalinone oxime by the template effect of Co(II) and Ni(II) ion has been determined by three dimensional X‐ray analysis.
Liquid Crystals with Large Negative Dielectric Anisotropy. Part V
Authors: Osman Maged A. 
Published: December 2004

AbstractLiquid crystals with negative Δϵ can be obtained by incorporating a cyano group in the terminal alkyl substituent or in an ethylene bridge between the cyclic units of the rigid core. The clearing points of such compounds are higher than those of the corresponding derivatives where the cyano group is laterally attached to a phenyl moiety. In compounds where both cyclic units of the rigid core are cyclohexyl, this type of substitution leads to an optimal contribution to ϵ⟂ in contrast to the cyanophenyl derivatives.
Synthese und Hydrolyse von 4‐substituierten p‐Nitrobenzolsulfonsäure (2‐adamantyl)estern
Authors: Grob Cyril A. , Wittwer Gerhard , Rama Rao K. 
Published: December 2004

Synthesis and Hydrolysis of 4‐Substituted 2‐Adamantyl p‐NitrobenzenesulfonatesSeveral 4e ‐substituted 2e‐ and 2a‐adamantyl p‐nitrobenzensulfonates have been prepared by new routes. Their hydrolysis products are described.
Synthesis and Antagonistic Activity of Two Covalently Linked Dimers of Adrenocorticotropin‐(11‐24)‐tetradecapeptide
Authors: Fauchère Jean‐Luc 
Published: December 2004

AbstractThe chemical synthesis of two dimers of the sequence 11 to 24 of adrenocorticotropin is described. The two monomers were covalently linked through their N‐or C‐termini, respectively, using N‐acetylglutamic acid or lysine amide as spacers. Compared to the monomer, the first dimer showed moderately, the second strongly increased inhibitory potency upon steroidogenesis in isolated adrenal cells.
Isomérisation cis‐trans en Série Alkyl‐4‐vinyl‐3‐pipéridine par Sigmatropie [3.3]. Synthèse des Epivinyl Isomères des Alcaloïdes du Quinquina
Authors: Engler Gérard , Strub Henri , Fleury Jean‐Pierre , Fritz Hans 
Published: December 2004

cis, trans Isomerization of 4‐Alkyl‐3‐vinylpiperidines by [3.3] Sigmatropic Rearrangement. Synthesis of Epivinyl Isomers of Cinchona AlkaloidsIsomerization of 4‐alkyl‐3‐vinylpiperidines induced by formaldehyde has been studied for ethyl meroquinate and quinotoxine. The equilibration of cis‐ and trans‐isomers occurs by involvement of a [3.3] sigmatropic rearrangement. This process permits an easy access to the trans‐isomers from natural products of cis‐configuration and has been used to obtain the epivinyl isomers of cinchona alkaloids.
The Synthesis and Some Physical Properties of New Laterally Substituted Phenyl Ethers Containing a trans‐1,4‐Disubstituted Cyclohexane Ring
Authors: Kelly Stephen M. , Schad Hanspeter 
Published: December 2004

AbstractThe synthesis, liquid‐crystal transition temperatures, and some physical properties of a variety of substituted phenyl ethers, most of which incorporate a lateral substituent, are reported. Many of the liquid crystals described exhibit nematic phases with negative dielectric anisotropy at elevated temperatures. The relationship between the nature of the lateral substituents and the observed liquid crystal phases and transition temperatures is discussed.
Reaction of Anthranilamide with Phosphorus Pentasulfide: Formation of 2‐Mercapto‐(1H)‐1,3,2λ5‐benzodiazaphosphorine‐2,4‐dithione
Authors: Nagarajan Kuppuswamy , Shenoy Sharada J. , Fritz Hans , Hosang Othmar , Richter Wilhelm J. 
Published: December 2004

AbstractThe reaction of anthranilamide with phosphorus pentasulfide in boiling pyridine leads to the benzodiazaphosphorine‐pyridine salt 2. The structure is established by elemental analysis, 1H‐ 13C‐ 15N‐ 31P‐NMR, and mass spectral data.
Makrocyclische Ionophore beruhend auf oligomeren Terephthaldiamiden mit von Gastmolekülen abhängiger Selektivität
Authors: Behm Felix , Simon Wilhelm , Müller Walter M. , Vögtle Fritz 
Published: December 2004

Macrocyclic Oligolactams Based on Terephthalic Acid as Ionophores with Selectivity Depending on Included Guest MoleculesMacrocyclic 20‐ to 60‐membered oligolactam hosts exhibit ion selectivities in poly(vinyl chloride) membranes which depend on the ring size and on the substituents of the amide N‐atoms. The selectivity may be changed by loading the macrocyclic host with CHCl3 as guest molecule.
Enzyme‐Catalyzed Peptide‐Bond Formation: Elastase‐ and δ‐Chymotrypsin‐Assisted Synthesis of Oligopeptides
Authors: Bizzozero Spartaco A. , Dutler Hans , Franzstack Ruth , Rovagnati Bruno A. 
Published: December 2004

AbstractA series of penta‐ and hexapeptides of the structure Ac‐Lxn‐ …‐Lx1‐Ly1‐…‐Lym‐NH2 with phenylalanine or tyrosine in Lx1 and glycine or alanine in the other positions were synthesized using elastase and δ‐chymotrypsin to catalyse the formation of the peptide bonds adjacent to the aromatic residue. Such oligopeptides are useful substrates for studying the secondary specificity of chymotrypsin‐like proteases.
Synthesis and Conformation of (5R,8R,10R)‐8‐(Methylthiomethyl)ergoline‐6‐carboxamidine
Authors: Nordmann René , Loosli Hans‐Rudolf 
Published: December 2004

AbstractThe title compound 7 and two related novel ergolines have been synthesised from (5R,8R,10R)‐8‐(methyl‐thiomethyl)ergoline‐6‐carbonitrile (4). The guanidine function of 7 induces a boat conformation of ergoline‐ring D, as demonstrated by a careful NMR spectroscopic analysis of 7 and its N‐hydroxy congener 6. Diphenylphosphinodithioic acid has been used to convert the cyanamide function of 4 into the thiourea function at (5R,8R,10R)‐8‐(methylthiomethyl)ergoline‐6‐thiocarboxamide (5).
Structures of Ring‐Enlargement Products
Authors: Aono Tetsuya , Bieri Jost H. , Hesse Manfred , Kostova Kalina , Lorenzi‐Riatsch Annalaura , Nakashita Yoshihiko , Prewo Roland 
Published: December 2004

AbstractCrystal structures have been determined of methyl trans‐1‐hydroxy‐6‐nitro‐3‐oxobicyclo[4.4.0]decane‐2‐carboxylate (19), cis‐3‐methyl‐6‐nitro‐2‐oxabicyclo[4.4.0]decan‐1‐ol (2), cis‐7‐hydroxy‐1‐nitrobicyclo[5.4.0]undecan‐9‐one (13), and the medium‐ring compounds 2‐acetyl‐4‐nitrocyclooctanone (9), methyl 5‐nitro‐2‐oxocyclooctane‐carboxylate (4), 2‐acetyl‐4‐nitrocyclononanone (11), 2‐acetyl‐4‐nitrocyclodecanone (15), benzyl 5‐nitro‐2,11‐dioxocycloundecanecarboxylate (24), methyl 5‐nitro‐2,12‐dioxocyclododecanecarboxylate (21), and 8‐nitro‐11‐oxo‐13‐tridecanolide (7), which are intermediates, side products, or end products of the ‘Zip’ ring‐enlargement reaction. The conformations of most of the medium‐ring compounds are very similar to equal‐sized ring compounds previously determine by other authors.
Thermal Rearrangement of 5,6‐Epimino‐5,6‐dihydro‐β‐ionone and Derivatives
Authors: Müller Ernst Peter 
Published: December 2004

AbstractThermolysis of 5,6‐epimino‐5,6‐dihydro‐β‐ionone (1) and its N‐methyl derivative (2) leads to their monocyclic isomers 6 and 10, respectively, presumably due to a direct [1,5]‐H shift; on prolonged heating, these isomers are converted easily into pyrrole derivatives. In contrast, the thermoisomer 12 resulting from 5,6‐(N‐methoxycarbonyl)epimino‐5,6‐dihydro‐β‐ionone (3) by the same mechanism, does not undergo further ring transformation, but equilibrates with its more stable tautomer 13.
The Quest for Bridgehead Bridgehead Dications with Bicyclo[2.2.2]octyl Skeletons
Authors: de Meijere Armin , Schallner Otto , Mateescu G. D. , Gölitz Peter , Bischof Peter 
Published: December 2004

AbstractIt is predicted by MINDO/3 calculations that the 1,5‐trishomobarrelenediyl dication 4 would be as much stabilized over the bicyclo[2.2.2]octanediyl dication 3 as the monocation 7‐H is energetically favored over the hypothetical 1‐bicyclo[2.2.2]octyl 10‐H. In spite of this, the bridgehead cations generated from the 1,5‐dihalo‐trishomobarrelenes 6‐F, 6‐Cl, 6‐Br, and 6‐I and from the 1,5‐diol 6‐OH under long‐lived ion conditions were only the 5‐substituted monocations 7‐F, 7‐Cl, 7‐Br, 7‐I, and 7‐OH, respectively, unequivocally identified by their 1H‐ and 13C‐NMR spectra as well as quenching products. Although there is efficient charge delocalization in 7‐X, as revealed by the 13C‐chemical shifts, the lack of formation of the bridgehead bridgehead dication 4 is not due to an unforeseen destabilization by the three α‐annellated cyclopropyl groups. Even the 1,5‐dichlorotetracyclo[3.3.2.02,4.06,8]decanes 17‐Cl2 and 19‐Cl2 and 1,5‐dichlorotricyclo[3.2.2.02,4]nonane 12‐Cl2 with only two and one α‐cyclopropyl groups, respectively, gave the bridgehead monocations 18‐Cl, 20‐Cl, and 13‐Cl, respectively.
Synthesis of Substituted 2‐Amino‐6H‐1,3‐oxazin‐6‐ones
Authors: Kristinsson Haukur , Winkler Tammo , Rihs Grety , Fritz Hans 
Published: December 2004

AbstractDerivatives of the unknown 2‐amino‐6H‐1,3‐oxazin‐6‐one 2 have been synthesized for the first time in two steps and in excellent yields, starting from N‐cyanocarbonimidates 3a–c and cyanoacetates. The structures of 2a–c are assigned by NMR‐spectroscopic methods and corroborated by an X‐ray structure analysis of 2c.
Propellanes. Part LXXXI. Why are tetrakis[organoboranediylbis(oxy)]cyclobutanes formed without a trace of the isomeric tetrakis‐dioxabora[3.3.2]propellanes?
Authors: Stanger Amnon , Apeloig Yitzhak , Ginsburg David 
Published: December 2004

AbstractMNDO and STO‐3G calculations rationalize the relative instability of the title propellanes vis‐à‐vis the title products that are formed exclusively.
Motional Anisotropy of 1‐Phenyladamantane
Authors: Kołodziejski Wacław , Laszlo Pierre 
Published: December 2004

Abstract13C‐NMR longitudinal relaxation rates are analysed with the Woessner equations: in CDCl3 solution at room temperature, 1‐phenyladamantane has rotational diffusion coefficients R‖ = 8.1 × 1010 rad · s−1 and R⊥ = 1.1 × 1010 rad · s−1 corresponding to high motional anisotropy (σ = 7.4).
Stereoselective Synthesis of Masked Amino‐polyols via Osmylation of 4,5‐Dihydro‐5‐vinylisoxazoles
Authors: Annunziata Rita , Cinquini Mauro , Cozzi Franco , Raimondi Laura , Restelli Angelo 
Published: December 2004

AbstractVariously substituted 4,5‐dihydro‐5‐vinylisoxazoles, obtained by regio‐ and stereospecific cycloaddition of nitrile oxides to dienes, undergo smooth OsO4‐catalyzed cis‐hydroxylation to give amino‐polyol precursors. The reaction is ‘anti’‐selective, the diastereoisomeric ratios ranging from 73:27 up to ≥ 99:1. Thus, the cycloaddition/osmylation sequence allows the control of the relative configuration of up to four contiguous asymmetric centers. A sulfoxide‐mediated approach to enantiomerically pure compounds is also described.
Stereospecific Molecular Design. Synthesis of a New Heterotricyclic System
Authors: Tschamber Théophile , Fritz Hans , Streith Jacques 
Published: December 2004

AbstractUV irradiation of the bicyclic enimine 1 led stereospecifically to the anti‐tricyclic isomer 2 which reverted back to 1, either by thermal activation or by acid catalysis at room temperature. Catalytic hydrogenation of 2 gave compound 4 whose configuration was fully ascertained by high‐field 1H‐NMR measurements.
Lösungsmittel‐, Viskositäts‐, Säure‐ und Substituenteneinflüsse auf die Photoisomerisierung und Relaxation symmetrischer Triazacarbocyanine bei 283 bis 323 K
Authors: Balli Heinz , Hellrung Bruno 
Published: December 2004

Influence of Solvents, Viscosity, Acid, and Substituents on the Photoisomerization and the Relaxation of Symmetrical Triazacarbocyanine Dyes at 283 to 323 KPhotobleaching and the reverse dark reaction of seven symmetrical triazacarbocyanine dyes with different heterocycles were studied dependent on solvent effects (protic and aprotic solvents), on effects of viscosity (glycerol/EtOH mixtures), and on effects of added acid. No effects of dissolved O2 or added I2 has been observed. Kinetic data (ΔH≠, ΔS≠, and ΔG) of the reverse reaction are given. The effect of the substituents has been studied on two series of substituted triazacarbocyanine dyes. The mechanism of the reverse reaction is discussed.
Synthese und flüssigkristalline Eigenschaften 2,6‐disubstituierter Naphthaline
Authors: Lauk Urs H. , Skrabal Peter , Zollinger Heinrich 
Published: December 2004

Synthesis and Liquid‐Crystal Properties of 2,6‐Disubstituted Naphthalene DerivativesThe syntheses and the mesomorphic properties of a series of novel 2,6‐disubstituted naphthalenes are described. 4‐[6‐(n‐Alkyl)‐2‐naphthyl]benzonitriles 5 and 4‐[6‐(n‐Alkoxy)‐2‐naphthyl]benzonitriles 8 exhibit widerange nematic mesophases. 6,6′‐Di(n‐alkyl)‐2,2′‐binaphthyls 6 have been isolated as by‐products from the reaction mixtures of 5. Some of these novel compounds have polymorphic properties. The esters 13 and 15 of 4‐(6‐hydroxy‐2‐naphthyl)benzonitrile show enhanced mesophase stabilities which reach maximum values in the series of α, β‐unsaturated esters 15. The 4‐(n‐pentyl)benzoate 14 of the same (hydroxynaphthyl)benzonitrile has a melting point of 125° and a clearing point of > 310°. This particular derivative belongs to those liquid‐crystalline compounds having the broadest purely nematic‐phase range. In addition, (RS)‐4‐(2‐pentyl‐6‐chromanyl)benzonitrile (20) and three compounds with two and four laterally arranged CN groups at the bicyclo[2.2.2]octene, bicyclo[2.2.2]octadiene, and the phenyl‐ring systems 31–33 were synthesized. Only 20 shows mesomorphic properties.
7‐Bromocavernicolenone, a New α‐Bromoenone from the Mediterranean Sponge Aplysina (= Verongia) cavernicola. Implied, Unprecedented Involvement of a Halogenated Dopa in the Biogenesis of a Natural Product
Authors: D'Ambrosio Michele , Mealli Carlo , Guerriero Antonio , Pietra Francesco 
Published: December 2004

AbstractA novel, mildly antibacterial, α‐bromoenone (7‐bromocavernicolenone) has been isolated from the Mediterranean sponge Aplysina (= Verongia) cavernicola. Its structure, 7‐bromo‐1,5‐dihydroxy‐2‐azabicyclo[3.3.1]non‐6‐en‐3,8‐dione (3), is based on X‐ray and NMR analysis and on the observation that acetylation of 3 affords two monoacetates. An unprecedented phenol oxidative biogenetic pathway is suggested leading to 7‐bromocavernicolenone via 3‐bromotyrosine and 5‐bromodopa.