bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthese und absolute Konfiguration von Clemastin und seiner Isomeren
Authors: Ebnöther Anton , Weber Hans‐Peter 
Published: December 2004

Synthesis and Absolute Configuration of Clemastine and its Isomers.Condensation of 4‐chloro‐α‐methylbenzhydrylalkohol (1) with 2‐(2‐chloroethyl)‐1‐methylpyrrolidine (2) gave an isomeric mixture of 2‐[2‐(p‐chloro‐α‐methyl‐=‐phenylbenzyloxy)ethyl]‐1‐methylpyrrolidine (3) and 4‐(p‐chloro‐=‐phenylbenzyloxy)‐1‐methyl‐hexahydroazepin (4). The separation of the four possible optically active isomers of 3 is described and their absolute configuration established by degradation to (R)‐ and (S)‐1‐methyl‐2‐pyrrolidineethanol (6), respectively, and by an X‐ray cristallographic analysis of the quarternary methiodide of the isomer 3‐A. Clemastine (3‐A) is (+)‐(2R)‐2‐[2‐((αR)‐(p‐chloro‐α‐methyl‐α‐phenylbenzyloxy)ethyl)]‐1‐methylpyrrolidine.
Thermolyse von Carbamoylaziden I. Hochvakuumthermolyse von Dialkylcarbamoylaziden
Authors: Reichen Werner 
Published: December 2004

Flash vacuum thermolysis of dialkylcarbamoyl azides.Thermolysis of several N,N‐dialkylcarbamoyl azides 1 in high vacuum gave good yields of 5,5‐dialkyl‐3‐dial‐kylamino‐2,4‐dioxo‐5‐azonia‐imidazolidin‐l‐id (4) formed by thermal Curtius rearrangements and dimerisation of the resulting N,N‐dialkylaminoisocyanates 2.
Steric Effects on Reaction Rates. Rate and equilibrium constants for oxidation of cyclanols
Authors: Müller Paul , Blanc Jacky 
Published: December 2004

AbstractEquilibrium constants for oxidations of cyclanols by cyclohexanone in benzene have been determined in the presence of aluminium isopropoxide. The free energies of the equilibrium (ΔGox) are correlated with equilibrium constants for dissociation of cyanohydrins, rate constants for cyclanol oxidation with chromic acid, ketone reduction with sodium borohydride and trifluoroethanolysis of tosylates.
Anil‐Synthese. 23. Mitteilung. Über die Herstellung von Styryl‐ und Stilbenyl‐Derivaten des Pyrimidins
Authors: Burdeska Kurt , Fuhrer Hermann , Kabas Guglielmo , Siegrist Adolf Emil 
Published: December 2004

Preparation of Styryl and Stilbenyl Derivatives of Pyrimidines2‐ and 4‐(p‐Tolyl)‐substituted pyrimidines react with anils of hetero‐aromatic aldehydes in the presence of dimethylformamide and potassium hydroxide or potassium t‐butoxide to yield the corresponding 2‐ and 4‐[4″‐(heteroaryl)stilben‐4′‐yl]pyrimidines or the 2‐ and 4‐[a‐(heteroaryl)‐4′‐styryl]pyrimidines respectively (‘Anil synthesis’). Furthermore, the Schiff′s bases derived from p‐chloroaniline and 4‐(pyrimidine‐2‐yl and 4‐yl)benzaldehydes give, with methyl‐ and with p‐tolyl‐substituted heterocycles, the corresponding heterocyclic substituted styryl and stilbenyl derivatives. Alkyl‐, alkoxy‐ or phenyl‐substituted pyrimidines undergo also the ‘Anil synthesis’.
Pseurotin B, C, D, and E. Further New Metabolites of Pseudeurotium ovalis STOLK
Authors: Breitenstein Werner , Chexal Kuldip K. , Mohr Peter , Tamm Christoph 
Published: December 2004

AbstractThe structures 2–5 are assigned to the pseurotin B, C, D and E, which are new metabolites of Pseudeutorium ovalis STOLK, based on spectroscopic data and chemical transformations.
Total Synthesis of (±)‐Lysergic Acid by an Intramolecular Imino‐Diels‐Alder Reaction. Preliminary communication
Authors: Oppolzer Wolfgang , Francotte Eric , Bättig Kurt 
Published: December 2004

Abstract(±)‐Lysergic acid (1) has been synthesized from 4‐hydroxymethyl‐1‐tosylindole (2) by a sequence of 9 steps. The crucial thermolysis 9 → 10 involves the in situ‐generation of the transient diene III which undergoes an intramolecular cycloaddition to a C, N‐double bond at 200° and at low stationary concentration of III.
The Reaction of Pyruvic Acid with Amines and Aminoesters Reexamined. Preliminary communication
Authors: Bradamante Silvia , Colombo Silvana , Pagani Giorgio A. , Roelens Stefano 
Published: December 2004

AbstractPhenylglycine esters react with pyruvic acid to give α‐methylsuccinic amides 9 instead of the expected Schiff bases 8, analogously to p‐anisidine but unlike aniline.
Methylierung von 4‐Hydroxy‐4‐(2‐piperidyl)‐4H‐pyrazolo [1,5‐a]indol mit Formaldehyd und Ameisensäure. 11. Mitteilung über metallorganische Reaktionen und Folgeprodukte
Authors: Rihs Grety , Fuhrer Hermann , Marxer Adrian 
Published: December 2004

AbstractIn the 10th communication of this series [1] the synthesis of 4‐hydroxy‐4‐(2‐piperidyl)‐4H‐pyrazolo[1,5‐a]indole (4) was described (Scheme). Surprisingly enough, methylation of this compound with formaldehyde and formic acid led via ring closure and a subsequent rearrangement to a pentacyclic ketone. By means of 13C‐NMR.‐spectroscopy and mass spectroscopy, this ketone could be identified as a indolizino‐pyrazolo‐indole (9). Its structure and configuration were determined by X‐ray structure analysis.
Photolysis of dimethylnitrosamine in the gas phase
Authors: Geiger Georg , Huber J. Robert 
Published: December 2004

AbstractPhotodecomposition of dimethylnitrosamine in the gas phase ( ∼ 1 Torr) has been investigated following irradiation into the S1 (nπ*) ← S0 (363.5 nm) and S2 (ππ*) ← S0 (248.1 nm) transitions at room temperature. With a quantum yield of unity, excitation into the S1 state yields the fragments (CH3)2N⋅ and NO which then recombine leaving no photoproducts. The addition of O2 results in only one photoproduct, (CH3)2NNO2. Irradiating into the S2 state, the products CH2NCH3, (CH2NCH3)3, CH2NOH, N2O, NO, H2, and N2 were identified by capillary gas chromatography mass spectrometry. In the presence of N2 as a buffer gas the photoproducts are only CH2NCH3, (CH2NCH3)3, N2O, and H2. For both excitation conditions a mechanism is proposed involving cleavage of the N, N‐bond as the main primary photolytic process.
Synthesis of Open‐Chain 2,3‐Disubstituted 4‐nitroketones by Diastereoselective Michael‐addition of (E)‐Enamines to (E)‐Nitroolefins. A topological rule for C, C‐bond forming processes between prochiral centres. Preliminary communication
Authors: Seebach Dieter , Goliński Jerzy 
Published: December 2004

AbstractThe Michael‐additions of aliphatic, alicyclic, and arylsubstituted nitroolefins and enamines lead to γ‐nitroketones 3 in good chemical and excellent (> 90%) diastereomeric yields (see Table 1).The known threo‐configuration of one type of adducts 3 (entries 8, 10, and 11 of Table 1) can be arrived at by assuming the approach 8 of the Michael‐acceptor and ‐donor; the reaction follows a topological rule, which is formulated and which is applicable to such diverse reactions as the diene synthesis, cyclopropanations, carbonyl olefinations and methylenations, aldol‐ and nitroaldol‐type additions, as well as additions of lithium, boron, and chromium derivatives to aldehydes (see 9, 10, 11, and Table 2).
Röntgenstrukturanalysen von Chiralen Ionophoren: NH4NCS‐Komplex von 9,9′‐Spirobifluoren‐22‐Krone‐5
Authors: Neupert‐Laves Katarina , Dobler Max 
Published: December 2004

X‐ray Structure Analyses of Chiral Ionophores: The NH4NCS Complex of 9,9′‐Spirobifluorene‐22‐crown‐5In the crystalline NH4NCS complex of 9,9′‐spirobifluorene‐22‐crown‐5 (1) the NH ion sits in the centre of the polyether ring, with distances of 2.92–3.15 Å to the five O‐atoms and shows at least twofold orientational disorder. In one orientation, three H‐atoms point toward O‐atoms and the fourth to the N‐atom of the anion situated 2.78 Å above the polyether ring. In another, only two H‐bonds are formed. The mean planes of the two fluorene parts of the molecule are perpendicular to each other.Crystals of 2,2′‐bis (hydroxymethyl)‐9,9′‐spirobifluorene (2), an intermediate for the synthesis of 1, contain occluded benzene, which cannot be removed under vacuum. X‐ray analysis shows that the benzene molecule does not interact with the spirobifluorene in a specific way but merely occupies cages in the crystal packing.
The π‐Anisotropy of the Double Bond of a syn‐11‐Oxasesquinorbornene Derivative.. Stereoselectivity of the Diels–Alder additions of (2‐norborneno)[c]furan. Crystal structure of 11‐oxa‐endo‐tetracyclo[6.2.1.13,6.02,7]‐dodec‐2(7)‐ene‐9,10‐exo‐dicarboxylic anhydride
Authors: Hagenbuch Jean‐Pierre , Vogel Pierre , Pinkerton A. Alan , Schwarzenbach Dieter 
Published: December 2004

AbstractThe reaction of (2‐norborneno)[c]furan (4) with maleic anhydride gave 11‐oxa‐endo‐tetracyclo[6.2.1.13,6.02,7]dodec‐2(7)‐ene‐9,10‐exo‐dicarboxylic anhydride (5) and, with methyl acetylenedicarboxylate, methyl 11‐oxa‐endo‐tetracyclo [6.2.1.13,6.02,7]dodeca‐2(7),9‐diene‐9,10‐dicarboxylate (7). The syn‐11‐oxa‐sesquinorbornenes 5 and 7 could be equilibrated with their cycloaddents. They are at least 2 kcal/mol more stable than the corresponding anti‐sesquinorbornenes 6 and 8. The structure of 7 was deduced from its spectral data, by epoxidation with air or a peracid to give the exo‐epoxide 13 and by catalytic hydrogenation to give 14. The structure of 5 was established by single‐crystal X‐ray diffraction. A dihedral angle of 163° was measured between the C(1,2,7,8) and C(2,3,6,7) planes in 5. This important deviation from planarity for the C(2,7) double bond is attributed to (π, ω)‐repulsive interactions that make the π‐electron density of 2‐norbornene and 7‐oxa‐2‐norbornene derivatives preferentially polarized toward the exo‐face. This finding is discussed in relation with the relative stability of the syn‐ and anti‐ 11‐oxasesquinorbornenes and with the endo‐stereoselectivity of the cycloadditions of the norbornenofuran 4.
Isolation of Four Hexaketides from Verticillium intertextum. Preliminary communication
Authors: Trifonov Latchezar S. , Dreiding André S. , Hoesch Lienhard , Rast Dora M. 
Published: December 2004

AbstractAus dem Kulturmedium von Verticillium intertextum wurden vier Metabolite isoliert: Vertinolid (1) und Bisvertinochinol (2), beide bisher unbekannt, sowie das auch von Penicillium chrysogenum (= P. notatum) gebildete Sorbicillin (3) und das früher synthetisch hergestellte, aber noch nicht als Naturprodukt bekannte Dihydrosorbicillin (4). Hypothesen über gemeinsame Biosynthesewege werden erörtert.
The Photoelectron Spectra of 4, 13‐Diaza‐ and 4, 16‐Diaza [24] (1,2,4,5)cyclophanes
Authors: Zhong‐zhi Yang , Heilbronner Edgar , Kang Hee Chol , Boekelheide Virgil 
Published: December 2004

AbstractA tentative assignment is proposed for the He (Ia) photoelectron (PE.) spectra of the title compounds. It is based on the assumption that the first four π‐bands occupy the same position in both spectra, as suggested by a qualitative correlation with the PE. spectrum of [24](1,2,4,5)cyclophane and by a previously proposed molecular orbital model. If this is accepted, then the bands due to electron ejection from the lone‐pair orbitals are split by roughly 0.8 eV in the case of the 4, 13‐diaza isomer, whereas no split can be detected in the case of the 4, 16‐diaza isomer.
Crystal Structure and Absolute Configuration of (+)‐(1S, 2R)‐5, 6‐Dimethylidene‐2exo‐norbornyl‐exo‐irontricarbonyl p‐Bromobenzoate
Authors: Barras Charles , Roulet Raymond , Chapuis Gervais , Chapuis Gervais 
Published: December 2004

AbstractThe title complex (+)‐13x has been prepared in an enantiomerically pure form. Its absolute configuration has been determined by single‐crystal X‐ray diffraction and has been correlated chemically to that of the 5, 6‐dimethylidene‐2‐norbornyl derivatives (—)‐1, (—)‐2, (—)‐3 and to (—)‐(1S, 2R)‐benzonorborn‐5‐en‐2‐yl acetate (s. Scheme 1), whose configuration was deduced by indirect techniques. A critical analysis of the chiroptical properties of the exocyclic dienes 1–3 is now possible. These compounds are limiting systems for the application of the allylic axial chirality rule, the generalized octant rule and the symmetry rule for βγ‐unsaturated ketones.
One‐Bond 13C, 13C‐Spin Coupling in η4‐, η3‐ and η2‐Olefin Transition Metal Complexes
Authors: Zobl‐Ruh Susanne , von Philipsborn Wolfgang 
Published: December 2004

AbstractOne‐bond 13C, 13C‐spin‐coupling constants have been measured, with natural isotope abundance, in η4‐diene, η3‐allyl and η2‐ene transition‐metal carbonyl complexes. Typical values of 1J(C,C) are given for Fe‐, Ru‐ and Os‐complexes with the three types of olefinic ligands. The effects of substituents and the structural significance of the C,C‐coupling constants are discussed.
Synthese von Astaxanthin aus β‐Jonon. I. Erschliessung der enantiomeren C15‐Wittigsalze durch chemische und mikrobiologische Racematspaltung von (±)‐3‐Acetoxy‐4‐oxo‐β‐jonon
Authors: Becher Elisabeth , Albrecht Robert , Bernhard Kurt , Leuenberger Hans G. W. , Mayer Hans , Müller Robert K. , Schüep Willy , Wagner Hans P. 
Published: December 2004

Synthesis of Astaxanthin from β‐Ionone. I. A Route to the Enantiomeric C15‐Wittig Salts by Chemical and Microbial Resolution of (±)‐3‐Acetoxy‐4‐oxo‐β‐iononeRacemic 3‐acetoxy‐4‐oxo‐β‐ionone (10) was synthesized from the industrially accessible intermediate β‐ionone (5). Resolution of 10 into its enantiomers was achieved via the corresponding diastereomeric camphanates and by microbial resolution. Site‐selective alkylation of racemic and of optically pure 3‐acyloxy‐4‐oxo‐β‐ionones with vinyl magnesium chloride at −70° furnished the corresponding 3‐acyloxy‐4‐oxo‐9‐vinyl‐β‐ionols which could be transformed to the Wittig salts 1, 3 and 4, respectively, following known procedures [1].
Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus 6‐Oxo‐isophoron. II. Ein neues Konzept für die Synthese von (3RS, 3′RS)‐Astaxanthin
Authors: Widmer Erich , Zell Reinhard , Broger Emil Albin , Crameri Yvo , Wagner Hans Peter , Dinkel Josef , Schlageter Markus , Lukáč T+odor 
Published: December 2004

Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6‐Oxo‐isophorone. II. A Novel Concept for the Synthesis of (3RS, 3′RS)‐AstaxanthinStarting from 6‐oxo‐isophorone (2) a new concept for a seven‐step synthesis of (3RS, 3′RS)‐astaxanthin (1) has been developed. As a key feature of the new approach, the oxidation state of astaxanthin (1) is adjusted already at an early stage of the synthesis. Thus, manipulation on more complex intermediates later in the synthesis is reduced to a minimum. Acetonide 10 or dimer 13 represent the key intermediates of this concept (Scheme 2). The whole sequence has been run on a kg scale with an overall yield of 52% (s. Scheme 5).
Umlagerung von α‐Halogen‐ in α′‐Halogen‐cyclobutanone, Schlüsselstufe einer variationsreichen Synthese von Pyrethroiden
Authors: Martin Pierre , Greuter Hans , Winkler Tammo , Belluš Daniel , Rihs Grety 
Published: December 2004

Rearrangement of α‐Halogen‐ to α′‐Halogen‐cyclobutanones, Key Step of a Highly Versatile Synthesis of Pyrethroidsα‐Halogenocyclobutanones, which are readily available by [2 + 2]‐cycloaddition of haloketenes to terminal olefins (e. g. 5 → 6), undergo an efficient and stereoselective cine‐rearrangement to α′‐halogenocyclobutanones in the presence of catalysts such as tertiary amines, HX acids or quaternary ammonium salts (e. g. 6 → 7, Table 1). Preparative as well as mechanistic aspects of the cine‐rearrangement are discussed. The 2,4‐cis‐disubstituted cyclobutanones 7–32 thus formed represent valuable intermediates in a new synthesis of pyrethroids 1.The X‐ray structure of 2‐chloro‐4‐(2,2,2‐trichloroethyl)‐3,3‐dimethylcyclobutanone (7), the most important precursor of cis‐3 (X = Cl) shows the following features: a puckered cyclobutanone ring (dihedral angle 31°), 2,4‐cis‐di‐pseudoequatorial arrangement of the chloro and trichloroethyl substituents, and an endo‐deviation (0.225 Å; 11°) of the carbonyl O‐atom from the plane formed by C(1), C(2) and C(4) (Fig. 2).
Azimine. VI. 1‐Alkoxycarbony 1‐2,3‐dialkyl‐ und ‐2,3‐diaryl‐azimine
Authors: Leuenberger Christian , Hoesch Lienhard , Dreiding André S. 
Published: December 2004

Azimines VI: 1‐Alkoxycarbonyl‐2,3‐dialkyl‐ and ‐2,3‐diarylaziminesAlkoxycarbonyl‐nitrenes 2 – generated in situ by α‐elimination from N‐[(4‐nitrophenyl)‐sulfonyloxy]carbamates 4 – were reacted with six aliphatic and aromatic azo compounds to yield 1‐alkoxycarbonyl‐azimines 11 (R′ = Alkyl). Thus, (2Z)‐ or (2E)‐ 1 ‐alkoxycarbonyl‐2,3‐diisopropyl‐azimines (8 or 9) were obtained stereospecifically from (E)‐ or (Z)‐1,1′‐dimethylazoethane (5 or 6) and 1‐alkoxycarbonyl ‐2,3‐(cis‐1,3‐cyclopentylene)‐azimines (10) resulted from 2,3‐diazabicyclo[2.2.1]‐2‐heptene (7), always using both ethoxy‐ and methoxycarbonyl‐nitrene (2a and 2b). With 2a, (E)‐azobenzene (14) was converted only to a single stereoisomer of 1‐ethoxycarbonyl‐2,3‐diphenyl‐azimine (17) and both stereoisomers of azo(p‐toluene) (15 or 16) reacted to give the same stereoisomer of 1‐ethoxycarbonyl‐2,3‐di(p‐tolyl)‐azimine (18).
On the Absolute Configuration of Indane‐1‐carboxylic Acid
Authors: Brewster James H. 
Published: December 2004

AbstractDoubts that have recently been expressed [1] about the currently accepted (+)‐(R), (−)‐(S) [2] absolute configuration of indane‐1‐carboxylic acid appear to be unwarranted. Our ORD. values for 1‐methylindane [12] are in error.
Über die Enantiomerentrennung durch Verteilung zwischen flüssigen Phasen
Authors: Prelog Vpm Vladimir , Stojanac Žarko , Kovčević Krunoslav 
Published: December 2004

Separation of Enantiomers by Partition between Liquid PhasesSalts of enantiomeric α‐aminoalocohols such as norephedrin, with lipophilic anions, such as hexafluorophosphate ion, can be separated by partition between aqueous and lipophilic phase containing esters of tartaric acid.
Structures of Ganoderic Acid A and B, Two New Lanostane Type Bitter Triterpenes from Ganoderma lucidum (FR.) KARST.
Authors: Kubota Takashi , Asaka Yukihiro , Miura Iwao , Mori Hideo 
Published: December 2004

AbstractThe structures of two new bitter triterpenes, ganoderic acid A and B. isolated from a mushroom Ganoderma lucidum (FR.) Karst. (Polyporaceae) were determined as 1 and 2 on the basis of spectral data. Ganoderic acid A is a novel highly oxidized triterpene bearing a boat‐shaped A‐ring of lanostane.
Desoxy‐nitrozucker. 2. Mitteilung Herstellung geschützter 1‐Desoxy‐1‐nitroaldosen
Authors: Aebischer Bernard , Vasella Andrea , Weber Hans‐Peter 
Published: December 2004

Synthesis of Protected 1‐Deoxy‐1‐nitroaldosesThe direct oxidation of the oxime 1 with t‐butyl hydroperoxide and vanadyl acetylacetonate yielding the nitro derivative 2 (54%, Scheme 1) could not be applied to other oximes. Diastereoselective bromination of the aldonolactone oxims 7 and 10–12 according to known procedures gave the corresponding bromonitroso compounds which were oxidized to the bromonitro compounds 9, 14, 18 and 22, respectively. Oxidation of the bromonitroso compound in the D‐mannopyranose series proved difficult, but the corresponding chloronitro derivative 23 was easily obtained according to Corey & Estreicher (Scheme 2 and 3). The structure of the bromonitro compound 9 was determined by an X‐ray analysis, and the configurations of the bromonitro compounds 14, 18 and 22 were deduced from their molecular rotations. Reduction of the bromonitro compounds gave the protected 1‐deoxy‐l‐nitroaldoses 2, 15/16, 19/20, and 24/25, respectively, in good overall yields. The ribose derivatives 15 and 16 were detritylated to give the nitro compound 4, and the mannose derivative 2 was partially deprotected to give the monoisopropylidene compound 26. The nitro group shows a normal anomeric effect which is reflected in the IR. spectra of the pyranose derivatives 19 and 20, and 24 and 25.
Studies Related to Biological Detoxification of Kraft Pulp Mill Effluent. III. The Biodegradation of Abietic Acid with Mortierella isabellina
Authors: Kutney James P. , Dimitriadis Eugene , Hewitt Gary M. , Singh Mahatam , Worth Brian R. 
Published: December 2004

AbstractA study relating to the biological detoxification of resin acids is described. Abietic acid was transformed into a number of non‐toxic hydroxylated derivatives by Mortierella isabellina. The biotransformation products have been identified and shown to be less toxic than abietic acid.
Synthesis and Mesomorphic Properties of 2,6‐Disubstituted Tetralins
Authors: Cereghetti Marco , Marbet Roman , Schleich Kuno 
Published: December 2004

AbstractSynthesis and mesomorphic behavior of nine members of each of the two classes of 6‐phenyl‐ and 2‐phenyltetralins and five members of the 2‐trans‐cyclohexyltetralins are reported. The synthesis of one member of each class is described in detail. Besides the target compounds, more than twenty intermediates showed liquid crystalline properties; their transition temperatures are recorded (see Tables 1‐6).
Isozeaxanthine: Chiralität und enantioselektive Synthese von (4R,4′R)‐Isozeaxanthin ((−)‐(4R, 4′R)‐β, β‐Carotin‐4,4′‐diol)
Authors: Haag Andreas , Eugster Conrad Hans 
Published: December 2004

Isozeaxanthin: Chirality and Enantioselective Synthesis of (4R,4′R)‐Isozeaxanthin ((−)‐(4R,4′R)‐β, β‐Carotin‐4,4′‐diol)The absolute configuration of optically active isozeaxanthin was established by synthesis using (−)‐(R)‐4‐hydroxy‐β‐ionon (2) [18] as starting material.
Molecular Receptors. Structural Effects and Substrate Recognition in Binding of Organic and Biogenic Ammonium Ions by Chiral Polyfunctional Macrocyclic Polyethers Bearing Amino‐Acid and Other Side‐Chains
Authors: Behr Jean‐Paul , Lehn Jeau‐Marie , Vierling Pierre 
Published: December 2004

AbstractThe stability constants of the complexes formed by the polyfunctional macro‐cyclic receptor molecules of type 1 with cationic substrates have been determined and analyzed in terms of structural factors. The binding strength is dominated by electrostatic interactions; the tetracarboxylate 1 (O−) forms by far the most stable complexes of all known macrocyclic polyethers. Lipophilic groups also significantly enhance stabilities, stressing the role of such residues in biological receptor sites. The complexation selectivity of organic ammonium cations is determined by two main factors: (a) central discrimination, resulting from the macrocyclic cavity, strongly favors binding of primary ammonium cations with respect to more highly substituted ones and also distinguishes among (R‐NH3+)‐substrates differently substituted on the C(α)‐atom; (b) lateral discrimination arises from interactions between the substrate and the side chains borne by the macrocycle; again electrostatic and lipophilic group effects play the major role; diammonium cations are especially strongly bound. Complexation of biogenic amines follows the same trends; for instance noradrenaline and norephedrine are selectively bound with respect to adrenaline and ephedrine, pointing towards potential applications in selective binding and transport of biologically active substances.
Computer‐Assisted Structural Interpretation of 1H‐NMR. Spectral Data
Authors: Egli Huidrych , Smith Dennis H. , Djerassi Curl 
Published: December 2004

AbstractInteractive computer programs for the establishment and maintenance of a 1H‐NMR. data base, the prediction of 1H‐NMR. shifts and the rank‐ordering of structural candidates based on comparison between observed and predicted spectra are presented. The programs take into account configuration, at stereocenters and double bonds, as well as diastereotopy. We demonstrate how, for purposes of structure elucidation, these new programs can be linked to the GENOA and STEREO programs.
Ringschlüsse an Chinonylmethanfarbstoffen und analogen Merocyaninen. 6. Mitteilung. Über die Reaktivität des Cyclohexylrestes in 2‐Chlor‐3‐[(1‐cyclohexyl‐6‐fluor‐3‐methyl‐1H‐chinoxalin‐2‐yliden)methyl]‐1,4‐naphthochinon
Authors: Schelz Dieter , Rotzler Niklaus 
Published: December 2004

Ring Closure in Quinonylmethane Dyes On the Reactivity of the Cyciohexyl Moiety in 2‐Chloro‐3‐[(1‐cyclohexyl‐6‐fluoro‐3‐methyl‐1H‐quinoxalin‐2‐ylidene)niethyl]‐1,4‐naphthoquinoncThe reactive title compound (1a, X = F, R1 = C6H11, R2=Cl) was obtained from the reaction of 1‐cyclohexyl‐6‐fluoro‐2,3‐dimethylquinoxalinium perchlorate with 2,3‐dichloro‐1,4‐naphthoquinone. Upon treatment with pyridine and acetic acid in acetone and separation of the desired naphthophenazinone 2a, an unexpected azepinoquinoxaline 4a was isolated. The structure of 4a was determined by its mass and 360‐MHz‐1H‐NMR. spectra in connection with decoupling experiments.