bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on the Stereochemistry of 2‐(Nitromethylidene)‐Heterocycles
Authors: Rajappa Srinivasachari , Nagarajan Kuppuswamy , Venkatesan Kailasam , Kamath Nirupa , Padmanabhan Vipanjeri Madabhusi , von Philipsborn Wolfgang , Chen Ban Chin , Müller Raffaelo 
Published: December 2004

AbstractThe 1H‐NMR spectra of 2‐(nitromethylidene)pyrrolidine (7), 1‐methyl‐2‐(nitromethylidene)imidazolidind (10) and 3‐(nitromethylidene)tetrahydrothiazine (11) in CDCl3 and (CD3)2SO indicate that these compounds have the intramolecularly H‐bonded structures (Z)‐7, (E)‐10 and (Z)‐11 while the N‐methyl derivative 8 of 7 is (E)‐configurated in both solvents. 1‐Benzylamino‐1‐(methyltio)‐2‐nitroehtylene (13), an acylic model, has the H‐bonded configuration (E)‐13 in CDCl3 and in (CD3)2SO. 2‐(Nitromethylidene)thiazolidine (3) has the (E)‐configuration in CDCl3 but exists in (CD3)2SO as a mixture of (Z)‐ and (E)‐isomers with the former predominating. Both species are detected to varying proportions in a mixture of the two solvents. 15N‐NMR spectroscopy of 3 ruled out unambiguously the nitronic acid structure 6 and the nitromethyleimine structure 5. The N‐methyl derivative 4 of 3 is (Z)‐configurated in (CD3)2SO. Comparison of the olefinic proton shifts of (Z)‐3 and (Z)‐4 with those of analogues and also of 1,1‐bis(methylti)‐2‐nitroethylene (12) shows decreased conjugation of the lone pair of electrons of the ring N‐atom in (Z)‐3 and (Z)‐4. This is also supported by 13C‐NMR studies. Plausible explanations for the phenomenon are offered by postulating that the ring N‐atoms are pyramidal in (Z)‐3 and (Z)‐4 and planar in other cases or, alternatively, that the conjugated nitroenamine system gets twisted due to steric interaction between the NO2‐group and the ring S‐atom. Single‐crystal X‐ray studies of 3 and 8 show that the former exists in the (Z)‐configuration and the latter in (E)‐configuration; the ring N‐atom in the former has slightly more pyramidal character than in the latter.
Total Synthesis of (±)‐2‐Pupukeanone
Authors: Fráter Georg , Wenger Jean 
Published: December 2004

Abstract(±)‐2‐Pupukenone (4) has been synthesized, the key step being the intramolcular Diels‐Alder reaction of the intermediate 13 to 14 (42%) and 15 (14%). The bromodiene 12 has been obtained from the reaction of α‐isopropylidene‐γ‐lactone (Scheme 2) 12 with sodium phenylselenide and subsequent esterification to 9, oxidation and thermal elimination of which furnished 10. Reduction of 10 with diisobutylaluminimum hydride and treatment of the resulting alcohol 11 with PBr3 led to the required bromodiene 12. Finally, hydrogenation of the 14 on Pt(C) in CH3OH gave a 4:1 mixture of 2‐pupukeanone (4) and epi‐2‐pupukeanone 16.
Deuterierung von Betanidin und Indicaxanthin, (E/Z)‐Stereoisomerie in Betalainen
Authors: Wyler Hugo , Dreiding André S. 
Published: December 2004

Deuteration of Betanidine and Indicaxanthine. (E/Z)‐Stereoisomerism in BetalainesPreviously unexplained1H‐NMR signals of the red‐violet betanidine and of the yellow indicaxanthine in CF3COOH are interpreted with the help of deuteration experiments in CF3COOD. They confirm the 1,7‐diazaheptamethinium chromophore of these pigments and further show an (E/Z)‐stereoisomerism at one of the partial double bonds: both betanidine and isobetanidine, in CF3COOH solution, consist of a ∼ 75:25 mixture of the (12E)‐ (1resp.12) and the (12Z)‐stereoisomer (2resp.13); indicaxanthine, in the same solvent, is made up of a ∼ 65:35 mixture of the (8E)‐ (14) and the (8Z)‐stereoisomer (15). The interconversions1⇆2,12⇆13and14⇆15in CF3COOH are so fast that these isomers cannot be separated from each other.
Bicyclo[2.2.2]octanes. Syntheses and Hydrolyses of 6‐exo‐substituted 2‐exo‐ and 2‐endo‐Bicyclo[2.2.2]octyl p‐Toluenesulfnates. Part 9
Authors: Grob Cyril A. , Sawlewicz Pawel 
Published: December 2004

AbstractThe synthesis of the title compounds and their hydrolysis products in 70% dioxane are described.
Cob(I)alamin‐Catalyzed Skeletal Migrations Observed during the Reduction of 4β‐(tert‐Butyl)‐1α‐(1‐methylvinyl)cyclohexanecarbaldehyde
Authors: Wan Terence S. , Fischli Albert 
Published: December 2004

AbstractThe cob(I) alamin(1(I))‐catalyzed2 transformation of the aldehyde 2 has been studied (cf. Table 1). Kinetic examinations showed a rapid isomerization of 2 to 3 (cf. Fig. 1 and 2). From the transformations in glacial AcOH, the two cyclopropanols 5 and 7 were isolated as main products (cf. Tables 1–3 and Fig. 1 and 2). Using large amounts of 1(I), the aldehyde 4 was very slowly transformed. Accepting the intermediate formation of 6 interconnected Co‐complexes, i. e. A, B, C, D, E and F (cf. Scheme), the generation of all the products observed can be explained.
Studies on Monoterpene Glucosides and Related Natural Products Part 51. Absolute Structures of Hydrangenosides A, B, C, D, E, F, and G. Novel Type Secoiridoid Glucosides from Two Hydrangea Plants
Authors: Uesato Shinichi , Takeda Yoshio , Hashimoto Toshihiro , Uobe Kenichi , Inouye Hiroyuki , Taguchi Heihachiro , Endo Toru 
Published: December 2004

AbstractFrom Hydrangea macrophylla var. Macrophylla, four new secoiridoid glucosides, hydrangenosies A, B, C and D, were isolated, along with the known iridoid glucosides loganin, secologanin, secologanic acid and sweroside. Moreover, hydrangenosides E, F, and G, the glucosides of the same class, were isolated together with hydrangenosides C and D from Hydrangea Scandens. Based on spectroscopic and chemical methods, the novel structures of the new glucosides consisting of secologanin and a shikimate‐malonate‐derived unit which are joined by a CC bond were elucidated. However, seven other Hydrangea plants were tested and found not to contain hydrangenoside‐type glucosides.
Effect of Substituents, Solvent, and Temperature on the Reactivity of the Zwitterionic Peroxides Arising from the Photo‐Oxygenation of 2‐(Methoxymethylidene)‐ and 2‐(Phenoxymethylidene)adamantane
Authors: Jefford Charles W. , Grant Hamish G. , Jaggi Danielle , Boukouvalas John , Kohmoto Shigeo 
Published: December 2004

AbstractThe photo‐oxygenation of 2‐(methoxymethylidene)adamantane (3) creates a zwitterionic peroxide which may be captured by acetaldehyde to give the corresponding pair of diastereoisomeric tricyclo[3.3.1.13,7]decane‐2‐spiro‐6′ ‐(3′ ‐methyl‐5′ ‐methoxyl′, 2′, 4′ ‐trioxanes) (4). Ease of capture depends strongly on solvent polarity and temperature. When these are low, yields of trioxine are high (∼ 80%). Conversely, 1,2‐dioxetane formation is favoured at high temperature and solvent polarity. 2‐(Phenoxymethylidene)adamantane (5), on photo‐oxygenation, only gives the corresponding 1,2‐dioxetene, even in the presence of acetaldehyde. From a Hammett, study of the‐oxygenation of the enol ether 5 and p‐methoxy, p‐methyl, p‐chloro and m‐chloro derivatives, 9, 11, 13, and (15), a good linear relation was found between substituent constants and oxygenation rates which yielded reaction constants (ρ) of 2.59, −2.40, −1.09, and −0.90 in benzene, AcOET, CH2Cl2, and MeOH respectively. This data to the formation of a zwitterionic peroxide which enjoys stabilization from its won substituents and by competing solvation and further explains the predominance of dioxetane to the detriment of trioxane formation.
Biogenetic‐Type Total Synthesis of (±)‐2‐Deoxystemodinone. Preliminary Communication
Authors: Lupi Alessandro , Patamia Maria , Grgurina Ingeborg , Bettolo Rinaldo Marini , Di Leo Ornella , Gioia Patrizia , Autnaroli Simonetta 
Published: December 2004

AbstractA biogenetic‐type total synthesis of(±)‐2‐deoxystemodinone (1), by solvolytic rearrangement of the 1‐methyl[2.2.2]oct‐2‐yl methanesulphonate 4, is described.
Probes for a Regulatory Site on the Nicotinic Acetylcholine Receptor‐Channel. Synthesis of (±)‐7‐Debutylperhydrohistrionicotoxin, (±)‐2‐Depentyl‐7‐debutylperhydrohistrionicotoxin, and their Analogues
Authors: Gessner Wieslaw , Takahashi Kimio , Witkop Bernhard , Brossi Arnold , Albuquerque Edson X. 
Published: December 2004

AbstractReaction of glutarimide with pent‐4‐enylmagnesium bromide, followed by cyclization of intermediate ketoamide, and hydrolysis of the formates 10 and 13 led to the mixture of the hydroxylactams 11 (cis) and 14 (trans) which could be separated via their benzenecarbamates. Reduction of cis‐hydroxylactam 11 with LiAlH4 yielded 2‐depentyl‐7‐debutylperhydrohistrionicotoxin (6), whereas reduction of trans‐isomer 14 gave the epimeric alcohol 9. cis‐Hydroxylactam 11 was converted via thiolactam 17 and the methylthio derivative 18 to ketimine 19 which was reduced with NaBH4 yielding a mixture of natural 4 and unnatural 7, analogues of perhydrohistrionicotoxin (2). Reduction of 4 with H2 in the presence of Pd/C yielded (±)‐7‐debutylperhydrohistrionicotoxin (5).
Halochrome Molekeln. 5. Mitteilung. Synthese substituierter 6H‐Chromeno[4,3‐b]indolizine und ihrer Aza‐analogen
Authors: Gunzenhauser Sigmund , Balli Heinz 
Published: December 2004

Halochromic Molecules. Synthesis of Substituted 6H‐Chromeno[4,3‐b]indolizines and their Aza‐analoguesWe have synthesized a series of substituted chromeno[4,3‐b]indolizines and their respective aza‐analogues. Dyes generated from them contain the electrondonating 2‐(2‐hydroxy‐5‐methylphenyl)indolizin‐3‐yl moiety. The 90 MHz FT 1H‐NMR spectra of starting and final products supported the postulated structures. Fragmentations in the mass spectra also were consistent with the assumed structures.
Syntheses of Racemic Diaminosugar Derivatives Starting from 1,2‐Dihydropyridines and from Nitrosobenzene
Authors: Augelmann Gérard , Streith Jacques , Fritz Hans 
Published: December 2004

AbstractRacemic diaminosugars were easily obtained by a regio‐ and stereoselective three‐step synthetis. In the first step, regiospecific hetero‐Diels‐Alder cycloadditions between 1,2‐dihydropyridines 1a and 10 and nitrosobenzene led to the bicyclic compounds 2a and 11, respectively, cis‐Glycol formation starting from these latter adducts, followed by hydrogenolysis of the NO bond and by exhaustive acetylation of the OH‐groups, led to the diaminolyxose 5, the diaminomannose 14 and the diaminoallose 15. When starting from benzyl 1,2‐dihydropyridine‐1‐carboxylate (1b) and using the same reaction sequence, the racemic piperidine derivative 8 was obtained.
Steric Effects on Reaction Rates. VI. Application of a New MM2 Force‐Field for Carbenium Ions to Solvolysis Rates of Secondary p‐Toluenesulfonates
Authors: Müller Paul , Mareda Jiri 
Published: December 2004

AbstractAn empirical force‐field for carbenium ions has been incorporated in Allinger's MM2 programme. Structural parameters of secondary carbenium ions calculated by this method are compared with those obtained with Schleyer's BIGSTRN calculations. The strain changes occurring upon solvolysis of secondary p‐toluenesulfonates are evaluated by means of this force‐field and correlated with the rate constants for solvolysis. The equation for correlation of acetolysis, relative to cyclohexyl p‐toluenesulfonate, of 28 kc substrates is ΔG = 0.67 ΔEst ‐ 0.20 (r = 0.958).
Alkylierung in der 2‐Stellung von (2S, 4R)‐ 4‐Hydroxyprolin unter Retention
Authors: Weber Theodor , Seebach Dieter 
Published: December 2004

Alkylation in the 2‐Position of (2S, 4R)‐4‐Hydroxyproline with Retention of ConfigurationO‐Acetyl‐4‐hydroxyproline (1b) is condensed with pivalaldehyde to give a single stereoisomer of the 2‐(tert‐butyl)‐4‐oxo‐3‐oxa‐1‐azabicyclo[3.3.0]oct‐7‐yl acetate (3). This is converted to the enolates 4 or 5, reactions of which with alkyl halides, aldehydes, and acetone (→6,9,10,11) are diastereoselective (lk‐1,3‐induction). Cleavage of the corresponding products furnishes the enantiomerically pure 2‐deuterio‐, 2‐methyl‐, 2‐allyl‐, and 2‐benzyl‐substituted 4‐hydroxyprolines 2a–2d.
d6 and d8 Metal Carbonyl Complexes of 7,7‐Dimethoxy‐5,6‐dimethylidenebicyclo[2.2.1]hept‐2‐ene. Stereoselective Hydroformylation of an [Fe(CO)4(olefin)] Complex
Authors: Loset Jacques , Roulet Raymond 
Published: December 2004

AbstractReaction of 7,7‐dimethoxy‐5,6‐dimethylidenebicyclo[2.2.1]hept‐2‐ene (2) with various metal carbonyls and their derivatives gave the η2‐M(CO)4 (M = Fe (17), Ru (18)), η4‐M(CO)3 (M = Fe (19x, 19n), Ru (20n)), and η2‐M(CO)5 and η6‐M(CO)3 (M = Cr, Mo, W) complexes. The trigonal bipyramidal η2‐M(CO)4 complexes present an exceptional C3v symmetry at the metal with the C,C‐double bond in an axial position. In all the η2‐complexes, this double bond is stereospecifically coordinated by its exo‐vs. endo‐η4‐Fe(CO)3 configuration was established by chemical correlation (hydrolysis, hydrogenation) with the corresponding complexes (24x, 24n) of 7,7‐dimethoxy‐2,3‐dimethylidenebicyclo[2.2.1]heptane (5). The relative rates of hydrolysis (AcOH/H2O 2:1, 50°C) of ligands 2 and 5 and of complexes 19x, 19n, 24x, and 24n to the corresponding ketones showed an acceleration effect only when the metal is coordinated to the exo‐face. This was attributed to an F‐strain effect on the leaving group of the substrate. Compound 17 was further metallated by [Fe2(CO)9] giving the bimetallic isomers 21xn and 21xx. The endocyclic C,C‐double bond of the latter can be stereospecifically hydroformylated (1 atm CO, AcOH/H2O, 25°C) giving 29x (49%). Hydroformylation of 17 gave the corresponding uncoordinated aldehydes 30x/30n in better yields (76%) but with lower selectivity (3:1). These are the first examples of hydroformylation of an isolated [Fe(CO)4(olefin)] complex.
Investigation of the Cyclopentenone Formation via the α‐Alkynone Cyclisation: Synthesis of the Acorone Intermediate 8‐Methylspiro[4.5]deca‐3,7‐dien‐2‐one
Authors: Ackroyd John , Karpf Martin , Dreiding André S. 
Published: December 2004

AbstractAs a further application of the cyclopentenone formation A→C via the thermal α‐alkynone cyclisation B→C and in order to test the fate of an isolated C,C‐double bond within a molecule under these conditions, we investigated the synthesis of the acorone intermediate 3starting from the known carboxylic acid 1. The α‐alkynone 2 was obtained from 1 via the acyl chloride 6 and a Pd(II)‐catalysed route (22%). The thermolysis of 2 at 550° provided the target molecule 3 (48%) together with the product 9 (20%) of a competing intramolecular ene reaction and its dimer 10 (4%). At a higher thermolysis temperature (650°), the spiro ketone 3 was found to be unstable, affording the retro‐Diels‐Alder fragments 4‐methylidene‐2‐cyclopentenone (12) (33%) and isoprene (32%). A further example of the influence of an isolated double bond on the yield of the cyclopentenone‐formation sequence A→C was provided by the comparison of the annelation 14→20 (5% overall with Pd(II)‐catalysed acylation) with that of its non‐olefinic analogue 17→21 (53% overall with Friedel‐Crafts acylation).
Light‐Induced and Thermal π‐Skeletal Rearrangement of Heptalenes with Retention of Configuration
Authors: Bernhard Werner , Brügger Paul , Schönholzer Peter , Weber Roland H. , Hansen Hans‐Jürgen 
Published: December 2004

AbstractIt is shown that dimethyl 5, 6, 8, 10‐tetramethyl‐ (3) and 8‐ (tert‐butyl)‐5,6,10‐trimethylheptalene‐1, 2‐dicarboxylate (5), and their derivatives rearrange reversibly on irradiation or on heating to yield the corresponding 1,6,8,10‐tetramethyl‐ (4) and 8‐(tert‐butyl)‐1,6,10‐trimethylheptalene‐1,2‐dicarboxylate (6), and their derivatives by double‐bond shift (π‐skeletal rearrangement) via a transition state with D2 symmetry as the highest possible one. This follows from the fact that (−)‐(P)‐3 is photochemically as well as thermally rearranged to give (−)‐(P)‐4 i.e. the π‐skeletal rearrangement occurs with retention of configuration of the heptalene skeleton and without loss of optical purity.
Peptide conformations. Part 30. Assignment of the 1H‐, 13C‐, and 15N‐NMR spectra of cyclosporin A in CDCl3 and C6D6 by a combination of homo‐ and heteronuclear two‐dimensional techniques
Authors: Kessler Horst , Loosli Hans‐Rudolf , Oschkinat Hartmut 
Published: December 2004

AbstractThe 1H‐, 13C‐, and 15N‐NMR spectra of the immunosuppressive cyclic undecapeptide cyclosporin A (1) have been analyzed at 300 MHz in CDCl3, C6D6, and mixtures of these solvents. A combination of different homo‐ and heteronuclear two‐dimensional NMR techniques enable complete assignment of all H‐, C‐ and 4 N‐signals. Recognition of the proton spin systems has been achieved via 1H,1H–COSY and double‐quantum‐1H‐NMR spectroscopy. NOESY spectra yield some sequence assignments, but two techniques using coupling across amide bonds have been applied to get independent assignments of all amino acids in the sequence: (i) An 1H,1H‐COSY spectrum optimized for small coupling constants enables the detection of long‐range couplings from N‐methyl groups to both α‐protons attached to that amide bond. (ii) An 1H, 13C‐COSY spectrum optimized for C,H‐long‐range couplings (J = 5 to 10 Hz) to the eleven CO groups again yields coupling to both α‐protons attached to that amide bond. Additionally these two experiments yield the assignment of N‐methyl protons and carbonyl C‐atoms. Normal and relayed 1H,13C‐COSY in both solvents have been applied to assign all C‐atoms via their directly attached and remote protons. An 1H,13C‐COLOC spectrum at 500 MHz in CDCl3, which uses H,C‐long‐range couplings confirms the assignment of all proton spin systems as well as the C‐signals of each individual amino acid. Ambiguities in the assignment of the C(δ)'s of MeLeu have thus been removed. An 1H,15N‐COSY spectrum enables the assignment of the 4 NH N‐atoms.
Peptide conformations. Part 31. The conformation of cyclosporin a in the crystal and in solution
Authors: Loosli Hans‐Rudolf , Kessler Horst , Oschkinat Hartmut , Weber Hans‐Peter , Petcher Trevor J. , Widmer Armin 
Published: December 2004

AbstractThe all‐light‐atom X‐ray crystal‐structure analysis of cyclosporin A (1), a cyclic undecapeptide containing seven N‐methylated amino acids, reveals a conformation very similar to that of the previously analysed iodo derivative which is characterised by a twisted β‐pleated sheet involving the residues Me‐Val‐11, MeBmt‐1, Abu‐2, Sar‐3, MeLeu‐4, Val‐5, MeLeu‐6, and Ala‐7. The β‐bend at Sar‐MeLeu‐4 is of type II′, and the loop of the residual amino acids involves a cis‐peptide bond between MeLeu‐9 and MeLeu‐10. The NH proton of D‐Ala‐8 closes a yi‐bend with a H‐bond to the MeLeu‐6 CO group. The crystal was grown from acetone. A closely similar backbone conformation in apolar solvents such as CDCl3 or C6D6 has been derived from the interpretation of the NMR spectral parameters (homo‐ and heteronuclear NOE effects, coupling constants, chemical‐shift values of the C‐, H‐, and N‐atoms). A minor variation in the backbone conformation between crystal and solution is observed in the region of D‐Ala‐8, where in solution a 3‐center H‐bond is established between the NH of D‐Ala‐8 und the carbonyl O‐atoms of both MeLeu‐6 (yi‐turn) and D‐Ala‐8 (C5‐bend). A recently proposed technique to identify intramolecular H‐bond via heteronuclear NOE from NH proton to carbonyl C‐atoms is critically analysed. The main difference between crystal and solution conformations lies in the orientation of the side chains of the unusual amino acid MeBmt (χ1 = +60° in solution, ‐168° in the crystal) and of MeLeu‐10 (X1 = −60° in solution, +60° in the crystal). The differences in crystal and solution are caused by the break of the intermolecular H‐bond of the OH group of MeBmt on dissolution of the crystal. The bifurcated H‐bond of D‐Ala‐8 twists the backbone in this region. Molecular modeling demonstrates that this is the origin of the change in the side chain conformation of MeLeu‐10. The intramolecular flexibility in the crystal indicated by the thermal parameters obtained from the X‐ray refinement, and in solution by an analysis of spin‐lattice relaxation times in the NMR experiments, indicate a fairly rigid backbone and fixed conformations for all the side chains except for that of Abu‐2 and the distal atoms of MeBmt.
Synthesis of 1H‐Cyclopropa[b]naphthalenes via Trapping of o‐Benzoquinodimethanes
Authors: Müller Paul , Rodriguez Domingo 
Published: December 2004

Abstract1H‐Cyclopropa[b]naphthalene (10a) and 3‐methyl or dimethyl derivatives have been synthesized by interception of appropriately substituted o‐quinodimethanes 3 with 1‐bromo‐2‐chlorocyclopropene 5, and subsequent dehydrohalogenation of the adducts. The o‐quinodimethane derivatives 3 in turn were obtained from the diynes 7 via base‐induced isomerization to bisallenes 8 and thermal electrocyclic ring closure.
Photooxygenolytic Degradation of the Vitamin‐B12 Derivative Heptamethyl Coα,Coβ‐Dicyanocobyrinate. Efficient Preparation of Bicyclic Fragments
Authors: Kräutler Bernhard , Stepánek René 
Published: December 2004

AbstractThe methylene‐blue sensitized photooxygenation of heptamethyl Coα,Coβ‐dicyanocobyrinate (1, cobester) at ca. −45° and in (D3)acetonitrile solution proceeds readily to the stage of selective double cleavage of the corrin macrocycle. It furnishes the bisected heptamethyl Coα,Coβ‐dicyano‐5,6:14,15‐tetraoxo‐5,6:14,15‐disecocobyrinate (3) in 91% yield after warming the photooxygenation mixture to room temperature. Complex 3 is also obtained by photooxygenation of the secocorrinoid oxygenation products of 1, namely of heptamethyl Coα,Coβ‐dicyano‐5,6‐dioxo‐5,6‐secocobyrinate (2a) and of its isomer heptamethyl Coα,Coβ‐dicyano‐14,15‐dioxo‐14,15‐secocobyrinate (2b). When the raw photooxygenation product of 1 is kept at low temperature, 3 is not formed in a significant amount; spectral analysis reveals 4 as intermediate that is transformed into 3 quantitatively upon warm‐up and storage at r.t. Compound 4 is assigned the structure of heptamethyl Coα,Coβ‐dicyano‐5,6‐epidioxy‐5,6‐dihydro‐14,15‐dioxo‐14,15‐secocobyrinate, based on NMR‐spectral data and since 4 is also formed cleanly in the corresponding low‐temperature photooxygenation of 2b. Catalytic reduction of the Co(III) complex 3 (H2, Pt/C) in the presence of EDTA produces a colourless oil, from which the bicyclic fragments 5 (corresponding to rings A and D of 1) and 6 (corresponding to rings B and C of 1) are obtained in 99 and 91% yield, respectively, after chromatographic separation.
Untersuchungen zur Carotinoidzusammensetzung in Blüten der Gartenhybride Narcissus cvv ‘Golden Harvest’
Authors: Berset Daniel , Pfander Hanspeter 
Published: December 2004

Investigation of the Carotenoid Composition in the Petals of a Garden Hybrid Narcissus cvv ‘Golden Harvest’The carotenoid composition of the petals of a yellow garden hybrid Daffodil is reported. As major compound (all‐E)‐lutein was isolated. As minor compounds phytoene, phytofluene, (all‐E)‐β‐carotene, (9Z)‐lutein, (9′Z)‐lutein, (13Z)‐lutein, violaxanthin, and luteoxanthin were identified. The position of the (Z)‐double bond of the different isomers of lutein could be proved by 1H‐NMR spectroscopy.
Physicochemical Properties of Deuterated Compounds. 8th Communication. The kinetic isotope effect for the reaction of hydrogen atoms with methylcyclohexane and perdeuteromethylcyclohexane in the gas phase
Authors: Fujisaki Noboru , Ruf Amanz , Gäumann Tino 
Published: December 2004

AbstractUsing H‐atoms produced in the radiolysis of water vapour, we determined the kinetic isotope effect for the reaction

where RH and R′D are methylcyclohexane and perdeuterated methylcyclohexane, respectively. The result obtained from the isotope competitive method can be expressed with the Arrhenius‐type equation kH/kD = (0.51 ± 0.04) exp[(8.58 ± 0.25) kJ mol−1/RT] over the temperature range from 363 to 483 K. The occurrence of H abstraction from primary, secondary, and tertiary CH bonds in methylcyclohexane is taken into consideration in the interpretation of the Arrhenius‐type expression obtained. Theoretical interpretation of the kinetic isotope effect has been achieved on the basis of the transition‐state theory and a semiempirical London‐Eyring‐Polanyi‐Sato potential‐energy surface. The tunnel effect is found to play a role in the H‐abstraction. Several methods for estimating the tunnel correction factors have been discussed.