bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrophilic Additions to Strained Bridgehead Olefins. Estimation of Strain by Comparison with the Solvolysis of Bridgehead Bromides
Authors: Becker Konrad B. 
Published: December 2004

AbstractThe addition of water, acetic acid, and hydrogen bromide to the strained bridge‐head olefins bicyclo[3.3.1]‐1(2)‐nonene (1), bicyclo[4.2.1]‐1(8)‐nonene (2), and bicyclo[4.2.1]‐1(2)‐nonene (3) gives exclusively the bridgehead alcohols, acetates, and bromides, respectively. The reaction rate constants for the addition of acetic acid to the bridgehead olefins 1,2 and 3, and the solvolysis rates for the related 1‐bromo‐bicyclo[3.3.1]nonane (4) and 1‐bromobicyclo[4.2.1]nonane (5) were measured. A comparison of the activation enthalpies of these two reactions gives an estimate of relative strain of the bridgehead double bond. The strain in the bicyclo[4.2.1]nonenes 2 and 3 is similar to that in trans‐cyclooctene (8‐9 kcal/mol).
Pyridinderivate als Komplexbildner. XI. Die Thermodynamik der Metallkomplexbildung mit Bis‐, Tris‐ und Tetrakis[(2‐pyridyl)methyl]‐aminen
Authors: Anderegg Giorgio , Hubmann Egon , Podder Nitya G. , Wenk Fritz 
Published: December 2004

Pyridine Derivatives as Complexing Agents XI. Thermodynamics of Metal Complex Formation with Bis‐, Tris‐ and Tetrakis[(2‐pyridyl)methyl]‐amines.The equilibria between H+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Cd2+, Pb2+, Hg2+ and Ag+, and the ligands bis(2‐pyridylmethyl)‐amine (=DPA), tris(2‐pyridylmethyl)‐amine (=TPA), tris(6‐methyl‐2‐pyridylmethyl)‐amine (=TLA) and N,N,N′,N′‐tetrakis(2‐pyridylmethyl)‐ethylenediamine (=TPEN) have been studied. Only the stability constants of DPA and TLA with almost all these cations were obtained using the pH method. For the other ligands, the complexes are already formed in acid solutions and only the use of different ligand‐ligand or metal‐metal exchanges as well as of pM methods were successful.The protonation constants indicate that for DPA the protonation occurs firstly at the aliphatic nitrogen atom whereas in all other cases only the pyridine groups can be protonated. The thermodynamic functions of protonation are in agreement with this interpretation.The stability constants of the complexes are often similar in magnitude to those of the analogous aliphatic amines, in spite of the much lower basicities of the pyridine derivatives. The Fe(II)N6 species of DPA and TPEN are appreciably more stable than those of the corresponding aliphatic ligands. This is due to the formation of low‐spin complexes with an unexpected ΔH value. Comparison of the thermodynamic data of formation of the complexes with TPA and TLA shows the effect of the three bulky methyl groups of the second ligand. As a consequence of steric hindrance and of the major dehydration, ΔH and less ΔS are more positive for M(TLA)2+ than for M(TPA)2+. Therefore M(TLA)2+ is normally much less stable than M(TPA)2+. The data for MnTPA2+ and ZnTPA2+ appear to indicate that in these complexes the coordination number of the metal ion is seven and four respectively. In addition to the complexes ML2+, with these two ligands hydroxo complexes ML(OH)+ are formed at remarkably low pH. Further TPEN seems to be sexidentate in the 1:1 complexes with Mn2+, Co2+ and Ni2+ but quinquedentate in those with Cu2+ and Zn2+, also in agreement with the spectra in solution and of the solid complex salts. The reaction: M(DPA)22+ + TPEN → M(TPEN)2+ + 2DPA is for all metal ions favoured by ΔH and ΔS, whereas in the case of the corresponding aliphatic ligands only by the second term. This result is explained in terms of a different magnitude of hydration of the two sexidentate ligands as a consequence of the presence of the hydrophobic aromatic rings in TPEN.
Metabolites of microorganisms. 162nd Communication. The crystal and molecular structure of lysolipin I
Authors: Dobler Max , Keller‐Schierlein Walter 
Published: December 2004

AbstractThe triacetate of the antibiotic lysolipin (1) crystallizes in the space group P21, a = 11.059, b = 21.453, c = 8.423 Å, β = 109.76°. X‐ray analysis was used to determine the structure of this compound.
Analyse des spectres de vibration infrarouge et Raman de benzothiazolines et de 2H‐chromènes, éléments constitutifs de spiropyrannes benzothiazoliniques. Aspect synthétique
Authors: Davin‐Pretelli Eliane , Guiliano Michel , Mille Gilbert , Chouteau Jacques , Guglielmetti Robert , Gelebart Christian 
Published: December 2004

Study of infrared and Raman spectra of benzothiazolines and 2H‐chromenes, constitutive parts of benzothiazolinic spiropyrans. Synthetic aspect.We have synthesized some benzothiazolines and some substituted 2 H‐chromenes as models of the two halves of benzothiazolinic spiropyrans with the aim of interpretation of infrared and Raman spectra of spiropyranic structure.While doing that, we have been able to improve the synthesis method of chromenes obtained from coumarins and we have prepared new nitro‐chromenes. By studying IR. and Raman spectra of the two halves of spiropyranic molecule, we could propose a rather good attribution of fondamental modes of vibration. This attribution will used as base for the interpretation of IR. and Raman spectra of a series a benzothiazolinic spiropyrans.
Synthèse de deux nouveaux acides amines phénoliques comportant un cycle 1,2,4‐oxadiazole
Authors: Moussebois Claude , Heremans Joseph F. , Merenyi Robert , Rennerts Walthère 
Published: December 2004

Synthesis of two phenolic amino acids containing the 1,2,4‐oxadiazole ringThe synthesis of α‐amino‐β [3‐(p‐hydroxyphenyl)‐1,2,4, oxadiazol‐5‐yl]propionic acid (9) and its β‐amino isomer (10) (see scheme 3) is reported. By condensation of p‐benzyloxy‐benzamide oxime and N‐benzyloxycarbonyl asparagine the derivatives 4 and 5 (see scheme 1) are obtained leading after deprotection to 9 and 10. The synthesis of N‐carboxyanhydride of 4 (6) and its corresponding amino acid (7) and amide (8) is also described.
Herstellung von Hilfsstoffen für die asymmetrische Synthese aus Weinsäure. Addition von Butyllithium an Aldehyde in chiralem Medium
Authors: Seebach Dieter , Kalinowski Hans‐Otto , Bastani Bahram , Crass Gerhard , Daum Hermann , Dörr Hennig , Dupreez Nicolaas P. , Ehrig Volker , Langer Werner , Nüssler Christa , Oei Hoc‐An , Schmidt Manfred 
Published: December 2004

Preparation of Auxiliaries for Asymmetric Syntheses from Tartaric Acid. Additions of Butyllithium to Aldehydes in Chiral Media.Chiral derivatives of the complexing 1,2‐diheterosubstituted ethanesA–Dare prepared from tartaric acid. The key starting materials are the succinic acid derivative1, the dioxolane2a, and the diamide3a. These are converted to the ethers, alkoxyamines, and alkylthio‐amines listed in the first column of Table 2 which also contains the derivatives21c, 22d, and23dmade from lactic acid, malic acid, and proline, respectively. It is shown that the highest optical yields (up to 40%) in reactions of butyllithium with aldehydes are obtained when mixtures of (−)‐1,2,3,4‐tetramethoxy‐butane (4b), (+)‐2,3‐dimethoxy‐N,N,N′,N′‐tetramethyl‐1,4‐butanediamine (17a), and (−)‐1,4‐dimethoxy‐N,N,N′,N′‐tetramethyl‐2,3‐butanediamine (14c) with pentane are used at temperatures down to −150° and ratios of auxiliary/butyllithium of up to 10:1 (see equation (1), Tables 2–4).
Photolytic closure of 4,5‐diphenyl‐oxazol‐2‐ones to phenanthro[9,10‐d]oxazol‐2‐ones and an improved synthesis of benzoins
Authors: Hakimelahi Gholamhosein H. , Boyce Charles B. , Kasmai Hamid S. 
Published: December 2004

AbstractThe synthesis of phenathrenes substituted by nitrogen and oxygen atoms in position 9 and 10 by photolysis of 4,5‐diphenyl‐oxazol‐2‐ones (cf. Scheme 4) is described. Moreover an improved general procedure for the synthesis of benzoins in aprotic solvent (tetra‐t‐butylammonium cyanide in DMF/DMSO) is developed.
Reaktionen mit phosphororganischen Verbindungen. XLII. Nucleophile Substitutionen an Hydroxysteroiden mit Hilfe von Triphenylphosphan/Azodicarbonsäureester
Authors: Loibner Hans , Zbiral Erich 
Published: December 2004

Nucleophilic Substitution Reactions of Hydroxysteroids using Triphenylphosphane/diethylazodicarboxylateNucleophilic substitution reactions by means of the title reagent on various more or less hindered steroid alcohols with suitable nucleophils in benzene is described. It was not possible to run this substitution process in the hitherto used solvent THF. Cholestan‐3α‐ol (1) was transformed to the 3β‐substituted products 3β‐benzoyloxy‐cholestane (1a) and 3β‐azido‐cholestane (1b). Testosterone (2) affords with the corresponding nucleophils after short heating in benzene the inverted 17α‐substituted products 3a, 3b and 3c. Analogously the 17α‐azido‐derivative 5a arises from 17β‐hydroxy‐androst‐3‐on (4). In the presence of a ketogroup in the substrate a competitive reaction can occur as it is shown in the case of cholestan‐3‐on (6): the products are the en‐hydrazo‐dicarboxylate‐steroids 7a and 7b. The sterically very hindered 11α‐position in 11α‐hydroxy‐4‐pregnen‐3,20‐dion (8) can be transformed also to the 11β‐azide 9a. The substitution of a 6β‐hydroxy group in androstane‐3β, 6β, 17β‐triol‐3,17‐diacetate (10) to the 6α‐azide 11a affords the elimination product 12 as main component. Trans‐diaxial vicinal diols such as cholestane‐2β,3α‐diol (13) give a mixture of the α‐ and β‐oxiranes 14a and 14b.
Solubility of Organic Solvents. I. Gas Chromatographic Determination of Olive Oil‐Gas Partition Coefficients
Authors: Olivier‐Droz Pierre , Fernández José 
Published: December 2004

AbstractA gas chromatographic method of measuring the olive oil‐gas partition coefficients is described. It is based on the relationship existing between the retention time of each substance and its solubility in olive oil used as a stationary liquid phase. The validity of this method has been tested by varying the length of the column, the percentage of liquid phase and the flow rate of the carrier gas. Using this technique, the partition coefficients of 24 hydrocarbons, 8 aliphatic, 6 aromatic and 10 chlorinated, have been determined (see Table 4).
Isolation, Structure Determination and Synthesis of New Acetylenic Steroids from the Sponge Calyx nicaaensis
Authors: Steiner Eric , Djerassi Carl , Fattorusso Ernesto , Magno Silvana , Mayol Luciano , Santacroce Circo , Sica Donato 
Published: December 2004

AbstractTwo acetylenic steroids, cholest‐5‐en‐23‐yn‐3β‐ol (5) and 26,27‐dinorcholest‐5‐en‐23‐yn‐3β‐ol (3), and another unsaturated steroidalcohol, stigmasta‐5,23‐dien‐3β‐ol (7), were isolated from the sponge Calyx nicaaensis. The structures of these two acetylenic steroids were established by synthesis. Several attempts to synthesize the marine steroids alcohol calysterol (1), with a cyclopropene‐containing side chain, starting from cholest‐5‐en‐23‐yn‐3β‐ol are also recorded. Addition of ethyl‐diazo‐acetate to the triple bond was performed, but the reduction to the methyl derivative yielded decomposition products.
Synthese von (±)‐α‐Chamigren. Vorläufige Mitteilung
Authors: Fráter György 
Published: December 2004

Synthesis of (±)‐α‐ChamigreneCis‐ and trans‐β‐ionol (cis and trans‐1) underwent acid catalysed dehydration to a mixture of the tetraenes 2–5 in 70–80% yield (Table 1). Irradiation of this mixtures made the 6‐(Z), 8‐(Z)‐isomer 5 accessible (columns 3 and 4 in Table 1). Pyrolysis of the different mixtures at 170° showed, that both isomers, 3 and 5 respectively undergo electrocyclization to dehydrochamigrene (6). The latter was reduced to α‐chamigrene (7) by hydrogen on Lindlar catalyst.
Etudes stéréochimiques XIV. Adduits de Diels‐Alder en série résiniques; action des peracides et ouvertures acido‐catalysées d'époxydes
Authors: Maciejewski Claude , Gastambide Bernard 
Published: December 2004

Studies in Stereochemistry XIV. Diels‐Alder adducts in the resin series; action of peracids and acid‐catalysed ring opening of epoxidesThe synthesis of Diels‐Alder compounds of type 2 with a 17‐nor‐13(14)‐atisène skeleton is described (cf. Schemes 1–3). Depending on the nature and configuration of substituents R1 and R2 on the carbon atoms 15 and 16, an epoxide (24–33) or a ketone (35–38) or a mixture of epoxide, ketone and lactone is obtained by the action of p‐nitroperbenzoic acid on the double bond of these adducts (cf. Scheme 4). A simplified reaction scheme is suggested to explain the formation of the various products. In an acid‐catalysed reaction, the epoxides isomerize mainly into ketones. Nevertherless, in some cases, dienes (e.g. 52) or hydroxy‐γ‐lactones of (13R*, 14S*)‐configuration (e.g. 50) resulting from the opening of the epoxide ring with retention of configuration were obtained.
Hélicènes pontés: Ethano‐3,15‐ et oxa‐2‐propano‐3,15‐[7]hélicène. Synthèse, spectrographie 1H‐RMN. et étude par diffraction aux rayons X
Authors: Joly Marc , Defay Nicole , Martin Richard H. , Declerq Jean Paul , Germain Gabriel , Soubrier‐Payen Bernadette , Van Meerssche Maurice 
Published: December 2004

Bridged helicenes: 3,15‐ethano‐ and 3,15‐(2‐oxapropano)‐[7]heliceneThe title compounds (35 and 33, see Scheme 4) have been synthesized from a common intermediate: 3,15‐dimethoxycarbonyl‐[7]helicene (26). The conformation of the bridged [7]helicenes (X‐ray diffraction) and their 1H‐NMR. spectra have been compared to the conformation and 1H‐NMR. spectra of [7]helicene and 3,15‐dimethyl‐[7]helicene (10).
Photochemie von tricyclischen β, γ‐γ′, δ′‐ungesättigten Ketonen. 50. Mitteilung über Photoreaktionen
Authors: Hayakawa Kenji , Schmid Hans , Fráter György 
Published: December 2004

Photochemistry of tricyclic β, γ‐γ′, δ′‐unsaturated ketonesThe easily available tricyclic ketone 1 (cf. Scheme 1) with a homotwistane skeleton yielded upon direct irradiation the cyclobutanone derivative 3 by a 1,3‐acyl shift. Further irradiation converted 3 into the tricyclic hydrocarbon 4. However, acetone sensitized irradiation of 1 gave the tetracyclic ketone 5 by an oxa‐di‐π‐methane rearrangement. Again with acetone as a sensitizer the ketone 5 was quantitatively converted to the pentacyclic ketone 6. The conversion 5 → 6 represents a novel photochemical 1,4‐acyl shift. The possible mechanisms are discussed (see Scheme 7). The tricyclic ketone 2 underwent similar types of photoreactions as 1 (Scheme 2). Unlike 5 the tetracyclic ketone 9 did not undergo a photochemical 1,4‐acyl shift. The epoxides 10 and 14 derived from the ketones 1 and 2, respectively, underwent a 1,3‐acyl shift upon irradiation followed by decarbonylation, and the oxa‐di‐π‐methane rearrangement (Schemes 3 and 4). The diketone 18 derived from 1 behaved in the same way (Scheme 5). The tetracyclic diketone 21 cyclized very easily to the internal aldol product 22 under the influence of traces of base (Scheme 5). Upon irradiation the γ, δ‐unsaturated ketone 24 underwent only the Norrish type I cleavage to yield the aldehyde 25 (Scheme 6).
Structurally Biased 2‐Fluoroallyl Cations as Generated ‐ or not Generated ‐ in Cyclopropane Ring‐opening Reactions
Authors: Schlosser Manfred , Bessière Yvonne 
Published: December 2004

AbstractThe silver ion‐catalysed ring‐opening of 2‐t‐butyl‐1‐chloro‐1‐fluoro‐2‐methyl‐cyclopropane (see Scheme 2) gave the expected mixture of primary and tertiary fluoroalkenols, whereas a tricyclic analog (bornane‐spiro‐chlorofluorocyclopropane) (see Scheme 3) exclusively underwent a Wagner/Meerwein rearrangement upon ionization to lose finally a proton affording a 2‐fluoro‐1,4‐diene.
Stereoselektive reduktive Dimerisierung von α‐Cyan‐β‐(4‐pyridyl)acrylsäurederivaten
Authors: Kompis Ivan , Schönholzer Peter 
Published: December 2004

Stereoselective Reductive Dimerisation of α‐Cyano‐β‐(4‐pyridyl)acrylic Acid DerivativesCatalytic hydrogenation of the α‐substituted β‐(4‐pyridyl)acrylonitriles 3 and 4 (see Scheme 3) yields via stereoselective reductive dimerization the substituted cyclo‐pentene derivatives 7 and 8 (see Scheme 4 and 5) instead of the expected dihydro‐products 5 and 6. The mechanism of this reaction is discussed. The structure and relative configuration of 10 have been established by X‐ray single crystal analysis.
Synthese von endo‐ und exo‐1,3‐Dimethyl‐2,9‐dioxa‐bicyclo[3.3.1]nonan
Authors: Gerlach Hans , Künzler Peter 
Published: December 2004

Synthesis of endo‐ and exo‐1,3‐dimethyl‐2,9‐dioxabicyclo[3.3.1]nonaneThe synthesis of a host‐specific substance in norway spruce infested by Trypodendron lineatum OLIV. is described (cf. scheme 1 and 2). Alkylation of the acetyl‐acetone di‐anion (II) with 3‐methyl‐3‐buten‐1‐yl‐bromide (I) followed by sodium boro‐hydride reduction yields erythro‐ and threo‐8‐methyl‐8‐nonen‐2,4‐diol (IV and V) which are separated by chromatography. Their configurations were established by converting them under equilibrium conditions into one (VI) or two (VII and VIII) benzal derivatives. Oxidative cleavage with ozone of the terminal double bond in the erythro diol IV produces a dihydroxy ketone IX which spontaneously cyclizes to endo‐1,3‐dimethyl‐2,9‐dioxa‐bicyclo[3.3.1]nonane (X). The threo diol V is converted by the same reaction sequence exclusively into exo‐1,3‐dimethyl‐2,9‐dioxa‐bicyclo‐[3.3.1]nonane (XII). Comparison of the NMR. data of the two acetals X and XII with that of the natural product establishes the endo configuration of the latter. A second, more convenient, synthesis of a mixture of the acetals X and XII starting from the bromo‐acetal XIII is also reported.
Direct Obtention of Pure Compounds from Crude Plant Extracts by Preparative Liquid Chromatography
Authors: Hostettmann Kurt , Pettei Michael J. , Kubo Isao , Nakanishi Koji 
Published: December 2004

AbstractIt has been possible to submit the crude hexane extract of the barks of a medicinal plant directly to preparative liquid chromatography. A two step solvent elution gave 6 peaks, four of which readily afforded crystalline material. The entire process required 2–3 hours whereas conventional chromatography required ca. 2 weeks.
Modellrechnungen an Hexacyanoferraten und Pentacyanoferraten mit stickstoff haltigen aromatischen Liganden
Authors: Calzaferri Gion , Felix Franz 
Published: December 2004

Model Calculations on Hexacyano‐ and Pentacyanoferrate Complexes with Aromatic Nitrogen HeterocyclesUsing the extended Hückel method, theoretically predicted chemical, photochemical and spectroscopic properties of these complexes are compared with experimental data. A better understanding of the photochemistry is attempted by analysis of the low energy CT absorption. Starting from the amminopentacyanoferrate the spectroscopic properties of the pentacyanoferrate complexes with aromatic heterocycles are described by adding the ‘d‐π*’ MLCT and the π‐π* transitions. The results obtained on the mononuclear pyrazine compounds suggest a very simple way to understand the binuclear pyrazine complexes. Some properties of the hexacyanoferrates can be better explained if all valence orbitals of the ligands are considered. In all examples the influence of the ‘π‐backbonding’ is discussed.
Mehrkernige Kobaltkomplexe. II. Herstellung und Struktur von [(tren) (NH3)Co(O2)Co(NH3) (tren)](SCN)4 · 2H2O
Authors: Thewalt Ulf , Zehnder Margareta , Fallab Silvio 
Published: December 2004

Polynuclear Cobalt Complexes. II. Preparation and Structure of [(tren) (NH3)Co(O2)Co(NH3) (tren)](SCN)4 · 2H2OThe title compound is obtained on oxygenation of [Co(tren)(H2O)2]2+ in 6M aqueous ammonia or by ligand exchange starting from [(NH3)5Co(O2)Co(NH3)5]‐(NO3)4. An X‐ray structure determination was made. The substance forms monoclinic crystals, space group P21/c, lattice constants a=10,135, b=8,473, c=19,484 Å, β=108,58°, with two formula units in the cell. The final R is 0,066. The binuclear cation has a center of symmetry, so the CoOOCo unit is planar; the CoOO angle is 111,5°. The tertiary nitrogen atoms of both chelate groups are cis to the O2 bridge, as found in doubly bridged [(tren)Co(O2,OH)Co(tren)](ClO4)3 · 3H2O.On acidification in solution, the singly bridged cation [(tren) (NH3)CoO2Co(NH3)(tren)]4+ (a) loses the bound O2 completely. But unlike the doubly bridged cation b, the rate of dissociation of a is independent of pH (Fig. 5). At higher pH (8–10) bridging a→b (Fig. 2) occurs. Both reactions must have the same rate determining step, the first order rate constants being of the order of 2 · 10−3 s−1 (25°, 0,35M KCl).
Nouveaux types de sucres acétyléniques. Communication préliminaire
Authors: Tronchet Jean M. J. , Bonenfant Alain 
Published: December 2004

Novel types of acetylenic sugarsThe coupling, following Cadiot's procedure, of a 6‐bromo‐5,6‐dideoxy‐1,2‐O‐isopropylidène‐3‐O‐methyl‐α‐D‐xylo‐hex‐5‐yno‐1, 4‐furanose (1) with phenylacetylene, 2‐propyn‐1‐ol or terminal acetylenic sugars gave with excellent yields the expected diynes (an enediyne when the terminal acetylene was the 3,5, 6‐trideoxy‐1,2‐O‐isopropylidene‐α‐D‐glycero‐hex‐3‐en‐5‐yno‐1,4‐furanose 7). The chloro analogue 8 of 1 on treatment with lithium thiophenate gave the corresponding phenylthio‐acetylenic sugar 9. An acetylene was also formed by reacting the gem‐difluoro‐olefinic sugar 10 with butyllithium whereas the same olefinic sugar and its 3‐O‐benzyl analogue 11 gave only a gem‐fluoro‐arylthio‐olefinic sugar (13–15) as a mixture of the Z and E isomers (Z/E > 4) when treated with the conjugate base of an arylmercaptan.
The Photochemistry of 2‐Cyclopentenyl Methyl Ketones
Authors: Gonzenbach Hans‐Ulrich , Tegmo‐Larsson Inga‐Mai , Grosclaude Jean‐Pierre , Schaffner Kurt 
Published: December 2004

Abstract2‐Cyclopentenyl and 3‐phenyl‐2‐cyclopentenyl methyl ketones (15–18, 30, 31) undergo a 1,3‐acetyl shift on direct irradiation, and the oxa‐di‐π‐methane rearrangement to photochemically non‐interconverting endo and exo bicyclo‐[2.1.0]pentyl methyl ketones on triplet sensitization. Exceptions include the 2‐methyl‐3‐phenyl‐2‐cyclopentenyl methyl ketone 32 and the 1‐phenyl‐2‐cyclo‐pentenyl methyl ketone 44 which are unreactive on direct irradiation and on triplet sensitization, respectively, and the 2‐phenyl‐2‐cyclopentenyl methyl ketones 42 and 43 which do not react under either condition. The reactive triplet of the 3‐phenyl‐2‐cyclopentenyl methyl ketone 30 has been identified as the localized styrene π,π*‐state of ET=59 kcal/mol by comparison of its phosphorescence at 77K in rigid glasses with that of 1‐phenyl‐cyclopentene, and by the independence of the quantum yield on sensitizer energy in the range of 61–74 kcal/mol.
N‐Alkyl‐2‐pyrrolidones as Derivatives for the Structure Elucidation of Long‐chain Primary Alcohols by Mass Spectrometry
Authors: Vetter Walter , Meister Walter , Oesterhelt Gottfried 
Published: December 2004

AbstractOne unsaturated and three branched long‐chain primary alcohols have been converted into N‐alkyl‐2‐pyrrolidones for investigation by mass spectrometry. The EI. mass spectra of these derivatives have been found to exhibit unambiguously the branching points and, albeit less clearly, the position of a double bond in the chain.
Diterpenoide Drüsenfarbstoffe: Coleon L, ein neues Diosphenol aus Coleus somaliensis S. MOORE; Revision der Strukturen von Coleon H, I, I′ und K
Authors: Rüedi Peter , Eugster Conrad Hans 
Published: December 2004

Leaf‐gland Pigments: Coleon L, a New Diosphenolic Compound from Coleus somaliensis, S. MOORE; Revision of the Structures of Coleon H, I, I′ and KFrom leaf‐glands of C. somaliensis a new, highly oxidized diosphenolic hydroquinone belonging to the abietane series was isolated in minute quantities. The new compound, coleon L (4c; C24H30O10), is very labile and transformed into its tautomer coleon K (5d) on standing in solution. 1H‐NMR. spectra of coleon L showed clearly that the points of attachment of the two acetoxy groups are at C(3) and C(16) contrary to the positions expected from our previously published structure 3 for coleon K. Application of a recently elaborated conversion of trans‐A/B‐6,7‐diketones of type 5 into the cis‐isomers 6 allowed to assign unambiguously the β‐configuration to the hydroxyl group at C(3) using pyridin induced solvent shifts. This confirmed structure 4c and 5d for coleon L and K, respectively. Based on similar reasons, the configuration at C(3) of coleon H, I and I′ had to be revised, the structures of these coleons being 4b, 5b and 5c, respectively.