bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conformations of the 10‐membered Ring in 5, 10‐Secosteroids. II. (E)‐3α‐Acetoxy‐5, 10‐seco‐1 (10)‐cholesten‐5‐one and (E)‐5, 10‐seco‐1 (10)‐cholestene‐3, 5‐dione
Authors: Fuhrer Hermann , Lorenc Ljubinka , Pavlović Vladimir , Rihs Grety , Rist Günther , Kalvoda Jaroslav , Mihailović Mihailo Lj. 
Published: December 2004

Abstract(E)‐3α‐Acetoxy‐5, 10‐seco‐1(10)‐cholesten‐5‐one (3) was synthesized by fragmentation of 3α‐acetoxy‐5α‐cholestan‐5‐ol (1) using the photochemical version [3] of the lead tetraacetate reaction [4], and transformed into the corresponding 3‐oxo‐compound (5). Two conformations (A and B) were deduced for the 10‐membered ring of 3 by analysis of the 1H‐ and 13C‐NMR. spectra in toluene. The major conformation (A) corresponds to that found in the solid state by X‐ray analysis. According to its NMR. spectra in toluene, the medium‐sized ring of the diketone 5 exists also predominantly in two conformations, the major one being analogous to A (the solid‐state conformation of the 3β‐acetoxy isomer (9) [1]) and the minor one to A (see above). The stereochemistry of the acidcatalyzed and thermal cyclisations of 3 as well as of the corresponding 5‐oxime is discussed in terms of conformational factors.
Inhaltsstoffe des Osmanthus‐Absolues 6. Mitteilung. (7S, 10S, 5E)‐ und (7R, 10S, 5E)‐2,6,10‐Trimethyl‐7,10‐epoxy‐2,5,11‐dodecatrien
Authors: Kaiser Roman , Lamparsky Dietmar 
Published: December 2004

Constituents of Osmanthus Absolute, 6th Communication. (7S, 10S, 5E)‐ and (7R, 10S, 5E)‐2,6,10‐Trimethyl‐7,10‐epoxy‐2,5,11‐dodecatrieneTwo novel sesquiterpenoid oxides 1a and 1b from Osmanthus absolute have been identified. Their structural proof is based on pectral data and synthesis starting from the known methyl [5‐methyl‐5‐vinyl‐tetrahydrofur‐1‐yl] ketones (4a and 4b, respectively), whose configuration is well established. The thus obtained compounds 1a/1b identical with the natural products, were accompanied by their corresponding 6‐methylidene isomers 3a and 3b which could not be detected in the natural substrate.
Ringerweiterungsreaktionen von N‐(2‐Aminoäthyl)‐, N‐(4‐Aminobutyl)‐, N‐(6‐Amino‐4‐aza‐hexyl)‐ und N‐(8‐Amino‐4‐aza‐octyl)‐lactamen. 7. Mitteilung über Umamidierungsreaktionen
Authors: Stephanou Euripides , Guggisberg Armin , Hesse Manfred 
Published: December 2004

Ring Enlargement Reactions of N‐(2‐Aminoethyl)‐, N‐(4‐Aminobutyl)‐, N‐(6‐Amino‐4‐aza‐hexyl)‐ and N‐(8‐Amino‐4‐aza‐octyl)‐lactamesThe N‐aminoalkyl‐lactams 1, 3, 4, 10 (Scheme 2) and 13 (Scheme 3) have been synthesized. In the presence of KAPA (potassium 3‐aminopropylamide in 1,3‐propanediamine) 1 is stable, whereas 3, 4 and 10 rearrange under ring enlargement to 5, 8 and 11, respectively. The 4‐aminobutyl derivate 13 rearranges in a fast reaction to 14; after a longer reaction time the 22membered ring 16 and the ring opened product 18 are formed. Hence it may be concluded that the 7membered lactam ring is more stable than the 10membered one, and the 11membered lactam ring is more stable than the 8 membered one. Moreover, the 5‐ and 6 membered ring intermediates of these transamidation reactions are prefered to the 7membered ring intermediates (cf. [10]).
Neue Phellandren‐Derivate aus dem Wurzelöl von Angelica archangelicaL
Authors: Escher Sina , Keller Urs , Willhalm Bruno 
Published: December 2004

New Phellandrene Derivatives from the Root Oil of Angelica archangelica L.2‐Nitro‐1,5‐p‐menthadiene (5), trans‐ and cis‐6‐nitro‐1(7), 2‐p‐menthadiene (6 and 7), trans‐1(7), 5‐p‐menthadien‐2‐yl acetate (9) and a formal phellandrene derivative, 7‐isopropyl‐5‐methyl‐5‐bicyclo [2.2.2]octen‐2‐one (16), have been identified in the root oil of Angelica archangelica L. Starting from (−)‐(R)‐α‐phellandrene (1) (R)‐5, (4R, 6S)‐6/(4R, 6R)‐7, (2S, 4R)‐9 and (1R, 4R, 7R)‐16 as well as (2S, 4R)‐11, (2R, 4R)‐12 and (2R, 4R)‐10 have been prepared.
Réaction d'ylures stabilisés sur des aldéhydosucres: influence de divers facteurs dont la structure de l'aldéhydosucre sur le pourcentage d'isomères géométriques obtenu
Authors: Tronchet Jean M. J. , Gentile Bernard 
Published: December 2004

Reactions of stabilized ylides with aldehydosugars: influence of some factors, particularly the structure of the aldehydosugar, on the ratio of the geometrical isomers formedAldehydosugars bearing no cis‐substituent on the C‐atom β to the carbonyl group (2, 3, 6, 7) or bearing a substituent without an electron lone‐pair (5) gave, upon treatment with acetylmethylidenetriphenylphosphorane, exclusively the E‐isomer, this representing the classical behaviour of aldehydes. On the other hand, aldehydosugars having a lone‐pair bearing substituent (1, 4, 8, 9) gave a mixture of E‐ and Z‐isomers. In the case of most of the aldehydosugars of the latter type (giving some Z‐isomer) a partial epimerization of the C‐atom α to the carbonyl group took place when the solvent of the Wittig reaction was HCONMe2. It is probable that the presence of an electron lone‐pair in the adequate position inhibits the reversion of the kinetic erythro‐betaine, allowing the formation of the Z‐isomer and, in particular solvent conditions, a cycloelimination leading to the epimeric aldehydosugar which ultimately reacts to give the epimeric E‐enone.
Transition Metal Complexes with Bidentate Ligands Spanning trans‐Positions. VIII. The reactions of the nucleophile trans‐[RuCl(NO)(1)] (1 = 2,11‐bis(diphenylphosphinomethyl)benzo[c]‐phenanthrene) with carbon monoxide and the phosphite ligand (2) (2 = 1‐ethyl‐3,5,8‐trioxa‐4‐phosphabicyclo (2.2.2)octane)
Authors: Holderegger Rolf , Venanzi Luigi M. , Bachechi Fiorella , Mura Pasquale , Zambonelli Luigi 
Published: December 2004

AbstractThe preparation of the nucleophile trans‐[RuCl(NO)(1)], where 1 is the bidentate ligand Ph2PCH2C18CH2PPh2, and of the five‐coordinate species [RuCl(CO)(NO)(1)], [RuCl(CO)(NO)(Ph2PCH2Ph)2] and [RuCl(NO)(2)(1)] are reported.The crystal structure of [RuCl(CO)(NO)(1)] shows that the coordination around the metal atom is distorted trigonal bipyramidal with the phosphorus atoms in axial positions. The RuNO bond angle is 142.8°. 1H‐ and 31P‐NMR. and \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \nu $\end{document}NO IR.‐data for the above complexes are reported and related to the coordination geometry.
Herstellung der reinen, bicyclischen Olefine Bicyclo[4.2.1]non‐2‐en, Bicyclo[4.2.1]non‐3‐en und Bicyclo[4.2.1]non‐7‐en
Authors: Stamm Erich , Leu Hans‐Rudolf , Keese Reinhart 
Published: December 2004

Synthesis of the pure, bicyclic olefines Bicyclo[4.2.1]non‐2‐ene, Bicyclo[4.2.1]non‐3‐ene and Bicyclo[4.2.1]non‐7‐eneThe synthesis of the olefines bicyclo[4.2.1]non‐2‐ene (3), bicyclo[4.2.1]non‐3‐ene (4) and bicyclo[4.2.1]non‐7‐ene (5) of high ‘certified’ purity from one common precursor (7) is described.
The Acid‐catalyzed Hydrolysis of CF3‐deactivated Diazoalkanes
Authors: Dahn Hans , Lenoir John Henri 
Published: December 2004

AbstractThe acid‐catalyzed hydrolysis of CF3CHN2 (1) follows an A2 mechanism of preequilibrium protonation and rate‐determining solvolysis of the intermediate diazonium ion 4; this was demonstrated by: (a) the inverse kinetic isotope effect; (b) H‐D exchange; (c) the unimportance of general acid catalysis; (d) strong rate acceleration by added nucleophiles. The activation parameters have been determined in two solvent systems. In contrast to 1 the secondary diazocompound CF3CN2CH3 (2) follows the normal A‐SE2 mechanism of rate‐determining proton transfer.
Umsetzungen von Dilithio‐nitroalkanen und ‐allylnitroderivaten mit Carbonylverbindungen
Authors: Lehr Friedrich , Gonnermann Jutta , Seebach Dieter 
Published: December 2004

Reactions of dilithio‐nitroalkanes and dilithio‐allynitroalkanes with carbonyl compoundsPrimary nitro compounds can by acylated via dilithium derivatives 5 with carbonic‐acid derivatives to give α‐nitro esters 6a–i and with carboxylic‐acid esters and anhydrides to give α‐nitroketones 6j–q. In the reaction of 1‐nitro‐1‐buten with two mol‐equiv. of butyllithium, the dilithium compound 10 is formed by successive Michael‐addition and nitronate deprotonation. Dilithium derivatives 5 also react with ketones and benzaldehyde (→18a–g); the nitro aldols 25 and 26 are likewise formed by addition of doubly deprotonated allylic nitro compounds. Some of the products have been further transformed by reduction or by Nef‐reactions to the hydrochloride of the α‐amino‐acid 26, to 2‐amino‐alcohols 28a and 28b, to α‐hydroxyamino‐acid esters 27a–c, to α‐hydroxyimino esters 35 and 36, to α‐hydroxyimino ketones 31 and 33, to the α‐diketone 34, and to the α‐keto ester 37.
Favorskii‐Umlagerung in Gegenwart von 3,4‐Dimethoxyfuran: 11endo‐oxa‐tricyclo [4.3.1.12,5]undec‐3‐en‐10‐on und Derivate
Authors: Matzinger Peter , Eugster Conrad Hans 
Published: December 2004

Favorskii‐rearrangement in the presence of 3,4‐dimethoxyfuran: preparation of 3,4‐dimethoxy 11endo‐oxo‐tricyclo [4.3.1.12,5]undec‐3‐en‐10‐one and any derivativesOn treatment with sodiumhydride of 2‐chloro‐cyclohexanone in the presence of 3,4‐dimethoxyfuran, a possible intermediate of the Favorskii‐rearrangement has been trapped as 3,4‐dimethoxy‐11endo‐oxa‐tricyclo [4.3.1.12,5]undec‐3‐en‐10‐one (3). This new compound contains a highly nucleophilic double bond. It can be cleaved in high yield by ozonolysis to 2exo, 4exo‐bis (methoxycarbonyl)‐3‐oxabicyclo [3.3.1]nonan‐9‐one (4). Addition of chlorine to 3 occurs in stereoselective exo‐cis‐manner to the crystalline 3exo, 4exo‐dichloro‐3endo,4endo‐dimethoxy 11endo‐oxa‐tricyclo [4.3.1.12,5]undecan‐10‐one (5). Silver ion assisted hydrolysis of 5, followed by thermal treatment of the intermediate hydrates, leads to the red 11endo‐oxa‐tricyclo [4.3.1.12,5]undecan‐3,4, 10‐trione (6), and methanolysis to 3,3,4,4‐tetramethoxy‐11endo‐oxa‐tricyclo [4.3.1.12,5]undecan‐10‐one (8). By photolytic decarbonylation, 8 is converted into 3,3,4,4‐tetramethoxy‐10‐oxa‐tricyclo‐[4.3.12,5.0]decan (9).
The Effects of Homoconjugated Cyclopropane and Oxirane Rings on the Diels‐Alder Reactivity of 2,3‐bis (methylidene)norbornane
Authors: Pilet Olivier , Chollet André , Vogel Pierre 
Published: December 2004

AbstractPreparation of 6exo, 7exo‐bis (methylidene)‐tricyclo[3.2.1.02,4]octane (6) is described. The reactivity of 6 towards tetracyanoethylene is evaluated and compared with that of exo‐2,3‐epoxy‐5,6‐bis (methylidene)norbornane (5), 2,3‐bis‐(methylidene)norbornane (1) and other related dienes. The cyclopropane group in 6 exerts an unsignificant rate retardation effect on the Diels‐Alder reactivity of this diene relative to that of 1, whereas a relatively important rate retardation effect is caused by the exo‐oxirane ring in 5. The observed effects are probably due to electronic factors (through‐space and through‐bond interactions).
Cob(I)alamin als Katalysator, 5. Mitteilung [1]. Enantioselektive Reduktion α,β‐ungesättigter Carbonylderivate
Authors: Fischli Albert , Süss Daniel 
Published: December 2004

Cob(I)alamin as Catalyst. 5. Communication [1]. Enantioselective Reduction of α,β‐Unsaturated Carbonyl DerivativesThe cob(I)alamin‐catalyzed reduction of an α,β‐unsaturated ethyl ester in aqueous acetic acid produced the (S)‐configurated saturated derivative 2 with an enantiomeric excess of 21%. The starting material 1 is not reduced at pH = 7.0 in the presence of catalytic amounts of cob(I)alamin (see Scheme 2). It is shown that the attack of cob(I)alamin and not of cob(II)alamin, also present in Zn/CH3COOH/H2O, accounts for the enantioselective reduction observed. All the (Z)‐configurated starting materials 1, 3, 5, 7, 9 and 11 have been transformed to the corresponding (S)‐configurated saturated derivatives 2, 4, 6, 8, 10 and 12, respectively. The highest enantiomeric excess revealed to be present in the saturated product 12 (32,7%, S) derived from the (Z)‐configurated methyl ketone 11 (see Scheme 3 and Table 1). The reduction of the (E)‐configurated starting materials led mainly to racemic products. A saturated product having the (R)‐configuration with a rather weak enantiomeric excess (5.9%) has been obtained starting from the (E)‐configurated methyl ketone 23 (see Scheme 5 and Table 2). The allylic alcohols 16 and 24 have been reduced to the saturated racemic derivative 17.
Alkali Cation Complexation and Transport Properties of Synthetic Bicyclic Decapeptides: Structural, Thermodynamic, and Kinetic Analysis
Authors: Moeschler Hans J. , Sargent David F. , Tun‐Kyi Aung , Schwyzer Robert 
Published: December 2004

AbstractAlkali cation complexation and bilayer transport by the bicyclic decapeptides S,S′‐bis‐cyclo‐glycyl‐L‐hemicystyl‐glycyl‐glycyl‐L‐prolyl (1), S, S′‐bis‐cyclo‐glycyl‐L‐hemicystyl‐glycyl‐glycyl‐D‐prolyl (2), S, S′‐bis‐cyclo‐glycyl‐L‐ hemicystyl‐sarcosyl‐sarcosyl‐L‐prolyl (3), and S, S′‐bis‐cyclo‐glycyl‐L‐hemicystyl‐sarcosyl‐sarcosyl‐D‐prolyl (4) were analyzed according to structural, thermodynamic and kinetic criteria; valinomycin was used as a reference ionophoretic system.Structural analysis of peptide 3 with spectroscopic methods showed different conformational arrangements in the bicyclic system depending on its state of complexation. Circular dichroism indicated the presence of a multitude of conformations with differing helicities around the disulfide bridge in both free and complexed states.Thermodynamic analysis by microcalorimetry demonstrated a far lower cation selectivity among the synthetic peptides than displayed by valinomycin. Peptide 3 shows cation affinities of about two orders of magnitude higher than peptide 4, but still much lower than found for the complexes of valinomycin with K+ and Rb+. In contrast to the latter case, the complexation reactions of peptides 3 and 4 are driven by both enthalpy and entropy contributions. Neither peptide 1 and 2 nor the cyclic partial structures of all four peptides displayed significant cation complexation.A kinetic analysis of the K+‐complexation by peptide 3 based on the microcalorimetry experiments showed far lower rates of cation exchange for the synthetic peptide than those reported for valinomycin. Transport studies with peptide 3 using artificial lipid bilayer membranes gave negative results. The apparent lack of ionophoretic properties of these synthetic peptides despite their considerable ability to form complexes with cations is discussed in terms of structural parameters.
Herstellung einiger verzweigter Paraffine im oligomeren Bereich
Authors: Zeltner Peter , Huber Gustav A. , Peters Reinhard , Tátrai Ferenc , Boksányi László , sz. Kováts Ervin 
Published: December 2004

Synthesis of some branched paraffins of high molecular weightSynthesis and properties of two series of branched paraffins of high molecular weight are described. In the course of the preparation of one of the starting materials the Wolff‐Kishner reduction of a sterically hindered ketone, unstable in basic medium, has been elaborated.
The Removal of S‐Cysteine Protection by Means of 2‐Pyridine Sulfenyl Chloride and the Subsequent Formation of Disulfide Bonds. Preliminary communication
Authors: Castell José V. , Tun‐Kyi Aung 
Published: December 2004

Abstract2‐Pyridine sulfenyl chloride (PS‐Cl) is a useful reagent for simultaneously deprotecting and activating the mercapto‐group of cysteine and of cysteine‐peptides preliminary to disufide‐bond formation. The S‐protecting groups that are amenable to this reaction include trityl, diphenylmethyl, acetamidomethyl, t‐butyl, and t‐butylsulfenyl.
The Structure of the Antibiotic Hedamycin. V. Crystal structure and absolute configuration
Authors: Zehnder Margareta , Séquin Urs , Nadig Heinz 
Published: December 2004

AbstractThe crystal structure of the antibiotic hedamycin (1) has been solved by direct method and refined by least squares techniques to R = 0.091 for 2289 of 2643 independent reflexions. Crystals of C41H50N2O11 are orthorhombic, space group P212121 with lattice parameters a = 24.239 (12), b = 21.440 (10), c = 7.369 (4) Å, Z = 4. The structural features of hedamycin derived earlier by chemical and spectroscopical means are confirmed. Optical rotation and circular dichroism indicate that hedamycin (1) has the absolute configuration of the related antibiotic kidamycin (3). The conformation of ring F is a chair form with the aryl substituent almost axial. The bioxirane part of the antibiotic is in a synclinal conformation.
The Absolute Configuration of the Fungal Metabolite Verrucarin B. Biosynthetic Consequences. Verrucarins and roridins, 36th communication
Authors: Breitenstein Werner , Tamm Christoph , Arnold Edward V. , Clardy Jon 
Published: December 2004

AbstractThe absolute configuration of verrucarin B (2) has been determined by a single crystal X‐ray diffraction analysis. This result permits the stereochemistry of the biogenetic transformation of mevalonic acid (12) to verrucarinic acid (7) to be deduced.
Diterpenoide Drüsenfarbstoffe aus Labiaten: 11 Coleone und Royleanone aus Coleus carnosus HASSK
Authors: Yoshizaki Fumihiko , Rüedi Peter , Eugster Conrad Hans 
Published: December 2004

Diterpenoid Leaf‐Gland Pigments: 11 Coleons and Royleanones from Coleus carnosus HASSK.The above mentioned plant has been investigated for its leaf‐gland pigments. The following diterpenoids have been isolated (listed according to their elution from Sephadex LH‐20, SiO2 and polyamide; in parentheses the yield of each product in g/kg dried leafs): royleanone (1)/6,7‐dehydroroyleanone (2) (0.004, as a mixture); 7α‐acetyloxyroyleanone (3, 0.009); a novel dimeric diterpene of hitherto unknown structure (0.03); horminone (4, 0.08); 6β‐hydroxyroyleanone (5, 0.04, new as a natural product); 7α‐acetyloxy‐6β‐hydroxyroyleanone (6, 5.45); 6β, 7α‐dihydroxyroyleanone (7, 1.20); 7α‐acetyloxy‐6β, 20‐dihydroxyroyleanone (8, 0.046, a novel compound); coleon U (9, 1.32); coleon V (10, 13.84); carnosolone (6α, 11, 12‐trihydroxy‐6,20‐epoxymethano‐abieta‐8, 11, 13‐trien‐7‐one (11), 1.25, a novel compound).Therefore, this plant is one of the richest one in royleanones and coleons so far investigated by us (pure crystalline compounds 2,3%, estimated total amount > 3% of dry weight). Among the isolated compounds carnosolone (11) is of special interest being the first of a group of colourless diterpenoids from Coleus‐ and Plectranthus‐ species turning blue on TLC. Its oxydation product 12 is one of the rare 4‐acyl‐ortho‐quinones having high reactivity and characteristic spectral properties.
Eine Suche nach 3′‐Epilutein ( = (3R,3′S,6′R)‐β,ε‐Carotin‐3,3′‐diol) und 3′, O‐Didehydrolutein (=(3R, 6′R)‐3‐Hydroxy‐β,ε‐carotin‐3′‐on) in Eigelb, in Blüten von Caltha palustris und in Herbstblättern
Authors: Buchecker Richard , Eugster Conrad Hans 
Published: December 2004

Search for the Presence in Egg Yolk, in Flowers of Caltha palustris and in Autumn Leaves of 3′‐Epilutein ( =(3R,3′S,6′R)‐β,ε‐Carotene‐3,3′‐diol) and 3′,O‐Didehydrolutein ( =(3R,6′R)‐3‐Hydroxy‐β,ε‐carotene‐3′‐one)3′.O‐Didehydrolutein ( =(3R, 6′R)‐3‐hydroxy‐β,ε‐carotene‐3′‐one; 2) has been detected in egg yolk and in flowers of Caltha palustris. This is the first record for its occurrence in a plant. The compound shows a remarkable lability towards base; therefore, it may have been overlooked til now, because it is destroyed under the usual conditions of saponification of the carotenoid‐esters. One of the many products formed from 2 with 1% KOH in methanol has been purified and identified as the diketone 3 ( =(3R)‐3‐hydroxy‐4′, 12′‐retro‐β,β‐carotene‐3′,12′‐dione). The identification of this transformation product from lutein might throw a new light on the metabolism of this important carotenoid in green plants.3′‐Epilutein ( =(3R,3′S,6′R)‐β,ε‐carotene‐3,3′‐diol; 1) was not detected in egg yolk, but is present besides lutein in flowers of C. palustris, thus confirming an earlier report of the occurrence of an isomeric (possibly epimeric) lutein (‘calthaxanthin’) in that plant [21].We were not able to detect even traces of 1 or 2 in the carotenoid fraction from autumn leaves of Prunus avium (cherry), Parrotia persica, Acer montanum (maple) and yellow needles of Larix europaea (larch).α‐Cryptoxanthin (4), a very rare carotenoid, was isolated in considerable quantity for the first time from flowers of C. palustris.
Substituent and Isotope Effects on the Hydrolysis Rates of 2‐Aryl‐2‐diazocarboxylic Esters
Authors: Bui‐Nguyen Mai‐Huong , Dahn Hans , McGarrity John F. 
Published: December 2004

AbstractThe overall kinetic solvent isotope effects on the acid catalyzed hydrolysis of a series of 2‐aryl‐2‐diazocarboxylic esters ArCN2COOCH3, and one 2‐aryl‐2‐diazocarboxamide C6H5CH2CON (CH3)2 vary inversely with the reactivity of the substrate, between limits of 3.14 and 1.46. A linear Hammett plot for the hydrolysis rates of the a‐diazocarboxylic esters indicates that there is no mechanistic change for the hydronium‐ion‐catalyzed reaction. The relation between hydrolysis rate and buffer acid concentration deviates from linearity for high values of the latter. It is shown on the basis of the solvent isotope effects for the non‐linear region that this deviation does not stem from a mechanistic change caused by the buffer base component. The specific salt effects on the general acid‐catalyzed reaction are discussed.
Photofragmentation of Dibenzyl Ketone in the Presence of Tetramethylpiperidine Derivatives. Studies on light stabilizer mechanisms [1]
Authors: Felder Bruno , Schumacher Rolf , Sitek Franciszek 
Published: December 2004

AbstractThe interaction of selected tetramethylpiperidine derivatives with radicals arising from the Norrish‐type I cleavage of dibenzyl ketone under oxygen was studied. Product analyses and kinetic studies showed that the investigated sterically hindered piperidine derivatives have a pronounced effect on both the nature and distribution of the products of photolysis of dibenzyl ketone in the presence of oxygen. Observations indicated that the phenylperacetoxyl radical is formed as an intermediate during irradiation and that it interacts with the additives used. Possible mechanisms of the reactions studied are discussed.The observation that oxidation of an isolated double bond by the radicals formed in dibenzyl ketone photolysis under oxygen is strongly inhibited in the presence of the studied sterically hindered amines is discussed in the light of the results presented. The findings are considered in relation to the problem of polymer stabilization.
Herstellung vonerythro‐2‐Hydroxybernsteinsäure‐Derivaten aus Äpfelsäureester. Vorläufige Mitteilung
Authors: Seebach Dieter , Wasmuth Daniel 
Published: December 2004

Preparation forerythro‐2‐Hydroxy‐succinic Acid Derivatives from Malic EstersAs a contribution to the much discussed diastereoselective synthesis of enantiomers of open chain compounds, > 90%erythro‐selective branching of malic esters by alkylation of the doubly deprotonated derivative2(alkoxide‐enolate) with methyl, allyl, and benzyl halides in THF at −78° (→3aa, 3ba, 3bb, 3bc,Table 1) is described. A second alkylation (→4) and addition of2to acetone (→5) are also possible. Cyclization of2to the enantiomerically puretrans‐epoxides6is achieved by treatment with iodine. Cuprate opening of6bfurnishes the same product3baobtained from the methylation of2b, establishing the configurational assignment.
Contribution à la phytochimie du genre Gentiana. XXV. Etude des composés flavoniques et xanthoniques dans les feuilles de Gentiana X marcailhouana RY. Nouveaux cinnamoyl‐C‐glucosides flavoniques
Authors: Luong Par Minh Duc , Fombasso Pierre , Jacot‐Guillarmod André 
Published: December 2004

Phytochemistry of genus Gentiana XXV: Study of the flavonic and xanthonic compounds in leaves of Gentiana X marcailhouana RY. New cinnamoyl‐C‐glucosyl‐flavonesNine flavonic compounds: isoorientin (1), isovitexin (2), isoorientin‐4′‐O‐β‐D‐glucoside (3), isovitexin‐4′‐O‐β‐D‐glucoside (4), luteolin‐7‐O‐β‐D‐glucoside (5), trans‐cafeoyl‐2′′‐isoorientin (6), trans‐feruloyl‐2′′‐isoorientin (7), trans‐p‐coumaroyl‐2′′‐isoorientin (8), p‐O‐β‐D‐glucosyl‐trans‐cafeoyl‐2′′‐isoorientin (9) and three xanthones: gentioside (10), isogentisine (11), mangiferin (12), have been identified from leaves of Gentiana X marcailhouana RY. Compounds 8 and 9 were described for the first time. The cyclitol L‐(+)‐bornesitol (13) has been also isolated.