bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Spirocyclic Tetrahydrofuran Derivatives of Monocyclonerolidol
Authors: Schulte‐Elte Karl H. , Umiker Thomas , Ohloff Günther 
Published: December 2004

AbstractEighteen new sesquiterpenoid theaspirane derivatives 3–20, representing potential natural compounds, were synthesized from 1,2‐didehydro‐β‐monocyclonerolidol (1). Their structure and configuration were determined by spectroscopic methods.
Ein einfacher Zugang zu 3‐Amino‐nocardicinsäure. Modifikationen von Antibiotika. 17. Mitteilung [1]
Authors: Schaffner‐Sabba Karl , Müller Beat W. , Scartazzini Riccardo , Wehrli Hansuli 
Published: December 2004

A Simple Route to 3‐Amino‐nocardicinic AcidStarting from nocardicin A (1), a novel and efficient procedure for the preparation of 3‐amino‐nocardicinic acid (4) and its protected derivatives 6 and 8–11 is described.
Strukturelle Abwandlungen an partiell silylierten Kohlenhydraten mittels Triphenylphosphin/Azodicarbonsäure‐diäthylester. 3. Mitteilung [1]
Authors: Brandstetter Hannelore H. , Zbiral Erich 
Published: December 2004

Structural Modification on Partially Silylated Carbohydrates by Means of Triphenylphosphine/Diethyl AzodicarboxylateReaction of methyl 2, 6‐bis‐O‐(t‐butyldimethylsilyl)‐β‐D‐glucopyranoside (1a) with triphenylphosphine (TPP)/diethyl azodicarboxylate (DEAD) and Ph3P · HBr or methyl iodide yields methyl 3‐bromo‐2, 6‐bis‐O‐(t‐butyldimethylsilyl)‐3‐deoxy‐β‐D‐allopyranoside (3a) and the corresponding 3‐deoxy‐3‐iodo‐alloside 3c (Scheme 1). By a similar way methyl 2, 6‐bis‐O‐(t‐butyldimethylsilyl)‐α‐D‐glucopyranoside (2a) can be converted to the 4‐bromo‐4‐deoxy‐galactoside 4a and the 4‐deoxy‐4‐iodo‐galactoside 4b. In the absence of an external nucleophile the sugar derivatives 1a and 2a react with TPP/DEAD to form the 3,4‐anhydro‐α‐ or ‐β‐D‐galactosides 5 and 6a, respectively, while methyl 4, 6‐bis‐O‐(t‐butyldimethylsilyl)‐β‐D‐glucopyranoside (1b) yields methyl 2,3‐anhydro‐4, 6‐bis‐O‐(t‐butyldimethylsilyl)‐β‐D‐allopyranoside (7a, s. Scheme 2). Even the monosilylated sugar methyl 6‐O‐(t‐butyldimethylsilyl)‐α‐D‐glucopyranoside (2b) can be transformed to methyl 2,3‐anhydro‐6‐O‐(t‐butyldimethylsilyl)‐β‐D‐allopyranoside (8; 56%) and 3,4‐anhydro‐α‐D‐alloside 9 (23%, s. Scheme 3). Reaction of 1c with TPP/DEAD/HN3 leads to methyl 3‐azido‐6‐O‐(t‐butyldimethylsilyl)‐3‐deoxy‐β‐D‐allopyranoside (10). The epoxides 7 and 8 were converted with NaN3/NH4Cl to the 2‐azido‐2‐deoxy‐altrosides 11 and 13, respectively, and the 3‐azido‐3‐deoxy‐glucosides 12 and 14, respectively (Scheme 4 and 5). Reaction of 7 and 8 with TPP/DEAD/HN3 or p‐nitrobenzoic acid afforded methyl 2,3‐anhydro‐4‐azido‐6‐O‐(t‐butyldimethylsilyl)‐4‐deoxy‐α‐ and ‐β‐D‐gulopyranoside (15 and 17), respectively, or methyl 2,3‐anhydro‐6‐O‐(t‐butyldimethylsilyl)‐4‐O‐(p‐nitrobenzoyl)‐α‐ and ‐β‐D‐gulopyranoside (16 and 18), respectively, without any opening of the oxirane ring (s. Scheme 6). ‐ The 2‐acetamido‐2‐deoxy‐glucosides 19a and 20a react with TPP/DEAD alone to form the corresponding methyl 2‐acetamido‐3,4‐anhydro‐6‐O‐(t‐butyldimethylsilyl)‐2‐deoxy‐galactopyranosides (21 and 22) in a yield of 80 and 85%, respectively (Scheme 7). With TPP/DEAD/HN3 20a is transformed to methyl 2‐acetamido‐3‐azido‐6‐O‐(t‐butyldimethylsilyl)‐2,3‐didesoxy‐β‐D‐allopyranoside (25, Scheme 8). By this way methyl 2‐acetamido‐3,6‐bis‐O‐(t‐butyldimethylsilyl)‐α‐D‐glucopyranoside (19b) yields methyl 2‐acetamido‐4‐azido‐3,6‐bis‐O‐(t‐butyldimethylsilyl)‐2,4‐dideoxy‐α‐D‐galactopyranoside (23; 16%) and the isomerized product methyl 2‐acetamido‐4,6‐bis‐O‐(t‐butyldimethylsilyl)‐2‐deoxy‐α‐D‐glucopyranoside (19d; 45%). Under the same conditions the disilylated methyl 2‐acetamido‐2‐deoxy‐glucoside 20b leads to methyl 2‐acetamido‐4‐azido‐3,6‐bis‐O‐(t‐butyldimethylsilyl)‐2,4‐dideoxy‐β‐D‐galactopyranoside (24). ‐ All Structures were assigned by 1H‐NMR. analysis of the corresponding acetates.
IsoméRisation avant la perte d'eau des ions aldéhydes et cétones protonés en spectrométrie de masse
Authors: Audier Par Henri Edouard , Milliet Arielle , Tabet Jean‐Claude 
Published: December 2004

Isomerization of Protonated Aldehyde and Ketone Ions in the Mass‐Spectrography Before the Loss of WaterIn mass spectrometry, protonated aldehyde and ketone ions isomerize before the loss of a molecule of water. In order to specify this process, the spectra of deuterium labelled protonated aldehydes and ketones have been compared to the spectra of the corresponding isomer ions.
Total Synthesis of Indole and Dihydroindole Alkaloids. XVIII. Isomers and analogues of vinblastine
Authors: Kutney James P. , Honda Toshio , Kazmaier Peter M. , Lewis Norman J. , Worth Brian R. 
Published: December 2004

AbstractThe synthesis and conformational analysis of (3′R)‐3‐hydroxyleurosidine (5), (3′S)‐3‐hydroxyleurosidine (10), (3′S)‐3‐acetoxy‐4′‐deoxyleurosidine (15), (3′R)‐3‐acetoxy‐4′‐deoxyleurosidine (23), (3′R)‐3‐acetoxy‐4′‐deoxyvinblastine (16), (3′S)‐3‐acetoxy‐4′‐deoxyleurosidine (28) is discussed.
Zur Synthese sulfonierter Derivate von 2,3‐Dimethylanilin und 3,4‐Dimethylanilin
Authors: Courtin Alfred , Tobel Hans‐Rudolf Von 
Published: December 2004

On the Synthesis of Sulfonated Derivatives of 2,3‐Dimethylaniline and 3,4‐DimethylanilineBaking the hydrogensulfate salt of 2,3‐dimethylaniline (1) or of 3,4‐dimethylaniline (2) led to 4‐amino‐2,3‐dimethylbenzenesulfonic acid (4) and 2‐amino‐4,5‐dimethylbenzenesulfonic acid (5), respectively (Scheme 1). The sulfonic acid 5 was also obtained by treatment of 2 with sulfuric acid or by reaction of 2 with amidosulfuric acid. 3‐Amino‐4,5‐dimethylbenzenesulfonic acid (3) and 5‐Amino‐2,3‐dimethylbenzenesulfonic acid (6) were prepared by sulfonation of 1,2‐dimethyl‐3‐nitrobenzene (9) to 3,4‐dimethyl‐5‐nitrobenzenesulfonic acid (11) and of 1,2‐dimethyl‐4‐nitrobenzene (10) to 2,3‐dimethyl‐5‐nitrobenzenesulfonic acid (12), respectively, with subsequent Béchamp reduction (Scheme 1). Preparations of 2‐amino‐3,4‐dimethylbenzenesulfonic acid (7) and of 6‐amino‐2,3‐dimethylbenzenesulfonic acid (8) were achieved by the sulfur dioxide treatment of the diazonium chlorides derived from 3,4‐dimethyl‐2‐nitroaniline (24) and from 2,3‐dimethyl‐6‐nitroaniline (31) to 3,4‐dimethyl‐2‐nitrobenzenesulfonyl chloride (29) and 2,3‐dimethyl‐6‐nitrobenzenesulfonyl chloride (32), respectively, followed by hydrolysis to 3,4‐dimethyl‐2‐nitrobenzenesulfonic acid (30) and 2,3‐dimethyl‐6‐nitrobenzenesulfonic acid (33), and final reduction (Scheme 3). Compound 7 was also synthesized by reaction of 4‐chloro‐2,3‐dimethylaniline (23) with amidosulfuric acid to 2‐amino‐5‐chloro‐3,4‐dimethylbenzenesulfonic acid (20) and subsequent hydrogenolysis (Scheme 2). 4′‐Bromo‐2′, 3′‐dimethyl‐acetanilide (13) and 4′‐chloro‐2′, 3′‐dimethyl‐acetanilide (14) on treatment with oleum yielded 5‐acetylamino‐2‐bromo‐3,4‐dimethylbenzenesulfonic acid (17) and 5‐acetylamino‐2‐chloro‐3,4‐dimethylbenzenesulfonic acid (18), respectively. Their structures were proven by hydrolysis to 5‐amino‐2‐bromo‐3,4‐dimethylbenzenesulfonic acid (21) and 5‐amino‐2‐chloro‐3,4‐dimethylbenzenesulfonic acid (22), followed by reductive dehalogenation to 3.
Über Pterinchemie. 73. Mitteilung [1]. Zum Verlauf der katalytischen Reduktion von 7‐Methylpterin
Authors: Ganguly Abhoy N. , Sengupta Pradip K. , Bieri Jost H. , Viscontini Max 
Published: December 2004

On the Pathway of the Catalytic Reduction of 7‐MethylpterinThe catalytic hydrogenation of 7‐methylpterin (VII) in a neutral solution occurs first by the reduction of the 7,8‐double bond (thermodynamically‐controlled reaction) followed by the reduction of the 5,6‐double bond. On the contrary, in an acidic medium like CF3COOH, the 5,6‐double bond is reduced first (kinetically‐controlled reaction). The dihydro‐intermediate then undergoes a [1,2]‐H‐rearrangement leading to the formation of the thermodynamically more stable 7‐methyl‐7,8‐dihydropterin (XV) which on further reduction gives 7‐methyl‐5,6,7,8‐tetrahydropterin (VIII). The catalytic reduction of 7‐methyl‐7,8‐dihydropterin (XV) with deuterium gives stereoselectively a sole product with D at C(6) in the equatorial position.
Synthèse de N‐Alkyl‐arylamines par Thermolyse ou Photolyse d'Alkyl‐3‐diaryl‐1,3‐triazènes
Authors: Julliard Par Michel , Vernin Gaston , Metzger Jacques 
Published: December 2004

Synthesis of N‐Alkyl‐arylamines by Thermolysis or Photolysis of 3‐Alkyl‐1,3‐bis(p‐chlorophenyl)triazenesThe thermolysis of 3‐alkyl‐1,3‐bis(p‐chlorophenyl)triazenes in benzene or methanol leads to the formation of N‐alkyl‐p‐chloroanilines (2) in 19–50% yield, N‐alkyl‐bis(p‐chlorophenyl)amines (3) in 7.5–15.5% yield and 4,4′‐dichlorobiphenyle (4) in 1–7% yield; besides with benzene as the substrate, 4‐chlorobiphenyle (5) (12–20% yield) was also formed. The photolysis in methanol gives only the N‐alkyl‐p‐chloroanilines (2) in 32–40% yield. In these two cases the results are consistent with a radical pair formation in a solvent cage, recombination (thermolysis) and/or diffusion (thermolysis and photolysis) with intermolecular abstraction of hydrogen. A free radical chain mechanism is involved in the photolytic process and the quantum yield is high.
Photochemical Rearrangement of a Steroidal α,β‐Epoxylactone. Photochemical reactions, XI [1]
Authors: Caus María Jesús , Cánovas Antonio , Bonet Juan‐Julio 
Published: December 2004

AbstractThe UV. irradiation of 17β‐acetoxy‐4α, 5α‐epoxy‐2‐oxaandrostan‐3‐one (7) yields 17β‐acetoxy‐2‐oxa‐10(5 → 4)abeo‐4ζ (H)‐androsta‐3,5‐dione (11). A non‐photochemical synthesis of 11, proceeding in lower yield, is also described.
Specific Ligands for the Affinity Chromatography of Cholinergic Proteins
Authors: Riggio Gaetano , Hopff Wolfgang Herbert , Hofmann Alfred André , Waser Peter Gaudenz 
Published: December 2004

AbstractAffinity chromatography of proteins requires a ligand covalently bound to a solid support separated by a spacer of sufficient length. In the specific case of acetyl‐cholinesterase we have reduced the conventional spacer synthesis from five to three steps.For affinity chromatography of cholinergic proteins the ideal ligand would be acetylcholine which, however, could not be used because it is easily hydrolyzed. We synthesized hydrolysis‐resistent ligands. Different specific ligands were synthesized for the affinity chromatography of serum esterase.
Aromatic Radical Anions in Neat Aromatic Hydrocarbons as Solvents. Direct evidence of through space spin‐density transfer to the ligand of the counter ion
Authors: Belser Peter , Desbiolles Guy , Ochsenbein Ueli , von Zelewsky Alexander 
Published: December 2004

AbstractContact ion pairs of aromatic radical anions, with a crown ether complex of potassium as cation in a neat aromatic hydrocarbon, can be obtained by reducing the aromatic hydrocarbon in which a small amount of crown ether is dissolved. The unpaired electron stays attached to one aromatic molecule during a time interval which is long on the ESR. time scale. The radicals are stabilized by ion‐pair formation in the low polarity solvent. As a consequence of this stabilization, radicals of compounds with low electron affinities, e.g. mesitylene, can be prepared. Mesitylene, m‐xylene, and toluene show additional hyperfine splitting in the ESR. spectra of their anion radical pairs of the order of 18 μT. The proton ENDOR. spectra have signals at the corresponding frequencies, indicating a hyperfine coupling with protons of the crown ether ligand. Using mixtures of two aromatic compounds, their relative electron affinities can be determined by studying the temperature dependence of the radical concentrations.
Notiz zur Synthese von (E)‐12‐Hydroxy‐10‐heptadecensäure, (5E, 10E)‐12‐Hydroxy‐5, 10‐heptadecadiensäure und (5Z, 10E)‐12‐Hydroxy‐5,10‐heptadecadiensäure
Authors: Kienzle Frank 
Published: December 2004

Note on the Synthesis of (E)‐12‐Hydroxy‐10‐heptadecenoic Acid, (5E, 10E)‐12‐Hydroxy‐5, 10‐heptadienoic Acid and (5Z, 10E)‐12‐Hydroxy‐5,10‐heptadienoic AcidThe syntheses of two heptadecadienoic and one heptadecenoic acid, compounds which formally may be derived from prostaglandin‐like molecules by removal of a C3‐fragment from the five‐membered ring, are described.
Photochemische reaktionen. 108. Mitteilung. Photochemistry of N‐acylazoles. VI. Photoreactivities of 1‐acyl‐1,2,4‐triazoles and of 2‐acyltetrazoles
Authors: Murato Kazuo , Yatsunami Takashi , Iwasaki Shigeo 
Published: December 2004

AbstractContrary to the findings in the photolysis of N‐acylimidazoles [2] irradiation of 1‐acyl‐1,2,4‐triazoles afforded no photo‐Fries product, but instead products formed via the corresponding acyl radicals and aldehydes. Photolysis of 2‐acyltetrazoles gave in part the same products as those obtained from the irradiation of the corresponding acyl‐triazoles as well as 2‐alkyl‐1,3,4‐oxadiazoles. N‐Acyltetrazoles didn't give any photo‐Fries product neither.
Synthesen und pharmakologische Eigenschaften von 2,2‐Dialkyl‐5‐aryl‐3‐pyridylpyrrolidinen
Authors: Aeppli Lislott , Bernauer Karl , Schneider Fernand , Strub Konrad , Oberhänsli Willi E. , Pfoertner Karl‐Heinz 
Published: December 2004

Syntheses and Pharmacological Properties of 2,2‐Dialkyl‐5‐aryl‐3‐pyridylpyrrolidinesReaction of the photochemically generated benzonitrile methylides 2 with vinylpyridines yields 2‐aryl‐4‐pyridyl‐1‐pyrrolines 3. Depending on reduction methods, the compounds 3 are selectively transformed to the corresponding cis‐ or the trans‐substituted pyrrolidines 10 or 11, respectively. Furthermore, a non‐photochemical synthesis has been developed: the easily available nitro‐ketones 8 provide through reductive cyclization the pyrrolines 3 or directly the pyrrolidines 11. Twenty‐seven compounds of types 10 and 11 have been evaluated in the writhing, hot plate and kaolin tests; especially the cis‐pyrrolidines 10 exhibit a valuable antinociceptive activity. Some of the pyrrolines and pyrrolidines have been separated into their enantiomers, which are easily interconverted.
Natural Abundance17O‐NMR. Study of Some Macrocyclic Complexes with Alkali Metal Cations
Authors: Popov Alexander I. , Smetana Alfred J. , Kintzinger Jean‐Pierre , Nguyêen Thi Thanh‐Tâam 
Published: December 2004

AbstractComplexation between crown ethers 12C4, 15C5, 18C6 and cryptand 222, and alkali cations Li+, Na+, K+in various solvents were studied by17O‐NMR. spectroscopy. Small diamagnetic shifts arising from the cation electric field are observed. They increase according to the sequence K+< Na+< Li+.17O‐linewidth are discussed and compared to the13C relaxation times. Linewidth modification results mainly from modifications of the effective correlation time. In general, for crown ethers, considerable line broadening occurs when the cation fits well into the cavity but line narrowing occurs when the cation is much smaller than the cavity.
Complete Racemization in the Base Hydrolysis of Optically Active mer‐[Chloro(diethylene triamine) (1,3‐diaminopropan‐2‐ol‐N,N′) cobalt (III)]tetrachlorozincate
Authors: Comba Peter , Marty Werner 
Published: December 2004

AbstractThe base hydrolysis of the optically active title compound proceeds with full racemization whilst the meridional arrangement of the diethylenetriamine ligand is fully retained. The optically active hydroxo complex prepared independently with retention of configuration racemizes ≳ 104 times slower. This unique result is discussed in terms of the classical π‐stabilization hypothesis for the base hydrolysis mechanism.
Stereospezifische 1,2‐Wanderungen von Hydroxyl‐, Aryl‐ und Alkyl‐ gruppen bei der Nitrosierung von Aminosäuren in Fluorwasserstoff/Pyridin. Vorläufige mitteilung
Authors: Keck Rolf , Rétey János 
Published: December 2004

Stereospecific 1,2‐Migration of Hydroxyl, Aryl and Alkyl Groups during the Nitrosation of Amino Acids in Hydrogenfluoride/Pyridine Vorläufige MitteilungThe nitrosation of α‐amino acids in hydrogenfluoride/pyridine was reinvestigated. In contrast to recent reports [1] [2] it was found that this reaction takes place either with entire (phenylalanine, tyrosine, threonine) or partial (valine, isoleucine) rearrangement to yield β‐fluorocarboxylic acids. Glycine, alanine and α‐aminobutanoic acid were converted exclusively into the α‐fluorocarboxylic acids. The substitution of the amino group takes place with stereochemical retention as revealed by NMR. examination of the 2‐fluoro‐3‐methylpentanoic acids obtained from L‐isoleucine and D‐alloisoleucine, respectively.
Synthesis of Tricyclo [6.2.1.01,5]undecadiones via Intramolecular Photoaddition of 5‐(1‐Cyclopentenylmethyl)‐3‐alkoxy‐2‐cyclopentenones
Authors: Oppolzer Wolfgang , Burford Sidney C. 
Published: December 2004

AbstractIrradiation of the dienone methyl ether 3a furnished the unstable regioisomeric photoadducts 4a and 5a which on Lewis acid‐catalyzed fragmentation afforded the tricyclic diketones 6,7 and 8. The same mixture was obtained from the isobutyl ether 3b (Scheme 2).
Die Synthese von 6exo‐substituierten p‐Toluolsulfonsäure‐[2exo‐norbornyl]estern. Norbornanreihe, 1. Mitteilung
Authors: Fischer Walter , Grob Cyril A. , Von Sprecher Georg 
Published: December 2004

The Synthesis of 6exo‐Substituted 2exo‐Norbornyl p‐ToluenesulfonatesA number of hitherto unknown 6exo‐substituted 2exo‐norbornanols and their p‐toluenesulfonates have been prepared by functionalization of intermediate norbornenes.
The Synthesis of 3,5‐Diamino‐1,2,4‐oxadiazoles. 1st Communication
Authors: Tilley Jefferson W. , Ramuz Henri 
Published: December 2004

AbstractReaction of the 1‐substituted‐3‐cyano‐isothioureas 6 with hydroxylamine gave mixtures of the 5‐amino‐3‐substituted‐amino‐1,2,4‐oxadiazoles 1 and the isomeric 3‐amino‐5‐substituted‐amino‐1,2,4‐oxadiazoles 8 in which 1 usually predominated. The structural assignment of these products is discussed. In a second method, the 2‐hydroxy‐1‐methyl‐1‐phenyl‐guanidine 15 was converted to the corresponding 3‐disubstituted‐amino‐5‐trichloromethyl‐1,2,4‐oxadiazole 16, a precursor to the 5‐amino derivatives 17 by nucleophilic displacement of the trichloromethyl group.
9, 10‐Secocholesta‐(5Z)‐5,8(14), 10(19)‐trien‐3β‐ol und 18‐Nor‐14β‐methyl‐9,10‐secocholesta‐(5E)‐5, 10(19), 13(17)‐trien‐3β‐ol, zwei neue Doppelbindungsisomere des Vitamins D3. Strukturelle Abwandlungen am Vitamin D3: 5. Mitteilung [1]
Authors: Reischl Wolfgang , Zbiral Erich 
Published: December 2004

9,10‐Secocholesta‐(5Z)‐5,8(14),10(19)‐triene‐3β‐ol and 18‐Nor‐14β‐methyl‐9,10‐secocholesta‐(5E)‐5,10(19), 13(17)‐trien‐3β‐ol, two new double bond isomers of vitamin D3. Structural modifications of vitamin D3: 5. Communication [1]The present paper reports the synthesis and structure elucidation of the two title compounds. Treatment of the 4‐phenyl‐1,2,4‐triazolin‐3,5‐dione adducts of vitamin D3 with BF3O (C2H5)2 and KOH/butanol yields these two new vitamin D3 double bond isomers.
Synthesen von Tricyclo [5.2.1.04,8]decan (2‐Homobrendan)
Authors: Jäggi Franz Josef , Buchs Peter , Ganter Camille 
Published: December 2004

Syntheses of Tricyclo [5.2.1.04,8]decane (2‐Homobrendane)Three different approaches to tricyclo [5.2.1.04,8] decane (5) (and derivatives thereof), one of the 19 isomeric hydrocarbons of the ‘adamantaneland’, are described: (1) Cyclization of properly functionalized bicyclo [3.2.1]octanes as 32(cyclialkylation), 40+42 (thermocyclization) and 44+45 (photocyclization); (2) Silver‐(I)‐ion catalyzed rearrangement of 5,7‐ and 5,10‐Dehydroprotoadamantane (63 and 64, respectively) yielding tricyclo[5.2.1.04,8]dec‐2‐ (39) and ‐5‐ene (59), respectively; (3) Thermal eliminative rearrangement of the 10endo‐p‐toluenesulfonate and ‐methanesulfonate of protoadamantane (71 and 72) and protoadamant‐4‐ene (76 and 77), respectively, yielding tricyclo [5.2.1.04,8]dec‐2‐ene (39) and ‐2, 5‐diene (15), respectively.
Zur Kinetik des Ringschlusses von 2‐Hydroxybenzaniliden zu Benzoxazolen
Authors: Seha Zdenek 
Published: December 2004

Kinetics of Cyclization of 2‐Hydroxybenzanilides to BenzoxazolesThe reaction rates of cyclization of 2‐hydroxybenzanilides to benzoxazoles have been measured in N‐methyl‐2‐pyrrolidone at different temperatures. The reactions follow second‐order kinetics.
Influence de composés à hétérocycle azoté et particulièrement d'azoles non condensés sur des réactions «prébiotiques» de condensation d'acides α‐aminés induites par les polyphosphates en milieu aqueux
Authors: Rabinowitz Joseph , Hampai Aioub 
Published: December 2004

Influence of Nitrogen Heterocyclic Compounds and of Non Condensed Azoles in Particular on ‘Prebiotic’ Condensation Reactions of α‐Amino Acids Induced by Polyphosphates in Aqueous SolutionIn previous experiments aqueous solutions of α‐aminoacids in the presence of cyclic or linear polyphosphates, pH range 7–11, yielded up to 40% of dipeptide but only 0.3‐0.5% of tripeptide [1] [2]. By addition of imidazole the yield of tripeptide could be increased about ten times [2]. Therefore, we have studied for the condensation reaction of glycine the influence of the addition to aqueous solutions 0.1 M in glycine and 0.1 M in trimetaphosphate at room temperature, pH range 6.7–8.9, of several azoles (pyrrole, pyrazole, imidazole, 1,2,4‐triazole and tetrazole), of adenine, guanine, uracil, cytosine, and of several nucleosides (adenosine, guanosine, uridine and cytidine). Among the products studied, only 1,2,4‐triazole and imidazole improve appreciably, by a factor of about 15, the yield of triglycine (up to 7.8%). While it is very likely that imidazole has played an important role during prebiotic chemical evolution, it is not clear at present whether 1,2,4‐triazole has a prebiotic significance.
A Short Synthesis of 3‐Methyl‐5‐(2,3,6‐trimethylphenyl)‐1‐penten‐3‐ol, a Sesquiterpene Isolated from Laurencia Nidifica
Authors: Oppolzer Wolfgang , Briner Paul H. , Snowden Roger L. 
Published: December 2004

AbstractThe racemic sesquiterpenoid alcohol 7 was synthesized in four steps (27% overall yield) from the cyclohexadienone 1. The key steps are the regioselective addition of the pentadienyllithium 2 to 1 and the Lewis‐acid induced aromatization 4 → 6.
Heterotricyclodecane. XXVI. 2,6‐Dioxatricyclo [3.3.2.03,7]decan, ein neuartiges isomers von 2,6‐dioxaadamantan
Authors: Buchs Peter , Ganter Camille 
Published: December 2004

Abstract2,6‐Dioxatricyclo [3.3.2.03,7]decane, a Novel Isomer of 2,6‐DioxaadamantaneRestriction among the great number of possible diheterotricyclodecanes to such with a carbocyclic 8membered ring (cyclooctane) as basic skeleton, which is crosswise bridged by two heteroatoms, and restriction to 5‐, 6‐ and 7membered heterocyclic rings results in the isomeric diheterotricyclodecanes of the following five different structural types: 2,6‐diheteroadamantane (a), 2,7‐diheteroisotwistane (b), 2,7‐diheterotwistance (c), 2,8‐diheterohomotwistbrendane (d), and 2,6‐diheterotricyclo [3.3.2.03,7]decane (e; s. Scheme 1).Starting from a suitably C (5)o(2)‐functionalized 2,7‐dioxaisotwistane, first representatives with the hitherto unknown skeleton of type e were prepared by molecular rearrangement involving neighboring group participation: 2,6‐dioxatricyclo [3.3.2.03,7]decane (41) and the derivatives 34–40 thereof (Scheme 7).
Xylostosidine: The First of a New Class of Monoterpene Alkaloid Glycosides from Lonicera XylosteumL
Authors: Chaudhuri Ratan K. , Sticher Otto , Winkler Tammo 
Published: December 2004

AbstractThe structure of xylostosidine (1), a novel sulfur‐containing monoterpene alkaloid glucoside, is presented.
Directional Preferences of Approach of Nucleophiles to Sulfonium Ions
Authors: Britton Doyle , Dunitz Jack D. 
Published: December 2004

AbstractAn analysis of the crystal environments of sulfonium ions shows that short nonbonded contacts (secondary bonds) to sulfur tend to occur along the extensions of the C‐S primary bonds. Non‐bonded contacts to the C (a)‐atoms of sulfonium ions are not especially short and do not show any striking directional preference, except in sulfonium ions derived from methionine where a specific intramolecular interaction between a carboxyl O‐atom and the C (γ)‐atom may represent an incipient stage of the internal nucleophilic displacement leading to formation of homoserine and mercaptan.