bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reaktion von 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirin mit 6‐Methyluracil; Kristallstruktur der Reaktionsprodukte
Authors: Dähler Marlise , Prewo Roland , Bieri Jost H. , Heimgartner Heinz 
Published: December 2004

Reaction of 3‐Dimethylamino‐2,2‐dimethyl‐2H‐azirine with 6‐Methyluracil; Crystal Structure of the ProductsThe reaction of 3‐dimethylamino‐2,2‐dimethyl‐2H‐azirine (1) with 6‐methyl‐uracil (4) in 2‐propanol at 80° yields the 4H‐imidazoje derivative 5 as the main product. This reaction is similar to the previously reported ones with heterocyclic compounds containing the sequence NHCONHCO. In the presence of water, 5 is easily hydrolyzed to 6. The structures of 5 and 6 have been established by X‐ray crystallography.
2‐[6′‐(O‐trans‐Cinnamoyl)‐β‐D‐glucopyranosyloxy]‐3‐methyl 4H‐pyran‐4‐one, a New Acylated Pyrone Glucoside from Silene vulgaris (Caryophyllaceae) Part 186. Papers on Organic Natural Products
Authors: Borris Robert P. , Hesse Manfred , Seifert Karlheinz , Johne Siegfried 
Published: December 2004

AbstractA previously unreported acylated 4‐pyroae glycoside, 2‐[6'‐(O‐trans‐cinnamoyl)β‐D‐glucopyranosyloxy]‐3‐methyl‐4 H‐pyran‐4‐one (1) has been isolated from the basic fraction of a chloroform/methanol extract of the shoots of Silene vulgaris (Moench) Garcke (Caryophyllaceae) and identified mainly on the basis of the spectral characteristics of this compound and its triacetate derivative as well as chemical degradation.
L‐Erythruronic Acid Derivatives as Building Blocks for Nucleoside Analogs. Synthesis of 4′‐C‐Aryl‐D‐ribonucleosides
Authors: Beer Dieter , Meuwly Roger , Vasella Andrea 
Published: December 2004

Abstract2, 3‐O‐Cyclohexylidene‐L‐erythruronic acid (6) available in 83% yield from D‐ribonolactone (7), was treated with phenvlmagnesium bromide to give the D‐ribo and L‐lyxo derivatives 10 and 11 in high yields (Scheme 1 and 2). The diastereoselectivity depended on the temperature and mode of operation (Table 1). The absolute configuration of 10 and 11 was determined by correlation with (R)‐ and (S)phenylethanediol (17 and 16) respectively, excluding intramolecular hydride shifts during formation of 10 and 11. Reaction of 6 with methcoxymethoxyphenyllithium gave the lactones 18 and 19. The L‐lyxo isomer 19 was transformed in high yields into the D‐ribo lactone 18. Compound 10 was transformed into the adenosine analoge 24 by reduction with Diisobutylaluminium hydride, hydrolysis, acetylation and nucleoside synthesis according to Vorbrüggen (Scheme 3). Its structure was deduced from its UV., NMR. and CD. data and from those of the isopropylidene derivative 25. Similarly, 18 was transformed into the adenosine analog 29 and into the isopropylidene derivative 30.
Triaziridine. II. Erste Beispiele: 2, 3‐Dialkyl‐triaziridin‐1‐carbonsäurealkylester
Authors: Hoesch Lienhard , Leuenberger Christian , Hilpert Hans , Dreiding André S. 
Published: December 2004

Triaziridines. II. First Examples: Alkyl 2,3‐Dialkyl‐triaziridine‐1‐carboxylatesThe first examples of substituted triaziridines 2 are described; they carry an alkoxycarbonyl and two alkyl groups (as in 4). The preparation of these novel threemembered nitrogen homocycles was achieved by photolysis of 1‐alkoxycarbonylazimines 3c. In this way, methyl 2, 3‐(cis‐1, 3‐cyclopentylene)triaziridine‐1‐carboxylate (6a), methyl trans‐2, 3‐diisopropyl‐triaziridine‐ 1 ‐carboxylate (8a) and their ethyl ester analogues 6b and 8b were obtained in 50, 18, 65 and 21 % yield, respectively. The structure of the triaziridines 6 and 8 was deduced from their spectroscopic properties which reveal several interesting features: 1) N (2) and N (3), carrying alkyl groups, are pyramidal and invert slowly; 2) the isopropyl groups of 8 are situated trans to each other on the three‐membered ring, whereas the two alkyl groups of 6 are cis as forced by the C‐ring system; 3) N (1) is also pyramidal, despite its «amidic» nature; it inverts with an activation energy of 62 (± 4) kJ/mol; 4) the alkoxycarbonyl, group does not conjugate with N (1) and rotates rapidly.The triaziridines 6 and 8 are thermally labile, isomerizing slowly at room temperature into the corresponding azimines 5 and 7 by cleavage of one of the bonds to N (1 ). The velocity of this ring opening reaction is almost the same for 6 and 8, so that a dependence on the relative configuration at N (2) and N (3) is not evident. The Arrhenius activation energy for the isornerization of 6a to the corresponding azimine 5a and the enthalpy difference between 6a and 5a were both determined as 100 (± 4) kJ/mol.The photolysis of 1‐alkoxycarbonyl‐2, 3‐diisopropyl‐azimines (7) in diethyl ether was accompanied by a side reaction leading to methyl and ethyl N‐(1‐ethoxyethyl)carbamate (9a and 9b, resp.), presumably by insertion of the alkoxycarbonylnitrene, generated by photofragmentation of the azimines, into the ethereal solvent.
Bildung eines hochexplosiven Valenzisomeren des Indens aus Dilithiopentalen und Chlorcarben
Authors: Burger Ulrich , Bianco Bernard 
Published: December 2004

Formation of a Highly Explosive Valence Isomer of Indene from Dilithiopentalene and ChlorocarbeneThe principal product of the reaction of dilithiopentalene (3) with methyllithium and methylene chloride is shown by difference‐FT‐NMR, spectroscopy to be tetracyclo[4.3.0.03,5.04,6]nona‐1,7‐diene (8). This laterally bridged benzvalene derivative explodes violently at temperatures as low as −40° when concentrated. Controlled rearrangement in diluted solution gives indene (4). The key step in the formation of the tetracyclic C9H8‐compound 8 is suggested to be an intramolecular 1,4‐carbene addition.
Nucleoside und Nucleotide. Teil 20. Synthese von Desoxyribooligonucleotiden nach der Diester‐ und Triestermethode mit 2(1H)‐Pyrimidinon als Base
Authors: Schneider Hans‐Dieter , Tamm Christoph 
Published: December 2004

Nucleosides and Nucleotides. Part 20, Synthesis of Desoxyribooligonucleotides According to the Diester and Triester Method with 2(1H)‐Pyrimidinone as BaseThe syntheses of the dinucleosidemonophosphate 1‐(2′‐deoxy‐b̃‐D‐ribofuranosyl)‐2(1H)‐pyrimidinon‐(3′‐5′)‐2′‐deoxycytidine (MdpCd; 4) and the trinucleoside‐diphosphate thymidyl‐(3′‐5′)‐thymidylyl‐(3′‐5′)‐1‐(2′‐deoxy‐b̃‐D‐ribofuranosyl)‐2(1H)pyrimidinon (TdpTdpMd; 1) are described, Compound 1 was synthesized by different variants of the triester method, and 4 by the diester method as well as the triester method.
The Methyl Enol Ethers of Ethyl 2, 4‐Dioxopentanoate
Authors: Haider Akhtar , Wyler Hugo 
Published: December 2004

AbstractMethylation of ethyl 2, 4‐dioxopentanoate with diazomethane gives a mixture of two enol ethers, the 2‐methoxy and the 4‐methoxy isomer, with a product ratio which depends upon reaction temperature. Both enol ethers, initially (Z)‐configurated, isomerize to the corresponding (E)‐conformers, the 4‐methoxy compound with particular ease.
ESR. Study of the Pentacoordinated Arsenic Radical Anion [(OH)3(O)AsCH2As(O)(OH)2]=
Authors: Geoffroy Michel , Llinares Antoine , Morton John R. 
Published: December 2004

AbstractThe anion [(OH)3(O)AsCH2As(O)(OH)2] has been trapped in an X‐irradiated single crystal of methylene diarsonic acid. The g‐tensor and the hyperfine coupling tensors of the two 75As‐nuclei have been obtained and the spin densities in the arsenic 4s‐ and 4p‐orbitals determined.
A Stereoselective Total Synthesis of (±)‐Maritimol, (±)‐2‐Deoxystemodinone, (±)‐Stemodinone, and (±)‐Stemodin
Authors: Bettolo Rinaldo Marini , Tagliatesta Pietro , Lupi Alessandro , Bravetti Doriano 
Published: December 2004

AbstractA simple and stereoselective total synthesis of (±)‐maritimol (2d) and its conversion into the other title compounds (±)‐(2a), ((±)‐2b), and ((±)‐2c) is described. The unique bicyclo[3.2.1]octane moiety, constituting their C/D‐ring system, is stereospecifically obtained by solvolytic rearrangement of the methanesulfonate 23.
Deoxy‐nitrosugars. 4th communication. Convenient synthesis of 1‐deoxy‐1‐nitroaldoses
Authors: Aebischer Bernard , Vasella Andrea 
Published: December 2004

AbstractA new synthesis of 1‐deoxy‐1‐nitroaldoses by ozonolysis of N‐glycosylnitrones according to the procedure of Bailey et al. is described. Based on the oxime 1, the mannofuranosylnitrones 3–5 were obtained in yields of 86–88% and the 1‐deoxy‐1‐nitromannose 6 in yields of 70–76%. In the same manner the 1‐deoxy‐1‐nitroaldoses 9, 12, 18, and 19 were prepared in yields of 61–90% from the oximes 7, 10, 14 and 15, the procedure being compatible with the presence of free hydroxy groups.
C,C‐Double Bond Participation in the Acid‐Catalyzed Cyclization of 9exo‐Methyl‐anti10,11‐tricyclo[4.2.1.12,5]deca‐3,7‐diene‐9endo, 10endo‐diol. Influence of Steric Compression on the Product Distribution
Authors: Tombo Gerardo M. Ramos , Chakrabarti Sarmistha , Ganter Camille 
Published: December 2004

AbstractAcid treatment of 9exo‐methyl‐anti10,11‐tricyclo[4.2.1.12,5]deca‐3,7‐diene‐9endo, 10endo‐diol (8) leads to the two isomeric pentacyclic ethers 7 and 9 by intramolecular nucleophilic substitution of a protonated OH‐group with participation of a C,C‐double bond.The higher steric compression in diol 8 on the side of the tertiary OH‐group at C(9) and the C(3), C(4)‐double bond, accounts for the preferred formation of 7 over 9.
Construction of Highly Substituted Nitroaromatic Systems by Cyclocondensation. Part I. Synthesis of 4‐nitro‐3‐oxobutyrate
Authors: Duthaler Rudolf O. 
Published: December 2004

AbstractMethyl 4‐nitro‐3‐oxobutyrate (1) is prepared by substitution of 4‐bromo‐ and 4‐iodo‐3‐oxobutyrate enol ether or enol acetate derivatives with nitrite and deprotection of the keto function (Schemes 2 and 3). A much more convenient access to 1 is, however, the nitration of acetoacetate dianion with alkyl nitrates (Scheme 4). Compound 1 is stable and storable, and can be handled safely. Its use in cyclocondensations is established by the reaction with acetylacetone (Scheme 5), affording 4,6‐dimethyl‐3‐nitrosalicylate 48 in 70% yield. The halogen‐substitution method for the synthesis of 1 gives also access to the crystalline (E)‐enol ether 18 of 1, as well as to its dimethyl acetal 25, (Z)‐enol acetate 32, and (E)‐enol acetate 33. The 3‐substituted 4‐bromobutenoates 15, 16 and 26 have been prepared from 4‐bromo‐3‐oxobutyrate 12, a useful alternative to existing methods applying N‐bromo‐succinimide.
15N‐NMR Spectra of Azoles with Two Heteroatoms
Authors: Chen Ban Chin , Von Philipsborn Wolfgang , Nagarajan Kuppuswamy 
Published: December 2004

AbstractThe15N‐NMR spectra of azoles, with natural isotope abundance, have been measured under different experimental conditions, and chemical shifts are reported for imidazoles, pyrazoles, oxazoles, isoxazoles, thiazoles, and isothiazoles. General trends of substituent effects in this heterocyclic series are discussed based on the data of 67 substituted azoles, dihydro‐ and tetrahydroazoles.15N,1H spin‐coupling constants have been determined from spectra obtained by [1H] →15N polarizationtransfer experiments,i.e.an application of INEPT and DEPT pulse sequences. Two‐bond and three‐bond coupling constants are fully assigned and are discussed in terms of the specific pathways in azoles. The potential of structural applications of the new data is illustrated for isomeric nitro‐imidazoles and highly‐substituted pyrazoles, and in the case of ring‐chain tautomerism of 2‐substituted tetrahydrooxazoles.
1,2,3‐Triazolidine durch Cycloaddition von Aziminen an Olefine
Authors: Egger Notker , Prewo Roland , Bieri Jost H. , Hoesch Lienhard , Dreiding Andre S. 
Published: December 2004

1,2,3‐Triazolidines by Cycloaddition of Azimines to OlefinesAzimines A can undergo [3+2]‐cycloadditions with olefines B to give 1,2,3‐triazolidines C, a class of hitherto unknown heterocycles. The three examples of this reaction realized here involved the azimine 1 with electron‐withdrawing substituents and the olefines 2, 3 and 4 with an electron‐donating substituent, yielding the cycloadducts 5,6 and 7. The triazolidine structure of 5 was established by an X‐ray diffraction analysis. Characteristic for 5 are also: (a) that the three N‐atoms are pyramidal (and thus centers of chirality), (b) that the five‐membered heterocycle takes on a twist (half‐chair) form, and (c) that the regioselectivity of the cycloaddition places the (E)‐substituent of the olefine 2 vicinal to the terminal (Z)‐substituent of the azimine 1. On this basis the constitutions of 6 and 7 are assigned. The spectral properties of the triazolidines 5, 6 and 7, including the 15N‐NMR signals of one example, are compared with those of the related triazane 12.
N‐Methyl‐C‐(trichlortitanio)formimidoylchlorid. Ein effizientes Reagenz zur Homologisierung von Aldehyden und Ketonen zu α‐Hydroxy‐carbonsäureamiden
Authors: Schiess Martin , Seebach Dieter 
Published: December 2004

N‐Methyl‐C‐(trichlorotitanio)formimidoyl Chloride, a Highly Efficient Reagent for Homologations of Aldehydes and Ketones to α‐HydroxycarboxamidesThe known title compound 6 formed by addition of titanium tetrachloride to methyl isocyanide in methylene chloride adds to the carbonyl group of aldehydes and ketones. The adducts 7 are hydrolized to N‐methyl‐α‐hydroxycarboxamides 8 which are (from ketones) or are not branched (from aldehydes) in the α‐position. The yields in this new modification of the Passerini reaction are near 90%, also with readily enolized ketones such as acetone and acetophenone. In contrast to the previously used organotitanium reagents of the type RTiX3, the preparation of the reagent 6 does not require any Li‐, Mg‐ or Zn‐derivative as a precusor.
Dediazoniation of Arenediazonium Ions. Part XXII. Reactions of 2, 6‐Dialkyl‐Substituted Benzenediazonium Ions in Super Acids, Acetonitrile and Acetone
Authors: Laali Khosrow , Szele Ivanka , Zollinger Heinrich 
Published: December 2004

AbstractReactions of 2,4,6‐trimethylbenzenediazonium (1), 2,6‐diethylbenzenediazonium (2) and 2,6‐diisopropylbenzenediazonium (3) tetrafluoroborates were studied in magic acid, SbF5/SO2ClF, acetonitrile and acetone by 1H‐NMR and by analysis of the dediazoniation products. The Nα‐Nβ rearrangement of β‐N15‐labelled tetrafluoroborates 1–3 was followed by 15N‐NMR of the corresponding arylazonaphthols, as well as by MS analysis of the anilines obtained by reduction of the azo compounds. Diazonium salts 2 and 3 were synthesized for the first time and the steric effect of substituents at C(2) and C(6) on the reactions under study is discussed. All the results obtained can be rationalized by heterolytic dediazoniation of diazonium salts 1–3 and product formation from the corresponding aryl cations.
New Carbonyl Compounds in the High‐Boiling Fraction of Lavender Oil. 1st Communication
Authors: Kaiser Roman , Lamparsky Dietmar 
Published: December 2004

AbstractA series of new carbonyl compounds with santalane (3–9) as well as cadinane skeleton (10–13) have been identified for the first time in lavender oil. Most of the structures established by spectra interpretation are corroborated by partial synthesis starting from well‐defined natural products.
New Carbonyl Compounds in the High‐Boiling Fraction of Lavender Oil. 2nd Communication
Authors: Kaiser Roman , Lamparsky Dietmar 
Published: December 2004

AbstractIn addition to the sesquiterpenoid compounds reported in [1] the in‐depth analysis of lavender oil also led to the identification of new constituents with caryophyllane (1–6), cedrane (7 and 8) and other skeletons (9–21). Spectroscopic properties as well as partial syntheses of these compounds are discussed.
Synthese von optisch aktiven, natürlichen Carotioiden und strukturell verwandten Naturprodukten. X. Synthese von (3R,3′S, 5′R)‐Capsanthin, (3S,5R,3′S,5′R)‐Capsorubin, (3′S,5′R)‐Kryptocapsin und einigen verwandten Verbindungen. Ein neuer Zugang zu optisch aktiven Fünfring‐Carotinoidbausteinen durch Hydroborierung
Authors: Rüttimann August , Englert Gerhard , Mayer Hans , Moss Gerard P. , Weedon Basil C. L. 
Published: December 2004

Synthesis of Optically Active Natural Carotenoids and Structurally Related Compounds. X. Synthesis of (3R,3′S,5′R)‐Capsanthin, (3S,5R,3′S,5′R)‐Capsorubin, (3′S,5′R)‐Cryptocapsin, and Some Related Compounds. A New Approach to Optically Active, Five‐Membered‐Ring Carotenoid Building Units by HydroboratonThe synthesis of (3R,3′S,5′R)‐capsanthin (1), (3S,5R,3′S,5′R)‐capsorubin (2), and (3′S,5′R)‐cryptocapsin (3), found in the red paprika Capsicum annuum, is described using (+)‐camphor (7) as a readily available starting material. As the key reaction, the unsaturated acetal 16 is hydroborated with (+)‐diisopinocampheylborane to give the hydroxy ketone 12a in very high chemical and optical yield. A subsequent aldol condensation with 13 in THF/toluene gives 2 in high yield. The C40‐compounds 1 and 3 are synthesized using the same type of condensation. The pigments 1–3 are transformed by an Oppenauer oxidation to (3R,5′R)‐capsanthone (5), (5R,5′R)‐capsorubone (4) and (5′R)‐cryptocapsone (6), respectively.
Halochrome Molekeln 4. Mitteilung. Chromogene Verbindungen durch Cyclisierung von [2‐(Benzothiazol‐2‐yl)amino‐4‐(diäthylamino)phenyl]heteroaryliumsalzen: Synthese und acidobasisches Verhalten
Authors: Ziegler Hugo , Balli Heinz 
Published: December 2004

Halochromic Molecules. Chromogenic Compounds by Cyclization of [2‐(Benzothiazol‐2‐yl)amino‐4‐(diethylamino)phenyl]heteroarylium Salts: Synthesis and Acidobasic BehaviourColoured [2‐(Benzothiazol‐2‐yl)amino‐4‐(diethylamino)phenyl]heteroarylium salts are deprotonated to colourless spiro‐compounds. The preparation of these products is described and their structure is explained by1H‐NMR and UV/VIS spectroscopy. An investigation of the halochromic properties is carried out by spectro‐photometric determination of εpH*‐ and εH0*‐curves in buffered MeOH/H2O solutions. pK*‐Values are determined, and the complex protonation equilibria are discussed. One of the heteroarylium salts does not form a spiro‐compound by deprotonation, but it is stabilized by a σ‐bond resonance.
An Enantioselective β‐Lactam Synthesis Starting from L‐(S)‐Glyceraldehyde Acetonide
Authors: Hubschwerlen Christian , Schmid Gérard 
Published: December 2004

AbstractComplete diastereoselectivity is observed during the cyclocondensation of activated glycine derivatives with aldimines derived from L‐(S)‐glyceraldehyde acetonide. 3,4‐cis‐β‐lactams are isolated in high optical and chemical yields. They are converted into key intermediates used in the syntheses of various mono‐ and bicyclic β‐lactam antibiotics. A mechanism is suggested to explain this remarkable diastereoselectivity.
Synthesis of Cyclosporine. I. Synthesis of enantiomerically pure (2S,3R,4R,6E)‐3‐hydroxy ‐4‐methyl‐2‐methylamino‐6‐octenoic acid starting from tartaric acid
Authors: Wenger Roland M. 
Published: December 2004

AbstractStarting from R,R‐(+)‐tartaric acid, the synthesis of (2S,3R,4R6E)‐3‐hydroxy ‐4‐methyl‐2‐methylamino‐6‐octenoic acid in 24 steps is reported. This novel amino acid is found in the cyclic undecapeptide cyclosporin A, isolated from the fungal strain Tolypocladium inflatum GAMS. Its stereospecific synthesis allowed, for the first time, the isolation and characterization of the new amino acid previously reported as the ‘C‐9‐amino acid’ [1].
Apomorphinans from Isoquinolines: Grewe cyclization of 1‐(2‐hydroxybenzyl)‐N‐methyloctahydroisoquinoline and its O‐methyl ether
Authors: Schmidhammer Helmut , Brossi Arnold , Flippen‐Anderson Judith L. , Gilardi Richard 
Published: December 2004

AbstractWolff‐Kishner reduction of the optically active ketomorphinan 5 afforded the optically active morphinan 6 differing chromatographically and spectroscopically from the material obtained in a Grewe‐cyclization of the isoquinoline 1. A single crystal X‐ray analysis of a hydrobromide salt of a phenolic amine obtained from 1 and 2 with refluxing hydrobromic acid showed this compound to be the N‐methylapomorphinan 4.
A Study of Stereoselective Hydrolysis of Symmetrical Diesters with Pig Liver Esterase
Authors: Mohr Peter , Waespe‐Šarčević Nada , Tamm Christoph , Gawronska Krystyna , Gawronski Jacek K. 
Published: December 2004

AbstractPig liver esterase‐(PLE) catalyzed hydrolysis of dimethyl esters of symmetrical dicarboxylic acids, including meso‐diacids, cis‐1,2‐cycloalkanedicarboxylic acids, and diacids with a prochiral center, was studied with 14 substrates. The products of these stereoselective hydrolyses are chiral monoesters of dicarboxylic acids, with an enantiomeric excess (e.e.) from 10% to 100%. Some of these optically active monoesters are valuable synthons in natural products synthesis.An additivity pattern of α‐ and β‐substituents with the glutaric esters on the stereoselectivity of enzymatic hydrolysis was observed. Analysis of the experimental results leads to a model of enzyme stereoselectivity of diester hydrolysis in which the substitution pattern at α‐ and β‐C‐atoms is found to determine the absolute configuration of the resulting monoester.
Synthesis of Cannabinoid Model Compounds. Part 3. (6aR, 10aR)‐N‐ethyl‐Δ8‐tetrahydrocannabinol‐18‐amide, (6aR, 10aR, 17 RS)‐N‐ethyl‐17‐methyl‐Δ8‐ tetrahydrocannabinol‐18‐amide and (6aR, 10aR)‐17,18‐didehydro‐Δ8‐tetrahydrocannabinol
Authors: Schmidt Burkhard , Franke Ingo , Witteler Franz‐Josef , Binder Michael 
Published: December 2004

AbstractThe novel cannabinoids (6aR, 10aR)‐N‐ethyl‐Δ8‐tetrahydrocannabinol‐18‐amide (15) and (6aR, 10aR, 17 RS)‐N‐ethyl‐17‐methyl‐Δ8‐ tetrahydrocannabinol‐18‐amide (16), designed as cannabinoid affinity ligands, were synthesized from the corresponding acids 11 and 12 via the N‐hydroxysuccinimide esters. Amide 16 was tested in the rat and was generalized to Δ9‐tetrahydrocannabinol, being 5 times less potent than the training drug. An improved synthesis of (6aR, 10aR)‐17,18‐didehydro‐Δ8‐tetrahydrocannabinol (23) is reported. As model reaction for the preparation of a tritiated Δ8‐tetrahydrocannabinol, compound 23 was selectively deuterated at C(17) and C(18) in benzene/Et3N using [(C6H5)3P]3RuCl2 as catalyst.
Untersuchungen an einem bei Raumtemperatur beobachtbaren langsamen Cycloheptatrien‐Norcaradien‐Gleichgewicht
Authors: Neidlein Richard , Martin Radke Christoph 
Published: December 2004

Investigations on a Cycloheptatriene‐Norcaradiene Equilibrium Observable at Room TemperatureAnalytical data of the bridged quinone hydrazones 7a, 8a, 7b, 8b, 7c, 8c are discussed. These products exist as tautomeric mixtures of their norcaradiene‐ and cycloheptatriene forms. The rate constants of these isomerizations are so small that the 1H‐and 13C‐NMR signals of the tautomers are well‐resolved. Kinetic and thermodynamic variables were determined by temperature‐dependent 1H‐NMR, measurements.
Nucleotide, XXI. Synthese und Eigenschaften Dihydrouridin‐haltiger Oligonucleotide
Authors: Flockerzi Dieter , Silber Gunter , Pfleiderer Wolfgang 
Published: December 2004

Nucleotides, XXI. Synthesis and Properties of Dihydrouridine‐Containing OligonucleotidesSubstituted 5,6‐dihydrouridine derivatives 1, 5, and 8 have been used in condensation reactions to form a series of dinucleosidemono‐ and dinucleosidediphosphotriesters, 13 and 16–22, respectively. Dihydrouridine‐containing fully blocked oligomers have also been obtained by stepwise chain‐elongation and block condensations including 5 trimers (25–29) and one pentamer (31), hexamer (32) and octamer (34) each. The new compounds were characterized by UV and partly CD spectra as well as elementary analyses. NMR spectra prove the structures but are not reported in detail.
Synthese und Hydrolyse von 6‐exo‐substituierten 2‐Methyl‐2‐exo‐norbornyl und 2‐Methyl‐2‐endo‐norbornyl‐(2,4‐dinitrophenyl)äthern Norbornane. 16. Mitteilung
Authors: Grob Cyril A. , Von Sprecher Georg , Waldner Adrian 
Published: December 2004

The Synthesis and Hydrolysis of 6‐exo‐Substituted 2‐Methyl‐2‐exo‐norbornyl and 2‐Methyl‐2‐endo‐norbornyl 2,4‐Dinitrophenyl EthersThe synthesis of the title compounds and their hydrolysis products in aqueous dioxane are described. Upon hydrolysis, the 2‐exo‐ethers 1 (X=N2phO) as well as the 2‐endo‐ethers 2 (X=N2phO) yield the corresponding 2‐methyl‐2‐exo‐norbornanols 3 only. Therefore, the 2‐exo‐ethers react with retention of configuration at C(2), the 2‐endo‐ethers 2 with inversion at C(2).