bluuebunny/crossref_metadata_2025 huggingface dataset:
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 Chlorocarbene

The 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.
ESR. Study of the Ph3ÅsBr‐Radical Trapped in an X‐Irradiated Single Crystal of Ph3As+CH3Br−
Authors: Geoffroy Michel , Llinares Antoine
Published: December 2004

Ph3ÅsBr is trapped in an X‐irradiated single crystal of Ph3As+CH3Br−. The g‐tensor, the 75As and 79Br magnetic hyperfine tensors and the 79Br quadrupolar interaction tensor are obtained at room temperature. They show that the structure of this arsoranyl radical is intermediate between the trigonal bipyramidal and the C3v‐symmetry structure. By the detection of several additional radical species, especially at 77 K, some steps of the radiation mechanism are elucidated.
X‐Ray Study of the Deformation Density in Tetrafluoroterephthalodinitrile: Weak Bonding Density in the C, F‐Bond
Authors: Dunitz Jack D. , Schweizer W. Bernd , Seiler Paul
Published: December 2004

A careful deformation density study of tetrafluoroterephthalodinitrile at 98K has been made from X‐ray diffraction measurements. Prominent ‘bonding density’ peaks are found at or near the mid‐points of the C, C‐ and C, N‐bonds but not for the C, F‐bonds, which show only weak density. Similarly weak bonding densities for C, F‐bonds are also found for 1, 1, 4, 4‐tetrafluorocyclohexane. The possible significance of these results in terms of bonding theory is briefly discussed.
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 Base

The 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

Methylation 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

The 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

A 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

A 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

Acid 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

Methyl 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

The15N‐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 Olefines

Azimines 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‐Hydroxycarboxamides

The 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.
A Dimer of Puupehenone
Authors: Amade P. , Chevelot L. , Perzanowski Herman P. , Scheuer Paul J.
Published: December 2004

The structure of a colorless dimer (4a) of puupehenone (1), which was isolated from Pacific marine sponges, has been elucidated from spectral data.
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

Reactions 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

A 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

In 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 Hydroboraton

The 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 Behaviour

Coloured [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

Complete 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

Starting 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

Wolff‐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

Pig 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

The 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 Temperature

Analytical 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 Oligonucleotides

Substituted 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 Ethers

The 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).
Synthesis of Cyclosporine. Part II. Synthesis of Boc‐D‐Ala‐MeLeu‐MeLeu‐MeVal‐OH, a part of the peptide sequence of cyclosporine, by different strategic ways and synthesis of its isomers Boc‐D‐Ala‐MeLeu‐D‐MeLeu‐MeVal‐OH, Boc‐D‐MeLeu‐DMeVal‐OH, and Boc‐D‐Ala‐MeLeu‐MeLeu‐D‐MeVal‐OH as reference compounds
Authors: Wenger Roland M.
Published: December 2004

Boc‐D‐Ala‐MeLeu‐MeLeu‐MeVal‐OH (DLLL) and its isomers DLDL, DLDD and DLLD were synthesized using several different strategic approaches and a modification of the mixed pivalic anhydride method for carboxyl activation. Alternatively, the tert‐butoxy‐carbonyl (Boc) or benzyloxycarbonyl (Z) amino‐protecting groups and the benzyloxy (OBzl) or tert‐butoxy (OtBu) carboxyl‐protecting groups were used to protect the reacting peptides. By monitoring the reaction temperature, it was possible to synthesize, starting from the tripeptide DLL as peptide model, either the tetrapeptide DLLL (−20°) or the tetrapeptide DLDL (+20°), selectively. Using 1H‐NMR spectroscopy to follow the mixed pivalic anhydride formation of the DLL‐ and DLD‐tripeptides, it could be shown that anhydride formation is strongly dependent on the temperature. It is slow at −20° (several hours) and fast at +20° (20 to 40min). The isomerization of the DLL‐anhydride to the more stable DLD‐anhydride can be reduced to a minimum by working at −20°, while this isomerization proceeds to near completion at +20°.
Neue Coleone und Royleanone aus Coleus somaliensis S. MOORE
Authors: Matloubi‐Moghadam Firouz , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Novel Coleons and Royleanones from Coleus somaliensis S. MOORE

Reexamination of the fraction of polar diterpenoids from the title plant, in addition to the previously identified compounds of Scheme 1 [2] [3], leads to the isolation of (15S)‐coleon D (8), the abeo‐royleanones 9–11 and the spirocoleons 12–17. Crystalline (15S)‐coleon I (3a) is characterized.
Kopsirachin, ein ungewöhnliches Alkaloid aus der Apocynaceae Kopsia dasyrachis Ridl. 189. Mitteilung über organische Naturstoffe
Authors: Homberger Katharina , Hesse Manfred
Published: December 2004

Kopsirachine, an Unusual Alkaloid from the Apocynaceae Kopsia dasyrachis Ridl.

From the leaves of Kopsia dasyrachis Ridl. a new type of alkaloid, kopsirachine (1), built up from catechin (2) and skytanthine (3) has been isolated. The structure elucidationis based on spectral and chemical evidence. Oxidative cleavage of its derivative 4 with KMnO4 afforded veratric acid wich was identified as its methylester by comparison with an authentic sample. Pyrolysis of 1 yielded δ‐skytanthine (3). The stereochemistry of the skytanthine substituents in 1 could not yet be established.
2′‐Nitro‐2′‐propen‐1′‐yl 2,2‐Dimethylpropanoate (NPP), A Multiple Coupling Reagent
Authors: Seebach Dieter , Konchel Paul
Published: December 2004

The title compound 1 (NPP) is prepared from formaldehyde, nitromethane, an pivaloyl chloride. It is shown to be a versatile nitroallylating reagent combining with nucleophiles as different as anilines, indoles, enolates, and organolithium compounds. This is documented by ca. 40 examples (2–30). The mechanism of the reaction is discussed. Some examples of addition of two different nucleophiles to the C3‐moiety of NPP are described (35‐46). This demonstrates the usefulness of NPP as a multiple coupling reagent for convergent syntheses, also of products not containing nitro groups ((Scheme 4)).
Reaction of alcohols and amines with diacetyldihydrofluorescein (DADF): Conversion into erythrosine‐derivatives on TLC‐plates by ammonia and iodine vapors
Authors: Sharma Paam N. , Brossi Arnold
Published: December 2004

Reaction of decetylcolchicine (2) and colchifoline (3) with diacetyldihydrofluorescein (1, DADF) afforded the corresponding amide and ester derivatives, converted on TLC‐plates after exposure to ammonia and iodine vapors into red colored pigments. This reaction, also observed with DADF‐derivatives of codeine, quinine and mescaline is highly sensitive. The red pigment produced from the DADF‐ester (6) of colchifoline formed by te ammonia‐iodine treatment is the corresponding erythrosine ester derivative. DADF emerges from these investigations as a useful reagent to detect alcohols and amines in crude mixtures and for dye labeling.
Percolative Phenomena in Microemulsions of the ‘One‐Component Macrofluid’ Type
Authors: Eicke Hans‐Friedrich , Hilfiker Rolf , Holz Manfred
Published: December 2004

The temperature dependence of the water self‐diffusion coefficients (D), as well as those of low‐ and high‐field (stationary and time‐dependent) specific conductivities (K), have been determined in the percolation regime of ternary mixtures of water, AOT, and oil. For the first time a pronounced similarity in the behavior of D and κ was detected giving instructive hints about the large variations in the specific conductivities of these systems. Results from kinetic and stationary experiments are consistent with a network‐structure model of micro phases in the percolation regime in which the micro phases retain their discrete character.
The mass spectra of organic compounds. 7th Communication. 4,4‐Dimethyl‐1‐pentene
Authors: Marques José Carlos Antunes , Falick Arnold , Heusler Andréas , Stahl Daniel , Tecon Pierre , Gäumann Tino
Published: December 2004

Loss of CH, CH4, C2H4, C3H, C3H6 and C3H7 from the molecular ions of a number of 13C‐labeled analogs of 4,4‐dimethyl‐1‐pentene was studied both in normal (source) 70‐eV electron impact (EI) spectra dn in metastable spectra. For loss of CH in the source, 96% of the methyl comes frm positions of 5, 5′ and 5″, while the remainder comes from position 1. In the metastable spectra, loss of C‐1 (16%) and C‐3 (9%) is increasing in importance. The loss of ethylene is a particular case: either C‐1 or C‐3 are lost with any other C‐atom from positions 2,5,5′, and 5″ (8 × 10%) in the metastable spectra, the probability for simultaneous loss of C‐1 and C‐3 being 6%. If C‐1 seems to these two positions become completely equivalent in the metastable time range. The T‐values (kinetic energy release) for the different positions show small, but statisticaly different values and a small isotope effect. Loss of C3H5 (allylic cleavage) is 100% C‐1, C‐2 and C‐3, i.e., no evidence for skeletal rearrangement is seen. This is also true for loss of C3C6 (McLafferty rearrangement) within the source, but in metastable decay the other positions gain in importance. The neutral fragment C3H appears to be the the result of consecutive loss of CH and C3H4, rather than a one‐step loss of propyl radical or the inverse reactions sequence. No metastable reaction can be seen for this reaction. Decomposition of labeled C6H and C5H secondary ions occurs in an essentially random fashion.
Ammonia chemical ionization mass spectrometry of alcohols: Structural, stereochemical, molecular‐size and temperature effects
Authors: Gülaçar Fazil O. , Mermound François , Winkler F. Johann , Vuchs Armand
Published: December 2004

Ammonia chemical ionization (CI) mass spectra of various open‐chain, cyclic and unsaturated C5‐ to C10‐alcohols were obtained at source temperatures ranging from 60° to 250°C. The reactivity of the ammonia adduct ion MNH and its fragmentation channels are characteristic for substrate structure. Although strongly temperature‐dependent, the spectra give nevertheless information on the OH‐group environment as well as on the C‐skeleton at any source temperature. Primary, secondary and tertiary alcohols as well as allylic and simple olefinic alcohols can be distinguished by their spectra, which show ammonium adduct ions [MNH4]+, adduct dehydrogenation ions [MNH4‐H2], ammonium substitution ions [MNH4‐H2O]+ and [M‐OH]+‐ions as the main characteristic peaks. Moreover, konfigurational assignments of stereoisomeric alcohols are possible for larger substrate‐size and source‐temperature ranges than with isobutane CI mass spectrometry. Homologous M NH‐ions show molecular‐size control of fragmentation and linear MNH‐ions are less stable than branched isomers due to incomplete energy randomization.
Synthesis of cyclosporine. Total syntheses of ‘cyclosporin A’ and ‘cyclosporin H’, two fungal metabolites isolated from the species Tolypocladium inflatum GAMS
Authors: Wenger Roland M.
Published: December 2004

The heptapeptide H‐MeBmt‐Abu‐Sar‐MeLeu‐Val‐MeLeu‐Ala‐OBzl (20) was synthesized for coupling with the previously described cyclosporine tetrapeptide sequence Boc‐D‐Ala‐MeLeu‐MeVal‐OH (21). The product of the coupling, the undecapeptide Boc‐D‐Ala‐MeLeu‐MeLeu‐MeVal‐MeBmt‐abu‐Sar‐MeLeu‐Val‐MeLeu‐Ala‐OBzl (22), was then deprotected and cyclized to cyclosporine (1).

The tetrapeptide diastereoisomer Boc‐D‐ala‐MeLeu‐MeLeu‐D‐MeVAl‐OH (23) could also be used as a starting material to produce selectively the desired undecapeptide 22. In this case, the N‐methyl‐D‐valine unit, was selectively isomerized to the L‐from by using the appropriate condensing agent. The diastereoisomeric undecapeptide Boc‐D‐ala‐MeLeu‐MeLeu‐D‐MeVal‐MeBmt‐Abu‐Sar‐MeLeu‐Val‐MeLeuAla‐OBzl (24) was also synthesized starting from 21 by using the mixed pivalic anhydride method to selectively invert the configuration of the N‐methyl‐L‐valine. The structure of the undecapeptide 24 was confirmed by deprotection and cyclization to ‘cyclosporin H’, a natural product known to have the structure [D‐MeVal11]cyclosporine (2).
1,3‐Dipolare Cycloadditionen von Nitrilium‐Betainen mit 4,4‐Dimethyl‐2‐phenyl‐2‐thiazolin‐5‐thion
Authors: Büchel Thomas , Prewo Roland , Bieri Jost H. , Heimgartner Heinz
Published: December 2004

1,3‐Dipolar cycloadditions of Nitrilium Betaines with 4,4‐Dimethyl‐2‐phenyl‐2‐thiazolin‐5‐thione

Benzonitrile ylides, imines, and oxides undergo smooth 1,3‐dipolar cycloaddition reactions with the exocyclic, C,S‐double bond of 4,4‐dimethyl‐2‐phenyl‐2‐thiazolin‐5‐thione (1), yielding heterocyclic spiro‐compounds. The structure of the cycloadducts 5c, 5c′, and 3f (Fig.) have been established by x‐ray structure analysis.

With the benzonitrile ylides, the two regioisomeric cycloaddition modes have been observed, depending on the substituents of the ylide‐C‐atom. It is questionable, whether the reaction of 1 and the oxazaphosphol 8 (Schemes 8 and 13) proceeds via the corresponding nitrile ylide as an intermediate.
The reaction of Nopadiene with 4‐Substituted 1,2,4‐Triazoline‐3,5‐diones
Authors: Ashkenazi Pnina , Benn Reinhard , Ginsburg David
Published: December 2004

The title dienophiles attack nopadiene from the less hindered side.
The Circular Dichroism of 5,6‐Dimethylidene‐2‐bicyclo[2.2.n]alky Esters. Chiral Exciton Coupling between Benzoate and Exocyclic s‐cis‐Butadiene Chromophores
Authors: Zhichen Zou , Carrupt Pierre‐Alain , Vogel Pierre
Published: December 2004

The optically pure aryl‐substituted 5,6‐dimethylidene‐2‐bicyclo[2.2.1]heptyl benzoates 12–21 were prepared; their UV absorption and CD spectra are reported. The (−)‐(1S,2S)‐esters 17–21 with carbonyl groups in endo‐position exhibit typical excitonsplit Cotton effects whereas the corresponding (−)‐(1S,2R)‐esters 12‐16 with carbonyl groups in exo‐position do not present such effects. The chiral exciton coupling between the exocyclic diene and a remote p‐substituted benzoate chromophore can be used for unambiguous assignment of the absolute configuration of 5,6‐dimethylidene‐2‐endo‐bicyclo[2.2.1]heptyl derivatives. The method is applied to establish the absolute configuration of 5,6‐dimethylidene‐2‐exo and ‐2‐endo‐bicyclo[2.2.2.]octyl p‐bromobenzoates (−)‐24 and (−)‐25.
Photochemistry of 2‐(Trifluoromethyl) cyclohexanone
Authors: Semisch Christoph , Margaretha Paul
Published: December 2004

The photochemical behaviour of the title compound 1a is compared to that of the non‐fluorinated parent ketone 2‐methylcyclohexanone (1b). Substitution of the CH3‐ group on C(2) by a trifluoromethyl group strongly enhances 2H‐ and RH‐ reduction product formation in cyclohexane or 2‐propanol and oxetane formation in the presence of 2‐methylpropene as olefinic component. Under all these conditions 1b exclusively undergoes a‐cleavage, a process observed for 1a only in non‐reducing solvents as benzene or tert‐butyl alcohol.
NMR Conformational Study of Aminoalkylbenzamides, Aminoalkyl‐o‐anisamides, and Metoclopramide, a Dopamine Receptor Antagonist
Authors: Anker Lucien , Van De Waterbeemd Han , Testa Bernard , Lauterweiin JÜRgen
Published: December 2004

The conformational behaviour of metoclopramide, a neuroleptic benzamide, and model compounds was investigated byt 1 H‐NMR spectroscopy. An intramolecular amide‐methoxy H‐bond is shown to exist in CDCl3‐solution, but not in D2O‐solution, independently of the length and protonation state of the basic side‐chain. This H‐bond creates a virtual cycle which may be a key feature for the binding of neuroleptic benzamides to the dopamine receptor. The conformational behaviour of the aminoethyl side‐chain is shown to be markedly condition‐dependent. For metoclopramide and its analogues in their protonated form, the gauche‐ and trans‐ rotamers have identical energies in D2O‐as well as in CDCl3‐solutins. For the non‐protonated molecules, the trans‐rotamer is favoured in D2O‐solutin, while the gauche‐rotamer is favoured in CDCl3‐solution (ΔG°≃|0.5|kcal/mol in both cases). The side‐chain conformation of neuroleptic benzamides is discussed in terms of receptor affinity.
Stereospecific, R2AlCl‐Promoted Intramolecular Ene Reaction of a 1,6‐Dienoate: Evidence for a Concerted Mechanism
Authors: Oppolzer Wolfgang , Mirza Sohail
Published: December 2004

Treatment of the 83%‐trans‐13CH3‐labelled 1,6‐dienoate 7 with Et2AlCl at–78° provided in high yield the ene product 9 containing 83% 13C localized in the olefinic C(8)‐methylene group. Accordingly, H‐transfer occurs exclusively from the trans‐methyl group of 7, consistent with a concerted ene process 7 9 thereby ruling out an intermediate cation 8 (Scheme 4).
Asymmetric Aldol Condensation of 1‐Naphtol and Pyruvates in the Presence of Lewis Acids Preliminary Communication
Authors: Piccolo Oreste , Filippini Lucio , Tinucci Laura , Valoti Ermanno , Citterio Attilio
Published: December 2004

Lewis acids catalyze teh condensation of methyl pyruvate and l‐naphtol to give menthyl 2‐hydroxy‐2‐(l‐hydroxy‐2‐naphtyl)propionate in a ratio of up 96:4 in favor of the levorotatory diastereoisomer. Epimerization, at 25°C for five days, occurs on benzylic carbon atom to give a 30:70 mixture enriched with the dextrorotatory isomer.
Absolute Conformation and Configuration of (2S, 3S)‐3‐Acetoxy‐5‐(dimethylaminoethyl)‐2‐(4‐methoxyphenyl)‐2,3‐dihydro‐1,5‐benzothiazepin‐4(5H)‐one Chloride (Dilthiazem Hydrochloride)
Authors: Kojić‐Prodić Biserka , Ružić‐Toroš ŽIva , Šunjić Vitomir , Decorte Enio , Moimas Flavio
Published: December 2004

Resolution of racemic cis‐3‐(2‐aminophenylthio)‐2‐hydroxy‐3‐(4‐methoxyphenyl) propionic acid (2) via the cinchonidine salt 3, and brucine salt 4, isolation of the calcium salts (+)‐ and (−)‐5, as well as their cyclization to enantiomeric 1,5‐benzothiazepines (+)‐ and (−)‐1, are described. X‐Ray single‐crystal analysis reveals (2S, 3S) absolute configuration of (+)‐1 on the basis of tentative comparison of CD data with those for the 1,4‐benzodiazepine derivative (+)‐8 of known absolute configuration.
Synthese und Struktur von Zink‐Komplexen von 2‐Amino‐1‐azetinen
Authors: Stierli Friedrich , Prewo Roland , Bieri Jost H. , Hemigartner Heinz
Published: December 2004

Synthesis ad Structure of Zinc Complexes of 2‐Amino‐1‐azetines

The 2‐dimethylamino‐3,3‐dimethyl‐1‐azetines 7a and 7b have been synthesized in analogy to the procedure reported by Ghosez et al. [1] (Scheme). The crystal structure of 1‐benzhydryl‐azetidindimethyliminium chloride 5a, a precursor of azetine 7a, has been established by X‐ray diffraction analysis. Treatment of azetines 7a and 7b with ZnBr2 in CH2Cl2/MeCN yielded tetrahedral bis (azetine)dibromozinc complexes 8a and 8b, respectively (Scheme 2). The molecular structure of 8a has been determined by X‐ray diffraction analysis too.
A Lipophilic Derivative of Vitamin B12 as Selective Carrier for Anions
Authors: Schulthess Peter , Ammann Daniel , Simon Wilhelm , Caderas Christian , Stepánek René , Kräutler Bernhard
Published: December 2004

Incorporation of the lipophilic Co(III)‐cobyrinate octadecyl‐cobester 1 and of its ionic aqua‐cyano perchlorate derivative 2 into poly(vinyl chloride)/bis(1‐butylpentyl) adipate liquid membranes induces a selectivity, measured potentiometrically, of about 103 for SCN− an NO with respect to CI−, but only of about 4 for ClO vs. CI−. This is in contrast to classical anion‐exchanger membranes, which exhibit a selectivity sequence ClO > SCN− ≫ NO > Cl− in accordance with the Hofmeister, series. The Co(III)‐corrins 1 and 2, when components in solvent polymeric membranes, undergo exchange of axial ligands an behave as highly selective carriers fof SCN− and NO.
Crystal and Molecular Structure of the 4:3 Complex between Lanthanum Nitrate and Pentaethyleneglycol Dimethyl Ether
Authors: Bünzil Jean‐Claude C. , Pfefferlé Jean‐Marc , Ammann Bruno , Chapuis Gervais , Zuniga F.‐Javier
Published: December 2004

The crystal and molecular structure of [La(NO3)3]4(C12H26O5)3 has been determined from low‐temperature single‐crystal X‐ray diffraction data. The complex crystallizes in the monoclinic space group I2 with Z = 2. Lattice parameters at 150 K are a = 12.234 (6) Å, b = 11.105 (5), c = 26.613 (9), β = 90.65 (4)°. The structure was solved by Patterson and Fourier techniques and refined to a conventional RF‐value of 0.068. The compound contains three dinitrato complex cations [La(NO3)2C12H26O6]+ with 10‐coordinate lanthanum ions and one hexanitrato anion, [La(NO3)6]3−, with a 12‐coordinate La(III)‐ion. One complex cation has a C2‐symmetry while the two others, which are crystallographically equivalent, have no symmetry and contain a disordered ligand molecule. The polyther adopts a ring‐like conformation in all the complex moietis. The LaO(nitrate) distances lie in the ranges 2.52–2.53 and 2.49–2.62 Å, with average values of 2.53 (7) and 2.56 (6) Å, respectively, fo the species with C2‐ and C1‐symmetry; the LaO(ether) bond lengths lie int he range 2.54–2.79 Å (average: 2.6 (1)) for the C2‐moiety and their mean value amounts to 2.6 (2) for the disordered species. The hexanitrate has a C2‐symmetry and the LaO distances range between 2.56 and 2.67 Å with an average value fo 2.64 (4) Å. The effective ionic radii of the 10‐ and 12‐coordinate La(III) ions are estimated as 1.28 and 1.33 Å, respectively.
Experiments on the Total Synthesis of Lysolipin I. Part I. On Configuration and Conformation of 5‐Substituted 1,2,3,4,4a,9,10,10a‐Ocathydrophenanthrene‐4,9‐diones
Authors: Duthaler Rudolf O. , Mathies Peter , Petter Walter , Heuberger Christoph , Scherrer Veronica
Published: December 2004

The substituted 1,2,3,4,4a,9,10,10a‐octahydrophenanthrene‐4,9‐dione 2, synthesized from the cyclohexanone 8 and quinone 11 (Scheme 2), was found by X‐ray analysis adn 1H‐NMR studies to be the isomer with cis‐junction of the saturated rings. The cis‐fusion could also be determined from the 1H‐NMR data of the related compound 17 (Scheme 4), which was previously considered to be trans‐fused. In contrary to previous argumentations, the interaction of the C(4)‐carbonyl O‐atom of trans‐fused octahydrophenanthenes is more severe with a 5‐methoxy than with a 5‐methyl substituent.
13C‐NMR spectra of cannbinoids. Part 2. Side‐chain substituted tetrahydrocannabinols and synthetic intermediates
Authors: Franke Ingo , Schmidt Burkhard , Dietrich Wolfgang , Binder Michael
Published: December 2004

The 13C‐NMR spectra of eight semi‐synthetic side‐chain substituted cannabinoids and of eight synthetic intermediates were analyzed in detail. Assignments of the signals are based on their chemical shifts, splitting patterns in 1H‐off‐resonance decoupling experiments, incremental calculations, and model considerations.
Interactions between Functional Groups. Part II. Structure of the 2‐Dimethylaminobenzenediazonium Cation: Retention of Planarity Despite Excessive Steric Crowding
Authors: Wallis John D. , Dunitz Jack D.
Published: December 2004

The crystal structure of 2‐dimethylaminobenzenediazonium tetrafluoroborate has been determined at 183 K by X‐ray diffraction. The cation is very nearly planar, the strong steric interaction between the ortho‐groups being diminished by in‐plane angular distoritions.
Oxidative Cyclopropanol Opening by Cob(III)alamin
Authors: Wan Terence S. , Fischli Albert
Published: December 2004

Starting from the cyclopropanol 2, the isomeric cyclopropanol 4 and the β, γ‐unsasturated aldehydes 7 and 8 have been produced by a cobalamin‐dependant transformation. In traces, the two acetoxycyclopropanes 3 and 6, the saturated aldehydes 5 and 11 and the β,γ‐unsaturated aldehyde 9 could be detected (cf. Structural Formulae and Table). Starting from 4 the same products in a rather similar distribution were obtained. The isomerization 2⇄4 as well as the transformations leading to 7,8, and 9 are shown to be mediated by cob(III)alamin (1(III)). The results are explained on the basis of rearranging Co‐complexes. The migrations might be driven by the electrophilic nature of the central Co(d6)‐atom.
Functionalized Cycloheptanes from Bicyclo[4.2.1]nonanes
Authors: Huston Rima , Rey Max , Dreiding André S.
Published: December 2004

Several oxidative, reductive and C,C‐cleavage reactions were performed starting from the three bicyclo[4.2.1]nona‐3,7‐diene‐2‐one derivatives 1, 5 and 18. The oxidations were selective and led to the diols 2,8 and 9, and the epoxides 6,9, and 20. The reductions were selective only in the case of 20 21; otherwise they led to mixtures of the alcohols 10 and 11, and of the dienes 14 and 15. The periodate ring cleavages afforded the functionalized cycloheptane derivatives 3, 12, 13 and 16. Configurational assignments were made on the basis of detailed 1H‐NMR and X‐ray analysis of 20.
Drüsenfarbstoffe aus Labiaten: Die polaren Diterpenoide aus Plectranthus argentatus S. T. BLAKE
Authors: Alder Alfredo Carlos , Rüdi Peter , Eugster Hans
Published: December 2004

Polar Diterpenoids from Leaf‐Glands of Plectranthus argentatus S. T. BLAKE

From the red leaf‐glands of the Australian Plectranthus argentatus the following novel diterpenoids were isolated: coleon‐U‐quinone (1), 8α,9α‐epoxycoleon‐U‐quinone (3), 6β‐formyloxy‐7α‐hydroxyroyleanone (7), and 5,6‐dihydrocoleon U (10), besides the already known compounds 6β, 7α‐dihydroxyroyleanone (4), 7α‐acetoxy‐6β‐hydroxyroyleanone (5), and 7α‐formyloxy‐6β‐hydroxyroyleanone (6). Epoxydation of 1 by perborate led in 32% yield to the epoxyquinone 3.
The synthesis and transition temperatures of benzoate ester derivatives of 2‐fluoro‐4‐hydroxy‐and 3‐fluoro‐4‐hydroxybenzonitriles
Authors: Kelly Stephen M.
Published: December 2004

The synthesis and the liquid‐crystal temperatures of sixty 4‐cyano‐2‐fluorophenyl and 4‐cyano‐3‐fluorophylen 4‐substituted benzoates are described. The nematic‐isotropic liquid transition temperatures of the most of these novel esters are only marginally lower than those of the corresponding esters containing an H‐atom in place of the F‐substituent. In several instances, the clearing points of the F‐substiuted‐phenyl esters are higher than those of the non‐substituted‐phenyl esters. The nematic ranges of several of the new esters are markedly broader than those of the analogous non‐F‐substituted‐phenyl esters.
Synthese von 2,3‐unsubstituierten, N‐acylierten Indolen durch sigmatrope[3,3]‐Umlagerung von O‐Vinyl‐N‐phenylhydroxylaminderivaten
Authors: Martin Pierre
Published: December 2004

Synthesis of 2,3‐Unsubstituted N‐Acylindoles by [3,3]‐Rearrangement of the N‐Phenyl‐O‐vinylhydroxylamine Derivatives

Summary, Treatment of N‐phenylhydroxamic acids with vinylacetate in the presence of Li2PdCl4 affords 2,3‐unsubstituted N‐acylindoles via hetero‐Cope‐rearrangement of the intermediate N‐O‐vinylhydroxylamine derivatives.
Studies on the Stereochemistry of 2‐(Nitromethylidene)‐Heterocycles
Authors: Rajappa Srinivasachari , Nagarajan Kuppuswamy , Venkatesan Kailasam , Kamath Nirupa , Padmanabhan Vipanjeri Madabhusi , von Philipsborn Wolfgang , Chen Ban Chin , Müller Raffaelo
Published: December 2004

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

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

Deuteration of Betanidine and Indicaxanthine. (E/Z)‐Stereoisomerism in Betalaines

Previously unexplained1H‐NMR signals of the red‐violet betanidine and of the yellow indicaxanthine in CF3COOH are interpreted with the help of deuteration experiments in CF3COOD. They confirm the 1,7‐diazaheptamethinium chromophore of these pigments and further show an (E/Z)‐stereoisomerism at one of the partial double bonds: both betanidine and isobetanidine, in CF3COOH solution, consist of a ∼ 75:25 mixture of the (12E)‐ (1resp.12) and the (12Z)‐stereoisomer (2resp.13); indicaxanthine, in the same solvent, is made up of a ∼ 65:35 mixture of the (8E)‐ (14) and the (8Z)‐stereoisomer (15). The interconversions1⇆2,12⇆13and14⇆15in CF3COOH are so fast that these isomers cannot be separated from each other.