bluuebunny/crossref_metadata_2025 huggingface dataset:
Stereoselektive Totalsynthese von natürlichem Phytol und Phytolderivaten und deren Verwendung zur Herstellung von natürlichem Vitamin K1
Authors: Schmid Max , Gerber Fernand , Hirth Georges
Published: December 2004

Steroselective Total Synthesis of Natural Phytol and Derivatives thereof; Use of these Compounds in the Synthesis of Natural Vitamin K1

The Li2CuCl4‐catalyzed couplings of the easily accessible bifunctional C5 allylic acetates (E)‐18a and (E)‐18b with racemic hexahydrofarnesylmagnesium bromide ((3 RS/RS, 7 RS/SR)‐19a) proceed with high chemo‐ and stereoselectivity (≥98% (E)‐retention) to give the (2E, 7 RS/RS, 11 RS/SR)‐phytol derivatives 1a and 1b, respectively, in yields of 72–80% (Scheme 5). The same couplings performed with optically active hexahydrofarnesylmagnesium bromide (3 R, 7 R)‐19a yielded the (E)‐phytol derivatives of the natural series (7 R, 11R)‐1a and (7 R, 11 R)‐1b. Acid‐catalyzed hydrolysis of(2 E, 7 R, 11 R)‐1b gave natural phytol((2 E, 7 R, 11 R)‐1c) Friedel‐Crafts alkylation of ‘menadiol monobenzoate’ 11b with (2 E, 7 R, 11 R)‐1a or (2 E, 7 R, 11 R)‐1b gave the dihydrovitamine K1 derivative (2 E/Z, 7′ R, 11′R)‐12b ((E/Z)≈︁ 9:l). Conversion of configurationally pure (2 E, 7′ R, 11′ R)‐12b (yield 73%; obtained after chromatographic removal of the (Z)‐isomer) into natural vitamine K1 ((2 E,7′ R, 11′ R)‐2) was achieved in the usual way by saponification and oxidation with air.

Some further investigations of the coupling reactions of bifunctional C5 allylic synthons with hexahydrofarnesylmagnesium bromide (3 RS/RS, 7 RS/SR)‐19a showed the outcome of these reactions to be critically dependent on the nature of the leaving group, the double‐bond geometry and the nature and concentration of the catalyst. Thus, the Li2CuCl4‐catalyzed couplings of (3 RS/RS,7 RS/SR)‐19a with the allylic halides 29a and 29c as well as with p‐toluenesulfonate 29b yielded besides the phytol derivatives 1a and 1b ‐ also the SN2′‐type products 30a and 30b (Scheme 8, Table 2); the same result was found for the coupling with the cis‐configurated allylic acetates (Z)‐18a and (Z)‐18b (Table 3). A similar loss of chemo selectivity as well as the loss of stereoselectivity in the coupling reactions of 19 with the bifunctional (E)‐olefins of type 18 was observed when the Li2CuCl4‐catalyst concentration was increased from 0.2 to 25 mol‐% or upon substitution of Li2CuCl4 by copper (I) chloride or iodide (Table 4).
Heterodiamantane und strukturell verwandte Verbindungen. IV. Pentacyclische Diäther der C12‐Reihe: 5,14‐Dioxapentaccology[7.5.0.02,6.03,13.04,10]terradecan,4,14‐Dioxapentacyclo[7.4.1.02,8.03n,11.05,10]tetradecan,3,11‐Dioxapentacyclo[8.3.1.02,8.04,13.07,12]tetradecan und 3,10‐Dioxapentacyclo[7.3.1.1.4,12.02,7.06,11]tetradecan (3,10‐Dioxadiamantan)
Authors: Ammann Willi , Pfund Holland A. , Ganter Camille
Published: December 2004

Heterodiamantanes and Structurally Related Compounds. Part IV. The Pentacyclic C12‐Diethers 5, 14‐Dioxapentacyclo[7.5.0.02,6.03,13.04,10]tetradecane, 4,14‐Dioxapentacyclo[7.4.1.02,8.03,11.05,10]tetradecane, 3,11‐Dioxapentacyclo[8.31.02,8.04,13.07,12]tetradecane, and 3,10‐Dioxapentacyclo[7.3.1.14,12.02,7.06,11]tetradecane (3,10‐Dioxadiamantane)

In connection with the studies on heterodiamantanes and structurally related compounds the four novel pentacyclic diethers 6–9 were prepared starting from the cyclopentadienone dimer 12, All five compounds have as common features a central carbocyclic 6‐membered ring with four axial alkyl substituents and two oxygen functions in 1,4‐positions. The required twelfth C‐ atom was introduced by dichlorocarbene addition to 11 (the rnonocarbene adduct of 12) (→ 10, Scheme 2). The two three‐membered rings in 10 had to be opened step wise. Controlled thermolysis of 10 yielded the chloride 13 and the acetate 14, respectively, from which the alcohols 16, 17 and 20 as well as the acetates 22 and 23 were obtained by reduction (Scheme 2). The remaining second ring was opened again thermally either to tricyclic compounds as 22 → 25 + 26, 23 → 27 + 28 or under simultaneous ether formation to tetra‐cyclic compounds as 16 → 29 + 30, 17 → 32 + 33, 20 → 34 + 35 (Scheme 3). The two compounds 29 and 30 were also obtained from 37, the dichlorocarbene adduct of the tricyclic C11‐ether 36 (Scheme 4). These tri‐ and tetracyclic compounds 25–30 and 32–35 were suitable intermediates for the syntheses of all four pentacyclic diethers 6–9.

Diether 6 was prepared from 25, 26, 29 as well as 30 via 38 (Scheme 5), and from 29 by the route depicted in Scheme 6. By a procedure analogous to the latter one, diether 7 was obtained from 30 (Scheme 6). Diether 8 was the result of transformations starting from either 27, 28, 32 or 33 (Scheme 7). The synthesis of diether 9 (3,10‐dioxadiamantane), the thermodynamically most stable of the four diethers 6–9, was achieved in three different ways : ring closure starting from the highly substituted tricyclic compounds 25 and 26 (Scheme 9), skeletal rearrangement of the group‐A
The Novel Adamantane Isomer 2,5‐Trimethylenenorbornane (Tricycio‐[5.3.0.3,9]decane, 4‐Homotwistbrendane)
Authors: Känel Hans‐Ruedi , Capraro Hans‐Georg , Ganter Camille
Published: December 2004

A synthesis of the novel C10H16 hydrocarbon 2,5‐trimethylenenorbornane (tricyclo[5.3.0.03,9]decane, 1), one of the 19 members of the ‘adamantaneland’, and its Lewis‐acid‐catalyzed rearrangement is described.
2‐Pyridylhydrazone als Carbonylderivate zur Steuerung der Fragmentierung in der Massenspektrometrie
Authors: Vetter Walter , Meister Walter
Published: December 2004

2‐Pyridylhydrazones as Carbonyl Derivatives to induce Fragmentation in Mass Spectrometry

It was found that the 2‐pyridylhydrazone is a derivative of the carbonyl group, which is able to induce fragmentation of an alicyclic skeleton with an efficiency comparable to that of the tertiary amino group and the ethylene acetal group.
The Crystal structure of 2‐Diisopropylamino‐3,7‐dehydrotropone
Authors: Grieb Rita , Gray Robert W. , Dreiding André S.
Published: December 2004

Die erste Röntgenstrukturanalyse eines 3,7‐Dehydrotropon (1)‐Derivates, nämlich von 2‐Diisopropylammo‐3,7‐dehydrotropon (4) zeigt das Ringsystem in 4 als planaren Bicyclus mit nahezu C2V‐Symmetrie. Dementsprechend enthalten Dehydrotropone formell zwei trans‐konfigurierte Doppelbindungen in einem 7‐gliedrigen Ring; auch das O‐Atom und das N‐Atom mit seinen Ligandatomen liegen in derselben Ebene wie die Ringatome. Die Bindung zwischen den beiden C‐Atomen, welche die Heteroatome tragen, (C(1) and C(2)), ist wesentlich langer (1,56 Å) als die anderen Bindungen im Ringsystem (1,37‐1,46 Å). Dies impliziert eine ‘push‐pull’‐π‐Elektronen‐Delokalisierung, in der auch das O‐und das N‐Atom involviert sind, und macht eine ‘aromatische’ Ring‐Delokalisierung weniger wahr‐scheinlich. Im Gegensatz zu 2‐(t‐Butyl)‐3,7‐dehydrotropon (3) existiert das 2‐Diiso‐propylamino‐3,7‐dehydrotropon (4) im Kristall als Monomeres, was dem stabili‐sierenden Einfluss der ‘push‐pull’‐Delokausierung zugeschrieben werden kann.
Diastereoselektive Synthese von β‐Methyl‐homoallylalkoholen durchlk‐Addition von (2‐Butenyl)triphenoxytitan an Aldehyde
Authors: Widler Leo , Seebaeh Dieter
Published: December 2004

Diastereoselective Synthesis of β‐Methyl‐homoallylic Alcohols bylk‐Addition of (2‐Butenyl)triphenoxytitanium to Aldehydes

(2‐Butenyl)triphenoxytitanium, prepared insitufrom (2‐butenyl)magnesium halogenide and chlorotriphenoxytitanium in tetrahydrofuran solution, adds to aldehydes withlike(Re,Re/Si,SiRe*,Re*) relative topicity in diastereoselectivities of 80–99%.
Über Pterinchemie 80. Mitteilung Die Herstellung von (6RS)Tetra‐ und (6RS)Pentaacetyl‐5,6,7,8‐tetrahydro‐L‐bioplerinen
Authors: Ganguly Subhendu Narayaa , Viscontini Max
Published: December 2004

Preparation of (6RS)Tetra‐ and (6RS)‐Pentaacetyl‐5,6,7,8‐tetrahydro‐L‐biopterines

Boiling of (6RS) l′‐O,2′‐O,2‐N‐triacetyl‐5,6,7,8‐tetrahydro‐L‐biopterine in acetic anhydride as described in [2], leads to a mixture of the diastereoisomeric (6R)‐ and (65)‐l′‐O,2′‐O,2‐N‐,5,8‐pentaacetyl‐5,6,7,8‐L,‐biopterines. One of the diastereoisomers can be obtained as pure crystals. It corresponds to the pentaacetate of the natural (6R)‐ or (6S).,5,6,7,8‐tetrahydro‐L‐biopterine. For the preparation of the earlier described (6RS)‐ and (6S)‐tetraacetyl‐tetrahydro‐L‐biopterines [2] improved conditions are reported.
Totalsynthese von Nojirimycin
Authors: Vasella Andrea , Voeffray Robert
Published: December 2004

Total synthesis of Nojirimycin

Addition of the nitrone 3 (from 8 and 9) to furane, followed by oxidation with OsO4 and then isopropylidenation gave the fully functionalized glycoside 12 (40% from 8) via the glycal 10 and the hemiacetal 11. Since the glycoside cleavage of 12, leading to 13 after benzyloxycarbonylation proceeded in a mediocre yield, and since the acetolysis of 12 giving 14 (69%) was not practical, compound 12 was transformed into the hydroxy ester 17 by sequential hydrogenolysis, hydrolysis and benzyloxycarbonylation (69% overall). The hydroxy ester 17 was lactonized to give 18 (87%). Reduction of 18 first with LiBH4 (97%) and then with H2/Pd gave the key compound 20 which was transformed into nojirimycin (1) and into 1‐deoxy‐nojirimycin (2) using prior art. The overall yield of 1 was 19.5%.
Stereospezifische Synthese einer neuen Morphin‐Teilstruktur
Authors: Haefliger Walter , Klöppner Edgar
Published: December 2004

We describe here a synthesis of the morphine partial structures 28 and 36, and of their enantiomers, which uses 7‐methoxy‐benzofurancarboxylic acid as starting material. A key intermediate in this scheme is compound 15, which is converted, via 1,2‐ketone shift, into 22. This latter is stereospecifically reduced to the alcohol 24 and converted to the amide 25. The diastereomer of 25 is afforded by stereospecific introduction of a ethoxycarbonyl group in 15 to yield the β‐ketoester 31, followed by Curtius degradation of the acid 32 to the acylamine 34.

An efficient method for removal of the methoxy group in methoxy‐dihydro‐benzofurans is presented (Scheme 9), as is the functionalization of the N‐atom in 27 with concurrent complex formation between the free hydroxy group and boric‐acid. The aromatization of the furan ring (Scheme 10) with DDQ gave the expected benzofuran derivative 30.
Preparation and Conformational Properties of Benzylpenicilloyl‐oligo‐L‐lysine Conjugates
Authors: Rolli Hanspeter , Lüscher Immanuel F. , Schneider Conrad H. , Toniolo Claudio , Bonora Gian Maria
Published: December 2004

Selected oligo‐L‐lysine carriers and a poly‐L‐lysine were penicilloylated with benzylpenicillin. The resulting conjugates 2–6 were studied by IR. absorption in the solid state and circular dichroism measurements in solution. The IR. data demonstrate the lack of β‐structure formation even in medium‐sized peptides where such structures might be expected on the basis of previous studies on differently substituted oligo‐L‐lysines. Considerable proportions of right‐handed α ‐helical conformation are exhibited by the icosa‐L‐lysine and poly‐L‐lysine conjugates 5 and 6 in water and 2,2,2‐trifluoroethanol. Difficulties in obtaining fully penicilloylated conjugates are not related to the extent of α‐helical conformation in aqueous solution.
Molecular Quantum Beat Spectroscopy in External Fields as a Sensitive Probe of Excited State Properties
Authors: Lendi Karl
Published: December 2004

The new phenomenon of the external field dependence of quantum beats in polyatomic molecules is studied on a model which offers analytical formulas for a series expansion to lowest order in the field. A comparison with recent experiments on the magnetic field effect in biacetyl suggests that, in addition to the level shift the triplet deactivation is also strongly field‐dependent. New experiments are proposed.
A Note on Intramolecular Photochemical Cycloaddition of N‐substituted Dimethacrylimides
Authors: Alder Alex , Bühler Niklaus , Bellus Daniel
Published: December 2004

The intramolecular photochemical [2+ 2]‐cycloaddition of N‐substituted dimethacrylimides 1a and 1c, respectively, proceeds under conditions of direct irradiation (λ = 254 nm) as well as triplet photosensitization highly regioselectively yielding predominantly the «cross» bonding (head‐to‐tail) cycloadducts 3a and 3c, respectively, with a 3‐azabicyclo [3.1.1]heptane ring system.
2, 3‐Alkadiensäureester als Dienophile; Anwendung bei der Synthese von (+)‐(R)‐Lasiodiplodin
Authors: Fink Margot , Gaier Hans , Gerlacho Hans
Published: December 2004

2,3‐Alkadienoates as Dienophiles, Application in the Synthesis of (+)‐(R)‐Lasiodiplodin

Methyl 2, 3‐alkadienoates 2 are shown to react at 80° with l, 1‐dimethoxy‐3trimethylsilyloxy‐l, 3‐butadiene (1) to give the adducts 3 in good yields. Rearrangement of 3, catalyzed by p‐toluenesulfonic acid or by sodium methoxide, affords the 6‐substituted methyl 4‐hydroxy‐2‐methoxybenzoates 4 (R  H, CH3, C6H5). An analogous reaction sequence starting with (‐)‐(11 R)‐dodeca‐2, 3‐dien‐11‐olide ((‐)‐6) and 1 leads, via the adduct (R)‐7, to (+)‐(R)‐lasiodiplodin ((+)−8) with properties identical to those of the natural product. The allene lactone (‐)‐6 was prepared by an intramolecular Wittig condensation of (R)−5, produced from (–)‐(R)‐9‐hydroxydecanoic acid.
Abkömmlinge der 3‐Chinolincarbonsäure mit Sauerstoffsubstitution in Stellung 4, 5 and 8: Synthese, Reaktionen, NMR.‐Studien
Authors: Link Helmut , Bernauer Karl , Englert Gerhard
Published: December 2004

Derivatives of 3‐Quinolinecarboxylic Acid with Oxygen Substitution in Positions 4, 5 and 8: Synthesis, Reactions, NMR. Studies

Starting from either 1, 4‐dibenzyloxybenzene (7) or 2, 5‐dimethoxyaniline (16), synthetic routes have been developed to benzenoid and quinoid derivatives of 4‐oxo‐1, 4‐dihydro‐3‐quinolinecarboxylic acid with O‐bearing substituents in the positions 5 and 8 (compounds 12‐15, 19, 20, 23, and 24). With the 1‐ethyl‐4, 5, 8 trioxo acid 14 as a dienophile, a series of linear tricyclic diene adducts (29‐32) has been prepared, the structures of which were further modified by aromatization, reduction or dehydrogenation (compounds 33‐40). A series of benzenoid and quinoid compounds with an additional substituent in position 6 or 7 (Table 1) has been derived mainly from the quinone 14, primarily by addition of nucleophiles and eventually subsequent steps, and by aromatic electrophilic substitution of the 1‐ethyl‐5, 8‐dimethoxy acid 23. The substitution pattern of some of these compounds has been elucidated by detailed 13C‐NMR. studies (Table 2) and/or nuclear Overhauser‐effect studies (Table 3). Correlations, based essentially on chemical arguments, allowed to define the structures of most of the residual new compounds (Table 4).
Stoffwechselprodukte von Mikroorganismen. 218. Mitteilung. Versuche zur Strukturaufklärung von Niphimycin, 1. Teil. Reinigung und Charakterisierung der Niphimycine Iα und Iβ sowie Abbau mit Salpetersäure
Authors: Bassi Luciano , Joos Beda , Gassmann Peter , Kaiser Hans‐Peter , Leuenberger Heinz , Keller‐Schierlein Walter
Published: December 2004

On the Structure Elucidation of Niphimycin, Part I. Purification and Characterization of the Niphimycins Iα and Ib̃; Degradation by Nitric Acid

From a sample of niphimycin the pure components, niphimycin Iα and Ib̃, were isolated by column chromatography and droplet counter‐current chromatography. They were characterized by UV., IR., 1H‐NMR. (300 MHz) and 13C‐NMR. spectra. A vigorous degradation of niphimycin with nitric acid, followed by esterification with diazomethane, gave a complex mixture, from which many components could be isolated and identified. Several of the degradation products were synthesized, one of them (dimethyl 2,4‐dimethyladipate) in a stereospecific manner, establishing the configuration of two of the centers of chirality of niphimycin.

Niphithricin was identified with copiamycin and yielded with nitric acid a degradation mixture very similar to that from niphimycin. The structures of the degradation products are in good agreement with a macrolide‐type structure of niphimycin and copiamycin.

Further work for structure elucidation of niphimycin and copiamycin is in progress.
Ein Beitrag zur Stereochemie der S′E‐Reaktion: Die Protonierung eines optisch aktiven 1, 1‐Disilyl‐2‐alkens
Authors: Wetter Hansjürg , Scherer Paul
Published: December 2004

A Contribution to the Stereochemistry of the S′E‐Reaction: the Protonation of an Optically Active 1, 1‐Disilyl‐2‐alkene

An optically active, 1, 1‐disilyl‐2‐alkene 2 was reacted with CF3COOH and HBF4·OMe2 and furnished with loss of one silyl group and migration of the double bond the corresponding vinylsilane 4. Determination of the absolute configuration and enantiomeric excess of 2 and 4 showed the S′E‐reaction to proceed in the case of CF3COOH with 48% (74% anti/26% syn) and in the case of HBF4·OMe2 with 44% (72% anti/28% syn) stereoselectivity. Deuteriodesilylation with CF3COOD resulted in the exclusive formation of at C (3)‐monodeuteriated vinylsilane 4.
Electron Spin Resonance of α‐(Alkoxycarbonyl)alkyl Radicals in Solution
Authors: Lung‐min Wu , Fischer Hanns
Published: December 2004

High‐resolution ESR. spectra of the radicals CH2COOR, CH3CHCOOR and (CH3)2CCOOR with RCH3, CH2CH3, CH(CH3)2 and C(CH3)3 in liquid solution confirm planar energy‐minimum structures with substantial barriers to internal rotation about the Ċ, CO‐bonds (⋍40 kJ/mol) and partial π‐electron delocalization. The assignments of coupling constants to protons in isomeric positions and the conclusions on radical structures are supported by INDO‐calculations.
Cycloaddition of 3,4‐Dimethoxyfuran with 1,4‐Benzoquinones under High Pressure
Authors: Jurczak Janusz , Koz̀gluk Tomasz , Tkacz Marek , Eugster Conrad Hans
Published: December 2004

High‐pressure cycloaddition of 3,4‐dimethoxyfuran with 1,4‐benzoquinone, toluquinone and 2,3‐dimethoxy‐1,4‐benzoquinone show, at 7 kbar and room temperature, prevailing formation of endo‐isomers. Raising pressure (or temperature) results in a surprising increase of the exo‐isomer. By catalytic hydrogenation of a mixture 3a/4a, followed by chromatography, the pure diastereomers 5 and 6 were obtained.
[2 + 4]‐Cycloaddition under High Pressure: First Realization of a Diels‐Alder Addition of Furan with Simple 1,4‐Benzoquinones. Preliminary Communication
Authors: Jurczak Janusz , Koz̀luk Tomasz , Filipek Stanislaw , Eugster Conrad Hans
Published: December 2004

For the first time a successful [2 + 4]‐cycloaddition of furan (1) with simple 1,4‐benzoquinones 2 has been realized.
Approaches to the Synthesis of Cytochalasans. Part 4. Improved Synthesis of the Tetrahydroisoindoline Subunits Related to the Cytochalasins and Aspochalasins
Authors: Schmidlin Tibur , Burckhardt Peter E. , Waespe‐Šarčevic̀ Nada , Tamm Christoph
Published: December 2004

A general scheme for the synthesis of the tetrahydroisoindolinone moiety of naturally occurring cytochalasans and unnatural analogs was developed. The key‐step consists of the intermolecular [2+4]cycloaddition of 4‐methylsorbinol (7) to an alkylidene malonic ester derivative such as 6, 9 or 10, obtained from the corresponding amino acids. The products obtained, 4a, 17, and 18 were converted to the desired lactams 5, 21, and 22.

Cycloaddition of the diene alcohol 7 to the optically active alkylidene malonic ester derivative 9b (s. Footnote 5) prepared from L‐leucine gave compound 17b with 98% enantiomeric excess. The optical activity was retained during the conversion of 17b to the lactam 21b. The latter is a subunit for the synthesis of the aspochalasins.
Stereospezifische Synthesecis/trans‐disubstituierter Tetrahydrofurane
Authors: Terlinden Rolf , Boland Wilhelm , Jaenicke Lothar
Published: December 2004

Multifidene1is a chemical messenger for male gametes of the brown algaCutleria multifida. The synthesis of messenger analogues with a tetrahydrofurane ring will be reported. The general synthetic approach offers the possibility to prepare a great variety of stereospecific 2,3‐ and 3,4‐cis/trans‐disubstituted tetrahydrofurans.
Production of (+)‐(S)‐Ethyl 3‐Hydroxybutyrate and (‐)‐(R)‐Ethyl 3‐Hydroxybutyrate by Microbial Reduction of Ethyl Acetoacetate
Authors: Wipf Beat , Kupfer Ernst , Bertazzi Roberto , Leuenberger Hans Georg Wilhelm
Published: December 2004

The production of (S)‐ethyl 3‐hydroxybutyrate (2) from ethyl acetoacetate (1) in higher yields and with higher optical purity than with the usual procedures was achieved by continuous addition of the substrate 1 and sucrose to an aerated suspension of bakers' yeast. The microbial reduction of 1 by the fungus Geotrichum candidum LINK yields ‐ for the first time ‐ the antipode 3.
Synthesis and Biological Activities of C (5)‐N‐Spin‐Labeled Uridines and Related Derivatives
Authors: Bobst Albert M. , Ozinskas Alvydas J. , De Clercq Erik
Published: December 2004

Direct introduction of a N‐atom in one step at C (5) of 5‐hydroxyuridine (4a) or 5‐hydroxy‐2′‐deoxyuridine (4b) by certain primary amines led to the synthesis of two novel C(5)‐N‐spin‐labeled nucleoside analogs and to several C(5)‐N‐aryl adducts. Substitution by 4‐amino‐2,2,6,6‐tetramethylpiperidinooxyl (3) at C(5) of 4a or 4b led to the spin‐labeled nucleosides 5‐[(1‐oxyl‐2,2,6,6‐tetramethyl‐4‐piperidinyl)amino]uridine and ‐2′‐deoxyuridine (2a and 2b, respectively). The analogous C(5)‐substituted aniline adducts 5‐anilino uridine (5a) and 5‐anilino‐2′‐deoxyuridine (5b) and the p‐toluidine adducts 5‐(p‐toluidino)uridine (6a) and 5‐(p‐toluidino)‐2‐deoxyuridine (6b) were also prepared. In addition, results of the antiviral and antimetabolic activity of some of these analogs are reported.
Cycloaddition von Chlorsulfonyliscyanat an «Maleinisoimide»
Authors: Capraro Hans‐Georg , Rihs Grety , Martin Pierre
Published: December 2004

Cycloaddition of Chlorosulfonylisocyanate to ‘Maleic Isoimides’

Cycloaddition reactions of chlorosulfonylisocyanate to ‘maleic isoimides’ are described. The not expected multifunctional (2:1)‐adducts 2 were converted to the crystalline compounds 3, whose structures were resolved by X‐ray analysis.
Nucleosides and Nucleotides. Part 21. Synthesis of a Tridecanucleoside Dodecaphosphate Incorporating the Unnatural Base 2 (1 H)‐Pyridone
Authors: De Bernardini Silvio , Graf Georg , Leach Colin A. , Bühlmayer Peter , Waldmeier Felix , Tamm Christoph
Published: December 2004

The modified nucleoside Πd (1) was used in the synthesis of the oligonucleotide d (TpTpΠpCpGpTpCpApApApApTpC). Diester methodology being unsatisfactory, the triester synthesis was investigated with the unnatural nucleoside. An improved method of nucleoside phosphorylation was developed for the synthesis of the fully‐protected nucleotide 2e. This molecule could be cleanly and selectively deprotected, and allowed the efficient synthesis of the desired oligonucleotide.
13C‐NMR.‐Spektren von Dicyanhydrochinonen und Dicyan‐p‐benzochinonen
Authors: Neidlein Richard , Kramer Walter , Leidholdt Rolf
Published: December 2004

13C‐NMR. Spectra of Dicyanohydroquinones and Dicyano‐p‐benzoquinones

The 13C‐NMR. spectra of 12 dicyanohydroquinones and fully substituted dicyano‐ and diazido‐p‐benzoquinones have been measured and assigned by comparison with related benzene and p‐benzoquinone derivatives. For p‐benzoquinones the influence of the cyano and azido substituents on the chemical shift of the CO‐, α‐ and β‐C‐atoms has been investigated.
Fundamental Aspects of Ionic Dissociations: The Fragmentation Pathways of Excited Bicyclobutane Cations
Authors: Bombach Rolf , Dannacher Josef , Stadelmann J.‐P. , Neier Reinhard
Published: December 2004

A most recently developed method to quantify the fragmentation pathways of excited radical cations is presented. Using bicyclobutane cation as an illustrative example, the RRKM analysis of the breakdown diagram determined by He‐Iα photoelectron‐photoion coincidence spectroscopy is outlined. The results imply complete isomerization to 1,3‐butadiene cation preceding the dissociative processes. The rate‐energy functions of four competitive primary fragmentation reactions, leading to C3H, C4H, C4H and C2H are established. There is compelling evidence that the production of C2H fragment ions does not compete effectively with these four reactions. The extent of kinetic and competitive shift effects is determined. The derived enthalpies of formation are in excellent accord with the available high quality reference data. The relative importance of different fragmentation pathways which ultimately lead to fragment ions of identical mass to charge ratio is assessed.
Synthesen Makrocyclischer Lactone durch Ringerweiterung. Vorläufige Mitteilung
Authors: Kostova Kalina , Hesse Manfred
Published: December 2004

Syntheses of Macrocyclic Lactones by Ring Enlargement Reaction

A general method is given for the synthesis of macrocyclic lactones by ring enlargement of 2‐nitrocycloalkanones by four ring members. By this procedure 2‐nitrocyclooctanone (1) is transformed to 8‐oxo‐dodecan‐11‐olid (5) in an overall yield of 63,5% and 2‐nitrocyclododecanone to 12‐oxo‐hexadecan‐15‐olid with 60% yield.
N‐Levulination of Guanosine
Authors: Hakimelahi Gholm Hosein , Khalafi‐Nezhad Ali
Published: December 2004

A procedure have been developed for the synthesis of the N‐levulinoyl derivative of guanosine.
TETRAMETHOPRIM and PENTAMETHOPRIM: Synthesis, Antibacterial Properties and X‐Ray Structures
Authors: Brossi Arnold , Sharma Padam N. , Takahashi Kimio , Chiang Joseph F. , Karle Isabella L. , Seibert Gerhard
Published: December 2004

TETRAMETHOPRIM (9) and PENTAMETHOPRIM (10), both prepared from the corresponding benzaldehydes 3 and 6 by conventional procedures, did not exhibit noteworthy antibacterial activity in vitro. A single crystal X‐ray analysis of 9 and 10 provided evidence that the out‐of‐plane methoxy groups in the two compounds created a completely different topographical situation to that present in TRIMETHOPRIM, and less ideal for the binding to bacterial dihydrofolate reductase.
Stereochemische Korrelationen zwischen (2R,4′R,8′R)‐α‐Tocopherol, (25S,26)‐Dihydroxycholecalciferol, (–)‐(1S,5R)‐Frontalin und (–)‐(R)‐Linalol
Authors: Barner Richard , Hübscher Josef
Published: December 2004

Stereochemical Correlations between (2R,4′R,8′R)‐α‐Tocopherol, (25S,26)‐Dihydroxycholecalciferol, (–)‐(1S,5R)‐Frontalin and (–)‐(R)‐Linalol

The optically active C5‐ and C4‐building units 1 and 2 with their hydroxy group at a asymmetric C‐atom were transformed to (–)‐(1S,5R)‐Frontalin (7) and (–)‐(3R)‐Linalol (8) respectively; 1 and 2 had been used earlier in the preparation of the chroman part of (2R,4′R,8′R)‐α‐Tocopherol (6a, vitamin E), and for introduction of the side chain in (25S,26)‐Dihydroxycholecalciferol ((25S)‐4), a natural metabolite of Vitamin D3. The stereochemical correlations resulting from these converions fit into a coherent picture with those correlations already known from literature and they confirm our earlier stereochemical assignments. A stereochemical assignment concerning the C(25)‐epimers of 25,26‐Dihydroxycholecalciferol that was in contrast to our findings and that initiated the conversion of 1 and 2 to 7 resp. 8 for additional stereochemical correlations has been corrected in the meantime by the authors [26].
Studies Related to Biological Detoxification of Kraft Pulp Mill Effluent. VI. The Biodegradation of 12,14‐dichlorodehydroabietic acid with mortierella isabellina
Authors: Kutney James P. , Dimitriadis Eugene , Hewitt Gary M. , Salisbury Philip J. , Singh Mahatam , Servizi James A. , Martens Dennis W. , Gordon Robert W.
Published: December 2004

A detailed study of the biodegradation of one of the fish toxic chlorinated resin acids, 12,14‐dichlorodehydroabietic acid

The correct IUPAC‐name is 12,14‐dichloro‐8,9,11,12‐tetradehydro‐7,8‐dihydroabietic acid.

(3) is presented. When exposed to the fungus Mortierella isabellina, 3 is converted into a number of hydroxylated and keto derivatives which show low levels of toxicity to fish. These metabolites were isolated and characterized.
New Synthetic Bromination Procedures for Use in Radiolabelling‐Chemistry: Reaction of C‐Metallated Derivatives of Carbohydrates with Bromide, in the Presence of Mild Oxidizing Agents
Authors: Neeser Jean‐Richard , Hall Laurance D. , Balatoni Julius A.
Published: December 2004

In the presence of 2 mol‐equiv. of AcONa, both triglycosylborane 1 and dicyclohexylglycosylborane 2 readily react with bromine chloride generated in situ from bromide and N‐chlorosuccinimide (NCS) to give the bromo‐sugar 3 (75 and 60%, resp.). The use of the BH3‐THF/bromide/NCS/2 AcONa procedure permits the rapid, face‐specific synthesis of 6 (58% uptake of bromine) and face‐selective synthesis of 8/9 (71% uptake of bromine), from vinyl ether derivatives 5 and 7, respectively. The dicyclohexylborane/bromide/NCS/2 AcONa procedure leads to the fast and quantitative conversion of 11 to the bromosugar 12 (91%). Hydroboration‐transmetallation sequences give access to C‐mercuriated carbohydrates 13 (71%) and 14 (78%). The bis(glycosyl)mercury derivative 13 is spontaneously cleaved by reaction with one equivalent of bromide/chloramine‐T/aqueous HCl‐solution to give 3 (87%) and 14 (76%). Hydrostannylation of acetylenic sugar 15 gave the (E)‐stannylvinyl derivative 16 as the major product. This latter precursor 16 is spontaneously cleaved by the bromide/chloramine‐T/aqueous HCl‐solution reagent to give the bromovinyl‐sugar 17 (96%).
Synthesis of D‐ and L‐5‐Oxaproline and of a New Captopril Analogue
Authors: Vasella Andrea , Voeffray Robert , Pless Janos , Huguenin René
Published: December 2004

The 1,3‐dipolar cycloaddition of the C‐t‐butyloxycarbonyl‐N‐mannosyl‐nitrone 5, formed in situ from the partially protected D‐mannose‐oxime 3 and the glyoxylate 4, to ethylene gave preferentially the (3S)‐N‐glycosyl‐isoxazolidine 6 which was transformed into the 3‐isoxazolidine‐carboxylate (L‐5‐oxaproline ester) 12 and into some derivatives thereof. The (S)‐configuration of 12 was proved by chemical correlation with a derivative of L‐asparagine. The D‐5‐oxaproline ester was obtained from the corresponding N‐ribosyl‐nitrone 24. Two protected dipeptides containing either C‐terminal‐ (28) or N‐terminal‐5‐oxaproline (= Opro) (30) were synthesized. Starting from 12, the analogue 1 of captopril® (2) was prepared and its activity as an inhibitor of the angiotensin‐converting‐enzyme (ACE) was examined.
Synthesis and Protonation Features of 24‐, 27‐ and 32‐membered Macrocyclic Polyamines
Authors: Dietrich Bernard , Hosseini Mir Wais , Lehn Jean‐Marie , Sessions Richard B.
Published: December 2004

Three macrocyclic polyamines [24]ane‐N6 1, [32]ane‐N8 2 and [27]ane‐N6O3 3 of ring size 24, 32 and 27, respectively, have been synthesized. They contain either trimethylenediamine of ethylenediamine units. The acyclic analog 4, as the reference compound, was also prepared. Compounds 1–3 are macrocyclic analogs of natural polyamines and are potential ligands for metal cations as well as, when protonated, for anions. The protonation constants of compounds 1–4 have been determined. They are high enough for compounds 1–4 to be fully protonated in a pH‐range close to neutrality, as required for binding of anions of weak acids. The effect of structural features on the protonation constants are briefly discussed in relation to the design of macrocyclic polyamine ligands.
Face Selectivity of the Diels‐Alder Reaction of 5,6‐Bis((D)methylidene)‐2‐bicyclo[2.2.2]octene
Authors: Avenati Macro , Vogel Pierre
Published: December 2004

The face selectivity (endo‐face vs. exo‐face attack onto the exocyclic s‐cis‐butadiene moiety) of the [4+2]cycloadditions of 5,6‐bis((D)methylidene)‐2‐bicyclo‐[2.2.2]octene (11) to strong dienophiles has been determined in benzene at 25°. It is ca. 95/5, 75/5, 70/30, 60/40 and 50/50 for N‐phenyltriazolinedione (NPTAD), tetracyanoethylene (TCE), dimethyl acetylenedicarboxylate (DMAD), maleic anhydride (MA) and singlet oxygen (1O2), respectively. The endo‐face preference is probably due to a participation of the homoconjugated double bond at C(2), C(3) which makes the etheno bridge more polarizable than the ethano bridge in 11. The absence of face selectivity with 1O2 is consistent with an entropy‐controlled mechanism involving the intermediacy of an exciplex.
Complexes macrocycliques des lanthanides: Stabilité et comportement électrochimique dans le méthanol et le carbonate de propylène
Authors: Almasio Marie‐Christine , Arnaud‐Neu Françoise , Schwing‐Weill Marie‐José
Published: December 2004

Macrocyclic Complexes of Lanthanides: Stability and Electrochemical Behaviour in Methanol and Propylene Carbonate

The stabilities of the 1:1 complexes of the trivalent lanthanides with the diazapolyoxamacrocycles (2.1.) and (2.2.1.) in anhydrous methanol and propylene carbonate have been determined at 25°, by competitive potentiometric methods using H+ or Ag+ as auxiliary cations, with Et4NClO4 as supporting‐electrolyte. Additional data are also reported for the crown ethers 15C5 and 18C6 in propylene carbonate.

It is shown that the diazapolyoxamacrocycles are much stronger complexing agents for trivalent lanthanides than macrocyclic polyethers, and that the bicyclic (2.2.1.) cryptates are more stable than the monocyclic (2.1.) complexes. With increasing atomic number of the lanthanides, the stability increases with diazapolyoxamacrocycles and decreases with cyclic polyethers.

The electrochemical reduction of the trivalent samarium and europium cryptates has been investigated by polarography on a dropping Hg‐electrode, in water and methanol. In both solvating solvents, the +2 oxidation states of the cations are stabilized by complexation.
Versuche zur Synthese von ‘Push‐Pull’‐Diacetylenen
Authors: Stämpfli Urs , Neuenschwander Markus
Published: December 2004

Attempted Synthesis of Push‐Pull Diacetylenes

Two alternative synthesis of push‐pull diacetylenes of type 1 (5‐amino‐2,4‐alkadiynals) are investigated. A bromination‐dehydrobromination sequence starting with 5‐dimethylamino‐2,4‐pentadienal (2) as well as the application of the well‐known Cadiot‐Chodkiewicz coupling reaction give new intermediates 3–5, and 7 and 8, respectively, but fail to give the target molecules 1.
The Vitamin‐B12‐derived Co(III)‐Complex ‘Pyrocobester’ as Photosensitizer and as Substrate in Reactions Involving ‘Singlet Oxygen’
Authors: Kräutler Bernhard , Stepánek René
Published: December 2004

The vitamin‐B12 derivative ‘pyrocobester’ (1) acts as photosensitizer in its light‐induced oxygenation which involves ‘singlet oxygen’ (1O2) and which gives ‘5,6‐dioxosecopyrocobester’ (2) cleanly. The identity of the photosensitizer is deduced from a match of the ‘photochemical action spectrum’ of the photooxygenation with the UV/VIS absorption spectrum of 1. The involvement of 1O2 in this reaction is established on the basis of solvent and solvent H/D isotope effects, of quenching studies with β‐carotene and of competition experiments with 9,10‐dimethylanthracene. Also, decomposition of the thermal 1O2‐source 1,4‐dimethylnaphthalene‐1,4‐endoperoxide in a solution of 1 induces a clean oxygenation of 1 to 2 in the dark as well.
Crystal and Molecular Structure of 2,3,5,6,7,8‐Hexamethylidenebicyclo [2.2.2]octane (‘[2.2.2]hericene’)
Authors: Pinkerton A. Alan , Schwarzenbach Dieter , Pilet Olivier , Vogel Pierre
Published: December 2004

The title molecule 1 has virtual D3h‐symmetry in the crystalline state.
Two‐Dimensional NMR Studies of Polyene Systems. I. All‐trans‐Retinal
Authors: Wernly Jacques , Lauterwein Jürgen
Published: December 2004

Two‐dimensional (2‐D) NMR results are presented for all‐trans‐retinal. 2‐D J‐resolved 1H‐NMR separated the multiplets of the olefinic protons and accurately determined their chemical shifts. 2‐D shift‐correlated 1H‐NMR gave the connectivities between scalar coupled protons. From the observed H,H long‐range couplings the assignment of the methyl resonances was possible. 2‐D J‐resolved 13C‐NMR separated overlapping C,H‐multiplets and allowed analysis of the C,H long‐range couplings, 2‐D shift‐correlated 13C‐NMR related each directly bonded C,H‐pair in this molecule. The potential of 2‐D NMR in resolving and identifying individual resonances in polyene spectra is discussed.
Attempts at Solvolytic Generation of Phenyl Cations
Authors: Laali Khosrow , Szele Ivanka , Yoshida Katsuhira
Published: December 2004

New substrates and reaction conditions which may be expected to yield phenyl cation intermediates have been investigated. The approaches used were: (a) solvolysis of PhX in fluorinated alcohols, where X = N (O) = NOTs (tosyloxyazoxy), N (O) = NONf (Nf = C4F9SO) and OSO2\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^{\rm + } $\end{document} (CH3)3ŌTf (Tf=CF3SO); (b) solvolysis of ArBr, PhOTf and PhOSO2\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^{\rm + } $\end{document}(CH3)3ŌTf (phenyl ‘betylate triflate’) in super‐acid solvents (FSO3H · SbF5, SbF5, AgSbF6). Analysis of the product mixtures provided no evidence for the intermediacy of phenyl cations as a major pathway in any of the reactions. This result is remarkable, since the ‘betylate’, for example, is a better leaving group by a factor of at least 105 than the ‘super’ leaving group triflate in the solvolysis of alkyl sulfonates. These results are a further indication of the extremely low stability of phenyl cations, as well as of the very special properties of the nitrogen leaving group in arenediazonium ions.
A Demonstrated Example of Competing D and Id Mechanisms for Dimethylformamide Exchange on the Octakis (dimethylformamide)‐erbium (III) Ion
Authors: Pisaniello Dino L. , Helm Lothar , Zbinden Donald , Merbach André E.
Published: December 2004

Dimethylformamide exchange on [Er(DMF)8]3+ is shown to take place via two competing dissociative‐type mechanisms: D and Id. It is concluded that a mechanistic crossover occurs along the series Tb‐Yb and this behaviour is contrasted with the changeover observed for the solvent exchange on the first‐row transition metal ions.
Zur Lenkung der intramolekularen Diels‐Alder‐Reaktion von Cyclopentadienen mit olefinischen Substituenten
Authors: Wallquist Olof , Rey Max , Dreiding André S.
Published: December 2004

On the Course of the Intramolecular Diels‐Alder‐Reaction of Cyclopentadienes with Olefinic Substituents

The 1:3 mixture of 4‐bromobicyclo [3.2.0]hept‐2‐en‐6‐one and ‐7‐one (1/2), available by N‐bromosuccinimide bromination of bicyclo [3.2.0]hept‐2‐en‐6‐one, reacted rapidly with the organo‐magnesium and ‐zinc reagents 3, 10a, 10b and 10d by cyclobutanone ring opening and bromide ion expulsion to give the 5‐substituted cyclopentadienes 5, 12a, 12b/12c, and 12d as non‐isolated intermediates. Further transformation occured in situ either by a direct intramolecular Diels‐Alder reaction (path a) or by a [1,5]‐H‐migration prior to the intramolecular Diels‐Alder reaction (path b). The intermediate 5 followed only path a to give the bridged norbornene derivative 7, the intermediates 12a, 12b and 12c followed only path b to give the annellated norbornene derivatives 15a, 15b and 15c, respectively, and the intermediate 12d followed both paths to give the bridged 14d and the annellated norbornene derivative 15d (in the ration of about 1.4:1). These observations are discussed in terms of the relative velocities of [1,5]‐H‐migrations and intramolecular Diels‐Alder reactions. The major conclusions are: (1) bridged norbornene derivatives with a six‐membered ring C (such as 14d) can be prepared by an intramolecular Diels‐Alder reaction from 5‐alkenyl‐cyclopentadienes 12, as long as the dienophilic double bond is activated by an appropriate substituent (as in 12d); (2) such 5‐alkenyl‐cyclopentadienes 12 are available from the reaction of the bromo‐bicyclo‐heptenones 1/2 with suitable C‐nucleophiles 10.
Total Synthesis of Neplanocin A
Authors: Jung Michael , Offenbächer Gustav , Rétey János
Published: December 2004

The first total synthesis of racemic neplanocin A (1)

After submitting our paper we learned that Arita et al. [J. Am. Chem. Soc.105, 4049(1983)] synthesized the natural enantioner of Neplanocin A.

from cyclopentadiene and acylnitroso‐3,5‐dinitrobenzoic acid is described. The synthesis is suitable for specific isotopic labelling of the hydroxymethyl group of neplanocin A.
Mechanism of Azo Coupling Reactions XXXIII. pH‐dependence and micromixing effects on the product distribution of couplings with 6‐amino‐4‐hydroxy‐2‐naphthalenesulfonic acid. Evidence for N‐coupling of a naphthylamine derivative
Authors: Kaminski Rafal , Lauk Urs , Skrabal Peter , Zollinger Heinrich
Published: December 2004

Azo coupling of 6‐amino‐4‐hydroxy‐2‐naphthalenesulfonic acid (1) with 3‐trifluoromethyl‐ and 4‐nitrobenzenediazonium ion in relative highly concentrated aqueous alkaline solutions gave ratios of aminoazo to hydroxyazo compounds which are much higher than expected on the basis of the acid‐base pre‐equilibria of 1. These product ratios are disguised by effects of micromixing. In dilute solution (≤10−2 mol/l) product ratios and kinetics both correspond to the theory of acid‐base pre‐equilibria. A bisazo dye 10 was formed as a by‐product in couplings with 3‐trifluoromethylbenzediazonium ion, as expected for reactions with micromixing effects. In the reaction with benzenediazonium ions, the products of azo coupling of diazotized 1 with 1 (compound 8) and of the monoazo compound 8 with benzenediazonium ion (compound 9) were found. It is likely that diazotized 1 is formed by N‐coupling of 1 with benzenediazonium ion, tautomeric rearrangement and protonation of the triazene to diazotized 1 and aniline. This seems to be the first case of N‐coupling of a naphthylamine which was assumed to be capable of C‐coupling only.
Stereoselectivity in reactions of metal complexes VII. Asymmetric synthesis of amino acids by metal ion‐promoted transamination
Authors: Bernauer Klaus , Deschenaux Robert , Taura Toshiaki
Published: December 2004

Enantioselective synthesis of phenylalanine was performed by reacting phenylpyruvic acid with pyridoxamine followed by ketimine‐aldimine isomerization of the Schiff base formed catalyzed by an optically active copper (II)‐complex. By UV and CD measurements it was shown that the enantiomeric excess strongly depends on the reaction conditions and on the reaction time. In favorable cases it reached values up to 80%. The selectivity of the reaction is discussed on the basis of possible structures of the intermediate mixed ligand complex.
Food‐Related Applications of High‐Resolution NMR. PART II. Differentiation between natural and synthetic vanillin samples using 2H‐NMR
Authors: Toulemonde Bernard , Horman Ian , Egli Huldrych , Derbesy Michel
Published: December 2004

Differences in the distribution of deuterium at individual atomic sites in vanillin samples are revealed by 2H‐NMR measurements, and can be used to determine whether the sample is of natural or synthetic origin.
Practical Asymmetric Diels‐Alder Additions to Camphor‐10‐sulfonic‐Acid‐Derived Acrylates. Preliminary Communication
Authors: Oppolzer Wolfgang , Chapuis Christian , Kelly Martha J.
Published: December 2004

Starting from (+)‐camphor‐10‐sulfonic acid (1) the chiral crystalline alcohols 3 and 11 were prepared in two steps. Lewis‐acid‐mediated [4+2]‐additions of their acrylates to 1,3‐dienes were studied. Notably, the crystalline acrylate 4 underwent TiCl2 (OiPr)2‐promoted Diels‐Alder addition to cyclopentadiene giving after recrystallization efficiently the pure (2R)‐adduct 5.
cis‐Bis(2‐Phenylpyridine)platinum(II) (CBPPP). A simple molecular platinum compound preliminary communication
Authors: Chassot Laurent , Von Zelewsky Alex
Published: December 2004

The deprotonated 2‐phenylpyridine forms a 2:1 chelate with platinum(II) in cis‐configuration, which exists as a dimer in a molecular solid.
Nucleophilic Addition to C,C‐Double Bonds. Part VIII. The standard enthalpies of formation of anti9,10‐10endo‐hydroxytricyclo [4.2.1.12,5]deca‐3,7‐dien‐9‐one and 9‐Oxatetracyclo [5.4.0.03,10.04,8]undec‐5‐en‐2‐one and kinetic data for the cyclization of the olefinic alcohol to the ether
Authors: Smeaton Alan A. , Steele William V. , Ramos Tombo Gerardo M. , Ganter Camille
Published: December 2004

In view of the significance of steric compression in the base‐catalyzed intramolecular cyclization of polycyclic olefinic alcohols, the standard enthalpies of formation of anti9,10‐10 endo‐hydroxytricyclo [4.2.1.12,5]deca‐3,7‐dien‐9‐one (1) and 9‐oxatetracyclo [5.4.0.03,10.04,8]undec‐5‐en‐2‐one (2) as well as the kinetics of the ether formation 1 → 2 were determined.
Voafrine A and Voafrine B, New Dimeric Indole Alkaloids from Cell Suspension Cultures of Voacanga africana Stapf
Authors: Stöckigt Joachim , Pawelka Karl‐Heinz , Tanahashi Takao , Danieli Bruno , Hull William E.
Published: December 2004

The structures of voafrine A and voafrine B, two novel dimeric indole alkaloids isolated from Voacanga africana Stapf cell suspension cultures, were established and the medium‐dependent formation of both alkaloids was investigated.
Transition Metal Complexes with Bidentate Ligands Spanning trans‐Positions. Part XIII. Preparation, properties and crystal and molecular structures of chlorocarbonyl‐2,11‐bis(diphenylphosphinophenyl) benzo[c]phenanthreneiridium (I) and trichlorocarbonyl‐2,11‐bis(diphenylphosphinomethyl) benzo[c]phenanthreneiridium(III)
Authors: Baumgartner E. , Reed F. J. S. , Venanzi L. M. , Bachechi Fiorella , Mura Pasquale , Zambonelli Luigi
Published: December 2004

The complex [IrCl3(CO)(1)](4,1=2,11‐bis (diphenylphosphinomethyl)benzo[c]phenanthrene) has been prepared by CuCl2‐oxidation of [IrCl(CO)(1)](2a). It is shown that the chlorine oxidation of 2a gives a mixture of products whose composition depends on the reaction conditions. The X‐ray crystal structures of 2a and 4 have been determined. The small conformational differences observed for the trans‐spanning ligand 1 in the two complexes are likely to be caused by the difference in Ir‐P bond lengths in square planar 2a and octahedral 4 (2.310(4) and 2.411(3) Å, respectively).
Die Acylierung von Acetylenen mit β, γ‐ungesättigten Säurechloriden. Eine neue Synthese von 5‐Cyclopentenonen
Authors: Karpf Martin
Published: December 2004

The Acylation of Acetylenes with β,γ‐Unsaturated Acid Chlorides, A New Synthesis of 5‐Substituted 2‐Cyclopentenones

The acylation of acetylenes with α,α‐disubstituted, β,γ‐unsaturated acid chlorides under Friedel‐Crafts‐type conditions leads to 5‐substituted 2‐cyclopentenones. Phenols are formed with β,γ‐unsaturated acid chlorides bearing at least one α‐H‐atom. These transformations are explained by the intramolecular cyclization of the initially formed vinyl cation, which, in the cases of α,α‐disubstituted acid chlorides, is followed by ring contraction. The reaction leading to 2‐cyclopentenones is applied to the synthesis of some spiro[4.4]nona‐ and spiro[4.5]deca‐2,6‐dienones.
Molecular Recognition in Anion Coordination Chemistry. Structure, Binding Constants and Receptor‐Substrate Complementarity of a Series of Anion Cryptates of a Macrobicyclic Receptor Molecule
Authors: Dietrich Bernard , Guilhem Jean , Lehn Jean‐Marie , Pascard Claudine , Sonveaux Etienne
Published: December 2004

The crystal structures of four anion cryptates [X− ⊂ BT‐6H+] formed by the protonated macrobicyclic receptor BT‐6H+ with F−, Cl−, Br− and N have been determined. They provide a homogeneous series of anion coordination patterns with the same ligand. The small F−‐ion is tetracoordinated, while Cl− and Br− are bound in an octahedron of H‐bonds. The non‐complementarity between these spherical anions and the ellipsoïdal cavity of BT‐6H+ is reflected in ligand distortions. Structural complementarity is achieved for the linear triatomic substrate N, which is bound by two pyramidal arrays of three H‐bonds, each interacting with a terminal N‐atom of N. The formation constants of the complexes formed by BT‐6H+ with a variety of anions (halides, N, NO, carboxylates, SO, HPO, AMP2−, ADP3−, ATP4−, P2O) have been determined. Very strong complexations are found, as well as marked electrostatic and structural effects on stability and selectivity; in particular the binding of F−, Cl−, Br−, and N may be analyzed in terms of the crystal structure data. The cryptand BT‐6H+ is a molecular receptor containing an ellipsoïdal recognition site for linear triatomic substrates of size compatible with the size of the molecular cacity. Further developments of various aspects of anion coordination chemistry are considered.