bluuebunny/crossref_metadata_2025 huggingface dataset:
CC Bond Formation via Carbon‐Centered Radicals Generated from Dicarbonyl(η5‐cyclopentadienyl) organoiron Complexes
Authors: Giese Bernd , Thoma Gebhard
Published: December 2004

Irradiation of benzyldicarbonyl(η5‐cyclopentadienyl)iron complex (2) leads to hemolytic cleavage of the FeC bond. In the presence of activated alkenes, radical addition occurs and both saturated and unsaturated addition products 7–9 are formed. Photolysis of alkyliron complexes 2,3 and 20 in the presence of acrylonitrile leads to the same products as the irradiation of the respective acyliron complexes 28–30. This indicates that, under photolytical conditions, alkyl and acyl complexes are in equilibrium with each other.
Glycosylidene Carbenes. Part 4. Synthesis of Spirocyclopropanes from Acetamidoglycosylidene‐Derived Diazirines
Authors: Vasella Andrea , Witzig Christian , Husi René
Published: December 2004

The synthesis of the first glycosylidene‐derived 2‐acetamido‐2‐deoxydiazirine 4 from N‐acetylglucosamine 6 is described. Thus, 6 was transformed into the 3‐O‐mesylglucopyranoside 9 by glycosidation with allyl alcohol, benzylidenation, and mesylation (Scheme 2). Solvolysis of 9 gave the allopyranoside 10 which, upon benzylation and glycoside cleavage, yielded the hemiacetals 12. Using our established method (via the lactone oxime 14 and the diaziridines 16), 12 gave the diazirine 4. Thermolysis of this diazirine in the presence of i‐PrOH gave the dihydro‐1,3‐oxazole 5 (Scheme 1); in the presence of acrylonitrile, the four diastereoisomeric spirocyclopropanes 17–20 and the acetamidoallal 21 were obtained and separated by prep. HPLC (Scheme 3). Assignment of the configuration of 17–20 is based on NOE measurements and on the effect of diamagnetic anisotropy of the CN group. The ratio of the four cyclopropanes, which is in keeping with earlier results, is rationalized.
From 1‐(Silyloxy)Butadiene to 4‐Amino‐4‐Deoxy‐DL‐Erythrose and to 1‐Amino‐1‐Deoxy‐DL‐Erythritol Derivatives via Hetero‐Diels‐Alder Reactions with Acylnitroso Dienophiles
Authors: Defoin Albert , Pires Joaquim , Streith Jacques
Published: December 2004

Acylnitroso dienophiles 4 reacted instantly with 1‐(silyloxy)butadiene 5α and led in good yield to the regioisomeric cycloadducts 6 (major) and 7 (minor; Scheme 2, Table 1). cis‐Hydroxylation of these primary cycloadducts with OsO4 (catalyst) occurred stereospecifically and in high yield (→8 and 9, resp.; Scheme 2). It was followed by reductive ring cleavage to give either 1‐amino‐1‐deoxy‐DL‐erythritol or 4‐amino‐4‐deoxy‐DL‐erythrose derivatives 10 and 14, respectively, depending on the nature of the reducing agent (Schemes 3 and 4).
2′‐Deoxyisoguanosine and Base‐Modified Analogues: Chemical and Photochemical Synthesis
Authors: Kazimierczuk Zygmunt , Mertens Ralf , Kawczynski Wieslaw , Seela Frank
Published: December 2004

The synthesis of 2′‐deoxyisoguanosine (2), and the pyrrolo[2,3‐d]pyrimidine and pyrazolo[3,4‐d]pyrimidine 2′‐deoxyribonucleosides 3 and 4 is described. Condensation of the imidazole precursor 5 with benzoyl isocyanate followed by reaction with ammonia gave 2. Its N(7) regioisomer was obtained from 6. Compound 2 was also prepared by the photochemically induced conversion of 2‐Chloro‐ and 2‐bromopurine 2′‐deoxyribofuranosides 9a and 10, respectively, in aqueous solution, The photo reaction was further used for the synthesis of the compounds 3 and 4 starting with the amino‐chloro‐2′‐deoxynucleosides 9b and 9c, respectively.
New Alkoxypyridine‐sulfonamides: Synthesis, Biological Evaluation, and Physicochemical Properties
Authors: Liegéois Jean‐François , Dive Georges , Dupont Léon , Delarge Jacques
Published: December 2004

As a further phanmacomodulation of benzamide derivatives, two structural modifications were introduced by synthesizing pyridinesulfonamides 5 and 6 (Scheme). The pharmacological profile of substituted benzamides such as metoclopramide (2) is not retained in the pyridine‐sulfonarm'des 6: the latter have very low toxicity but do not exhibit any affinity for D2 and 5‐HT2 receptors, and gastrointestinal prokinetic activity is weak (Table 3), Lipophilicity does not seem to be a determining factor for this lack of activity. A conformational analysis shows that the sulfonamide group in 6 is rather unfavorable for an intramolecular H‐bond formation when compared to the carboxamide group of, e.g., 2. Nevertheless, the interaction remains possible and leads to a stable conformation (Fig. 1, Table 5.) Moreover, the sp3 character of the sulfonamide N‐atom of 6 modifies the relative spatial orientation of one substituent in relation to each of the others. This feature seems to be more important for the observed very low activity than the H‐bond formation itself.
A Novel Synthesis of tert‐ Alkyl Sulfides
Authors: Katritzky Alan R. , Perumal Subbu , Kuzmierkiewicz Wojciech , Lue Ping , Greenhill John V.
Published: December 2004

tert‐ Alkyl sulfides are conveniently prepared from α‐(1H‐benzotriazol‐1‐yl)alkyl sulfides by displacement of the 1H‐benzotriazol‐1‐yl group with Grignard reagents. The 1‐[α‐(alkylthio)alkyl]‐ and 1‐[α‐(arylthio)alkyl]‐1H‐benzotriazole intermediates are easily available by several routes: (i) displacement of the halogen from appropriate halides by sodium salts of thiols, (ii) condensation of 1H‐benzotriazole and thiols with carbonyl compounds, or (iii) lithiation of N‐substituted 1H‐benzotriazoles and subsequent treatment with electrophiles.
Photocycloaddition of Quinoxaline‐2(1H)‐thiones to Alkenes
Authors: Nishio Takehiko
Published: December 2004

A synthetically useful CC bond formation involving the photochemical addition of quinoxaline‐2(1H)‐thiones to alkenes is described. Irradiation of the quinoxaline‐2(1H)‐thiones 1–4 in the presence of the alkenes 7 gave the 2‐(2′‐mercaptoalkyl)quinoxalines 8–11 in moderate‐to‐good yields via ring cleavage of an intermediate aminothietane with aromatization of the quinoxaline ring. The latter was formed by [2+2] photocycloaddition of the CS bond of the quinoxaline‐2(1H)‐thione and the CC bond of the alkene.
Regioselective Transformations of 2′,3′‐Seconucleosides into Anhydro Structures and Chiral Crown Ethers
Authors: Škarić Vinko , Čaplar Vesna , Škarić Đurđica , Žinić Mladen
Published: December 2004

Intramolecular cyclisation of properly protected and activated derivatives of 2′,3′‐secouridine ( = 1‐{2‐hydroxy‐1‐[2‐hydroxy‐1‐(hydroxymethyl)ethoxy]‐ethyl}uracil; 1) provided access to the 2,2′‐, 2,3′‐, 2,5′‐, 2′,5′‐, 3′,5′‐, and 2′,3′‐anhydro‐2′,3′‐secouridines 5, 16, 17, 26, 28, and 31, respectively (Schemes 1–3). Reaction of 2′,5′‐anhydro‐3′‐O‐(methylsulfonyl)‐ (25) and 2′,3′‐anhydro‐5′‐O‐(methylsulfonyl)‐2′,3′‐secouridine (32) with CH2CI2 in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene generated the N(3)‐methylene‐bridged bis‐uridine structure 37 and 36, respectively (Scheme 3). Novel chiral 18‐crown‐6 ethers 40 and 44, containing a hydroxymethyl and a uracil‐1‐yl or adenin‐9‐yl as the pendant groups in a 1,3‐cis relationship, were synthesized from 5′‐O‐(triphenylmethyl)‐2′,3′‐secouridine (2) and 5′‐O,N6‐bis(triphenylmethyl)‐2′,3′‐secoadenosine (41) on reaction with 3,6,9‐trioxaundecane‐1,11‐diyl bis(4‐toluenesulfonate) and detritylation of the thus obtained (triphenylmethoxy) methylcompound 39 and 43, respectively (Scheme 4).
Cyclization of Hydroxyenol Ethers into Spiroacetals. Evidence for the position of the transition state and its implication on the stereoelectronic effects in acetal formation
Authors: Pothier Normand , Goldstein Solo , Deslongchamps Pierre
Published: December 2004

Acid‐catalyzed cyclizations under thermodynamically and kinetically controlled conditions of the hydroxyenol ethers 18–21 are reported. Thermodynamically controlled cyclizations of 18, 19 and 21 produced only the more stable corresponding spiroacetals 22 and 27. Thermodynamically controlled cyclization of compound 20 produced a 1:1 mixture of non‐epimerisable spiroacetals 24 and 26. On the other hand, kinetically controlled cyclizations of the same four hydroxyenol ethers produced, along with the more stable spiroacetals mentioned above, the less stable spiroacetals 23, 25, and 28. These results show that the kinetically controlled cyclization takes place via an early transition state which produces a mixture of the less stable and the more stable isomers. These results are explained by an early transition state taking into account the principle of stereoelectronic control while following the antiperiplanar lone‐pair hypothesis (Bürgi‐Dunitz angle of attack of a nucleophile on a π system).
Channel‐Type Molecular Structures. Part 2. Synthesis of Bouquet‐Shaped Molecules Based on a β‐Cyclodextrin Core
Authors: Canceill Josette , Jullien Ludovic , Lacombe Liliane , Lehn Jean‐Marie
Published: December 2004

A new series of channel‐type molecules presenting the features of potential transmembrane structures is described. They result from the grafting of amphiphilic side chains on a β‐cyclodextrin derivative 3 that constitutes the organizing core. They belong to the ‘bouquet’ family (B). Compounds bearing poly(oxyethylene) side chains, B16 and 17, and their polymethylene analogues B18 and 19, were synthesized. The properties investigated emphasize the suitability of such molecules to be incorporated into lipid bilayer membranes.
Tritium Labelling of Cyprodime ( = (—)‐17‐(Cyclopropylmethyl)‐4,14‐dimethoxymorphinan‐6‐one), a μ Receptor‐Selective Opioid Antagonist
Authors: Ötvös Ferenc , Tóth Géza , Schmidhammer Helmut
Published: December 2004

The preparation of [1‐3H]cyprodime (2), which has a specific activity of 31.6 Ci/mmol was carried out by catalytic tritiodehalogenation of 1‐bromocyprodime (3). Bromination of cyprodime was performed by using chloroperoxidase, KBr, and H2O2.
Highly Selective Benzylic CH Bond Activation of Toluene 1 by ‘Bare’ FeO+ in the Gas Phase. Short communication
Authors: Schröder Detlef , Florencio Helena , Zummack Waltraud , Schwarz Helmut
Published: December 2004

The reaction of FeO+ with toluene in the gas phase occurs at collision rate (kr = 1.36 × 10−9 cm3 molecule−1 s−1), and labeling experiments demonstrate that the total products due to CH bond activation involve to > 92% the benzylic position. In the ‘hydride’ abstraction process (formation of FeOH and C7H), the H‐atom originates elusively from the benzylic position to generate a benzyl cation, and an intramolecular kinetic isotope effect kH/kD = 1.75 has been obtained. There is no evidence for the existence of isotopically sensitive branching (‘metabolic switching’) in the system studied.
Magnetic Circular Dichroism and Electronic Spectra of Tropothione
Authors: Higashi Miwako , Yamaguchi Hiroyuki , Machiguchi Takahisa , Hasegawa Toshio , Baumann Harold
Published: December 2004

The magnetic circular dichroism (MCD) and electronic absorption spectra of tropothione have been measured. The circular‐dichroism (CD) spectrum of the β‐cyclodextrin complex with tropothione is also reported. The absorption bands of tropothione are assigned.
8‐Azaadenine 2′,3′‐Dideoxyribonucleosides: Synthesis via 1,2,3‐ triazolo[4,5‐d]pyrimidinyl anions
Authors: Seela Frank , Mersmann Karin
Published: December 2004

The 8‐azaadenine 2′,3′‐dideoxyribonucleosides 1–3 were synthesized via glycosylation of the 7‐methoxy‐ or 7‐amino‐3H‐1,2,3‐triazolo[4,5‐d]pyrimidinyl anion with 5‐O‐[(tert‐butyl)dimethylsilyl]‐2,3‐dideoxy‐D‐ glycero‐pentofuranosyl choride (6). As 6 was an anomeric mixture, anomeric glycosylation products were formed. Moreover, three regioisomers (N1, N2, and N3) were obtained in the case of the methoxy compound, but only two (N1 and N2) using 8‐azaadenine. They were characterized by 13C‐NMR and CD spectra. The N‐glycosylic bond of 8‐aza‐2′,3′‐dideoxyadenosine (1) was ca. 10 times more stable against acid than that of 2′,3′‐dideoxyadenosine. Compound 1 was deaminated by adenosine deaminase and showed inhibitory activity on HIV reverse transcriptase in form of its O‐5′‐triphosphate.
Glycosylidene Carbenes. Part 9. Regioselective glycosidation of diols and triols: Intra‐ and intermolecular hydrogen bonds
Authors: Uhlmann Peter , Vasella Andrea
Published: December 2004

Glycosidation of the myo‐inositol derivatives 2 and 3 by the diazirine 1 yields 90% of a diastereoisomer pair of β‐D‐glycosides in a 1:1 ratio, i.e. 5/6 and 7/8, respectively (Scheme 1). The crystal structure of 3 shows a strong intramolecular H‐bond, which persists in solution, as indicated by FT‐IR and 1H‐NMR spectra. Yields and diastereoselectivity are lower for the glycosidation of 24 by 1 (Scheme 3). The resulting 1,2‐ and 1,4‐linked disaccharides 25–28 were isolated as their acetates 29–32. The previously determined crystal structure of 24 shows no intramolecular H‐bonds. The yield of the glycosidation of 24, but not of 3, depends upon the concentration, indicating that activation of 24 by intermolecular H‐bonds is required. Glycosidation of 2 and 3 with the trichloroacetimidate 14 gave mixtures of four (5,6,15, and 16), and six (7,8, and 17–20) disaccharides, respectively (Scheme 2).
Pyrazolo[3,4‐d]pyrimidine 2′ ‐Deoxy‐ and 2′,3′ ‐Dideoxyribonucleosides: Studies on the glycosylation of 4‐methoxypyrazolo[3,4‐d]pyrimidine
Authors: Seela Frank , Winter Holger , Möller Marianne
Published: December 2004

The glycosylation of the 4‐methoxypyrazolo[3,4‐d]pyrimidine (5) anion with 1‐halo‐2‐deoxyribose 6 in MeCN/TDA‐1 gives N2‐deoxynucleoside 9 (29%) together with N1‐isomer 7 (48%) and its anomer 8 (6%) [7]. The α‐D‐anomer 8 is not formed and the yield of the ß‐D‐anomer 7 increased to 62% when dimethoyethane is used as solvent and [18]crown‐6 as catalyst. Employing 1‐halo‐2,3‐dideoxyribose 10 instead of halogenose 6, the 2′,3′ ‐didexoynucleosides 12 and 14 were formed which desilylated (→ 1b and 2b) and converted into the ddI and ddA derivatives 3b (c7z8Idd), 15b (c7z8Add), and 17 (c7z8A′dd). Contrary to 7‐deazapurine nucleotides, the triphosphates of 3b and 15b showed on appreciable activity against HIV‐reverse transcriptase.
On the Novel Free Porphyrins Corallistin B, C, D, and E: Isolation from the demosponge Corallistes sp. of the Coral Sea and Reactivity of Their Nickel 55 (II) Complexes toward Formylating Reagents
Authors: D'Ambrosio Michele , Guerriero Antonio , Pietra Francesco , Debitus Cécile , Ribes Olivier
Published: December 2004

Reported here are the novel free porphyrins corallistin B, C, D, and E, isolated as methyl esters 2a, 3a, 4a, and 5a, respectively, from the sponge Corallistes sp. (Lithistida) collected at the basis of the south New Caledonian coral reef. A protocol is also established for formylation of their NiII complexes, which show a different reactivity pattern toward DMF/POCl3 from metal complexes of deuteroporphyrins. Together with corallistin A, Previously isolated as the methyl ester 1a, and the known deuteroporphyrin IX (isolated as 6a) also present in the sponge, the new corallistins, which may be thought to derive from protoporphyrin via heme, account for an amazing 60% of the EtOh extract from the sponge.
Die massenspektrometrische Wasserabspaltung aus makrocyclischen Amino‐ketonen
Authors: Benz Herbert , Hesse Manfred
Published: December 2004

The Mass Spectral Loss of Water from Macrocyclic Amino‐ketones

Macrocyclic oxo‐lactams containing an N‐alkylamino side chain are stable natural products. Their electron‐impact mass spectra are characterized by intensive [M − H2O]+ signals, the molecular ion signal itself is missing. Under electrospray ionization conditions, on the other hand, the [M + 1]+ ion is the only detected signal. The loss of water is explained in terms of an internal (thermal) Schiff‐base formation, leading to a e.g. bicyclo[11.9.4]‐system. The alcohol corresponding to the macrocyclic ketones and/or lactams show an expected mass‐spectral behavior following well known rules.
Zur Herstellung von PQQ in kg‐Mengen
Authors: Martin Pierre , Steiner Eginhard , Auer Kurt , Winkler Tammo
Published: December 2004

Preparation of PQQ in the kag Scale

The improvement of the PQQ synthesis according to the method of Corey and Tramontano allows the preparation of the triester of this cofactor in the kg scale with an overall yield of 13% (average 78% per step), without a bottleneck in the sequence and with crystalline, analytically pure intermediates. The new purification of free PQQ from conc. H2SO4 is remarkable with respect to the application as well as to the stability of this natural product.
Das Diazo‐chinon von PQQ als mögliches Reagenz für die Kartierung von Chinoproteinen mittels Photoaffinitätsmarkierung
Authors: Martin Pierre , Winkler Tammo
Published: December 2004

The Diazo‐quinone of PQQ as a Possible Reagent for Mapping Quinoproteins by Photo‐affinity Labeling

PQQ is an organic redox cofactor found in a class of enzymes called quinoproteins. The synthesis and the photochemistry of the diazo‐quinones of PQQ and PQQ‐triester are described. The photogenerated Wolff‐rear‐rangement products have been caught with water and methanol as model nucleophiles. The products show a strong fluorescence. The diazoquinone of PQQ may be considered as possible reagent for mapping quinoproteins by photo‐affinity labeling.
Dehydroalanine‐Containing Peptides by AcOH‐Elimination from O‐Acetylserine Residuces with DBU/LiClO4 in Tetrahydrofuran
Authors: Sommerfeld Thimo L. , Seebach Dieter
Published: December 2004

The elimination of H2O from serine residues in peptides was found to be feasible by the following two steps: O‐acylation with AcCl/pyrideine in CH2Cl2 and treatment with an imidine base (DBU or DBN) in THF in the presence of large amounts of LiClO4 (10 examples). Other Li salts such as LiBr and LiCl can also be used. No epimerization of the amino acid residues in te peptide could be detected under these conditions. Thus, a simple method for the preparation of peptides with dehydroalanine residues in high yield, directly from serine‐containing precursors, is available.
Preparation and ESR‐Spectroscopical Investigation of Remarkably Persistent Oxoisobenzofuranyl Radicals
Authors: Kruppa Gary , Hug Paul , Liégard André , Rist Guenther , Nesvadba Petr
Published: December 2004

The synthesis of the diastereoisomeric 1,1′‐diaryl‐1,1′‐bi(isobenzofuran)‐3,3′(1H,1′H)‐diones 3a–d starting from the readily available 2‐aroylbenzoic acids 1a–d is described (Scheme 1). Of the colourless dimers 3a–d, only the sterically congested 3a and 3b dissociate at ambient temperature in solution to the deep red free 3‐oxoisobenzofuran‐1‐yl radicals 4a and 4b, respectively. The radicals 4a, b are extremely persistent in the absence of O2. The structures of these radicals are confirmed and the coupling constants assigned by ESR and ENDOR spectroscopy and computer simulation of their ESR spectra. The dissociation equilibrium constant at 20° in toluene for 3a is determined to be 1.18 · 10−5 M. By studying the steady‐state radical concentration as a function of temperature, the enthalpy and entropy changes for the homolytic dissociation of 3a are determined.
Conformational Analysis of Open‐Chain 1,2:3,4‐Diepoxides: Comparison of crystal structures, NMR data, and molecular‐orbital calculations
Authors: Bur Daniel , Nikles Martin , Séquin Urs , Neuburger Markus , Zehnder Margareta
Published: December 2004

Several pairs of diastereoisomeric open‐chain 1,2:3,4‐diepoxides with different substitution patterns were prepared (see 3–9). As far as possible, crystal structures were determined to corroborate the relative configurations and to give insight into the solid‐state conformations of these compounds. The comparison with our earlier molecular‐orbital calculations and with 1H‐NMR measurements shows that the solid‐state conformations of eight out of the nine open‐chain 1,2:3,4‐diepoxides, whose crystal structures had been determined, correspond to minima on the calculated energy profiles for these compounds or for closely related derivatives. In solution, highly substituted diepoxides of the erythro‐series (e‐6, e‐7, e‐9) seem to prefer the same conformation as in the crystal. The solution conformations of all other diepoxides differ from the arrangement in the solid state.
Isolierung und Struktur von langkettigen Alkylphenolen und ‐pyrocatecholen aus Plectranthus albidus (Labiatae)
Authors: Bürgi Christoph , Rüedi Peter
Published: December 2004

Isolation and Structure of Long‐Chain Alkylphenols and ‐catechols from Plectranthus albidus (Labiatae)

From the title plant, a series of even‐numbered long‐chain, phenol‐ or pyrocatechol‐derived 1‐arylalkan‐5‐ones was isolated by classical chromatography and preparative reversed phase HPLC. By chemical and spectroscopic methods, including coupled chromatographic techniques (GC/MS/FT‐IR, HPLC/MS), their structures were established to be 1‐(4′‐hydroxyphenyl)tetradecan‐5‐one (2a), 1‐(4′‐hydroxyphenyl)hexadecan‐5‐one (2b), 1‐(4′‐hydroxyphenyl)octadecan‐5‐one (2c), and (Z)‐1‐(4′‐hydroxyphenyl)octadec‐13‐en‐5‐one (2d); (E,E)‐1‐(3′,4′‐dihydroxyphenyl)deca‐1,3‐dien‐5‐one (1a), 1‐(3′,4′‐dihydroxyphenyl)dodecan‐5‐one (3a), 1‐(3′,4′‐dihydroxyphenyl)‐tetradecan‐5‐one (3b), 1‐(3′,4′‐dihydroxyphenyl)hexadecan‐5‐one (3c), 1‐(3′,4′‐dihydroxyphenyl)octadecan‐5‐one (3d), 1‐(3′,4′‐dihydroxyphenyl)icosan‐5‐one (3e), and (Z)‐1‐(3′,4′‐dihydroxyphenyl)octadec‐13‐en‐5‐one (3f). In vitro, the compounds show significant antioxidant activity, the inhibitory concentration of the most potent one, 1a, being slightly lower than for 2‐(tert‐butyl)‐4‐methoxyphenol (BHA) and 2,6‐di(tert‐butyl)‐4‐methylphenol (BHT) in the Fe2+‐catalysed autooxidation of linoleic acid, whereas the acitivities of phenols 2a–d are in the same order of magnitude as α‐tocopherol.
Hetero‐Diels‐Alder cycloadditions of α,β‐unsaturated acyl cyanides. Part 2. Reactions with N,N‐dimethyluracils, a new route to 5‐substituted uracil derivatives
Authors: Zhuo Jin‐Cong , Wyler Hugo
Published: December 2004

The [4 + 2] cycloadditions of 2‐oxobut‐3‐enenitrile (1a), 2‐oxopent‐3‐enenitrile (1b), and ethyl 4‐cyano‐4‐oxobut‐2‐enoate (1c) with 1,3‐dimethyluracil (2), 1,3, 6‐trimethyluracil (9), or 1,3,5‐trimethyluracil (16) were investigated. The reactions of 1a with 2 or with 9 lead to bicyclic adducts 3 and 10, respectively. These hexahydro‐cis‐pyranopyrimidines undergo ring opening under acidic conditions, restoring in 4 and 11, respectively, an uracil system comprising 2‐hydroxybut‐2‐enenitrile as a side chain at C(5). The surprisingly stable enols tautomerize slowly to the corresponding acyl cyanides 6a and 13a, respectively. Reacting 1b or 1c with 2 and with 9 does not afford cycloadducts; instead the uracil derivatives 6b, c and 13b, c, respectively, show up, carrying at C(5) α‐oxobutanenitrile side chains. Cleavage of the acyl cyanide functions in 6a–c and 13a–c with nucleophilic agents produces various acids, esters, or amides, i.e. derivatives 8a–c and 15–c, respectively. The methyl esters 8a (X  MeO, R  H) and 15a (X  MeO, R  H) are also formed directly from the adducts 3 and 10, respectively, with acid or base catalysis in presence of MeOH. The cycloadducts 17a and 17c, resulting from the reaction of 1a and 1c with 16, respectively, have a Me group at the ring junction C(4a) and are stable. The structure of 17c proves that this hetero‐Diels‐Alder addition of inverse electron demand follows the endo‐mode.
Synthesis and NMR‐Spectroscopic Structure Determination of Novel 7,7′‐Diphenyl‐7,7′‐diapocarotenoids
Authors: Hand Elli S. , Belmore Kenneth A. , Kispert Lowell D.
Published: December 2004

Wittig reaction of crocetindial (1) and benzylidenetripenylphosphorane (2) gave (7E, 7′Z)‐7,7′‐diphenyl‐7‐7′‐diapocarotene (3), instead of the previously reported (7E, 7′E)‐isomer. Similar reaction of 8,9‐didehydrocrocetindial (4) with 2 yielded the three acetylenic isomers 5a–c which differ in the configuration of the terminal double bonds. Structures were established by 1D‐ and 2D‐NMR studies. Illustrative spectra and their interpretation are presented. Most chemical shifts of corresponding protons in 3 and 5 and nearly identical, but 13C shifts differ considerably.
Catalytic Cyclophanes. Part VIII. Cytochrome P‐450 activity of a porphyrin‐bridged cyclophane
Authors: Benson David R. , Valentekovich Robert , Tam Suk‐Wah , Diederich François
Published: December 2004

Following a known synthetic procedure, the porphyrin‐cyclophane 1 having a porphyrin attached by two straps to an apolar cyclophane binding site was prepared. Upon metallation, the ZnII and FeIII derivatives 2 and 3, respectively, were obtained in good yields. Treatment of 3 with base yielded the μ‐oxo dimer 4 in which the two oxo‐bridged porphyrins moieties are both capped by cyclophane binding sites. All compounds 1–4 are freely soluble in protic solvents such as MeOH and CF3CH2OH, and the FeIII derivatives 3 and 4 are active cytochrome P‐450 mimics in these protic environments. Strong inclusion complexation of polycyclic aromatic hydrocarbons by 1 and 3 in alcoholic solvents was observed and quantified by 1H‐NMR and UV/VIS titrations. Acenaphthylene binds in an ‘equatorial’ orientation which locates its reactive 1,2‐double bond near the porphyrin center, whereas phenanthrene binds ‘axially’ with the reactive 9,10‐double bond oriented away from the porphyrin. The reduction potential of 3 was not significantly altered by substrate binding. In the unbound form, the FeIII center in porphyrin 3 was found by ESR and 1H‐NMR to prefer a high‐spin state (S = 5.2). In CF3CH2OH, using iodosylbenzene as O‐transfer agent, the FeIII derivative 3 catalyzed the oxidation of acenaphthylene to acenaphthen‐1‐one (14). Phenanthrene inhibited the reaction, possibly as a result of strong but nonproductive binding. Under similar conditions, isotetralin (18) was aromatized with high turnover to 1,4‐dihydronaphthalene. The μ‐oxo dimer 4 also showed high activity in the oxidation of acenaphthylen in MeOH, a result which provides strong evidence for efficent supramolecular catalysis. Due to as yet unknown reaction channels leading to polymeric products, poor mass balances were generally obtained in the oxidations effected in MeOH and CF3CH2OH in the presence of PhIO.
Preparation of optically active flowery and woody‐like odorant ketones via Corey‐Chaykovsky oxiranylation: Irones and analogues
Authors: Chapuis Christian , Brauchli Robert
Published: December 2004

α‐, β‐, and γ‐Irones and analogues have been prepared from optically active ketones (+)‐1, (+)‐6a,b, and (+)‐17, via a Corey‐Chaykovsky oxiranylation (Me2S, Me2SO4, Me2SO, NaOH) followed by isomerisation (SnCl4 or MgBr2). (+)‐Dihydrocyclocitral (19a), obtained from (−)‐citronellal, and analogue (+)‐19b, were condensed with various ketones to afford (+)‐21a–f, and after hydrogenation (+)‐22a–f. A mild oxidative degradation of aldehydes (+)‐trans‐and (−)‐cis‐8a,b, to ketones (−)‐16a,b, as well as olfactive evaluations, 13C‐NMR assignments, and absolute configurations of the intermediate epoxides, aldehydes, and alcohols are presented.
Reactions of Nucleosides with 1,8‐Diazabicyclo[5.4.0]undec‐7‐ene (DBU). Syntheses of N(3)‐Methylene‐Bridged Bis‐uridines and Secouridine‐Dinucleoside Analogs
Authors: Čaplar Vesna , Škarić Vinko
Published: December 2004

Diasteroisomeric secouridine derivatives, appropriately protected and activated, served as starting compounds in the reactions with 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) in various solvents (CH2Cl2, MeCN, or dimethylformamide (DMF)). Reactions with DBU/CH2Cl2 gave N(3)‐methylene‐bridged bis‐secouridines and bis‐uridines (Scheme 3), while the reactions with DBU in non‐alkylating solvents resulted in formation of secdinucleosides as the result of intermolecular ‘dimerizations’ (Scheme 2).
Sponge‐Derived Polyunsaturated C16 Di‐ and Tribromocarboxylic Acids
Authors: Ichiba Toshio , Scheuer Paul J. , Kelly‐Borges Michelle
Published: December 2004

One previously described and two new bromo‐substituted polyunsaturated C16 fatty acids were isolated from an Indonesian sponge, Oceanapia sp. Their common structural feature is an (13E, 15Z)‐14,16‐dibromodiene terminus. They differ in their C(5) to C(10) portions in unsaturation and halogenation. All three compounds are unstable oils. The mixture exhibits mild cytotoxicity against KB cells.
Cationic RhI Complexes of Azulenes and Their Catalytic Activity on the Formation of Heptalene‐1,2‐dicarboxylates from Dimethyl Acetylenedicarboxylate and Azulenes
Authors: Rippert Andreas Johannes , Linden Anthony , Hansen Hans‐Jürgen
Published: December 2004

[Rh1(η5‐azulene)(cod)]+BF complexes 3a–g (cod = (Z,Z)‐cycloocta‐1,5‐diene) have been synthesized by reaction of [Rh1(cod)]+BF in THF with the corresponding azulenes 1a–g (Table 1). The structure of [Rh1(cod)(η5‐guaiazulene)]+BF (3a) has been determined by X‐ray diffraction analysis (Fig. 1 and 2). The Rh‐atom is oriented above the five‐membered ring of the azulene with almost equal RhC distances to all five C‐atoms of the ring. The (Z,Z)‐cycloocta‐1,5‐diene ring occurs in two enantiomorphic distorted (C2v → C2) tub conformations in the crystals (Fig. 3). In CDCl3 solution, the cod ligand in the complexes 3 shows a dynamic behavior on the 1H‐NMR time scale which is best explained by rotation of the cod ligand relative to the azulene ligands around an imaginary codRhazulene axis. The new complexes 3 catalyze the formation of heptalene‐1,2‐dicarboxylates 2 from dimethyl acetylenedicarboxylate (ADM) and the corresponding azulenes 1 just as effectively as [RuH2(PPh3)4] and the analogous [RhH(PPh3)4] complex in MeCN solution (Table 3). On grounds of simplicity, 3 can be generated in situ, when [RhCl(cod)]2 is applied as catalyst (Table 3).
Intramolecular Site Exchange of Carbonyl Ligands in the Cluster Compounds Nonacarbonyl{μ3‐[η3‐(1,3,5‐trithiane)]}triruthenium ([Ru3(CO)9{μ3‐(η3‐C3H6S3)}]) and (tert‐Butyl Isocyanide)octacarbonyl‐{μ3‐[η3‐(1,3,5‐trithiane)]}triruthenium ([Ru3(t‐BuNC)(CO)8{μ3‐(η3‐C3H6S3)}])
Authors: Laurenczy Gábor , Merbach Andrée. , Moullet Bertrand , Roulet Raymond , Hoferkamp Lisa , Süss‐Fink Georg
Published: December 2004

Variable‐temperature and ‐pressure 13C‐NMR studies of the 1,3,5‐trithiane‐capped triruthenium clusters [Ru3(CO)9{μ3‐(η3‐1,3,5‐trithiane)}] (1) and [Ru3(t‐BuNC)(CO)8{μ3‐(η3‐1,3,5‐trithiane)}] (2) revealed that CO site exchanges occur via an intramolecular merry‐go‐round process, involving a transition state mostly dissociative in character.
Synthese und Eigenschaften der Furo‐ und Thieno‐Analogen von PQQ‐Triester
Authors: Martin Pierre , Winkler Tammo
Published: December 2004

Synthesis and Characterization of the Furo and Thieno Analogues of the Triester of PQQ

We report here the synthesis and properties of the furo and thieno analogues of 4,5‐dihydro‐4,5‐dioxo‐1H‐pyrrolo[2,3‐f]quinoline‐2,7,9‐ tricarboxylic acid ( = PQQ), i.e. the furo‐ and thieno[2,3‐f]quinoline‐4,5‐quinone (FQQ and TQQ, resp.) derivatives B and C, obtained as triesters. The triester of PQQ derivative A is much more stable than the triesters of B or C, and only the triester of A shows strong activity in nonenzymatic catalytic oxidations.
Metal complexes with macrocyclic ligands. Part XXXVI. Thermodynamic and kinetic studies of bivalent and trivalent metal ions with 1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acid
Authors: Cai Hui‐Zhi , Kaden Thomas A.
Published: December 2004

NMR, potentiometric, and UV/VIS measurements were run to study the protonation and the In3+ and Cu2+ stability constants of 1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acid (do3a, L). The protonation of do3a follows the typical scheme with two high and several low log KH values. Between pH 11 and 13, the protonation mainly occurs at the N‐atom, which is not substituted by an acetate side chain. The In3+ complex is not appreciably protonated even at low pH values (pH ⋐ 1.7), whereas [CuL] can add up to three protons in acidic solution to give the species [CuLH], [CuLH2], and [CuLH3], the stability of which was determined. The formation rates of the Y3+, Gd3+, Ga3+, and In3+ complexes with do3a were measured using a pH‐stat technique, whereas that of Cu2+, being faster, was followed on a stopped‐flow spectrophotometer. In all cases, the reaction scheme implies the rapid formation of partially protonated intermediates, which rearrange themselves to the final product in the rate‐determining process. ([MLH])in, an intermediate, in which the metal ion probably is coordinated by two amino acetate groups, proved to be the reactive species for Y3+, Gd3+, and Ga3+. The formation of [Cu(do3a)] was interpreted by postulating that either ([CuLH])in or ([CuLH])in, and ([CuLH2])in are the reactive complexes. The rates of dissociation of the Y3+, Gd3+, and Cu2+ complexes with do3a were studied spectrophotometrically. For Y3+ and Gd3+, arsenazo III was used as a scavenger, whereas for Cu2+ the absorption associated with d‐d* transition was followed. For [Y(do3a)] and [Gd(do3a)], the rate law follows the kinetic expression kobsd  k0 + k1[H+]. The dissociation of [Cu(do3a)] goes through the proton‐independent dissociation of [CuLH3], which is the main species at low pH.
Enantioselective Formation of Bicyclic Lactones by Rhodium‐Catalyzed Intramolecular CH‐insertion reactions
Authors: Müller Paul , Polleux Philippe
Published: December 2004

The decomposition of cyclohexyl diazoacetate (5a) in the presence of the chiral [Rh2{(2S)‐mepy}4] catalyst leads to a 3:1 cis/trans mixture of bicyclic lactone 6a with an enantiomeric excess of 95–97% (cis) and 90% (trans). The conformationally rigid tert‐butyl derivatives 5b and 5c afford, in the presence of the same catalyst, 6b and 6c, respectively, via insertion into the equatorial CH bonds exclusively, with ee's of ca. 95%. A remarkable degree of induction (92–95%) results in the lactone 6g upon decomposition of 1‐isopropyl‐2‐methylpropyl diazoacetate (5g). The diazoacetates derived from 1‐methylcyclohexanol, cyclopentanol and 1‐methylcyclopentanol (5d–f) afford under similar conditions insertion products with higher diastereoselectivity, but significantly lower enantioselectivity. Other dirhodium catalysts are less efficient.
Synthesis of a New Bivalent Hirudin Analog (hirufos), which includes a stable 4′‐phosphono‐L‐phenylalanine mimic of (L‐tyrosine O4‐sulfate)‐63
Authors: Thurieau Christophe , Guyard Christel , Simonet Serge , Verbeuren Tony J. , Fauchère Jean‐Luc
Published: December 2004

The synthesis on solid phase of a new derivative of the anticoagulant protein hirudin is described (see Scheme and Fig.1, I). The henicosapeptide is a bivalent conjugate of the C‐terminus of hirudin and of the active‐site‐binding tetrapeptide D‐Phe‐Pro‐Arg‐Pro linked via a tetraglycine spacer. The peptide, for which the name hirufos was coined, incorporates a stable phosphono derivative of L‐phenylalanine which, combined with the other structural modifications, leads to a potent anticoagulant agent. Synthesis was readily achieved by the (9H‐fluoren‐9‐yl)‐methoxycarbonyl (Fmoc) strategy followed by acidolytic cleavage from the resin and deprotection, including the liberation of the crucial phosphonic group on L‐phenylalanine.
Solvent Isotope Effect on the Rate Constants of Singlet‐Oxygen Quenching by edta and Its Metal Complexes
Authors: Hessler Diane P. , Frimmel Fritz H. , Oliveros Esther , Braun André M.
Published: December 2004

The reactivity of singlet oxygen (O2(1Δg)) with edta and its metal complexes with Al3+, Cu2+, Fe3+, and Mn2+was investigated. The emission of singlet oxygen at 1270 nm in D2O was measured in order to determine the quenching efficiency of edta and edta‐metal complexes for different metal/edta ratios. The sum of the rate constant (kr+kq) of the chemical reaction between singlet oxygen and the acceptor (kr) and of the physical quenching of singlet oxygen by the acceptor (kq) was obtained by aStern‐Volmeranalysis. Measurements of the oxygen consumption in H2O were used to determine quantum yields of the sensitized photooxidation, and the combined results of these experiments allowed the determination ofkrandkqseparately. A strong isotope effect was observed between the deuterated and the hydrogenated solvents. This effect was shown to be independent of the analytical procedure used. The isotope effect, as well as the reactivity of edta and its metal complexes, depend markedly on the complexed metal ion.
Xenicane Diterpenes Revisited: Thermal (E)→(Z) isomerization and conformational motions. A unifying picture
Authors: Guella Graziano , Chiasera Giuseppe , N'Diaye Ibrahima , Pietra Francesco
Published: December 2004

Kinetic and equilibrium studies show that typical xenicanes such as dictyolactone (1) and 4‐hydroxydictyolactone (3) undergo slow conformation medium‐ring flipping between the predominant trans‐(1a or 3a; Me(20) trans to H–C(3)) and the minor cis‐conformers (1b or 3b; Me(20) cis to H–C(3); see Scheme 1). The formation of the latter is inhibited in heterocyclic‐ring‐opened congeners such as 18‐acetoxy‐4‐hydroxydictyo‐19‐al (7). Molecular‐mechanics calculations suggest that typical‐xenicane cis‐conformers are disfavoured by mainly C(4)–C(5) torsional strain. This is confirmed by the observation of two sizably populated cis‐and trans‐conformers for the unnatural 4‐oxoxenicanes 10–12. Unusually facile thermal (E)→(Z) isomerization of xenicanes 1,3,10–12, and 7 is also observed (→ 13–17 and 9, resp.; Scheme 3), reflecting great strain relief in the transition state. Conflicting results in the literature now fit into this scheme which provides a basis for unravelling recognition phenomena with these biologically active systems.
Synthesis, Crystal Structure, and Thermal Behaviour of Some New Copper Complexes with tridentate β‐iminoketone ligands
Authors: Becht Michael , Gerfin Tobias , Dahmen Klaus‐Hermann
Published: December 2004

The reaction of Cu(AcO)2 · H2O and tridentate β‐iminoketone ligands yielded four new copper complexes: acetato{4‐{[2‐(dimethylamino)ethyl]amino}pent‐3‐en‐2‐onato}copper(II) (1), triacetato{4‐{[3‐(dimethylamino)‐propyl]amino}pent‐3‐en‐2‐onato}dicopper(II) (2), {4‐{[2‐(dimethylamino)ethyl]amino}‐1,1,1‐trifluoropent‐3‐en‐2‐onato}( trifluoroacetato)copper(II) (3), and pentaacetato{4‐{[3‐(dimethylamino)propyl]amino}‐1,1,1‐trifluoropent‐3‐en‐2‐ onato}tricopper(II) (4). All compounds were coloured and air‐stable solids. The crystal structures of 1 and the dioxane adduct of 3, μ‐(1,4‐dioxane)bis{{4‐{[2‐(dimethylamino)ethyl]amino}‐1,1,1‐trifluoropent‐3‐ en‐2‐onato}(trifluoroacetato)copper(II)} (3a), were determined. Complex 1 consists of dimeric units [{Cu(AcO)L}2] in the solid state (L = β‐iminoketonato ligand). In 3a, two [Cu(CF3COO)L] are linked via the O‐atoms of the coordinated solvent 1,4‐dioxane. Compound 1 crystallized in the monoclinic space group P21/n with a formula unit in a cell having the dimensions a = 11.152(6)Å, b = 10.104(3)Å, c = 11.805(7)Å, and β = 99.02(4)Å, and compound 3a crystallized in the triclinic space group P1 with a formula unit in a cell having the dimensions a = 8.709(3)Å, b = 9.439(4)Å, c = 12.395(3)Å, α = 67.57(3)°, β = 77.01(2)°, and β = 84.17(3)°. Mass spectra (MS), thermal analysis (DTA/TG), and evaporation‐rate measurements are reported for all compounds. The influence of fluorination on the structure and volatility will be discussed.
Efficient Synthesis of Methyl 2‐(tert‐Butyl)acrylate and Analogous Esters
Authors: Xu Long‐He , Kündig Ernst Peter
Published: December 2004

The title products are prepared via an efficient three‐step synthesis which involves hydroalumination of methyl propiolate and Lewis‐acid‐promoted reaction with acetone in the presence of BF3 followed by two highly selective SN2′ reactions. The key step is the reaction of 2‐(chloromethyl)acrylates with R2CuLi/ZnCl2 reagents which takes place with complete allylic rearrangement.
Radical Arylation Reactions of 4, 6, 8‐Trimethylazulene
Authors: Briquet Anne Andrée Sophie , Hansen Hans‐Jürgen
Published: December 2004

The synthesis of 1‐ and 2‐aryl‐substituted (aryl = Ph, 4‐NO2C6H4, and 4‐MeOC6H4) 4, 6, 8‐trimethylazulenes (4 and 3, respectively) in moderate yields by direct arylation of 4, 6, 8‐trimethylazulene (8) with the corresponding arylhydrazines 13 in the presence of CuIIions in pyridine (see Scheme 4) as well as with 4‐MeOC6H4Pb(OAc)3 (16) in CF3COOH (see Scheme 5) is described. With 13, also small amounts of 1, 2‐ and 1, 3‐diarylated azulenes (see 14 and 15, respectively, in Scheme 4) are formed. The 4‐methoxyphenylation of 8 with 16 yielded also the 1, 1′‐biazulene 17 in minor amounts (see Scheme 5). 4, 6, 8‐Trimethyl‐2‐phenylazulene (3a) was also obtained as the sole product in moderate yields by the reaction of sodium phenylclopentadienide (1a) with 2, 4, 6‐trimethylpyrylium tetrafluoroborate (2) in THF (Scheme 1). The attempted phenylation of 8 as well as of azulene (9) itself with N‐nitroso‐N‐phenylacetamide (10) led only to the formation of the corresponding 1‐(phenylazo)‐substituted azulenes 12 and 11, respectively (Scheme 3).
X‐Ray Crystal Structure of the 2‐Phenyladamant‐2‐yl Cation
Authors: Laube Thomas , Hollenstein Sandro
Published: December 2004

The crystal structure of the Sb2F11 salt of the 2‐phenyladamant‐2‐yl cation, 1 · Sb2F11, was determined at 183 K (P21/c, R1 = 0.0652, σ(CC) = 0.02 Å), because earlier published results indicated a charge delocalization from the cationic C(2) into the σ framework (CC hyperconjugation) and a bending of the C(2) bridge. In the structure of 1, a displacement of the C(2) bridge by 7.8(12)° from the symmetrical position and CC bond‐length deviations from expectation values were found which are in agreement with preferential CC hyperconjugation on one face of C(2). The interactions of 1 with two Sb2F11 counterions nearest to C(2) also indicate different behaviour of the two faces of C(2). The benzylic resonance in 1 is confirmed.
Syntheses of Bile Pigments. Part 18. Synthesis and conformational studies of oxa‐ and thia‐deaza‐biliverdin analogues
Authors: Nesvadba Petr , Ngoc‐Phan Do , Nydegger Fredy , Ferao Arturo Espinosa , Gossauer Albert
Published: December 2004

Following the conventional methodology used for the synthesis of bile pigments, some oxa‐ and thia‐deazabiliverdin analogues were synthetized for the first time. Both UV/VIS spectroscopic and 1H{1H}‐NOE difference studies reveal that the oxa‐deaza‐biliverdin analogue 8a occurs in apolar solvents in a partly ‘stretched’ conformation, whereas the corresponding thia derivative 8b behaves rather like a genuine bile pigment. Unexpectedly, the helical‐shaped conformation is also preponderant in a trioxa‐trideaza‐biliverdin analogue, which could be only characterized in its protonated form 14.
Imidazolone and Imidazolidinone Artifacts of a Pivotal Imidazolthione, Zyzzin, from the poecilosclerid sponge Zyzza massalis from the coral sea. The first thermochromic systems of marine origin
Authors: Mancini Ines , Guella Graziano , Pietra Francesco , Debitus Cécile , Duhet Daniel
Published: December 2004

Dry acetone extracts of the freeze‐dried, deep‐red powder of the poecilosclerid sponge Zyzza massalis (DENDY) from the Coral Sea gave the orange alkaloid zyzzin (= 4‐(1H‐indol‐3‐yl)‐1,5‐dihydro‐5‐thioxo‐1H‐imidazol‐2‐one 14), which underwent exchange of the 5‐thioxo for the 5‐oxo group during aqueous chromatographic workup, giving yellow 13. Both 13 and 14 added hydroxylic solvents at C(4)=N giving colourless, racemic products, 3 and 8, respectively, by incorporation of MeOH and 10 and 11, respectively, by incorporation of H2O. On warming 3 or 10 in DMSO, 13 was recovered, thus furnishing a novel thermochromic system. Optically active (+)‐12, which may be viewed to derive from enzymatic reduction of 14 at C(4)=N followed by S→O exchange, was also isolated from this sponge, along with the linear amides 16 and 19. Compound 3 proved to have antibacterial and antifungal activities.
Synthesis and Addition Reactions of 1,3‐Thiazole‐5(4H)‐thione Oxides
Authors: Shi Junxing , Tromm Peter , Heimgartner Heinz
Published: December 2004

1,3‐Thiazole‐5(4H)‐thione oxides 2 were prepared by oxidation of the corresponding 1,3‐thiazole‐5(4H)‐thiones 1 with m‐chloroperbenzoic acid (Table 1). Addition reactions of 2 with organolithium and Grignard reagents yielded 4,5‐dihydro‐4,4‐dimethyl‐1,3‐thiazol‐5‐yl methyl sulfoxides of type 4 via thiophilic attack (Table 2). Whereas the reaction with the organolithium compounds proceeded with fair‐to‐excellent yields, the Grignard reagents reacted only very sluggishly. The sulfoxides 4 could also be prepared via oxidation of 4,5‐dihydro‐4,4‐dimethyl‐5‐(methylthio)‐1,3‐thiazoles of type 3 with m‐chloroperbenzoic acid, together with the corresponding sulfones 5 (Scheme 1).
Multiorganyltin Compounds. Designing a novel phosphate‐selective carrier
Authors: Tsagatakis John K. , Chaniotakis Nikolas A. , Jurkschat Klaus
Published: December 2004

A series of distannyl derivatives, 1–9, were studied for their application as phosphate‐selective carriers in polymer‐based liquid membranes. A drastically different potentiometric behavior was observed depending on the distance between the tin(IV) coordinating centers and the ligands attached to them. Some of the compounds examined, i.e. (PhSnBr2)2CH2(1) and (Me3SiCH2SnCl2CH2)2 (3) showed very high potentiometric selectivity towards phosphate over other lipophilic anions such as perchlorate and thiocyanate. Results indicate that (1) the optimal number of CH2 groups between the Sn‐centers are either one or three, (2) the electron‐withdrawing power of the organic ligands attached to Sn‐centers strongly influences the overall response towards phosphate, and (3) the steric effect of the organic substituents is important in the potentiometric selectivity observed.
Conformational Parameters of the Sandalwood‐Odor Activity: Conformational calculations on sandalwood odor
Authors: Buchbauer Gerhard , Hillisch Alexander , Mraz Karin , Wolschann Peter
Published: December 2004

The conformational parameters responsible for sandalwood odor were investigated by the “active‐analog approach”. The pharmacophoric (osmophoric) pattern of sandalwood‐odor molecules can be outlined as three points: the OH group (point PI), a lipophilic group (point P2) 2.9–3.0 Å distant from the OH group, and a bulky rigid group (point P3), represented as a dummy atom in the middle of the alicyclic system (norbornane bicycle or cyclopentene ring) or a quaternary C‐atom. This concept was tested on a series of representative sandalwood‐odor compounds and on some structurally similar, but odorless substances.
Cyclopropanization of Methyl Carboxylates with Tebbe‐Type Reagents
Authors: Fallahpour Reza‐Ali , Hansen Hans‐Jürgen
Published: December 2004

The methylenation reaction of methyl azulene‐2‐carboxylates (cf. Schemes 1 and 2) with Tebbe's or Takai's reagent is described. When the prescribed amount of Takai's reagent is applied in a four‐fold excess, the corresponding cyclopropyl methyl ethers are formed instead of the enol ethers (cf. Schemes 2 and 3). Similarly, methyl benzoate and methyl 2‐naphthoate yield, after treatment with Takai's reagent and hydrolysis, the corresponding cyclopropanols 18 and 19, respectively (Scheme 3). The cyclopropyl methyl ether 4 or cyclopropanol 5 rearrange, on acid catalysis, into the l‐(azulen‐2‐yl)propan‐l‐one 20 (Scheme 4). whose reduction with Et3SiH in CF3COOH yields the 2‐propylazulene 21.