bluuebunny/crossref_metadata_2025 huggingface dataset:
Cuprous complexes and dioxygen. IX. Formation of a unique trimeric species Cu3L and Ligand Oxidation (L  cis, cis‐1, 3, 5‐cyclohexanetriamine)
Authors: Szeverényi Zoltan , Knopp Ursula , Zuberbühler Andreas D.
Published: December 2004

The complexation of Cu+ by the potentially tripod like ligand cis, cis‐1, 3, 5 cyclohexanetriamine (chta) has been studied potentiometrically in aqueous acetonitrile (an). The expected tetracoordinated species Cu (chta) ⇌ (an)+ was formed only at rather high pH with log K (Cu (an)+ + chta ⇌ Cu (chta) · (an)+) = 6.94. Quite unexpectedly the most stable complex in neutral solution was the trimetric species Cu3 (chta) with log K (3 Cu+ + 2 chta ⇌ Cu3 (chta)) = 31.75. In addition, the ternary complexes Cu (LH2) · (an)3+ and Cu (LH) · (an)2+ (L = chta) are formed at low pH.

From model considerations, Cu3 (chta) must contain two ligand molecules with all amino groups in equatorial position, linked by three linearly coordinated Cu+‐ions. Cu3 (chta)3+2 shows no measurable reactivity towards dioxygen. At pH values above 9, very rapid O2‐uptake due to Cu (chta) · (an)+ is observed. In this reaction, Cu+‐autoxidation is stoichiometrically coupled to ligand oxidation, followed by a much slower Cu‐catalyzed secondary reaction of the primary oxidation product of chta. Hydrogen peroxide and likely also superoxide, are involved in the coupled Cu+/ligand oxidation.
Verbascenin, ein macrocyclisches Spermin‐Alkaloid aus verbascum 184. Mitteilung über organische Naturstoffe
Authors: Seifert Karlheinz , Johne Siegfried , Hesse Manfred
Published: December 2004

Verbascenine, a Macrocyclic Spermine Alkaloid Isolated from Verbascum

The new spermine alkaloid verbascenine (1) has been isolated from extracts of the aerial parts of Verbascum phoeniceum L. and V nigrum L. The structure of the alkaloid was elucidated by chemical degradation and by a study of the spectral properties of the alkaloid and its derivatives. Compared to the 13‐membered alter native 7 the 17‐membered structure 1 is preferred on the basis of mass spectral arguments.
Phototransformations of Some 2‐Substituted 4 H‐Chromen‐4‐ones (4‐Chromones) Related to the Antitumor Antibiotic Hedamycin
Authors: Fredenhagen Andreas , Séquin Urs
Published: December 2004

The 2‐substituted 4 H‐chromen‐4‐ones (4‐chromones) 2 and 3 have epoxysubstituted side chains at C(2) resembling that of the antibiotic hedamycin (1). They were chosen as model compounds and subjected to photolysis either in the presence or in the absence of oxygen. The products obtained were isolated by repeated HPLC., and their structures were determined by spectroscopic methods, mainly 1H‐ and 13C‐NMR. Especially noteworthy are the oxygen dependent formation of the tertiary alcohols 11 and 12 as well as the transformation of the diepoxychromone 3 to the allylic alcohols 13 and 14, the spiro compounds 15 and 16, and the 2‐ethylchromone 19.
Propellanes. LXVII. Reactions of 1, 6‐bridged [10]annulenes with 4‐methyl‐1,2,4‐triazoline‐3, 5‐dione
Authors: Ashkenazi Pnina , Vogel Emanuel , Ginsburg David
Published: December 2004

Reactions of 11‐substituted‐1, 6‐methano [10]annulenes and 1, 6‐methano [10]‐annulenes substituted in the aromatic ring with the title dienophile are described.
A New Route to the Synthesis of 2‐Amino‐6‐(methoxycarbonyl)amino‐4‐(tetrahydropyridyl)pyrimidine 1‐Oxide
Authors: Muller Jean‐Claude , Ramuz Henri , Wagner Hans‐Peter
Published: December 2004

A new approach to 2‐amino‐6‐(methoxycarbonyl)amino‐4‐(1,2,3,6‐tetrahydro‐1‐pyridyl)pyrimidine 1‐oxide (3) is described. Methyl [1‐ethoxy‐2‐(ethoxycarbonyl)‐ethylidene]carbamate (5) reacted with guanidine to the pyrimidinecarbamate 6, which was successively transformed into methyl 2‐amino‐6‐(p‐tolyslulfonyl)oxy‐4‐pyrimidinecarbamate (8). Oxidation of 8 led to the corresponding pyrimidine N‐oxide 9, a useful starting material to 3.
Favorskii‐Reaktion von enolisierbaren Cyclobutanonen: Abhängigkeit der Stereoselektivität von der Abgangsgruppe, der Temperatur und dem Lösungsmittel
Authors: Martin Pierre
Published: December 2004

Dependence of the Stereoselectivity on the Leaving Group, the Temperature and the Solvent in the Favorskii‐Reaction of Enolisable Cyclobutanones

The base‐induced contraction of enolisable 2‐halocyclobutanones is often not stereoselectiv. The cis/trans‐isomer ratio in the cyclopropanecarboxylic acid 9 derived from 2,4‐cis‐substituted cyclobutanones 7 depends on the nature of the leaving group. In addition, the choice of the base, the temperature and the solvent can profoundly affect the stereoselectivity of the Favorskii‐reaction. The use of the p‐bromophenylsulphonyloxy group as leaving group and an inhomogenous reaction medium leads exclusively to cis‐carboxylic acid 9.
Further Investigation of Grapefruit Juice Flavor Components (Citrus paradisi MACFAYDEN). Valencane‐ and Eudesmane‐type Sesquiterpene Ketones
Authors: Demole Edouard , Enggist Paul
Published: December 2004

Fourteen sesquiterpene ketones D–Q pertaining to the valencane (D–J) and eudesmane (K–Q) groups have been identified for the first time in grapefruit juice flavor. These novel grapefruit constituents, which include the six new compounds I, J, L, M, N and O, were identified by direct comparison with synthetic samples. Organoleptically, their total contribution to grapefruit flavor is not negligible. In particular, (+)‐8,9‐didehydronootkatone (E) has a powerful flavor with good grapefruit juice character.
Heterocyclole als Zwischenprodukte einer neuen, überraschenden Umlagerung bei der Reaktion von 3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirin mit monosubstituierten Parabansäuren. Vorläufige Mitteilung
Authors: Dähler Marlise , Prewo Roland , Bieri Jost H. , Heimgartner Heinz
Published: December 2004

Cyclols as Intermediates in the Reaction of 3‐(Dimethylamino)‐2,2‐dimethyl‐2H‐azirine with Monosubstituted Parabanic Acids; a New and Unexpected Rearrangement

The reaction of 3‐(dimethylamino)‐2,2‐dimethyl‐2H‐azirine (1) with N‐methylparabanic acid (4) in 2‐propanol at room temperature gives the cyclol 5 in 97% yield. In acetonitrile solution 5 rearranges to the imidazoline derivative 6 (Scheme 2). The structures of the unexpected products 5 and 6 have been established by X‐ray crystallography.
Ru‐Catalyzed Oxidations with Iodosylbenzene Derivatives. Substituent Effects on Selectivity in Oxidation of Sulfides and Alcohols
Authors: Müller Paul , Godoy José
Published: December 2004

Oxidation of sulfides with PhIO/RuCl2 (PPh3)3 leads to sulfones. Electronwithdrawing substituents in the aromatic ring of PhIO reduce the reactivity and improves selectivity of the system. Thus, with m‐iodosylbenzoic acid sulfides are converted to sulfoxide. Under the same conditions aliphatic primary alcohols are transformed to aldehydes with m‐iodosylbenzoic acid, while PhIO affords carboxylic acids.
Absolute Configuration of Multifidene and Viridiene, the Sperm Releasing and Attracting Pheromones of Brown Algae
Authors: Boland Wilhelm , Mertes Karin , Jaenicke Lothar , Müller Dieter G. , Fölster Elsbet
Published: December 2004

The absolute configurations of the two algal pheromones multifidene1and viridiene2were determined as (+)‐(3S, 4S)‐3‐[(Z)‐1‐butenyl]‐4‐vinylcyclopentene and (+)‐(3R, 4S)‐3‐[(1Z)‐1, 3‐butadienyl]‐4‐vinylcyclopentene, respectively. The strategy involves enzyme‐initiated asymmetric synthesis of the ring‐saturated pheromone analogues (+)‐8aand (−)‐8band their subsequent catalytic hydrogenation to the chiral cycloalkanes9aand9b, only the letter of which is also obtained from the two natural messengers (+)‐1or (+)‐2. Biological activity assays proved these enantiomers of1or2to be the characteristic pheromones for male gametes of the seaweedsSyringoderma,Cutleria multifidaandChorda tomentosa.
Interaction of Enzyme with Polymer Matrix in Immobilized Enzymes
Authors: Kumakura Minoru , Kaetsu Isao
Published: December 2004

Thermolysin was immobilized by radiation polymerization of hydroxyalkyl acrylate and tetradecaethylene glycol dimethacrylate monomers at low temperatures in the presence of the enzyme, and the degree of interaction of the enzyme with the polymer matrix was studied by measuring the thermal stability of the immobilized enzyme. The thermal stability was affected by the molecular structure of the monomer; the thermal stability of the immobilized enzyme from hydrophilic monofunctional monomers in the wet state was higher than that from hydrophobic bifunctional monomers. The thermal stability in polymers formed from hydroxy‐alkyl acrylates decreased with an increase in the number of methylene units in the monomer, owing to a change of the state of the enzyme trapped in the porous polymer matrix. The enzyme molecule trapped in a hydrophilic porous polymer matrix appeared to be stabilized by interaction with the polymer chains.
Synthesen und chemische Reaktionen neuer Chinonderivate mit 1,6‐Methano[10]annulenpartialstruktur oder ihrer Valenztautomeren
Authors: Neidlein Richard , Martin Radke Christoph
Published: December 2004

Syntheses and Chemical Reactions of New Quinone Derivatives with 1,6‐Methano[10]annulene Fragments or their Valencetautomers

The coupling of 2‐Methoxy‐1,6‐methano[10]annulene with aryldiazonium salts leads to the corresponding quinone hydrazones. These compounds undergo reduction with LiAlH4, condensation with hydrazines and hydrazides and alkylation at the carbonyl O‐atom or the hydrazone N‐atom.
Propellanes. Part LXX. The oximes of [4.3.3]propellane‐8,11‐dione
Authors: Bhanumati Soundararajan , Ashkenazi Pnina , Ginsburg David
Published: December 2004

The mono‐oxime and dioxime of the title compound have been prepared.
Transition metal complexes with bidentate ligands spanning trans‐positions. Part XIV. Some complexes of 2,11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene with platinum (0) and their reactivities
Authors: Boron‐Rettore Patrizia , Grove David M. , Venazi Luigi M.
Published: December 2004

The ligand 2,11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene (1) has been used to prepare complexes of the type [PtL(1)] (L  C2H4, CH2CHCO2Me, PhCCPh, MeCCMe, MeO2CCCCO2Me, (i‐Pr)O2CCCCO2(i‐Pr), Ph3P and CO). It is shown that these complexes are less labile than the corresponding species [PtL(Ph3P)2]. The preparation of complexes trans‐[PtX(R)(1)] by oxidative addition of RX (RX  PhCH2Br and Mel) to [Pt(C2H4)(1)] is described. The isolation of [PtO2(CH3)2CO(1)] is also reported.
Photochemical reactions. 134th Communication. Photochemistry of 5,6‐epoxy‐5,6‐dihydro‐3,4‐methano‐β‐ionone: Influence of a cyclopropane ring on the reactivity of an ylide intermediate
Authors: Bischofberger Norbert , Frei Bruno , Jeger Oskar
Published: December 2004

On 1n,π*‐excitation(λ > 347 nm), the diastereomeric methanoepoxyenones (E)‐6 undergo isomerization via C,O‐cleavage of the oxirane leading to diastereomeric photoproducts ((E)‐5→(E/Z)‐13 and 14; (E)‐6→(E/Z)‐16 and 17). On 1π,π*‐excitation (λ = 254 nm) of either (E)‐5) or (E‐6 the photoproducts 9, 10 and 11 are formed. By laser flash photolysis (λ = 265 nm) the ylide intermediate 3 was detected, with a lifetime of 10 μs in MeCN at ambient temperature. Stern‐Volmer analysis of the ylide quenching by MeOH disclosed that compounds 9 and 10, but not 11, arise from the ylide intermediate e.
Die diastereomeren Mutatochrome. Trennung, absolute Konfiguration sowie chiroptische, spektroskopische und chromatographische Charakterisierung
Authors: Eschenmoser Walter , Märki‐Fischer Edith , Eugster Conrad Hans
Published: December 2004

Diastereoisomeric Mutatochromes: Separation, Absolute Configuration, and Spectra and Chromatographic Behaviour

(5S, 6R)‐5, 6‐Epoxy‐5, 6‐dihydro‐β, β‐carotent (2), prepared from azafrinal (1) was rearranged in an acid‐catalyzed reaction into the mixture of (5S, 8S)‐ and (5S, 8 R)‐5, 8‐epox‐5, 8‐dihydro‐β, β‐carotenes = ‘mutatochrome’. HPLC separation of the individual diastereoisomers led to the pure isomers for the first time. Their structures were assigned by analysis of the characteristic pattern of the signals of HC(7) and HC(8), respectively, in 1H‐NMR spectra. Although many reports of the occurrence of ‘mutatochrome’ exist, it is as yet not clear whether optically active or racemic forms predominate in nature. Combination of HPLC separations with UV/VIS and CD spectra should now allow an unambigous identification of the isomer in question.
(6′RS,8′RS,2E)‐ und (6′RS,8′SR,2E)‐3‐Methyl‐3‐(2y,2′,6′‐trimethyl‐7′‐oxabicyclo[4.3.0]non‐9′‐en‐8′‐yl)‐2‐propenal ([(5RS,8RS)‐ und (5RS,8SR)‐5,8‐Epoxy‐5,8‐dihydro‐ionyloinden]acetaldehyd): Synthese und Röntgenstrukturanalyse
Authors: Acemoglu Murat , Prewo Roland , Bieri Jost Hans , Eugster Conrad Hans
Published: December 2004

Synthesis and X‐Ray Structure of (6′RS,8′RS,2E)‐ and (6′RS,8′SR,2E)‐3‐Methyl‐3‐(2′,2′,6′‐trimethyl‐7′‐oxabicyclo[4.3.0]non‐9′‐en‐8′‐yl)‐2‐propenal ([(5RS,8RS)‐ and (5RS,8SR)‐5,8‐Epoxy‐5,8‐dihydro‐ionylidene]acetaldehyde)

To check our previous spectroscopic assignments of the structures of trans‐ and cis‐substituted furanoid end groups of carotenoid‐5,8‐epoxides, we now have synthesized the title compounds. An X‐ray structure determination of a single crystal of the trans‐isomer (±)‐‐10A is in agreement with the 1H‐NMR spectroscopic arguments: isomers with Δδ (HC(7), HC(8)) = 0.15–0.22 ppm and J > 1.4 for HC(7) belong to the cis‐series; Δδ in trans‐compounds is < 0.07 ppm, and HC(7) appears as a broad singulett.
1,6‐Eliminationsreaktionen an Spirocoleonon; Charakterisierung der ersten Spiro[(methylcyclopropan)‐phenanthren]‐1,3‐dion‐Derivate
Authors: Matloubi‐Moghandam Firouz , Rüedi Peter , Eugster Conrad Hans
Published: December 2004

Preparation of the First Spiro[(methylcyclopropan)‐phenanthrene]‐1,3‐dione Derivatives by 1,6‐Elimination Reactions of Spirocoleons

Spirocoleons, e.g. coleon J (1), on treatment with 1,5‐diazabicyclo[4.3.0]non‐5‐ene (DBN) in aprotic solvents, undergo enolization followed by a rapid 1,6‐elimination with formation of the hitherto unknown 2‐methyl‐spiro[cyclopropane‐1,2′(1′H)‐phenanthrene]‐1′,3′(4′bH)‐dione system, e.g. 3. In protic solvents, base‐catalyzed solvolysis of the spirocyclopropane predominates.
Further Investigation of the Nature of the C‐Li Bond. Structures of a Phenylthiomethyllithium Complex and ofa Methylthiomethyllithium Complex
Authors: Amsturz René , Laube Thomas , Schweizer W. Bernd , Seebach Dieter , Dunitz Jack D.
Published: December 2004

Phenylthiomethyllithium/N,N,N′,N′‐tetramethylethylenediamine (TMEDA) (1:1) is shown by X‐ray analysis to be dimeric in the crystalline state. The structural unit contains a six‐membered ring in which each Li is bonded to the terminal C atom of one thioanisole and to the S atom of the other, as well as to the two N atoms of a TMEDA. Methylthiomethyllithium/TMEDA (1:1) is also dimeric, but the structural unit contains a four‐membered ring in which each Li is bonded to two C atoms and to the two TMEDA N atoms. An error has been detected in an earlier published electron‐density difference map for 2‐lithio‐2‐phenyl‐1, 3‐dithiane/TMEDA/THF (1:1:1). The conclusion drawn then that this complex exists as a tight ion‐pair in the crystal is now retracted.
Synthese und 1H‐NMR‐Studie der vier unverzweigten peracetylierten β‐D‐Glucopyranosyl‐β‐gentiobiosen
Authors: Rychener Martin , Bigler Peter , Pfander Hanspeter
Published: December 2004

Synthesis and 1H‐NMR Study of the Four Unbranched Peracetyl‐β‐D‐glucopyranosyl‐β‐gentiobioses

With regard to the structure elucidation of an unknown trisaccharide isolated from the stigmas of garden crocusses (Crocus neapolitanus var.), the four unbranched (1→6)‐, (1→4)‐, (1→3)‐, and (1→3)‐, and (1→2)‐connected β‐D‐glucopyranosyl‐β‐gentiobiose peracetates were synthesized. A complete analysis of the 1H‐NMR spectra of the four trisaccharide peracetates was carried out.
Isolierung und Strukturaufklärung von Neapolitanose (O‐β‐D‐Glucopyranosyl‐(1→2)‐O‐[β‐D‐glucopyranosyl‐(1→6)]‐(D‐glucose), einem neuen Trisaccharid aus den Stempeln von Gartenkrokussen (Crocus neapolitanus var.)
Authors: Rychener Martin , Bigler Peter , Pfander Hanspeter
Published: December 2004

Isolation and Structure Elucidation of Neapolitanose (O‐β‐D‐Glucopyranosyl‐(1→2)‐O‐[β‐D‐glucopyranosyl‐(1→6)]‐D‐glucose), New Trisaccharide from the Stigmas of Garden Crocusses (Crocus neapolitanus var.)

From the stigmas of Crocus neapolitanus var. ‘Blue Bird’ two new crocetin glycosyl esters were isolated. They contained a hitherto unknown trisaccharide. For the structure elucidation a homonuclear 2D‐1H‐NMR‐shift‐correlation experiment was carried out with the peracetate of the isolated trisaccharide. This experiment revealed that the carbohydrate is O‐β‐D‐glucopyranosyl‐(1→2)‐O‐[β‐D‐glucopyranosyl‐(1→6))]‐D‐glucose, for which we suggest the name ‘neapolitanose’. The two new C20‐carotenoids from Crocus neapolitanus are crocetin (β‐gentiobiosyl) (β‐neapolitanosyl) ester (4) and crocetin di(β‐neapolitanosyl) ester (5).
Sambucinol and sambucoin, two new metabolites of Fusarium sambucinum possessing modified trichothecene structures. 41st Communication on verrucarins an roridins
Authors: Mohr Perer , Tamm Christoph , Zürcher Werner , Zehnder Margareta
Published: December 2004

Sambucinol (2) and sambucoin (4), two C15‐trichothecenes, have been isolated from cultures of Fusarium sambucinum. The structures were deduced from spectroscopic data and by X‐ray diffractoin. A hypothetical biogenetic pathway is proposed.
1,4‐Diazobicyclo[2.2.2]octane‐catalyzed coupling of aldehydes and activated double bonds. Part 3. A short ans practical synthesis of mikanecic acid (4‐vinyl‐1‐cyclohexene‐1,4‐dicarboxylic acid)
Authors: Hoffmann H. M. R. , Rabe Jürgen
Published: December 2004

The title dicarboxylic acid 1d has been prepared in 24% overall yield via, 1,4‐diazabicyclo[2.2.2]octane (DABCO)‐catalyzed coupling of ethanal and tert‐butyl propenoate (3) to 4, SN2′‐reaction to tert‐butyl (Z)‐2‐romomethyl‐2‐butenoate (5a), dehydrobrominatin to tert‐butyl 2‐methylidene‐3‐butenoate (2c), dimerizatoin to di‐tert‐butyl 4‐vinyl‐1‐cyclohexene‐1,4‐dicarboxylate (1c) and acidic ester cleavage. Acidic cleavage of easily obtainable 5a affords (Z)‐2‐bromomethyl‐2‐butenoic acid (5a) in 68% yield with respect to ethanal.
Intermolecular Electron Spin Transfer between Naphthalene π‐Systems Separated by a Variable Number of Spirobonded Cyclobutane Rings, An. ESR and ENDOR Study
Authors: Gerson Fabian , Huber Walter , Martin Wiliam B. , Caluwe Paul , Pepper Tim , Szwarc Michael
Published: December 2004

The radical anions of the compounds N1N, N3N and N5N, in which two naphthalen π‐systems are separated by 1, 3 and 5 spirobonded cyclobutane rings, respectively, and tha tof the reference compound N1, containing one naphthalene π‐system and one cyclobutane ring, have been studied by ESR and ENDOR spectroscopy under a variety of experimental conditions. The intramolecular electrons spin transfer between the two π‐moieties in N3N and N5N is slow on the hyperfine time‐scale, irrespective of the applied conditions. It is also slow in N1N, except for media of high solvating power. In such media, with a slight reduction of N1N to its radical anion, a paramagnetic species is observed, the hyperfine data for which are consistent with N1N to its radical anion, a paramagnetic species is observed, the hyperfine data of which are consistent with N1N, undergoing a fast intramolecular electron spin tansfer. The ESR and ENDOR spectra of this species are superimposed on those characteristic of a slow transfer. It is suggested that the fast and slow transfer involve the syn‐ and anti‐conformations, respectively, since the distance, r, between the two naphthalene π‐systems of N1N is considerably shorter in the former than in the latter (r = 740 vs. 880 Pm for the distance between the centres of the π‐systems). Glassy solutions of exhaustively reduced N1N display signals of the dianion triplet state, whereas no such signals are found for N3N and N5N. The zero‐field splitting parameter, D, is 4.7 mT, corresponding to r ≈ 480 pm.
Trennung und absolute Konfiguration der C(8)‐epimeren (all‐E)‐Neochrome (Trollichrome) und ‐Dinochrome
Authors: Märki‐Fischer Edith , Buchecker Richard , Eugster Conrad Hans
Published: December 2004

Separation and Absolute Configuration of the C(8)‐Epimeric (app‐E)‐Neochromes (Trollichromes) and ‐Dinochromes

The C(8′)‐epimers of (all‐E)‐neochrome were separated by HPLC and carefully characterized. The faster eluted isomer, m.p. 197.8–198.3°, is shown to have structure 3 ((3S,5R,6R,3′S,5′R,8′R)‐5′,8′‐epoxy‐6,7‐dodehydro‐5,6,5′,8′‐tetrahydro‐β,β‐carotene‐3,5,3′‐triol). To the other isomer, m.p. 195‐195.5°, we assign structure 6, ((3S,5R,6R,3′S,5′R,8′R)‐5′,8′‐epoxy‐6,7‐didehydro‐5,6,5′,8′‐tetrahydro‐β,β‐carotene‐3,5,3′‐triol). The already known epimeric dinochromes (= 3‐O‐acetylneochromes) can now be formulated as 4 and 5, (‘epimer 1’ and its trimethylsilyl ether) and 7 and 8, (‘epimer 2’ and its trimethylsilyl ether), respectively.
Enantioselective synthesis of (+)‐ and (−)‐cis‐2‐methyl‐4‐propyl‐1,3‐oxathiane and their olfactive properties
Authors: Pickenhagen Wihelm , Brönner‐Schindler Helene
Published: December 2004

The enantioselective synthesis of (+)‐ and (−)‐cis‐2‐methyl‐4‐propyl‐1,3‐oxathine 8 and 9 form (E)‐2‐hezen‐1‐ol (1) as common starting material is described. The two enantiomeric forms exhibit different organoleptic properties.
Synthesis of (−)‐Hobartine and Related Indole Alkaloids
Authors: Darbre Tamis , Nossbaumer Cornelius , Borschberg Hans‐Jürg
Published: December 2004

An improved method for obtaining optically pure (S)‐(l‐p‐menthen‐8‐yl)amine (12) has led to expedient syntheses of two hypothetical biogenetic intermediates on the way to aistoteline (7), namely (S)‐(N)‐(l‐p‐menthen‐8‐yl)‐2‐(3‐indolyl)ethylamine (3) and (S)‐(N)‐(l‐p‐menthen‐8‐yl)‐2‐(3‐indolyl)ethylideneamine (4). The latter has been transformed into (−)‐hobartine (6) in 64% yield via a stereoselective biomimetic cyclization by treatment with HCOOH. This unambiguous synthesis establishes the hitherto unknown absolute configuration of (−)‐hobartin (6). Several model cyclization reactions of N‐substituted α‐(terpen‐8‐yl)imine derivatives yielding unsaturated 3azabicyclo [3.3.1]nonane compounds are described.
Low‐Temperature 13C‐NMR Spectra of 6Li‐ and 13C‐Labelled Sulfur‐ and Selenium‐Substituted Organolithium Derivatives
Authors: Seebach Dieter , Gabriel Josef , Hässig Robert
Published: December 2004

The 13C‐NMR spectra of 19 different, singly, doubly, and triple 13C‐labelled α‐sulfur‐ and α‐selenium‐substituted 6Li‐derivatives generated from methyl and phenyl thioethers, thioacetals, trithio‐orthoesters and from their selenium analogues have been recorded in ethereal solutions (tetrahydrofuran (THF), 2‐methyltetrahydrofuran (MTHF) at temperatures between −30° and −110°. The effects of H/Li‐exchange upon chemical shifts and coupling constants, as well as the values and multiplicities of Li, 13C‐coupling are interpreted in vie wof crystal structures of some of the same compounds. In two thirds of the cases studied, the H‐decoupled 13C‐NMR signals observed below −80° were triplets, proving that the C‐atoms are bonded to single 6Li‐atoms. This is compatible either with monomeric or with dimeric, heteroatom‐bridged structures. The direct 1H, 13C‐ and 13C, 13C‐coupling constants (1J) decrease, the 13C, 77Se‐coupling constants increase upon lithiation. More striking is that the geminal coupling 13C‐S‐13C (2J) is too small to be observed in the non‐metalated species, while it ranges from 3.7 to 7.5 Hz in the lithiated derivatives. These observations may be interpreted as resulting from delocalization of electron density from the carbonionic center towards the adjacent heteroatom.
Kobalt‐katalysiert Cycloadditionen von Alkinen und Nitrilen zu Pyridinen: Ein neuer Zugang zu Pyridoxin (Vitamin B6)
Authors: Geiger Rudolf E. , Lalonde Michel , Stoller Hansijörg , Schleich Kuno
Published: December 2004

Cobalt‐Catalyzed Cycloaddition of Alkynes and Nitriles to Pyridines: A New Route to Pyridoxine (Vitamin B6)

A new synthesis of pyridoxine hydrochloride (1) based on a Co‐catalyzed cycloaddition of MeCN with substituted di(2‐propynyl) ethers (3 and 16) is described. The reaction sequences following cycloaddition and leading to 1 involve as key steps the rearrangement f the pyridine‐N‐oxide 6 to the 3‐hydroxypyridine 7 with Ac2O and a modified Curtius rearrangement of the acid 19 and subsequent diazotation and hydrolysis to the same pyridoxine precursor 7, respectively. The intermediate 7 is transformed to 1 by well‐known procedures.
Novel, racemic or nearly‐racemic antibacterial bromo‐ and chloroquinols and γ‐lactams of the verongiaquinol and the cavernicolin type from the marine sponge Aplysina (= Verongia) cavernicola
Authors: D'Ambrosio Michele , Guerriero Antonio , Pietra Francesco
Published: December 2004

Butanolic extracts of the Mediterranean sponge Aplysina (= Verongia) cavernicola have given, by reverse‐phase HPLC, the antibacterial quinols (±)‐3‐bromoverongiaquinol (= (±)‐3‐bromo‐1‐hydroxy‐4‐oxo‐2,5‐cyclohexadine‐1‐acetamide; 1d) and (±)‐3‐bromo‐5‐chloroverongiaquinol (= (±)‐3‐bromo‐5‐chloro‐1‐hydroxy‐4‐oxo‐2,5‐cyclohexadine‐1‐acetamide; 1c) besides the products of their formal cyclization 5‐chlorohexadiene‐1‐acetamide; 1c) besides the products of their formal cyclization 5‐chlorocavernicolin (= 5‐cloro‐3,3a,7,7aβ‐tetrahydro‐3aβ‐hydroxy‐2,6(1H)‐indoledione; 6), the C(7)‐epimerizing 7β‐bromo‐5‐chlorocavernicolin (=7 β‐bromo‐5‐chloro‐3,3a,7,7aβ‐tetrahydro‐3aβ‐hydroxy‐2,6(1H)‐indoledione; 4a and 7α‐bromo‐5‐chlorocavernicolin (4b), and the C(7)‐epimerizing 5‐bromo‐7β‐chlorocavernicolin ( = 5‐bromo‐7β‐chloro‐3,3a,7,7aβ‐tetrahydro‐3aβ‐hydroxy‐2,6(1H)‐indoledione; 5a) and 5‐bromo‐7α‐chlorocavernicolin (5b). The latter four were isolated as mixtures of C(7)‐epimerizing monoacetates 4a′/4b′ and 5a′/5b′. Both 1 and 1c proved to be racemic from NMR examination of their esterification products with (–)‐methyl‐oxyacetic acid, whilst 6 had a ca. 6% enantiomeric purity as shown by a 1H‐NMR study of its monoacetate 6′ in the presence of a chiral shift reagent. These chiroptical data of the first chiral quinols from the Verongida and of 6 suggest phenol oxidative routes from tyrosine precursors for their formation. In view of their bioactivities, 1d and 1c have been synthesized from (p‐hydroxyphenyl)acetic acid byt phenol oxidative routes.
Aminierende, reduktive Kupplung aromatischer Aldehyde mit Tris(dialkylamino)methylvanandium (IV) zu N,N,N′,N′‐Tetraaalkyl‐1,2‐diaryläthylendiaminen
Authors: Imwinkelried René , Seebach Dieter
Published: December 2004

Aminative Reductive Coupling of Aromatic Aldehydes to N,N,N′,N′‐Tetraalkyl‐1,2‐diarylethylenediamines, Induced by Tris(dialkylamino)methylvanadium (IV)

In a novel type of reaction, certain aromatic aldehydes (benzaldehyde, p‐methoxybenzaldehyde, 1‐naphthaldehyde, furan‐2‐carbaldehyde) and secondary amines are coupled to give N,N,N′,N′‐tetraalkyl‐1,2‐diarylethylenediamines 1–6. The reagents are tris(dialkylamino)methylvanadium(IV) compounds (cf. Eqn. 2). These are generated in situ either from isolable chlorotris(dialkylamino) vanadium(IV) (Eqn. 3), or preferably, from an Et2O/pentane solution of VCl4 which is treated sequentially with 3 equiv. of lithium dialkylamide, 1 equiv. of MeLi, and 0.8 equiv. of an aromatic aldehyde, to give the products 1–6 in a one‐pot preparation (Scheme 2). The yields range from 14 to 54%. The diastereoisomeric mixtures (meso‐ and (±)‐forms) obtained are separated by chromatography (Al2O3, petroleum ether/Et2O/Et3N), and the pure stereoisomers fully characterized. A mechanism of the reductive coupling induced by CH3V (NR2)3 is proposed (Scheme 1).
Über die Totalsynthese vo Betalainen
Authors: Hilpert Hans , Dreiding André S.
Published: December 2004

On the Total Synthesis of Betalains

Improved total syntheses of the red‐violet aglucone of the beet coloring matter and of the yellow cactus coloring matter indicaxanthine are presented. Formyl‐olefination of the piperidone‐diester 6 with the acetaldehyde synthon 5 led to the piperidylidene‐acetaldehyde derivative 8, which was converted into the 2,4,4‐trimethylsemicarbazone of rac‐betalamic acid dimethyl ester (10) by treatment with t‐BuOCl and then Et3N. Exchanging the semicarbazone moiety with the (S)‐cyclodopa derivative 18, with (S)‐proline (19) and with indoline (20) transformed 10 to betanidin (21/22), to indicaxantihin (23/24) and to rac‐indo‐betalaine (25), respectively. The latter, a new, relatively stable betalaine, was hydrolyzed and esterified to rac‐betalamic acid dimethyl ester (29). Under the influence of NH3/MeOH, 26 (the dimethyl ester of 25) was dehydrogenated spontaneously to indo‐neobetalaine dimethyl ester (27).

Synthetic betanidin consisted of a 4:6 mixture of the (natural) (2S, 15S)‐ (21) and the (2S, 15R)‐isomer (22) and both of a 75:25 mixture of the (E)‐ and the (Z)‐isomer. Synthetic indicaxanthin (23/24) and the indo‐betalaine (25) represented a 65:35 and a 70:30 mixture, respectively, of (E)‐ and the (Z)‐isomers. All (E)‐ and (Z)‐isomers are rapidly interconvertible. Temperature‐dependent 1H‐NMR‐measurements of 25 established ΔG≠ = 84.7 kJ/mole for the (E)‐to‐(Z)‐conversion.

The t‐BuOCl/NEt3 method for the introduction of an enaminic double bond was applied to the model transformations of the amines 6, 12 and 15 to the conjugated enamiens 11, 13 and 17, respectively.
Diastereoselektive synthese neuartiger Mannich‐Basen mittels titanderivaten, vorläufige mitteilung
Authors: Seebach Dieter , Betschart Clauida , Schiess Martin
Published: December 2004

Diastereoselective Synthesis of Novel Mannich (Bases1) through Titanium Reagents

Trichlorotitanium dialkylamino‐alkoxides (2; titanates of N, O‐hemiacetals) are generated either from the corresponding lithium alkoxides and titanium tetrachloride (Scheme 1) or by addition of trichloro‐dialkuylamino‐titanium to aldehydes. The electrophilic (dialkylamino) alkylating reagents 2 are used to convert lithium enolates to β‐dialkylamino‐ketones and ‐esters 5 (Mannich bases), see Scheme 2 and Table. One diastereoisomer of the products 5g–5p thus obtained with cyclohexenolate is formed preferentially (66‐84%). The configuration of the products of this first diastereoselective version of the Mannich reaction could not yet be determined. A typical procedure for carrying out the reaction is given.
Steuerung der katalytischen Pyridinsynthese aus Alkien and Nitrilien durch (η6‐Borinato)‐Liganden am Cobalt
Authors: Bönnemann Helmut , Brijoux Werner , Brinkmann Rainer , Meurers Willi
Published: December 2004

Control of the Catalytic Synthesis of Pyridine from Alkynes and Nitriles by the (η6‐Borinato)‐Nigands at Cobalt

η6‐Borinato groups as ligands at cobalt have unique effects on the chemo‐ and negioselectivity of the catalytic co‐cyclization of alkynes and nitriles. The turnover number of the conversion of acrylonitrile and acetylene to give 2‐vinylpyridine is considerably enhanced. Cyano compounds wih polar substitutents such as amino or thio groups can also be reacted. The homogeneous reaction of HCN with acetylene giving pyridine has been achieved for the first time.
Synthesen makrocyclischer Lactone durch Ringerweiterung Herstellung von (±)‐Phoracantholid I, (±)‐Dihydrorecifeiolid und (±)‐15‐Hexadecanolid
Authors: Kostava Kalina , Hesse Manfred
Published: December 2004

Syntheses of Macrocyclic Lactones by Ring Enlargement Reaction Reaction. Preparation of (±)‐Phoracantholide I, (±)‐Dihydrorecifeiolide and (±)‐15‐Hexadecanolide

A general procedure for the synthesis of macrocyclic lactones is described. The Michael adducts of 2‐nitrocycloalkanones and acrylaldehyde were regiospecifically methylated with CH3Ti[OCH(CH3)2]3 or (CH3)2Ti[OCH(CH3)2]2 at the aldehyde carbonyl group. Treatment of the so‐formed alkohols with tetrabutylammonium fluoride gave the lactones enlarged by four ring members. This method was used to synthesize the 10‐membered (±)‐phoracantolide I (11), the 12‐membered (±)‐dihydrorecifeiolide (17), and (±)‐15‐hexadecanolide (24) in 52%, 26.5%, and 58.7% respectively.
Inductivity and Bridging in 2‐Bicyclo[2.2.2]octyl Cations. Polar Effects, Part 11
Authors: Grob Cyril A. , Sawlewicz Pawel
Published: December 2004

The solvolysis rates and products of several 6‐substituted 2‐exo‐ and 2‐endo‐Bicyclo[2.2.2]octyl p‐toluenesulfonates, 12 and 13, respectively, are reported. Inductivity, as measured by the reaction constants ρI, is considerably less in the exo‐series 12 (ρI = −1.50) than in the corresponding 2‐exo‐norbornyl p‐toluenesulfonates 1 (ρI= −2.0). It is proposed that, for geometrical reasons, bridging of the cationic center C(2) by C(6) is not as strong in the bicyclooctane series 12 as it is in the norbornane series 1. On the other hand, inductivity is higher in the 2‐endo‐bicyclooctane series 13 (ρI= −1.0) than in the corresponding 2‐endo‐norbornane series 3 (ρI = 0.78), probably, because in the former case bridging of C(6) is less hindered by the departing anion. The relative yields of exo‐ and endo‐substitution products from the series 12 and 13, are in accord with graded bridging of C(6) in the incipient bicyclooctyl cations. But almost constant bridging of C(2) by C(7) is indicated in the ionization of the 2‐endo‐bicyclooctane series 13. Consequently, in the free unsubstituted bicyclooctane cation C(2) is bridged symmetrically by C(6) and C(7), in contrast to the current concept of ‘non‐classical’ two‐electron‐three‐center bonding.
Nature et stabilité des complexes métalliques de cryptands dinucléants en solution. I. Polyazapolyoxa macrotricycle cylindrique et monocycle constitutif
Authors: Arnaud‐Neu Francoise , Sanchez Maria , Yahya Raïda , Schwing‐Weill Marie‐José , Lehn Jean‐Marie
Published: December 2004

Nature and Stability of Some Metallic Complexes of Dinucleating Cryptands in Solution. I. A Polyazapolyoxa Cylindrical Macrotricycle and its Monocyclic Subunit

pH‐metry and UV spectrophotometry were used to study the complexing properties of the cylindrical macrotricycle, 1,7,13,19‐tetraaza‐4,16‐dioxa‐10,22,27,32‐tetraoxatricyclo[17.5.5.5]tetratriacontane (1) and of its constitutive monocyclic subunit, 1,7‐diaza‐4,10‐dioxacyclododecane (2) with some transition and heavy metal cations (Cu2+, Co2+, Ni2+, Zn2+, Cd2+, Pb2+, Ag+), in aqueous medium 0.1M Et4NClO4, at 25°. The protonation constants of the ligands as well as the nature and the stabilities of the complexes formed in the pH‐regions studied were determined. The tricycle 1 only formed dinuclear M2L complexes with Cu2+, Zn2+, and Ag+, accompanied in the latter case by a protonated mononuclear MLH species, and with Cu2+ and Zn2+ at high pH‐values by dinuclear hydroxo complexes. Only mononuclear complexes were evidenced with the other cations, ML being accompanied either by protonated or hydroxy mononuclear species. The mononuclear complexes of 1, when they existed, were more stable than the corresponding complexes of 2, except for cobalt which formed complexes of comparable stability with both ligands. In the other cases (Cd2+, Pb2+, Ag+), the stability differences between the complexes of 1 and 2 increased with the size of the cation.
Stoffwechselprodukte von Mikroorganismen. 232. Mitteilung. (E)‐3‐(1H‐Pyrrol‐3‐yl)‐2‐propensäure und (E)‐3‐(1H‐Pyrrol‐3‐yl)‐2‐propensäureamid aus Streptomyces parvulus, Stamm Tü 2480
Authors: Keller‐Schierlein Walter , Müller André , Hagmann Leonhard , Schneider Ursula , Zähner Hans
Published: December 2004

(E)‐3‐(1H‐Pyrrol‐3‐yl)‐2‐propenoic Acid and (E)‐3‐(1H‐Pyrrol‐3‐yl)‐2‐propenamide from Streptomyces parvulus, Strain Tü 2480

The title compounds were isolated from cultures of Streptomyces parvulus. They give a deep blue colour reaction with Ehrlich reagent. Their structures were elucidated by spectroscopy and comparison with synthetic samples. They do not show any antimicrobial activity.
Photochemische Synthesen potentiell hypoglykämisch wirkender 3‐Oxazoline
Authors: Pfoertner Karl‐Heinz , Bernauer Karl , Kaufmann Franz , Lorch Eckehard
Published: December 2004

Photochemical Syntheses of 3‐Oxazolines which Possibly Exhibit Hypoglycemic Activity

Reactions of photochemically generated benzonitrile methylides 2 with carbonyl compounds 3 yielded 3‐oxazolines of the types 5 and 6 (Scheme 1). Photooxidation of 5‐[p‐(dimethylamino)phenyl]‐2,2‐dimethyl‐4‐phenyl‐3‐oxazoline (5a) gave 4′‐(2,2‐dimethyl‐4‐phenyl‐3‐oxazolin‐5‐yl)‐N‐methylformanilide (6r) which could be transformed to 2,2‐dimethyl‐5‐[p‐(methylamino)phenyl]‐4‐phenyl‐3‐oxazoline (6s) by photodecarbonylation. Thirty 3‐oxazolines of types 5 and 6 have been synthesized and tested by oral and/or intraperitoneal administration to starved rats and obese‐hyperglycemic mice.
Nature et stabilité des complexes métalliques de cryptands dinucléants en solution. III. Le monocycle [22]‐Py2N4
Authors: Arnaud‐Neu Françoise , Sanchez Maria , Schwing‐Weill Marie‐José
Published: December 2004

Nature and Stability of Some Metallic Complexes of Dinucleating Cryptands in Solution III. The Monocycle [22]‐Py2N4

The nature and stability of complexes formed by a new 22‐membered monocycle L = [22]‐Py2N4 with the cations Mn+ = Cu2+, Co2+, Ni2+, Zn2+, Cd2+, Pb2+, and Ag+ have been determined in aqueous solutions (0.01M NaClO4, 25°) by pH‐metry and also, for the copper system, by UV‐absorption spectrophotometry. The stepwise protonation constants of the four amine functions of L were 9.1, 8.3, 7.1 and 3.7 logarithms units, respectively. No evidence was found for the protonation of the two pyridine nitrogen atoms. Mononuclear complexes MLn+ were identified in all systems investigated, but the dinuclear species M2L2n+ were only found with Cu2+ and Ag+. The logarithms of the overall stability constants for the copper and silver complexes are CuL2+, 12.9; Cu2L4+, 18.6; Agl+, 6.3; Ag2L2+, 10.9, respectively. Mononuclear hydroxy species MLOH(n−1)+ were identified in all systems except those of copper and silver. No dinuclear hydroxy complexes were detected. The complexing properties of L are compared to those of the large and less rigid bis‐dien.
Solvolysen von 4‐Alkylidenbicyclo[3.2.0]hept‐2‐en‐6‐olen. Synthese von 1‐Vinylfulvenen und 8,8‐Diphenylheptafulven
Authors: Stadler Heinz , Rey Max , Dreiding André S.
Published: December 2004

Solvolysis of 4‐Alkydenbicyclo[3.2.0]hept‐2‐en‐6‐oles. Synthesis of 1‐Vinylfulvenes and 8,8‐Diphenylheptafulvene

Four 4‐alkylidenebicyclo[3.2.0]hept‐2‐en‐6‐ones 2–5, obtained via ketene cycloaddition to fulvenes, were reduced to separated mixtures of the ‘endo’ ‐alcohols ‘endo’‐6 to ‘endo’‐9 (68–73%) and ‘exo’‐6 to ‘exo’‐9 (3–20%). Treatment of some of these alcohols with (CF3SO2)2O in CH2Cl2/pyridine caused a spontaneous solvolysis to yield unsaturated 7‐membered rings as pyridinium triflates 10–12 or 1‐vinylfulvenes 13 and 14, a new class of reactive tetraenes: Both ‘endo’‐9 and ‘exo’‐9, having two methyl groups at C(7), were converted into the vinylfulvene 13 (≈ 80%). The alcohols with two H‐atoms at C(7) exhibited a stereochemically controlled reaction selectivity, inasmuch as ‘endo’‐6 to ‘endo’‐8 afforded only the corresponding 7‐membered‐ring pyridinium salts 10–12 (66–79%), while ‘exo’‐6 produced only the vinylfulvene 14 (77%). A stereoelectronic control argument explains the C(1), C(5)‐bond cleavage with ‘endo’‐B and ‘endo’–6‐‘endo’‐8, as well as the C(1), C(7)‐bond cleavage with ‘exo’‐B, ‘exo’‐6, and with both ‘endo’‐ and ‘exo’‐9. Thermolysis (120°) of the pyridinium triflates 10 and 11 yielded the 3‐isopropenyl‐cycloheptatrienes 18 and 19, respectively (≈90%); similar conditions (145°) applied to the triflate 12 produced the doubly cyclized fluorene derivative 21 (60%). When the iodide 22 derived from the triflate 12 with Nal was heated in refluxing toluene, 8,8‐diphenylheptafulvene (23, 86%) was obtained.
Selektive Herstellung von l‐ oder u‐Aldolen aus Äthyl‐trityl‐keton und aromatischen Aldehyden über Lithium‐ bzw. Aluminium‐Enolate
Authors: Ertaş Mümtaz , Seebach Dieter
Published: December 2004

Selective Preparation of l‐ or u‐Aldols from Ethyl Trityl Ketone and Aromatic Aldehydes through Lithium and Aluminium Enolates, Respectively

The ethyl trityl ketone (1) is deprotonated to the (Z)‐enolate 2 which adds to aromatic aldehydes with relative topicity ul to give the aldols 3(−78°, THF, kinetic control). If, on the other hand, 1 is heated with trimethylaluminium in toluene, the aluminium enolate formed combines with aromatic aldehydes and with cinnamic aldehyde with opposite relative topicity (lk) to the aldols 5 (+20°, toluene, 2 d, precipitation of the aluminium aldolate 4, thermodynamic control). The mechanism is discussed (cf. Fig. 1). The adducts to benzaldehyde (3a, 5a), furfural (3f, 5f), and cinnamaldehyde (3i, 5i) are O‐(2‐methoxyethoxy)methyl (MEM) protected and cleaved by lithium triethylborohydride to the 1,3‐diol derivatives 9–11 with a free primary and a protected secondary OH‐group. Analogous conversions of 1 and other ketones may also be diastereoselective, but turned out to be of less preparative value (see 6–8, 12).
Intramolekulare 1,3‐dipolare Cycloadditionen von Diarylnitriliminen aus 2,5‐Diaryltetrazolen
Authors: Meier Hansruedi , Heimgartner Heinz
Published: December 2004

Intramolecular 1,3‐Dipolar Cycloadditions of Diaryl‐nitrile‐imines Generated from 2,5‐Diaryl‐tetrazoles

Alkenyl‐substituted diaryl‐nitrile‐imines – generated by photolysis or thermolysis of alkenyl‐substituted 2,5‐diaryl‐tetrazoles ‐ undergo a regioselective intramolecular [2 + 3] cycloaddition to yield new heterocyclic compounds, e. g. fused 2‐pyrazolines. With alkinyl derivatives, the corresponding pyrazoles have been formed. UV evidence is given for the intermediate nitrile‐imine at − 190°. The latter can be trapped using an excess of carboxylic acid (UV evidence for a new intermediate at − 120°). In this case, the corresponding rearranged addition product N′‐acyl‐N′‐aryl‐benzohydrazide is isolated in good yield.
Radicaux libres dérivés de sucres. Partie. VII. Analogues de nucléosides marqués par un spin. Communication préliminaire
Authors: Tronchet Jean M. J. , Mekhael Kamal , Graf‐Poncet Joëlle , Benhamza Rachid , Geoffroy Michel
Published: December 2004

Sugar Free Radicals. VIII. Spin‐Labeled Nucleosides Analogs

A series of 5′‐deoxy‐5′‐hydroxylamino derivatives of adenosine and uridine have been prepared by reduction of the corresponding oxime or nitrone. ‘Second generation’ 3′‐deoxy‐3′‐N‐aryl(or N‐alkyl) hydroxylamino‐β‐D‐xylofuranosyluracils have also been synthesized by a one‐pot reaction including the following elementary steps: deblocking of the starting material, reduction of the 3′‐deoxy‐3′‐oximinouridine, condensation of the resulting hydroxylamine with an aldehyde, reduction of the nitrone formed. The deoxy‐hydroxylaminonucleosides oxidized spontaneously in the air (or in presence of traces of PbO2) to give the corresponding nitroxide free radicals, ESR spectra of which furnished useful informations on their structures. Some of these modified nucleosides bore notable cytotoxic or antiviral activities.
Synthèse d'une nouvelle depsidone dérivée de l'acide furfurique, le diméthoxy‐3,8‐(diméthoxy‐2,4‐méthoxycarbonyl‐5‐diméthyl‐3,6‐benzyl)‐9‐triméthyl‐1,4,6‐oxo‐11‐11H‐dibenzo[b,e]dioxépinne[1,4]carboxylate‐7 de méthyle
Authors: Gunzinger Jan , Tabacchi Raffaele
Published: December 2004

Synthesis of a New Depsidone, Derivative of Furfuric Acid: Methyl 3,6‐dimethoxy‐9‐(2,4‐dimethoxy‐5‐methoxycarbonyl‐3,6‐dimethylbenzyl)‐1,4,6‐trimethyl‐11‐oxo‐11H‐dibenzo[b,e] [1,4]dioxepin‐7‐carboxylate

The total synthesis of the title compound 1b is described. Starting from simple orcinol and β‐orcinol units, the benzophenone 4 has been prepared. Using a biomimetic reaction, the intramolecular oxydative coupling, lead to the grisadienedione 25. By thermal interconversion and permethylation, the depsidone 1b has been obtained.
Neue Synthese von Vinblastinderivaten; 20′‐Deethyl‐20′‐deoxyvinblastin und 20′‐Deethyl‐20′‐deoxy‐C′‐homovinblastin Vorläufige Mitteilung
Authors: Schill Gottfried , Priester Claus Ulrich , Windhövel Udo Frank , Fritz Hans
Published: December 2004

A New Synthesis of the Vinblastine Derivatives 20′‐Deethyl‐20‐deoxyvinblastine and 20′‐Deethyl‐20′‐deoxy‐C′‐homovinblastine

A new synthesis of vinblastine derivatives is described. In the key step, the chloroindolenine derivative 14 was reacted with vindoline (2) to give, after cyclization, stereospecifically 17/I and 20′‐deethyl‐20′‐deoxyvinblastine (17/II). In an analogous manner, the epimeric C′‐homovinblastine derivatives 21/I‐21/IV were synthesized.
Anion Selectivity of Metalloporphyrins in Membranes
Authors: Ammann Daniel , Huser Marin , Kräutler Bernhard , Rusterholz Bruno , Schulthess Peter , Lindemann Bernhard , Halder Ernst , Simon Wilhelm
Published: December 2004

Lipophilic Co(III) and Mn(III) complexes of 5,10,15,20‐tetrakis[4‐(hexyloxycarbonyl)phenyl]porphyrin act as positively charged carriers for anions and induce anion selectivities in membranes clearly deviating from the sequence of classical anion exchangers. Different anion selectivities are observed for the Co(III) and Mn(III) porphyrins.
Pteridine. Teil LXXXI. Mechanismus der Photooxidation von 5,6‐Dihydro‐1,3‐dimethyl‐6‐thioxopteridin‐2,4(1H,3H)‐dion
Authors: Heckel Armin , Pfleiderer Wolfgang
Published: December 2004

Mechanism of the Photooxidation of 5,6‐Dihydro‐1,3‐dimethyl‐6‐thioxopteridine‐2,4(1H,3H)‐dione

The mechanism of the photooxidation of 5,6‐dihydro‐1,3‐dimethyl‐6‐thioxopteridine‐2,4(1H,3H)‐dione (9) has been investigated in dependence of the pH. Photooxidation of the anion species in weak alkaline solution takes place by singlet oxygen as well as the superoxide radical anion forming 1,2,3,4‐tetrahydro‐1,3‐dimethyl‐2,4‐dioxopteridine‐6‐sulfinate (5) as the first detectable reaction product. In acidic medium, a more complex photooxidation process is observed leading, in a radical‐chain mechanism, to 6,6′‐dithiobis[1,3‐dimethylpteridine‐2,4(1H,3H)‐dione] (6).
Synthèse d'acétals de désoxy‐3‐hydroxyamino‐3‐furannoses. Note de laboratoire
Authors: Tronchet Jean M. J. , Habashi Ford , Fasel Jean‐Pierre , Zosimo‐Landolfo Guido , Barbalat‐Rey Françoise , Moret Gilles
Published: December 2004

Synthesis of 3‐Deoxy‐3‐(hydroxyamino)furanose Acetals

Reduction of sugar ketoximes with NaBH3CN under acidic conditions constitutes a good synthetic pathway to deoxy(hydroxyamino)sugar derivatives. These compounds which are useful building blocks for the preparation of analogs of various classes of biologically important carbohydrates are reasonably stable.
Fragmentation of Optically Active (1‐Phenylethyl)‐ and (1‐Naphthylethyl)ureas in Refluxing Alcohols: Easy Preparation of Optically Active Amines of High Optical Purity
Authors: Schönenberger Bernhard , Brossi Arnold
Published: December 2004

(1‐Phenylethyl)‐ and (1‐naphthylethyl)ureas, obtained in the reaction of racemic amines with optically pure isocyanates, are separated and then decomposed in refluxing alcohols, to afford optically pure secondary amines and optically pure alkyl carbamates in quantitative yields. The scope of this fragmentation for the resolution of racemic mixtures of amines is illustrated by several examples of biologically important compounds. Carbamates obtained by this fragmentation can readily be recycled.
Nonapentafulvalen
Authors: Escher André , Neuenschwander Markus
Published: December 2004

Nonapentafulvalene

(1) has been prepared by oxidative coupling of sodium cyclopentadienide (6) and sodium cyclononatetraenide (7) with CuCl2 in THF, two‐fold deprotonation of cyclopentadienyl‐cyclononatetraene 8 to give dianion 16, and oxidative treatment of 16 with CuCl2 (Schemes 2 and 3). Compound 1 is a highly reactive and thermally instable molecule, since valence isomerisation 1 → 17 proceeds easily even at low temperature (the half‐life of 1 is ca. 30 min at −15° in CDCl3). NMR investigations show that nonapentafulvalene is an olefinic molecule with strongly alternating bond lengths, its nine‐membered ring deviating strongly from planarity. Comparison of the NMR data of 1 with those of a series of sterically similar pentafulvenes 18 and nonafulvenes 19 (Tables 1 and 2) demonstrates that (a) with regard to the pentafulvene unit of 1, the cyclononatetraene ring acts as very weak electron‐donating group, while (b) with regard to the nonafulvene unit of 1, the cyclopentadiene ring acts as weak electron‐accepting group. So nonapentafulvalene may be regarded as a ‘nonafulvene of inverse π‐polarisation’.