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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 138-141 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-(2′-Deoxy-5′-O-dimethoxytrityl-′-D-ribofuranosyl)-1 H-benzimidazole 3′-[(p-chlorophenyl)(2-cyanoethyl) phosphate] (6) has been synthesized from 1-(β-D-ribofuranosyl)-1H-benzimidazole (3b) using regiospecific 2′-deoxygenation. The latter compound was obtained by glycosylation of benzimidazole with the D-ribose derivative 2 leading exclusively of the β-D-anomer.
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  • 2
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photochemical-reaction yields after IR multiphoton excitation of CHFCl-CF2Cl are reported and evaluated in terms of the steady-state rate coefficient for reactant decay \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm st}) = 10^{6.1 \pm 0.3} ({I \mathord{\left/ {\vphantom {I {{\rm MWcm}^{- 2}}}} \right. \kern-\nulldelimiterspace} {{\rm MWcm}^{- 2}}}){\rm s}^{- 1} $$ \end{document} The dominant primary reaction channels are α,β HCl and HF elimination, although minor pathways seem to include Cl2 elimination and other channels, which are discussed. The major uncertainty in the comparison with theoretical estimates resides in the fraction of C—F chromophore band strength which contributes to excitation. The total band strength for the range from 940 cm-1 to 1310 cm-1 is reported to be G = ∫σ(ṽ) (dṽ/ṽ) = 8.2 pm2.
    Additional Material: 4 Ill.
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  • 3
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation of Neutral Sodium-Selective Ionophores and their Characterization in Membrane ElectrodesDifferent ionopbores based on N,N′-dibenzyl-N,N′-diphenyl-1,2-phenylenedioxydiacetamide (1) have been prepared by substitution of the aromatic ring carrying the ether O-atoms. Substituents of widely different electronegativity (CH3, CH3O, CHO, CN NO2, Br) do not relevantly influence the ion selectivity.
    Additional Material: 1 Ill.
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  • 4
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bidentate diphosphine ligand, 3,3′-oxybis[(dipenylphosphino)methylbenzene] (1) forms monomeric, trans-square-planar complexes MX2(1) (M = Ni, Pd, Pt; X = Cl-, Br- I-, and, in part, N3-, NCS-, CN-, NO3-) as well as Pt(H)Cl(1), Pt(H)Br(1), and RhCl(CO)(1). Polymeric species have been observed with substitutionally inert metal centres: trans-[PtCl2(1)]2 and cis-[PtCl2(1)]n (mean value of n ≈ 4-5) 31P-NMR, and selected IR and UV/VIS parameters are reported. Ligand 1 shows a marked preference for trans-spanning and monomeric chelate formation, despite its various degrees of freedom of internal rotation in the lignad backbone. The readily available ligand 1 as well as analogues with other donor atoms, therefore, appear useful in most potential applications of trans-spanning chelate ligands. The crystal structure of AgCl(1)·0.5 (CH3)2C=O·0.39 C6H12 (space group C2/c,a = 21.02 Å, b = 14.57 Å, c = 24.79 Å, β = 99.77°, V = 7531.4 Å3, Z = 8) confirms the presence of three-coordinate Ag(I), with a coordination intermediate between a trigonal-planar and a T-shaped geometry (P-Ag-P = 145.61(8)°).
    Additional Material: 1 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 196-202 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lipstatin (1), a natural product, and tetrahydrolipstatin (2) are pancreatic lipase inhibitors. Non-stereoselective and partially stereoselective syntheses of 2 are used to establish the absolute configuration of tetrahydrolipstatin and lipstatin.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 203-209 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Formation of two unknown, tricyclic trimers of diketene, 3 and 4, was observed in diketene solutions containing (CH3)3SiCl/NaI or TsOH.
    Additional Material: 1 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 232-236 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An Enantionselective Synthesis of L-ThreonineAn enantioselective synthesis of L-threonine (1) is described. Racemic ethyl 2-acetamido-3-oxobutyrate (6) was synthesized from ethyl acetoacetate (2) [4][5] and then transformed to the epimeric optically active alcohols 7a and 7b by microbiological reduction with Saccharomyces rouxii. The Mixture 7a/7b could be converted to 1 by slightly modified, known Methods in a yield of ca. 52% with respect to 7a/7b.
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  • 8
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral enolates of imidazolidinones and oxazolidinones from the title amino acids react with carbonyl compounds to afford the corresponding alcohols in excellent yields (see Scheme 5). Furthermore, the addition to aldehydes proceeds with high diastereoselectivity to give, after acid hydrolysis, threo-α-amino-β-hydroxy acids of high enantiomeric purity. Some of the threo-α-amino-β-hydroxy acids prepared in this work are the proteinogenic (S)-threonine (26), the naturally occurring (S)-3-phenylserine (28), and (S)-3-hydroxyleucine (27) as well as the unnatural (S)-4,4,4-trifluorothreonine (30) and (S)-3-(4-pyridyl)serine (31). The N-methylamide of (2S,3R,4R,6E)-3-hydroxy-4-methyl-2-(methylamino)-6-octenoic acid (32), the unique amino acid in the immunosuppressive cyclosporine, was prepared by the new method. This report presents also information suggesting that both steric and stereoelectronic effects are responsible for the good stereoselectivities observed.
    Additional Material: 2 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 272-274 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gloeosporone, the germination self-inhibitor from the fungus Colletotrichum gloeosporioides f.sp. jussiaea, is shown by spectroscopic data and X-ray analysis to have the constitution and relative configuration as shown in Formula 2 (either (1S,6R,12R)-1-hydroxy-6-pentyl-5,15-dioxabicyclo[10.2.1]pentadecan-4,13-dione or its enantiomer), rather than the previously assigned constitution 1.
    Additional Material: 3 Ill.
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  • 11
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 292-298 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electrochemical Oxidation of (S)-Malic-Acid Derivatives: a Route to Enantiomerically Pure Alkylmalonaldehydic EstersThe 3,3-dialkymalic-acid diesters, prepared by the previously described diastereoselective alkylations through dilithium alkoxide enolates, are saponified to the monoesters containing a free α-hydroxycarboxylic-acid moiety(Scheme 3). The monoesters are subjected to electrochemical oxidative decarboxylation in MeOH. If the intermediate monoacids are purified, the malonaldehydic esters (2-formy1-2-alkylcaroxylates) Obtained by this procedure are enantiomerically pure; they have the same structural features, i.e. two enantiotopic functionalized branches on the (persubstituted) stereogenic center, as the well known 3-hydroxy-2-methylpropanoic acid (‘Roche acid’) which was employed frequently as a starting material for the preparation of either enantiomer of various target molecules.
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 308-314 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ring Enlargement by Lactonization of Methylated 1-(3′-Hydroxypropy1)-2-oxocyclododecane-1-carbonitrilesThe title compounds were prepared by Michael reaction of 2-oxocyclododecane-1-carbonitrile (1) and acrylaldehyde and its derivatives followed by NaBH4 reduction or methylation of the aldehyde group with [(CH3)2Ti(i-PrO)2] (Scheme 1). In all cases, the ring enlargement was performed with Bu4NF/THF to give different methylated derivatives of 12-cyano-15-pentadecanolide (13) in 95-99% yield. The Yields of the rearrangement products are not dependent on the positions and numbers of the CH3 groups in the side chain of 3. The lactonization reaction is of unremarkable stereoselectivity.
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  • 13
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidation of cedrol (1), β- and γ-eudesmol (6 and 7, resp.), sclareol (14) manoyl oxide (15), 1,9-dideoxyforskolin (22) (±)-methyl trans-dihydrojasmonate (28), and tetrahydrolinalool (32) nearly all of natural terpenoid origin, by the ‘Gif system’ has afforded a number of novel products (3, 11, and 12, 16/17, 18/19, 26, 29-31, and ketones corresponding to 34-35, res.). The structures of these compounds were established by spectroscopic techniques including 2D-NMR and, where appropriate, by comparison with authentic samples.
    Additional Material: 12 Tab.
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  • 14
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 2232-2244 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Position 5 at the Oxotremorine Skeleton as the Stearing Position for Activity at the Muscarinic ReceptorsSubstitution of the Ch2 group at position 5 of oxotremorine (2) by electronegative atoms like O- or N-atom, or by sterically bulkier groups like methyl, N-formyl, or N-acetyl Changes the pharmacological profile of oxotremorine drastically. The O- and N-analogues were potent but unselective (M1/M2) muscarinic agonists. The methyl analogue ((R)-BOK-1) is a muscarine antagonist which is 10 times more potent on the ganglion cervical superius (pA2 = 9.3) than pirenzepine and is able to distinguish between the ileal and ganglion receptor by a factor of 100. The N-formyl derivative differentiates between the two receptors by a factor of 500 with a potency comparable to pirenzepine. The two M1-selective antagonists have higher affinity to the rat-ganglion receptors compared to the affinity to rat-cortex homogenate. The synthesis and the pharmacological activity of several new oxotremorine analogues are discussed.
    Additional Material: 1 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 16
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the preparation of (+)-(R)-methyl hydrogen 2-(tert-butoxymethyl)-2-methyl-malonate (5e) in synthetically useful amounts from readily available starting material.
    Additional Material: 1 Tab.
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  • 17
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Diels-Alder Reactions of 2,4-Bis{[(tert-Butyl)dimethylsilyl]oxy}-3-aza--1,3-pentadien with HeterodienophilesThe 2,4-bis{[(tert-butyl)dimethylsilyl]oxy}-3-aza-1,3-pentadien(2) reacts via the Diels-Alder adducts 3, 6a-c, and 8a, b, which cannot be isolated, giving the triazines 4, 7a-c, and the oxadiazines 9a, b. The hydrolysis of 4 in MeOH affords the N-acetyl-acetamid derivative 5. The formula of 9a is proven by an X-ray-structure analysis.
    Notes: No. Abstract.
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  • 18
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 1302-1306 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A 6-step synthesis of (±)-grandisol (1) is presented, which involves dichloroketene addition to 3-methyl-3-butenyl acetate (4), reductive dechlorination of the adduct 6 to the ketone 7 and saponification to 8, aldolization of 7 or 8 with acetone and cyclization to the bicyclic ketone 9, Wolff-kishner, reduction to 14, and finally ring opening to 1. Since 9 is a known intermediate of the synthesis of (±)-lineatin (2), the latter can now be obtained in 6 steps.
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  • 19
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 1333-1340 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Macrocyclic α,β-Unsaturated γ-Oxolactones by Ring-Enlargement Reactions; a New Path to the Macrocyclic Lactone Antibiotic A 26771 BA new synthetic route to the α,β-unsaturated γ-oxolactones 2a and 2b, involving two ring-enlarement reactions, is described. Ring opening of bicyclic α-nitroketones of the type 3 gave ring-enlarged compounds of the type 4 which were converted to monoprotected diketones of the type 10 by using a variation of the Nef reaction as a key step. Macrocyclic lactones of the type 11 were obtained by Baeyer-Villiger oxidation and converted into compounds of the type 2. The conversion of 2b to the macrocyclic lactone antibiotic A 26771 B (1) is already described in the literature.
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  • 20
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nucleophilic Ring Opening of Aryl α-Nitrocyclopropanecarboxylates with Sterically Protected but Electronically Effective Carbonyl and Nitro Group. A New Principle of α-Amino Acid Synthesis (2-Aminobutanoic Acid a4-Synthon)The readily available 2,4,6-tri(tert-butyl)-and 2,6-di(tert-butyl)-4-methoxypahenol esters 2 of α-nitrocyclo-propanecarboxaylic acid ring opening with C-, N-, O-, and S-nucleophiles (cyanide, malonate, azide, anilines, alkoxides, phenoxides, thiolates) in DMF or alcohol solvents (80-95% yield). The products 6-14 are 2-nitrobutanoates with the newly introduced substituent in the 4-position. Reduction of the NO2 group with Zn/AcOH/Ac2O gives N-acetyl-α-amino acid esters 16-22 (40-90% yield). Subsequent oxidative cleavage (H2O2/HCOOH) of The p-methoxy-phenyl esters 18 and 20 produces free amino acids (65% 23 and 67% 24, respectively). Thus, the nitro ester 2 corresponds to a 2-aminobutanoic-acid a4-synthon, it is a ‘homo-Michael acceptor’ producing γ-substituted α-amino acids.
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  • 21
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On protonation of the diolefin complexes [M(C5R5)(diene)] (R = H, CH3; M = Co, Rh, Ir; diene = 2,3-dimethylbutadiene, 1,3-cyclohexadiene) with HBF4, cationic species are isolated which, at room temperature, show fluxional behaviour on the NMR time scale. Depending on R and M, three different ground states are observed for these cationic complexes in the NMR spectra at low temperatures. While for M = Ir a classical metal-hydride structure M-H is observed, the Co and Rh complexes show ground states with ‘agostic’ H-bridges M‥H‥C. The protonated species are characterized by 1H-, 13C- and 103Rh-NMR spectra. Total line-shape analysis of the 1H and 13C spectra in the 298-154 K range gave the free enthalpies of activation ΔG ≠ for methyl rotation and 1, 4-H shift in the agostic structures 2b, 2b′, 2c, and 2c′. The Rh complexes show the lowest ΔG± values for the 1,4-H shift, and the strength of the agostic bond appears to decrease in the order CoC5H5 〉 CoC5Me5 〉 RhC5H5 〉 RhC5Me5. Only for R = H and M = Rh and in the presence of traces of Lewis bases (H2O, Pyridine, or acetone), variable amounts of coordinatively saturated allyl complexes competing with the agostic species are observable. Morethan equimolar amounts of basic solvents lead to irreversible deprotonation and recovery of the starting complexes. Stable allyl-halide complexes are formed on reaction with HCI, while protonation with HBF4, in the presence of CO, gives high yields of complexes [M(CO)(allyl)(C5R5)] [BF4]. The different ground states observed for the protonated complexes and the dynamic behaviour in solution are compared with other hydride-transfer reactions observed in organometallic chemistry, specifically with the β-hydride elimination and the catalytic hydrogenation of olefins.
    Additional Material: 5 Ill.
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  • 22
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of temperature on the dimethylformamide exchange on Mn(DMF)2+6 and Fe(DMF)2+6 has been studied by 13C- and 17O-NMR, respectively, yielding the following kinetic parameters: k298 equals; (2.2±0.2). 106 S-1, ΔH≠ = 34.6 ± 1.3 kJ mol-1, ΔS≠ = -7.4 ± 4.8 J K-1mol-1 for Mn2+ and K298 = (9.7 ± 0.2).105 S-1, Delta;H≠ = 43.0 ± 0.9 kJ mol-1, ΔS≠ = + 13.8 ± 2.8 J K-1mol-1 for Fe2+. The volumes of activation, ΔV≠ in cm3mol-1, derived from high-pressure NMR on these metal ions, together with the previously published activation volumes for Co2+ and Ni2+ (+2.4 ± 0.2 (Mn2+), +8.5 ± 0.4 (Fe2+) +9.2 ± 0.3 (Co2+), + 9.1 ± 0.3 (Ni2+)) give evidence for a dissociative activation mode for DMF exchange on these high-spin first-row transition-metal divalent ions. The small positive ΔV≠ value observed for DMF exchange on Mn2+ seems to indicate that a mechanistic changeover also occurs along the series, (probably from Id to D), as for the other solvents previously studied (Ia to Id, for H2O, MeOH, MeCN). This changeover is shifted to the earlier elements of the series, due to more pronounced steric crowding for dimethylformamide hexasolvates.
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  • 23
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermolysis of the steroidal 5α,8β-peroxide 1, under acidic conditions afforded in addition to the expected 5,10:8,9-diseco derivative 2, the rearranged 5α,8β-epoxide 3, the structure of which was determined by NMR spectroscopy and X-ray analysis.
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  • 24
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 43-48 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two CH3 groups at C(6) of 2-exo- (10a) and 2-endo-norbornyl p-toluenesulfonate 11a lower their solvolysis rates in 80% EtOH by factors of 28 and 16, respectively. A spirocyclopropyl group including C(6), as in 21a and 22a, reduces the rate of exo- and endo-ionization by factors of 250 and 8, respectively. The geminally dimethyl-substituted tosylates 10a and 11a yield the 2-exo-alcohol 10b, whereas the spirocyclopropyl-substituted tosylates 21a and 22a furnish rearranged 3-brendanol 23. These findings are readily rationalized by the inductive model, according to which norbornyl cation formation is controlled by the inductive effect of dorsal substituents.
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  • 25
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 49-58 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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’.
    Additional Material: 4 Ill.
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  • 26
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The alcyonacean Alcyonium ( = Parerythropodium) coralloides (PALLAS 1766) is the first Mediterranean organism shown to contain cembranoids. These are of unusual type like coralloidolide A ( = (-)-(1R*, 2R*, 3R*, 12S*, 5Z, 7Z, 9Z)-1, 2:7, 10-diepoxy-12-isopropenyl-5, 9-dimethylcyclotetradeca-5, 7, 9-triene-1, 3-carbolactone; (-)-6) and coralloidolide B ( =(-)-(1R*,2S*,3R*,7S*,10S*,12S*,5Z,8Z,)-2, 7:7, 10-diepoxy-1, 10-dihydroxy-12-isopropenyl-5, 9-dimethylcyclotetradeca-5,8-diene-1,3-carbolactone; (-)-8). Structural assignments are mainly based on 1D- and 2D-NMR data and on chemical transformations.
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  • 27
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radical anion of 1,2:9,10-dibenzo[2.2]paracyclophane (3) has been studied by ESR, ENDOR, and TRIPLE resonance spectroscopy under a variety of experimental conditions. The coupling constants of the eight protons in the deck-benzene rings, and of the four inner and four outer protons in the side-benzene rings are 0.234, 0.123, and 0.036 mT, respectively (solvent: 1,2-dimethoxyethane; counterion: K+). All three values have the same sign which is predicted to be negative. Comparison of the largest coupling constant (0.234 mT) with the corresponding value (0.297 mT) for the radical anion of the parent [2.2]paracyclophane (1) points to similar nodal properties of the singly occupied orbitals in \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document}. Notwithstanding this similarity, \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document} seems to associate less readily than \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document} with alkali metal counterions, since tight ion pairs of \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document} with K+ are formed only in solvents of low solvating power. Effects of conformational changes on the ESR spectra, such as those previously observed for the radical anion of [2.2]paracyclophane-1,9-diene (2), are not apparent for \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document} in the temperature range of investigation. Hyperfine data are also reported for the radical anion of a derivative 4 which has a CH3 substituent in one of the side-benzene rings of 3.
    Additional Material: 8 Ill.
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  • 28
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 116-120 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of ‘D-Isothreonine’ and ‘L-Alloisothreonine’ Starting from L-AlanineStarting from L-alanine, ‘D-isothreonine’ ( = (2R, 3S)-3-amino-2-hydroxybutanoic acid) and ‘L-alloisothreonine’ ( = (2S, 3S)-3-amino-2-hydroxybutanoic acid) were synthesized.
    Additional Material: 2 Ill.
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  • 29
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 342-346 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel Triterpene Lactones of Helenium autumnale L.Three novel triterpene lactones 1-3 could be detected by investigating a pentane extraxt of the Helenium autumnale L. (Asteraceae) roots. The structures are especially elucidated by 1H- and 13C-NMR spectroscopy. The lactones 1-3 formally represent Diels-Alder products of a reaction between a sesquiterpene lactone and an α,β-unsaturated sequiterpene aldehyde.
    Additional Material: 2 Ill.
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  • 30
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 354-368 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selective Amide Cleavage in Peptides Containing α,α-Disubstituted α-Amino AcidsA new synthesis of dipeptides with terminal α,α-disubstituted α-amino acids, using 2,2-disubtituted 3-amino-2H-azirines 1 as amino-acid equivalents, is demonstrated. The reaction of 1 with N-protected amino acids leads to the corresponding dipeptide amides in excellent yield. It is shown that the previously described selective hydrolysis (HCl, toluene, 80°, or HCl, MeCN/H2O, 80°) of the terminal amide group results in an extensive epimerization of the second last amino acid. An acid-catalyzed enolization in the intermediate oxazole-5(4H)-ones is responsible for this loss of configurational integrity. In the present paper, a selective hydrolysis of the terminal amide group under very mild conditions is described: In 3N HCl (THF/H2O 1:1), the dipeptide N,N-dimethylamides or N-methytlanilides are hydrolized at 25-35° to the optically pure dipeptides in very good yield.
    Additional Material: 1 Tab.
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  • 31
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 375-380 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrochemistry of potassium heptacyanorhenate(III) in aqueous solution was studied by cyclic and by rotating disk voltammetry at planar microelectrodes. The results are consistent with a single, reversible electron transfer: Re(CN)3-7 + e⇄Re(CN)4-7 with E′0 = 643 mV vs. NHE. A single protonation equilibrium is observed: Re(CN)4-7 + H+⇄ Re(CN)7H3- with pK = 1.31 determined from combined voltammetric and pH data. The Re-CN bond appears to be kinetically inert, and none of the cyano complexes in other oxidation states of Re claimed in the literature was found in the potential range - 2 V to + 1 V.
    Additional Material: 2 Ill.
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  • 32
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Starting from γ- and δ-lactones 1-3, a two-step preparation of 3-hydroxypropyl and 4- hydroxybutyl propenyl ketones 10-18 is described, involving as the key step the β-cleavage of the bis(homoallylic) potassium alkoxides 4a-9a. The novel methodology is illustrated by a short synthesis of (±)-rose oxide(20).
    Additional Material: 2 Tab.
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  • 33
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrophilic additions of 2-nitrobenzenesulfenyl chloride to (1RS,2SR,4RS)-spiro[bicyclo[2.2.1]hept-5-ene-2,2′-oxirane] (12) and (1RS,2SR,4RS)-spiro[bicyclo[2.2.2]oct-5-ene-2,2′-oxirane] (14) were not regioselective under condition of kinetic control. However, good regioselectivity was observed for the addition of 2-nitro-benzenesulfenyl chloride to (1RS,2RS,4RS)-spiro[bicyclo[2.2.1]hept-5-ene-2,2′-oxirane] (13), giving (1RS,2SR,4SR,5RS,6RS)-6-exo-(2-nitrophenylthio)spiro[bicyclo[2.2.1]heptane-2.2′-oxirane]-5-endo-yl chloride (24) and for the exo addition to (1RS,2RS.4RS)-spiro[bicyclo[2.2.2]oct05-ene-2,2′-oxirane] (15), giving preferntially (1RS,2SR,4SR,5RS,6 RS)-6-exo-(2-nitrophenylthio) spiro[bicyxlo[2.2.2]octane-2,2′-oxirane]-5-endo-yl chloride (30). The facial selectivity (electrophilic exo vs. endo attack on the bucyclic alkene) depended on the relative configuration of the spiroepoxide ring in the bicyclo[2.2.2]octenes 14 and 15. The exo-epoxide 14 was attacked preferentially (6:1) on the endo face by sulfenyl whereas exo attack was preferred (7:2) in the case of the endo-epoxide 15. No products resulting from transannular ring expansion of the spiro-epoxide moieties could be detected.
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  • 34
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    Helvetica Chimica Acta 70 (1987), S. 1937-1943 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Oxidation of 3-(1-Nitro-2-oxocycloalkyl)propanalOxidation of the title compound 1 with KMnO4 under neutral conditions led to the corresponding acid 2, 5-(2,3,4,5-tetrahydro-2-nitro-5-oxo-2-furyl)pentanoic acid (4), and 4-oxononadioic acid (6). On the basis of experimental results the mechanism of the formation of 4 is discussed (Scheme 1). Oxidation of 1 with KMnO4 under basic conditions gave 6 which was transformed to (E)-4,5-dihydro-5(2′-oxocyclopentyliden)furan-2(3H)-one (12) with benzene/TsOH (Scheme 3). In contrast to this result the corresponding 4-oxoheptandioic acid (22) yields 1,6-dioxaspiro[4,4]nonan-2,7-dione (23) only (Scheme 4).
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  • 35
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1,2,3,4-tetrahydro-N-pivaloyl-isoquinoline-3-carboxylic acids 1d, 2d, and 3d, derived from (R)- or (S)-phenylalanine, (S)-dopa, and (S)-α-methyldopa, respectively, are doubly deprotonated with (tert-butyl)lithium in THF and alkylated at the 1-position (products 5-10). The major diastereoisomers formed are the result of electrophilic attack from the face opposite to the carboxylate group (rel. topicity ul-1,3). Even the addition to benzaldehyd (→7,8) is highly stereoselective (one of four diastereoisomers is formed exclusively (300-MHz 1H-NMR analysis)), if MgBr2 etherate is added prior to the electrophile. Some of the obtained amino-acid derivatives are decarboxylated by anodic oxidation in MeOH (→11, 12, 17) and NaBH3CN reduction, and converted to the known 1-methyl- and 1-benzyltetrahydroisoquinolines (15, 16) of 〉 95% ee as well as to the phthalide isoquinoline alkaloid (+)-corlumine of ≥80% ee. The synthetic approach described here is compared with other methods of synthesizing enantiomerically pure 1-substituted tetrahydroisoquinolines (and thus an important group of alkaloids, Scheme 1).
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  • 36
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 1981-1982 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 37
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 1981-1987 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Determination of the Chirality Sense of (+)-(R)-1-Azabicyclo[3.3.1]nonan-2-oneOptically active (+)-(R)-1-azabicyclo[3.3.1]nonan-2-one ((+)-1) of known absolute configuration is synthesized in the following way: Resolution of (±)-piperidin-3-ethanol ((±)-2) by fractional recrystallization of its diastereoisomeric salts with (+)-3-bromocamphor-8-sulfonic acid from EtOH gave a less soluble salt that yielded(+)-2. The chirality sense of (+)-2 was shown to be (R) by chemical correlation with the enantiomers of 3-oxocyclopentaneacetic acid ((±)-8) of known absolute configuration. This correlation was effected by a Beckmann rearrangement of the oxime (R)-9 to the pyridone (S)-10 followed by a direct reduction with LiAlH4 to give the enantiomer (-)-(S)-2 that was characterized as its benzyloxycarbonyl derivative (-)-(S)-3. The alcohol (+)-3 was converted via (+)-4 into the nitrile (+)-5 which gave by hydrogenolysis and hydrolysis the (R)-configurated hydrochloride (+)-6 which was cyclized to the bicyclic (5R)-lactam (+)-1 in 67% yield by heating with 2 equiv. of dibutyltin(IV) oxide in toluene. The nonplanar amide function in (+)-1 with the substituents at the N-atomarranged in a trigonal pyramid causes two rather intense Cotton effects at 242 (Δ∊max = +19.5) and 211 nm(Δ∊max = -17.9) in the CD spectrum. If the molecules of (+)-1 do exist mainly in the chair-twistboat conformation, the amide chromophore is pyramidally deformed in a sense defined by the absolute configuration at C(5). Therefore, the CD spectrum of the (5R)-lactam (+)-1 can be used to test theories describing the chiroptical properties of distorted amides.
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  • 38
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    Helvetica Chimica Acta 70 (1987), S. 2028-2038 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chemical synthesis of 3′-deoxyadenyly-(2′-5′)-3′-deoxyadenylyl-(2′-5′)-3′-deoxyadenosine (30; trimeric cordycepin) is described by three different routes using various protecting groups and applying the phosphotriester approach. The intermediates have been isolated and characterized by elemental analyses and spectroscopic means. High yields of 30 have been obtained on deprotection making this biologically very active compound available in preparative scale.
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  • 39
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomeric decahydro-2-naphthalenols (+)-5 and (-)-5 were prepared by enantioselective hydrolysis of the racemic chloroacetate (±)-2 catalyzed by porcine pancreatic lipase, and converted to the corresponding acetates (+)-1 and (-)-1 and ketones (+)-6 and (-)-6. The absolute configurations of the ketones, alcohols, and acetates were established by chemical correlation with natural manool ((+)-7) by making use of a retro-ene cleavage reaction of the known manool degradation product 8 to (-)-6. A distinct odour difference between the two enantiomers of each pair (+)-1/(-)-1 and (+)-6/(-)-6 has been found.
    Additional Material: 1 Tab.
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  • 40
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    Helvetica Chimica Acta 70 (1987), S. 2065-2072 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radical cations and the radical anions of 1,6-dithiapyrene (1) and 3,10-dithiaperylene (2) as well as those of three further Weitz-type S-donors 3, 4, and 5 have been studied by ESR spectroscopy. The experimental findings for \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document} (widths and behaviour on saturation of hyperfine lines) suggest that the ground state of this radical anion is effectively degenerate. With the exception of \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}, the ESR studies of all radical ions could be complemented by the use of the ENDOR and general TRIPLE resonance techniques. In addition to proton hyperfine data, 33S coupling constants have been determined for \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{+ \atop \dot{}} $\end{document} (0.53mT), \documentclass{article}\pagestyle{empty}\begin{document}$ 2^{+ \atop \dot{}} $\end{document} (0.46mT), and \documentclass{article}\pagestyle{empty}\begin{document}$ 4^{+ \atop \dot{}} $\end{document} (0.34mT); they are in agreement with the predicted substantial π-spin populations at the S-atoms.
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  • 41
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (-)-(4S,16S)-8, 12-bis[de(2-carboxyethyl)]mesourobilin-IIIα hydrochloride (8) has been synthesized from the enantiomerically pure 1,4,5,10-tetrahydro-1-oxodipyrrin-9-carboxylic-acid precursor 6a whose absolute configuration was determined by X-ray diffraction analysis of the N-[(S)-1-(1-naphthyl)ethyl] carboxamide 7b. The present results prove unequivocally that an (S,S)-configurated urobilin chromophore displays a negative Cotton effect in the VIS absorption range. However, the helicity of the inherently dissymmetric chromophore remains undetermined.
    Additional Material: 4 Ill.
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  • 42
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A useful synthetic principle for the preparation of N-heterocycles consists in the base treatment of azoma-lonates carrying electrophilic centers in the side chain. Thus, pharmacologically active triazolo[1,4]benzodiazepine-carboxamides can be prepared in one step from azomalonates derived from 2-aminobenzophenones and diethyl (2-chloroacetamido)malonate. The same malonate coupled with diazotized 3-amino-2-chloropyridine leads in 2 steps to 3 novel pyridotriazoloazines. Similarly, N-protected 2-amino-diphenylamine derivatives are converted into triazoloquinoxaline-carboxylic acids. The heteocycles are further characterized by functional-group inter-conversion. Some mechanistic aspects of the azomalonic-ester synthesis are discussed.
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  • 43
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    Helvetica Chimica Acta 70 (1987), S. 2152-2158 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Combined Application of NOE Experiment and Force-Field Calculations for the Solution of a Stereochemical ProblemThe determination of NO effects using modern NMR techniques yields valuable information on internuclear distances in molecules. The correct interpretation of these effects in highly flexible molecules with anisotropic internal motions can be improved in reliability and efficiency by the concomitant application of force field calculation. The evaluation of an additional parameter from the results of such a calculation, which can directly be correlated with the experimental data, is demonstrated. Nevertheless, inherent problems in both the NOE measurements and molecular mechanics should be taken into account for a careful interpretation of the results.
    Additional Material: 2 Ill.
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  • 44
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of the tricyclic psychotropic drug opipramol (1) with an excess of HNO2 affords a product mixture mutagenic for Salmonella typhimurium. The main product is a tetracyclic furoxan 2 (yield ca. 80%), resulting from nitrosation at C(10) and C(11) of 1. Compound 2 is not mutagenic. The essential mutagen is a nitroarene 3 formed via contraction of the central ring of 1, and nitrosation at C(2). Its yield is extremely low (〈0.1%). Nitroarenes have previously not been encountered as mutagenic products of the interaction of drugs with nitrite.
    Additional Material: 1 Tab.
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  • 45
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    Helvetica Chimica Acta 70 (1987), S. 1307-1311 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of 3-(2-Carboxy-4-pyridyl)-and 3-(6-Carboxy-3-pyridyl)-DL-alanineAs starting materials for potential photochemical approaches to betalaines C(R = COOH) and to muscaflavine F(R = COOH), β-(2-carboxy-4-pyridyl)- and β-(6(carboxy-3-pyridyl))-DL-alanine (A and D with R = COOH or 4 and 11), respectively, were prepared (Scheme 1). The synthesis of 4 (= A, R = COOH) started with the 2-[(4-pyridyl)methyl]malonate 1 and proceeded via the N-oxide 2, cyanation and hydrolysis (Scheme 2). Amino acid 11 was obtained from (3-pyridyl)methyl-bromide (6) via the malonate 7 by an analogous sequence of reactions (Scheme 3).
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  • 46
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    Helvetica Chimica Acta 70 (1987), S. 1312-1319 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The macrocyclic polyamines 4-6, when protonated, bind strongly and selectively nucleotides (AMP, ADP, ATP) and pyrophosphate in aqueous solution. The stoichiometry of the complexes formed was determined by titration experiments followed by 31P-NMR spectroscopy. Compounds 4 and 5 form 1:1 complexes with ATP, ADP, and pyrophosphate, whereas 6 forms complexes with ATP and ADP involving 2 nucleotides and 1 receptor molecule. The stability constants of these complexes have been determined by pH-metric measurements. At pH 7, both 5 and 6 give complexes of mainly the fully protonated species 5.6H+ and 6.8H+, whereas 4 yields predominantly complexes of 4.5H+ and 4.4H+.
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  • 47
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    Helvetica Chimica Acta 70 (1987), S. 1320-1325 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Simple Conversion of (R)-3-Hydroxybutanoic Acid to the (S)-Enantiomer and its Lactone (-)-(S)-4-Methylixetan-2-oneCondensation of (R)-3-hydroxybutanoic acid (1) with ethyl orthoacetate gives a 2-ethoxy-substituted (1,3)dioxanone 2 which is thermally labile: at ca. 100°, two competing processes commence, one leading to ethyl (R)-3-acetoxybutanoate (3), the other one - with complete inversion of configuration - to the (S)-4-methylixetan-2-one (4) and ethyl acetate. These can be readily separated by fractional distillation. Thus, enantiomerically pure (S)-3-hydroxybutanoic acid (ent-1) and l-2-alkyl-3-hydroxybutanoic-acid derivatives (such as 6 and 8) become available from the biopolymer PHB, the precursor to the acid 1.
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  • 48
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation of Enantiomerically Pure Derivatives of 3-Amino- and 3-Mercaptobutanoic Acid by SN2 Ring Opening of the β-Lactone and a 1,3-Dioxanone Derived from 3-Hydroxybutanoic AcidFrom (S)-4-methyloxetan-2-one (1), the β-butyrolactone readily available from the biopolymer (R)-polyhydroxybutyrate (PHB) and various C, N, O and S nucleophiles, the following compounds are prepared:(s)-2-hydroxy-4-octanone (3), (R)-3-aminobutanoic acid (7) and its N-benzyl derivative 5, (R)-3-azidobutanoic acid (6) (R)-3-mercaptobutanoic acid (10), (R)-3-(phenylthio)butanoic acid (8) and its sulfoxide 9. The (6R)-2,6-dimethyl-2-ethoxy-1,3-dioxan-4-one (4) from (R)-3-hydroxybutanoic acid undergoes SN2 ring opening with benzylamine to give the N-benzyl derivative (ent-5) of (S)-3-aminobutanoic acid in 30-40% yield.
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  • 49
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and antiallergic activity of a series of 4-(arylamino)-2,5-dihydro-2-oxo-N-(trans-2-phenyl-cyclopropyl)furan-3-carboxamides 10 are described. Treatment of N-substituted 2-amino-4,5-dihydro-4-oxofuran-3-carboxylic acids 9 with chlorooxobis(2-oxo-1,3-oxazolidin-3-yl)phosphorus (2) and an appropriate aromatic amine in the presence of Et3N, resulted in a novel 3(2H)-furanone-→2(5H)-furanone rearrangement that led to the facile preparation of the new amides 10. The latter exerted a potent antiallergic activity when tested in the dermal vascular permeability and active anaphylaxis assays in rats. The most active compound 10b inhibited the action of serotonin, histamine, and bradykinin by 94, 92, and 100%, respectively, when administered intraperitoneally to rats at doses of 100 mg/kg. The present series of 10 represents a novel class of antiallergic agents.
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  • 50
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    Helvetica Chimica Acta 70 (1987), S. 1531-1536 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The occurrence of a negative birefringence in water-in-oil (W/O) microemulsions has been substantiated and analyzed. The analysis is based on the well-established aqueous nanodroplet model of W/O microemulsions. In the particularly investigated water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/aliphatic oil systems, the AOT monolayer exhibits a negative induced intrinsic birefringence, which is brought about by the pronounced polarizability of the alkyl moiety of the AOT molecule approximately perpendicular to the direction of its permanent dipolement.
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  • 51
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomers of various chiral five- and six-membered-ring lactones, Which are important classes of compounds (flavour and Pheromone components, key intermediates in the synthesis of biologically active substances) have been separated chromatographically on the chiral phase cellulose triacetate, crystallographic form I (CTAI). For different series of five-membered-ring lactones, relationships have been found between the elution order of the enantiomers and their absolute configuration. Preparative resolutions of γ-Phenyl-γ-butyrolactone (1) and of the Pheromone component 5b have been carried out to demonstrate the applicability of the method to g-scale separations.
    Additional Material: 8 Ill.
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  • 52
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    Helvetica Chimica Acta 70 (1987), S. 2087-2097 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Saponification of homodiazepine 1a and 1b, in the absence of any proton donors, led to the formation of the 6π electron anionic species A which, by virtue of a 1,5-electrocyclization, is in equilibrium with the allylic anion B. This latter tricyclic species is thermodynamically less favoured than its bicyclic isomer A. Nevertheless, B could be trapped by acylation and led tupe-2 compounds which are the major reaction products. This is due to the fact that B is more nucleophilic and, therefore, much more reactive than A. The transoid topology of the tricyclic products 2 was demonstrated by 1H-NMR and by an X-ray diagram of 2d. The transoid geometry of 2 is a consequence of a torquospecific 1,5-electrocyclization (of A), which is due to a steric, and possibly even to an electronic factor.
    Additional Material: 2 Ill.
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  • 53
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Iodo-2-(methylthio)ethane was synthesized via a ring-opening reaction of thiirane with MeI in MeCN. The S-centered radical cation of this compound undergoes an intermolecular stabilization with the I substituent of a second unattacked substrate molecule to yield an bonded radical cation. The oxidation was initiated by solvent radical cations in irradiated 1,2-dicloroethane and hexane solutions. The 2ρ/ρ* three-electron-bonded species exhibits an optical absorption band at 410 nm, detectable by pulse radiolysis. During its decay, a new, longer-lived absorption band is formed at 380 nm which is assigned to \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm I}_{\rm 2}^{+ \atop \dot{}} $\end{document}. The latter is suggested to result from anchimeric assistance in the generation of a cyclic sulfonium salt. The radical cations of 1-bromo-and 1-chloro-2-(methylthio)ethane are assumed to undergo raped cyclization to the sulfonium salt without stabilization in any intermolecular S-Br or S-Cl interaction.
    Additional Material: 2 Ill.
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  • 54
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (R)-5-Bromo-6-(bromomethyl)-2-(tert-butyl)-2H,4H-1,3-dioxin-4-one (2) derived from (R)-3-hydroxybutanoic acid is used for substitutions and chain elongations at the side-chain C-atom in the 6-position of the heterocycle (→3-6, 10-13). Subsequent simultaneous reductive debromination and double-bond hydrogenation (Pd/C,H2)occurs with essentially complete diastereoselectivity (〉98% ds), with H transfer from the face opposite to the t-Bu group (→15-20, Table 1). Hydrolytic cleavages of the dioxanones then lead to enantiomerically pure β-hydroxy-acid derivatives (overall self-reproduction of the stereogenic center of 3-hydroxybutanoic acid or alkylation in the 4-position of this acid with preservation of configuration).
    Additional Material: 2 Tab.
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  • 55
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    Helvetica Chimica Acta 70 (1987), S. 2159-2165 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Rh-catalyzed reaction of 1,3-butadiene with ethyl 3-diazopyruvate leads, inter alia, to a dihydro-oxepinecarboxylate whose oxidation and functinal-group manipulation produce salicylates. Wittig reactions on the acylcyclopropane accompanying the dihydrooxepine yields acrylates whose pyrolyses afford cycloheptadiene-carboxylates. Oxidation and functional-group transformation produces the natural tropone, nezukone.
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  • 56
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1,4-addition of alkylmagnesium chlorides to conjugated N-enoylsultams and subsequent ‘enolate trapping’ with aq. NH4Cl or MeI/hexamethylphosphoric triamide generated centers of asymmetry at C(β) and/or at C(α) with good to excellent π-face defferentiation as demonstrated by the conversions 1→2, 1→4, and 8→9. This holds also for the regioselective 1,4-addition of EtMgC1 to a dienoylsultam (15→16). Reactive conformations 1≠, 8≠, 13, and 14 are postulated in agreement with X-ray evidence which also served for the structure determination of the product 9j.
    Additional Material: 4 Tab.
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  • 57
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    Helvetica Chimica Acta 70 (1987), S. 2245-2245 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 58
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    Helvetica Chimica Acta 70 (1987), S. 2305-2306 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 59
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 60
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    Helvetica Chimica Acta 70 (1987), S. 321-328 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [2 + 2]-cycloaddition of dichloroketene (prepared in situ from CCl3COCl and Zn(Cu)) with three alkynes 1a-c to form 2,3-dimethyl-(2a), 2,3-diethyl-(2b) and 3-butyl-4,4-dichlorocyclobut-2-enone (2c) proceeds rapidly in the absence of POCl3. The primary products 2a-c rearrange in situ to the 2,4-dichlorocyclobut-2-enones 3a-c under the influence of ZnCL2 produced during the reaction. ZnCl2 converts both 2a and 3a into a 4:6 equilibrium mixture of the two; this isomerization does not occur with LiCl. The Cl-atoms of both 2a, b and 3a, band of 2c may reductively be removed with Zn(Cu) in AcOH/pyridine to afford the alkylcyclobutenones 4a-c. Without pyridine, this reduction gives ca. 1:1 mixtures of the double-bond isomers 4 and 5 in low yields. The cyclobutenones 2c and 4c may be deuterated by CD3COOD in the presence of pyridine. D-Atom is introduced into 2c at C(4) and at C(γ), and into 4c at C(2) and C(4). A mechanism for this deuteration is considered, which does not involve a cyclobutadienolate 7, but rather a cyclobutenolate of type 8. The reductions of 2 and 3 to 4 might also pass through the same type of intermediate 8.
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  • 61
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    Helvetica Chimica Acta 70 (1987), S. 339-341 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Propargyl-alkyl biradical 12 generated by photodecarbonylation of title ketone 3 undergoes ring closure to cyclobutane 7 and to vinyl carbene 13, this latter intermediate rearranging to the 5-ethylidenecyclopentenes 8a and 8b.
    Additional Material: 1 Tab.
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  • 62
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A stereoselective synthesis of tricarbonyl-[((1RS,2RS,4RS,5RS,6RS)-C-5,6,C-η-(5,6,7,8,-tetramethylidenbicyclo[2.2.2]octan-2-ol)]iron (11),and of its tosylate 12 and benzoate 13 is reported. The bulk of the ‘endo’-Fe(CO))3 moiety and of the ester groups in 13 renders its Diels-Alder additions to methyl propynoate (15)), butynone (16), and 1-cyanovinyl acetate highly ‘para’ regioselective. The cycloadditions of diene-alcohol 11 are either ‘meta’- or ‘para’-regioselective depending on the nature of the dienophile. In the presence of BF3. Et2O, the addition of 11 to methyl vinyl ketone is highly stereo- (Alder mode) and ‘para’-regioselective, giving adduct 52 (tricarbonyl [((1 RS,4RS,8RS,9RS,10RS,12RS)-C,9,10,C-η-(12-hydroxy-9,10-dimethylidenetricyclo[6.2.2.02,7]dodec-2(7)-en-4 yl methyl ketone)]iron) whose structure has been established by single-crystal X-ray crystallography.
    Additional Material: 4 Ill.
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  • 63
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    Helvetica Chimica Acta 70 (1987), S. 1261-1267 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 4-hydrazinobenzyl alcohol (3 was prepared (58%)) by diiobutylaluminiumhydride reduction of methyl 4-hydrazinobenzoate (4), whereas LiA1H4 or LiBh4 reduction of4 proceeded further to yield (via intermediate 3) (4-tolyl)hydrazine (5). The alcohol 3 was stable under O2-free conditions and exhibited no tendency to eliminate H2O, neither thermally nor with H+ catalysis. Oxidation of 3 with SeO2 yielded 4-(hydroxymethyl)benzine-diazonium ion (8), identified by its azo coupling product 9 with 2-naphthol. Condensation of 3 with 1-benzyl 5-Hydrogen N-(benzyloxycarbonyl)-L-glutamate (10) in presence of dicyclohexylcarbodiimide afforded 81% of N2-(benzyloxycarbonyl)-L- glutamic acid 1-(benzyl-ester) 5-{2-[4-(hydroxymethyl)phenyl]hydrazide} (11) which upon controlled hydrogenolysis (quinoline-sulfur-poisoned Pd/C catalyst) gave 82% of L-Glutamic acid 5-{2-[4-(hydroxymethyl)phenyl] hydrazide} (1), i. e. agaritine, a metabolite of Agaricus bisporus. Without poisoning of the catalyst, hydrogenolysis of (11) yielded L-glutamic acid 5-[2-(4-tolyl)hydrazide] (12).
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  • 64
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    Helvetica Chimica Acta 70 (1987), S. 1279-1285 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of (-)-(1R,2S)-Norephedrine HomologuesThe amino function of esters of some simple natural amino acids I is blocked in the form of a cyanoenamine by means of 2-oxocyclopentanecarbonitrile, so that the corresponding cyanoenamino esters II are obtained. The reaction of a disubstituted lithium amide with II leeds to the cyanoenamino-amides VI. The amide function present in VI is then transformed into an aromatic ketone by means of phenyllithium, to give the (benzoylalkyl)aminocyclopentenecarbonitriles VII. Reduction of Compounds VII with NaBH4 in EtOH -80° affects only the keto function and leads to the [(α-hydroxybenzyl)alkyl]amino-cyclopentenecarbonitriles VIII. The amino function is then deprotected by acid hydrolysis to give the amino-alcohols IX with yields close to 50%; in every amino-alcohol IX, the erythro isomer, homologous to natural (-)-(1R,2S)-norephedrine is the more abundant or the single product. All the polyfunctional compounds prepared conserve optical activity; it has been demonstrated that the amino-alcohols IX are pure enantiomers and that no racemisation lakes place at any step of their synthesis.
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  • 65
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new, versatile phosphorylating agent, bis[2-(p-nitrophenyl)ethyl] phosphorochloridate (3), has been prepared and is used for 3′- and/or 5′-phosphorylations of nucleosides. The resulting bis[2-(p-nitrophenyl)ethyl] phosphotriesters are versatile synthons in oligonucleotide synthesis leading finally to 3′- and/or 5′-terminated monophosphates in excellent yields.
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  • 66
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A preparation of glycosylphosphonates (27, 28, 36, 38, and 39) from 2-azido-2-deoxy-glycoses (26,35, and 37) and the synthesis of the non-isosteric phosphonate analogue 3a of lipid X(2) are described. The 2-azido group was introduced by azidonitration. Treatment of the 1-O-acetyl-2-azido-2-deoxy-β-D-galactopyranose 22 with 1.5-3 equiv. of P(OMe)3 and 1.2-2.5 equiv. of TfOSiMe3 gave mainly recovered starting material. In P(OMe)3 as the solvent, the dimethyl phosphoramidate 24 was obtained by way of a Staudinger reaction, even in the presence of TfOSiMe3. Treatment of the benzylated α-D-galacto-trichloroacetimidate 26, however, with P(OMe)3 and TfOSiMe3 gave a 1:1 mixture of the α- and β-D-galacto-phosphonates 27 and 28, while the acetylated α-D-gluco- imidate 35 led to the α-D-gluco-configurated phosphonate 36. The stereoselectivity of the phosphonate formation is related to the relative ease of formation of oxonium-ion intermediates from 26 and 35. Starting from the phosphonate 36, deacetylation, benzylidenation, reduction of the azido group, acylation with (R)-3-(benzyloxy)tetradecanoic acid and deprotection yielded the desired compound 3a which was crystallized in the presence of 2 equiv. of (aminomethylidyne)trimethanol (Tris.). The structure of the phosphonates was deduced from their 1H-, 13C-, and 31P-NMR spectra.
    Additional Material: 2 Tab.
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  • 67
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diastereoselective Hydroxyalkylations in Position 1 of Tetrahydroisoquinolines and Synthesis of Aporphine, Protoberberine, and Pathalide AlkaloidsUnsubstituted and 6,7-dialkoxy-N-pivaloyl-tetrahydroisoquinolines 1-3 are converted to 1-bromomagnesium derivatives by sequential treatment with t-BuLi (-75°/THF) and MBr2.OEt2. Addition of the metalated tetrahydroisoquinolines to aliphatic or aromatic aldehydes occurs with relative topicity ul (Scheme 2). The 1-hydroxyalkylated 2-pivaloyl-tetrahydroisoquinolines a of u-configuration thus obtained (14 examples) can be converted to free aminoalcohols c of either l-or u-configuration (9 examples; Scheme 3). The depivaloylation with retention (→ u-c) is best achieved by heating in EtOH/KOH, the conversion to 1-aminoalcohols l-c by treatment with CF3COOH/(CF3CO)2O (→ l,-pivalates l-b), followed by alkaline saponification or by LiAlH4 reduction of the esters. The configuration of the products is assigned by 1H-NMR spectroscopy, by X-ray crystal structure analysis, by chemical correlation, and by comparison of the chemical properties of the l- and the u-isomers. The diastereoselective hydroxybenzylation of the tetrahydroisoquinoline is used for short syntheses of ushinsunine/oliveroline (Scheme 4), β-hydrastine, and ophiocarpine/epiopliocarpine (Scheme 6; aporphine, phthalide, and protoberberine alkaloids, respectively).
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  • 68
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    Helvetica Chimica Acta 70 (1987), S. 1380-1388 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of 4-(Benzylthio)-and 4-(Arylthio)-1,3-oxazole-5(2H)-onesFollowing a known procedure, 4-(benzylthio)-1,3-oxazol-5(2H)-one (4a) was synthesized starting from sodium cyanodithioformate (1) and cyclohexanone (Scheme 1). The structure of the intermediate 4-(benzylthio)-1,3-thiazol-5(2H)-one (3a) was established by X-ray crystallography. An alternative route was developed for the synthesis of 4-(arylthio)-1,3-oxazol-5(2H)-ones which are not accessible by the former reaction. Treatment of ethyl cyanoformate (5) with a thiophenol in the presence of catalytic amounts of Et2NH and TiCl4, followed by addition of a ketone and BF3.Et2O in a one-pot-reaction, gave 4f-i in low-to-fair yields (Scheme 3). Both synthetic pathways-complementary as for benzyl-S and aryl-S derivatives-seem to be limited with respect to variation of substituents of the ketone.
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  • 69
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    Helvetica Chimica Acta 70 (1987), S. 1389-1392 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compound was prepared from 2-nitrocyclodecanone (2). Compound 2 was treated with 2-methylpro-penal to give the Michael-addition product 3 which was reduced to the alcohol 5 and the latter ring-enlarged with Bu4NF to 12-methyl-10-nitro-13-tridecanolide (6) followed by reductive elimination of the NO2 group by Bu3SnH.
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  • 70
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    Helvetica Chimica Acta 70 (1987), S. 1393-1399 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phase-transfer alkylation of the 2-oxocycloalkane-l-carbonitriles 1a and 1b with ethyl 4-bromo-3-methoxy-2-butenoate (2), followed by deprotection and base-catalyzed cyclization gave the annulated cyclopentenones 5a and 5b, respectively, in high overall yields (Scheme 1). Stereoselective catalytic hydrogenation of 5b followed by de-ethoxycarbonylation afforded 14-oxo-cis-bicyclo[10.3.0]pentadecane-l-carbonitrile (7). Treatment of 7 with LiN(i-Pr)2 in THF gave the known synthetic muscone precursor 8 (Scheme 2). The tricyclo[10.4.0.01,15]hexadecan-14-one (14) was prepared from 7 in 5 steps by a reaction sequence proceeding without affecting the chiral centres (Scheme 2). The structure of 14 was established by X-ray structure analysis (Figure).
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  • 71
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The raspailynes (novel long-chain enol ethers of glycerol having the enol ethers double bond conjugated in sequence, to an acetylenic and an olefinic bond, isolated from the North-East-Atlantic sponges Raspailia pumila and R. ramosa) are stable under normal hydrolytic conditions for enol ethers. In contrast, when their solutions are evaporated, these lipids such as raspailyne Bl (=(-))-3-[(1Z,5Z)-(tetradeca-1,5-dien-3-ynyl)oxy]-1,2-propanediol;(--2) rapidly react with aerial O2 under normal laboratory-daylight conditions, with rupture of the C=C enol ether bond to give 1-O-formylglycerol (3) and an aldehyde (such as tridec-4-en-2ynal(4) from (-)-2). This reaction must be caused by triplet O2, since thermally generated singlet O2 has no effect on (-)-2 in solution. That the mere presence of an enol-ether moiety conjugated to an acetylenic group is responsible for such a behaviour is demonstrated with the model compounds 1-methoxypentadec-1-en-3-yn-5-ol (6a) and its 5-O-acetyl or 5-O-tetra-hydropyranyl derivatives 6b and 6c, respectively. Resistance to both hydroytic conditions and singlet O2 of these compounds is thought to arise from electron depletion at the enol-ether C(beta;) atom by the acetylenic group. Plausible reaction pathways for enol-ether bond rupture in these compounds by aerial O2 are outlined.
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  • 72
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    Helvetica Chimica Acta 70 (1987) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 73
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    Helvetica Chimica Acta 70 (1987), S. 1412-1418 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrahydrolipstatin (1) and itsanalogue 2 are representatives of a new class of pancreatic-lipase inhibtors. Two stereoselective synthetic approaches are described.
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  • 74
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Furans with side-chains at C(2) of various lengths terminating in diazomethyl keto groups are shown to undergo Rh2(OAc)4-catalyzed furan unravelling with the production of 2-cyclopentenone, 2-cyclohexenone, and 2-cycloheptenone to each of whose olefinic C(β) is attached an acrylaldehyde unit. Interposition of a cyclohexane or a methylaminomethylene moiety between the furan and diazoketo functions leads to the formation of a hydroindenone and pyrrolone, respectively. Replacement of the diazomethylketo terminus by an α-diazoethylketo system or a α-diazo-β-keto-ester function produces 2-substituted 2-cycloalkenones. A furan with a C4, diazo-methylketo-terminating side-chain at C(3) is described to be transformed into a 4-formylmethylidene-2-cyclohe-xenone.
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  • 75
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diels-alder Reactions of 2′-Substituted 3-Vinyl-1H-indoles to New Annellated Indole and Carbazole DerivativesNew regio- and stereoselcctive cycloadditions between 2′- substituted 3-vinyl-lH-indoles and the dienophiles N-Phenylmaleimide, dimethyl acetylendicarboxylate, and methyl acrylate are reported. Products include some new carbazole derivatives and Michael adducts. In the presence of AlCl3 as dicnophile-activating catalyst, ‘endo’ preference for deriving cycloadducts is observed. In some cases, Michael addition competes with[4+2] cycloaddition.
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  • 76
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    Helvetica Chimica Acta 70 (1987), S. 1439-1460 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-(Alkoixycarbonyl)heptalene-2-carboxylic acids as well as 2-(alkoxycarbonyl)heptalene-1-carboxylic acids react with the iminium salt formed from N,N-dimethylformamide (DMF) and oxalyl chloride, in the presence of an alcohol, to yield the corresponding cyclic ‘ortho’ -anhydrides (ψ-esters; cf. Schemes 2,3,6, and 8). When the alkoxy moiety of the acids and the alcohols is different, then diastereoisomeric ‘ortho’ -anhydrides are formed due to the non-planarity of the heptalene skeleton. The approach of the alcohol from the β-side is strongly favored (cf. Scheme 5 and Table 1). This effect can be attributed to the bent topology of the heptalene skeleton which sterically hinders the approach of the nucleophile from the α-side of the postulated intermediates, i.e. the charged O-alkylated anhydrides of type 19 (cf. Scheme 6). Whereas the ‘ortho’-anhydrides with four substituents in the ‘peri’ -positions of the heptalene skeleton are configurationally stable up to 100°, the ‘ortho’ -anhydrides with only three ‘peri’ -substituents slowly epimerize at 100° (cf. Scheme 7) due to the thermally induced inversion of the configuration of the heptalene skeleton.
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    Helvetica Chimica Acta 70 (1987), S. 1482-1486 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of corycavine, a protopine-type alkaloid, has been determined by X-ray analysis. A conformational feature observed is the existence of a strong electrostade interaction between the N- and C-atom at a distance of 2.618 Å. Such an interaction stabilizes the 10-membered ring conformation of the structure. Analyses of NMR spectra indicate that corycavine has the same conformation in solution as in the crystal state.
    Additional Material: 2 Ill.
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  • 78
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pd(dba)2[dba = dibenzylideneacetone]/PPh3-or Pd(PPh3)4-catalyzed cyclizations of acetoxy-dienes 2 → 3 and 10 → 11 gave 1-vinyl-2-methylidene-subsituted cyclopentances and cyclohexanes in high yield, consistent with a palladium-ene/β-elimination mechanism (D → E → F, Scheme 2). The efficient and highly stereoselective cyclizations 7 → 7 and 8 → 9 illustrate intramolecular allylpalladium insertions into 1,2-dialkyl-, trialkyl-, trialkyl-, and cyclic alkenes followed by elimination of the exocyclic β-H giving 1,2-divinylcyclopentanes. These new olefin insertions proceed faster in AcOH (compared to THF) and occur preferentially cis relative to the Pd (13 → 14 → 15).
    Additional Material: 2 Tab.
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  • 79
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of phosphite anions and of tris(trimethylsilyl) phosphite (P(OSiMe3)3) to N-glycosyl-C-arylnitrones was examined. While these nitrones proved inert towards the phosphite anions, they reacted with P(OSiMe3)3 under catalysis by Lewis acids. Thus, P(OSiMe3)3 reacted with the crystalline (Z)-N-glycosylnitrones 2 and 8 to give the optically active N-hydroxy-α-aminophosphonic acids 4 and 10, respectively, and hence the α-aminophosphonic acids 5 and 11 in yields up to 92% and with an enantiomeric excess (e.e.) up to 97% (Scheme 1). The absolute configuration of the phosphonates depend upon the nature and - in one case - upon the quantity of the catalyst (Figure). Upon catalysis by HCIO4 or Zn(OTF)2, p(OSiMe3)3 added to 2 to give, in both cases, the (+)-(R)-phenylphosphaglycine 5 (optical purity 79-84 and 90-93%, resp.). The optical purity (o.p.) was hardly influenced by the amount of these catalysts (0.02-;1 equiv.). However, catalysis by ZnCl2 gave, with trace quantities of the catalyst, (-)-(S)-5 (o.p. 79%), while an equimolar amount of ZnCl2 yielded (+)-(R)-5 (o.p. 82%). The HClO4-catalyzed addition of P(OSiMe3)3 to the nitrone 14 (Scheme 2) led to (+)-(R)-N-hydroxyphosphavaline 15 (78%) and hence to (-)-(R)-phosphavaline 16 (71% from 14 e.e. 95%). Under conditions leading from the nitrones 2, 8, 14, and 20 (Schemes 1 and 2) predominantly to (R)-α-aminophosphonic acids, the addition of P(OSiMe3)3 to nitrone 18, possessing a benzyloxy substituent as an additional potential ligand for the catalyst, gave (S)-phosphaserine 19. The addition of P(OSiMe3)3 to the nitrone 20, catalyzed by Zn(OTf)2, led to (+)-(R)-N-hydroxyphosphamehionine 21 (71%, e.e. 77%) and hence to (-)-(R)-phosphamethionine 22 (77% from 20, e.e. 79%). Catalysis by trace quantities of ZnCl2 gave (+)-(S)-22 (85%, e.e. 61%). The enantiomerically pure aminophosphonic acids 5, 11, and 16 were obtained by recrystalliztion. The e.e. of the N-hydroxyaminosphosphonic acids 10, 15, and 21 and the aminophosphonic acids 5, 11, 16, and 22 were determined by the HPLC analysis of the dimethyl N-naphthoyl-α-aminophosphonats 7, 13, 17, and 23, on a chiral stationary phase.
    Additional Material: 1 Ill.
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  • 80
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 1537-1539 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Note on the Use of 3-(Arylsulfonyl)-2-cycloalkenones as Synthesis Equivalents of 2-Cycloalkynones3-(Arylsulfonyl)-2-cyclopentenones and 3-phenylsulfonyl-2-cyclohexnone undergo Diels-Alder reactions with cyclopentadiene. Elimination of arylsulfinic acid leads to products, which would have been obtained directly from a Diels-Alder reaction of 2-cyclopentynone or 2-cyclohexynone.
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  • 81
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The HE(Iα) photoelectron (PE) spectra of 2,3,5,6-tetramethylidene-2-bicyclo[2.2.1]heptanone (12), 5,6-dimethylidene-2-bicyclo[2.2.1]heptanone (14), 5,6-dimethylidene-2-bicyclo[2.2.2]octanone (16), and 5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octanone (17) have been recorded, Comparison with the PE data of other β,γ-unsaturated ketones and parent alkenes, and with the result of ab initio STO-3G calculations, confirm the existence of significant interactions between the oxygen lone-pair orbital no and the double-bond π orbital(s). It is argued that the major contributions to the basis energy shifts and to the cross term between the no and π orbitals are due to a ‘through-bond’ mechanism.
    Additional Material: 3 Ill.
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  • 82
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 1551-1557 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two novel naphthoxirene derivatives 1 and 2 their glucosides 3 and 4 have been isolated from the root bark of Sesamum angolense Welw. (Pedaliaceae) by preparative liquid chromatography. The structure of 1 was established by X-ray diffraction analysis. The identities of the other naphthcxirenes were deduced by spectroscopic (IR, UV, 1H-NMR, 13C-NMR, EI-MS, DCI-MS) and chemical methods (oxidation, acid and enzymatic hydrolysis). Compounds 1-3 exhibited antifungal activity. Naphthoxirene 1 was, in addition, cytotoxic to human colon carcinoma cells.
    Additional Material: 1 Ill.
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  • 83
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 1558-1568 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ESR, ENDOR, and TRIPLE resonance studies have been performed on the radical anions of 1,2-diphenylcyclohex-1-ene (4), 1,2-di(perdeuteriophenyl)cyclohex-1-ene ((D10)4) the trans-configurated 3,4-diphenyl-8-oxabicyclo[4.3.0]non-3-ene (5) and its 2,2,5,5-tetradeuterio derivative (D4)5, and 2,3-diphenyl-8,9,10-trinorborn-2-ene (6). The spectra of \documentclass{article}\pagestyle{empty}\begin{document}$ 4^{- \atop \dot{}} $\end{document} exhibit strong temperature dependence along with a specific broadening of ESR hyperfine lines and proton ENDOR signals. The coupling constant, which bears the main responsibility for these features, is that of the β-protons in the quasi-equatorial positions of the cyclohexene ring, and the experimental findings are readily rationlized in terms of relatively modest conformational changes without invoking the inversion of the half-chair form. The hyperfine data for the β-protons in \documentclass{article}\pagestyle{empty}\begin{document}$ 5^{- \atop \dot{}} $\end{document} closely resemble the corresponding low-temperature values for \documentclass{article}\pagestyle{empty}\begin{document}$ 4^{- \atop \dot{}} $\end{document}, However, the ‘unusual’ features observed for \documentclass{article}\pagestyle{empty}\begin{document}$ 4^{- \atop \dot{}} $\end{document} are absent in the ESR and ENDOR spectra of \documentclass{article}\pagestyle{empty}\begin{document}$ 5^{- \atop \dot{}} $\end{document}, because the half-chair conformation of the cyclohexene ring in \documentclass{article}\pagestyle{empty}\begin{document}$ 5^{- \atop \dot{}} $\end{document} is deprived of its flexibility. Although the boat form of this ring in \documentclass{article}\pagestyle{empty}\begin{document}$ 6^{- \atop \dot{}} $\end{document} is also rigid, the spectra of \documentclass{article}\pagestyle{empty}\begin{document}$ 6^{- \atop \dot{}} $\end{document} are temperature-dependent, due to an interconversion between two propeller-like conformations of the phenyl groups. The pertinent barrier is 30 ± 5 kJ·mol-1. An analogous interconversion presumably takes place in \documentclass{article}\pagestyle{empty}\begin{document}$ 4^{- \atop \dot{}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ 5^{- \atop \dot{}} $\end{document} as well, but, unlike \documentclass{article}\pagestyle{empty}\begin{document}$ 6^{- \atop \dot{}} $\end{document}, it is not amenable to experimental study.
    Additional Material: 7 Ill.
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  • 84
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 10′-Apolycopen-10′-ol and 10′-Apolycopen-10′-oic Acid from the Petals of the Rose Hybrid ‘Maréchal Niel’The novel 10′-apolycopen-10′-ol (1) and 10′-apolycopen-10′-oic acid (4) were isolated from the yellow petals of the once world-renowned rose hybrid ‘Maréchal Niel’. The relative amount of either 1 or 4 produced by the plant depends upon the climatic conditions. Both 1 and 4 together with related compounds were synthetisized and characterized by spectral data.
    Additional Material: 1 Ill.
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  • 85
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    Helvetica Chimica Acta 70 (1987), S. 2011-2018 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Spectra and chemical transformations allow to establish the gross structure 6,7-epoxy-4,7-dimethyl-l-oxa-spiro[4.4]non-3-en-2-one for adriadysiolide (1), the first monoterpenoid isolated from a marine sponge, a Dysidea sp. of the Adriatic Sea. Its configuration 5R*, 6S*, 7S* as given in 1a is derived from diastereoselective total syntheses of both 1a and its diastereoisomer 1b via stereochemically predictable peracid epoxidations of olefinic precursors. Thus, OH assistance in allylic alcohol 8 leads to oxirane 13 which is subjected to methyl cuprate conjugate addition to give epiadriadysiolide (1b), whilst electronic deactivation by a neighboring heterocyclic O-atom in intermediate 5, derived from 8 mainly leads to adriadysiolide (1a). Comparative 1H-NMR shift-reagent effects with 1a and 1b, evaluated with the aid of molecular-mechanics calculations, support these conclusions.
    Additional Material: 1 Tab.
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  • 86
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    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 1045-1054 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: α-Glucosidase Inhibitors, 5. - Investigations towards a Synthesis of C1-Branched Cyclitols from D-GlucoseThe glucose derivatives 1 and 2 were transformed by Ferrier rearrangement as one of the reaction steps into the cyclitol derivatives 3a, b and 4a, b, respectively. The attachment of a functional C1-side chain at the carbonyl group was tested with 2-lithio-1,3-dithiane, dimethylsulfoxonium methylide, and diazomethane. Compounds 7a, b and 11 were obtained as interesting reaction products. Dithioacetal formation from 3a, b, subsequent cyano/mercapto group exchange, and cyano group reduction afforded the cyclitol derivatives 19a, b as important intermediates. Oxidation, reduction, elimination, and [2,3]-sigmatropic rearrangement reactions conveniently gave the ring-saturated or -unsaturated compounds 18a, 28a, 29a, b, and 30a, b.
    Notes: Aus den Glucose-Derivaten 1 und 2 wurden u.a. durch Ferrier-Umlagerung die Cyclit-Derivate 3a, b bzw. 4a, b hergestellt. Untersuchungen zur Anknüpfung einer funktionellen C1-Seitenkette an der Carbonylgruppe wurden mit 2-Lithio-1,3-dithian, mit Dimethylsulfoxonium-methylid und mit Diazomethan durchgeführt. Als interessante Folgeprodukte wurden dabei die Cyclit-Derivate 7a, b und 11 erhalten. Dithioacetalbildung aus 3a, b anschließender Cyanid/Mercapto-Austausch und Reduktion der Cyangruppe führten zu den Cyclit-Derivaten 19a, b als wichtigen Zwischenstufen. Durch Oxidations-, Eliminierungs-, [2,3]-sigmatrope Umlagerungs- und Reduktions-Reaktionen wurden daraus die Ring-gesättigten und -ungesättigten Cyclite 18a, 28a, 29a, b und 30a, b zugänglich.
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  • 87
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Geometrie und Konformation des α-Aminoisobutyryl-Restes in einfachen Derivaten und Dipeptiden. Vier neue Röntgen-Struktur-Analysen und eine statistische Analyse mit bekannten KristalldatenDie Resultate der Röntgen-Strukturanalysen von zwei α-Aminoisobuttersäure(Aib)-Derivaten, N-Acetyl-α-aminoisobuttersäure-methylester (Ac-Aib-OMe, 1) und N-(Benzyloxycarbonyl)-α-aminoisobuttersäure-benzylester (Z-Aib-OBzl, 2) sowie von zwei terminal blockierten Aib enthaltenden Dipeptiden, N-Acetyl-L-alanyl-α-aminoisobuttersäure-methylester (Ac-L-Ala-Aib-OMe, 3) und N-(Benzyloxycarbonyl)-α-aminoisobutyryl-L-alanin-tert-butylester (Z-Aib-L-Ala-OtBu 4), werden beschrieben. In der asymmetrischen Zelle aller vier Verbindungen befinden sich zwei unabhängige Moleküle. In allen Fällen außer einem (Molekül A von 3) ist der Aib-Rest gefaltet, die Torsionswinkel Θ, ψ (oder Θ, ψτ) fallen in den Bereich der Konformationsenergiekarte, wo α- und 310-Helices liegen. Eine vergleichende statistische Analyse der Bindungslängen, Bindungswinkel und Torsionswinkel aus Kristallstrukturen von 20 Aib-Derivaten und 11 Aib enthaltenden linearen Dipeptiden wurde durchgeführt. Diese liefert genaue Information über die Geometrie und Konformation des Aib-Restes ohne den Einfluß der Restriktionen durch intramolekulare Wasserstoffbrücken, denen längere gefaltete oder helikale Peptide ausgesetzt sind.
    Notes: The results of X-ray diffraction analyses on two α-aminoisobutyric acid (Aib) derivatives, methyl α-(acetylamino)isobutanoate (Ac-Aib-OMe, 1) and benzyl α-[(benzyloxycarbonyl)amino]isobutanoate (Z-Aib-OBzl, 2), and two terminally blocked, Aib-containing dipeptides, methyl α-[(acetyl-L-alanyl)amino]isobutanoate (Ac-L-Ala-Aib-OMe, 3) and tert-butyl α-{[(benzyloxycarbonyl)amino]isobutanoyl}-L-alaninate (Z-Aib-L-Ala-OtBu, 4) are described. In the asymmetric unit of all four compounds two independent molecules were found. In all cases but one (molecule A of 3) the Aib residue is folded, the sets of Φ, ψ (or Φ, ψT) torsion angles falling in the region of the conformational energy map where both α- and 310-helices are found. A correlating statistical analysis of bond lengths, bond angles, and torsion angles from available crystal structures of 20 Aib derivatives and 11 Aib-containing linear dipeptides was also performed to obtain precise information on the geometry and conformation of the Aib residue without the influence of the constraints imposed by the intramolecular hydrogen bonds characterizing higher-order folded and helical peptides.
    Additional Material: 5 Ill.
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  • 88
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: v-Triazoline, XXVIII. - Reaktionen von 1-Aryl-4,5-dihydro-4-methylen-5-morpholino-v-triazolen mit 2,4-Diaryl-5(4H)-oxazolonen5(4H)-Oxazolone 1a-d mit elektronenliefernden Resten in 2-Position des Arylrests reagieren mit 4,5-Dihydro-v-triazolen 2a-c zu 4-[(4-Triazolyl)methyl]-5-(4H)-oxazolonen 3a-i als Haupt- und zu 2,5-Diaryl-3-pyrrolcarbaldehyden 4a-d sowie Glycindiamiden 5a-d als Nebenprodukten. 5(4H)-Oxazolone mit elektronenziehenden Substituenten (1e-h) liefern mit den 4,5-Dihydro-v-triazolen 2c-e die 2-[(4-Triazolyl)methyl]-5(2H)-oxazolone 7a-e als Hauptprodukte. Die Produkte 3 und 7 werden durch nucleophilen Angriff des Anions von 1 am exo-Methylenkohlenstoff von 2 gebildet. Die Aldehyde 4 entstehen durch Umlagerung eines labilen Cycloaddukts aus 1 und 2.
    Notes: The 5(4H)-oxazolones 1a-d with an electron-rich aryl substituent on C-2 react with 4,5-dihydro-v-triazoles 2a-c to afford the 4-[(4-triazolyl)methyl]-5(4H)-oxazolones 3a-i as main reaction products and 2,5-diaryl-3-pyrrolecarbaldehydes 4a-d and glycine diamides 5a-d as secondary reaction products. The 5(4H)-oxazolones 1e-h bearing an electron-withdrawing substituent on the aryl group on C-2 react with the 4,5-dihydro-v-triazoles 2c-e affording the 2-[(4-triazolyl)methyl]-5(2H-oxazolones 7a-e as main reaction products. Compounds 3 and 7 are produced by nucleophilic attack of the anion of 1 at the exo methylene carbon. Aldehydes 4 are formed through rearrangement of an unstable cycloaddition product from 1 and 2.
    Additional Material: 1 Tab.
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  • 89
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    Liebigs Annalen 1987 (1987), S. 1117-1119 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Ethyl 2,3-Bis(ethoxycarbonyl)-1H-pyrrole-1-propionateEthyl 2,3-bis(ethoxycarbonyl)-1H-pyrrole-1-propionate (7) can easily be obtained in high yields from ethyl 4-iodobutyrate (1) via reaction with dibenzylamine and diethyl oxalate, catalytic debenzylation to diethyl cis-2,3-pyrrolidinedicarboxylate (5), subsequent dehydrogenation to diethyl 1H-pyrrole-2,3-dicarboxylate (6), and further N-alkylation to the desired title compound 7.
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  • 90
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    Liebigs Annalen 1987 (1987), S. 1123-1124 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of Hydroxylated Bipyridines, II. - 3,4′-Dihydroxy-2,3′-bipyridineThe title compound 1 is obtained by coupling of 2-iodo-3-methoxypyridine (3) and 3-bromo-4-methoxypyridine (4) with Nickel(0) - to yield the dimethyl ether 2 (plus 5 and 6) - and by subsequent ether cleavage. 1 is not identical with the alkaloid described under this structure.
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  • 91
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    Liebigs Annalen 1987 (1987), S. 1125-1127 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structure and Odor, VI - Preparation and Reactions of LongicampheniloneLongicamphenilone (2) can readily be prepared by phase-transfer-catalyzed potassium permanganate oxidation of longifolene (1). The ketone 2 is a convenient starting material for the preparation of the fragrance compounds 3-6.
    Additional Material: 1 Tab.
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  • 92
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses with Nitriles, LXXVIII. - Studies on the Structure of Dimers of Malononitrile, Cyanoacetate, and CyanoacetamideThe 13C- and 15N-NMR data of dimers and codimers of malononitrile, cyanoacetate, and cyanoacetamide 1-6 are discussed In the case of the unsymmetrically substituted derivatives 2, 4 and 5 it is possible to distinguish between E- and the predominantly existing Z-isomers. In the case of 2 the structure is confirmed by X-ray structure analysis.
    Additional Material: 2 Tab.
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  • 93
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    Liebigs Annalen 1987 (1987), S. 1133-1133 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 94
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese von 2,3-Dihydrothiazolo[3,2-c]chinazolinium-Salzen aus 4(3H)-Chinazolinthionen oder 4H-1,3-Benzothiazin-4-thionen4-(Allylthio)chinazoline 2 und 4-(Propargylthio)chinazoline 8 lassen sich mit Brom zu 3-(Brommethyl)-2,3-dihydrothiazolo-[3,2-c]chinazolinium- und 3-(Brommethyl)thiazolo[3,2-c]chinazolinium-Salzen 3 bzw. 9 cyclisieren. Bromierung der 3-Allyl-4(3H)-chinazolinthione 6 liefert 2-(Brommethyl)-2,3-dihydrothiazolo[3,2-c]chinazolinium-bromide 7. Umsetzung von 4H-1,3-Benzothiazin-4-thionen 5 mit Propargylamin ergibt die Imidazole 10 anstelle der erwarteten 3-Propargyl-4(3H)-chinazolinthione.
    Notes: 4-(Allylthio)quinazolines 2 and 4-(propargylthio)quinazolines 8 undergo cyclization by action of bromine to give 3-(bromomethyl)-2,3-dihydrothiazolo[3,2-c]quinazolinium and 3-(bromomethyl)thiazolo[3,2-c]quinazolinium salts 3 or 9, respectively. Bromination of 3-allyl-4(3H)-quinazolinethiones 6 leads to 2-(bromomethyl)-2,3-dihydrothiazolo[3,2-c]quinazolinium bromides 7. Reaction of 4H-1,3-benzothiazine-4-thiones 5 with propargylamine yields imidazole derivatives 10 instead of the expected 3-propargyl-4(3H)-quinazolinethiones.
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  • 95
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    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 89-101 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Structure-Odor Correlation, V. - From Menthone to Shyobunone - Change of Odor with StructureDerivatives of menthone (4) were prepared by substitution at C-2 or C-3 whereby increasing similarity with the shyobunones (1, 2) should be achieved. Thus, the 3,3-disubstituted ketones 5-11 were synthesized by 1,4-addition to piperitone (3). The ketones 18 and 19 substituted at C-2 were prepared via the silyl ether 15. Analogously the ketones 22-25 have been synthesized. The ketones 28 and 29 were obtained from 15 via the diketone 20 and the aldol 21. - Key compound for the synthesis of 43 and 44 as well as 1 and 2 by 1,4-addition was the known ketone 40. While preparing 40 the side products 41 and 42 have also been obtained. The olfactory properties of the substituted menthones change stepwise from the minty odor of 4 by addition of spicy and woody notes up to those of 1 and 2 which possess a fruity-earthy-woody odor.
    Notes: Durch Substitution an C-2 oder C-3 wurden Derivate des Menthons (4) hergestellt, wobei zunehmende Ähnlichkeit mit den Shyobunonen (1, 2) erreicht werden sollte. So wurden die 3,3-disubstituierten Ketone 5-11 durch 1,4-Addition an Piperiton (3) dargestellt. Die in 2-Stellung substituierten Ketone 18 und 19 wurden über den Silylether 15 synthetisiert. Entsprechend gelang die Synthese der Ketone 22-25. Die Ketone 28 und 29 wurden aus 15 über das Diketon 20 und das Aldol 21 erhalten. - Schlüsselsubstanz zur Synthese von 43 und 44 sowie 1 und 2 durch 1,4-Addition war das bekannte Keton 40, bei dessen Herstellung noch die Nebenprodukte 41 und 42 erhalten wurden. Die olfaktorischen Eigenschaften der substituierten Menthone ändern sich schrittweise von dem minzigen Geruch von 4 durch Hinzutreten würziger und holziger Noten bis zu dem von 1 und 2, die fruchtigerdig-holzig riechen.
    Additional Material: 8 Tab.
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  • 96
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    Liebigs Annalen 1987 (1987), S. 153-160 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: New Synthesis of the Corticosterone Side-ChainCondensation reactions between azlactone 2 and 17-ketosteroids 1 followed by opening of the azlactone ring with sodium methanolate yields methyl 20-benzoylamino-17(20)-pregnen-21-oates 6. Reduction of the ester and subsequent hydrolysis produce compounds with the corticosterone side-chain as well as a ring-closed product of new type.
    Notes: Kondensation des Azlactons 2 mit 17-Ketosteroiden 1, gefolgt von Öffnung des Azlacton-Ringes durch Natriummethylat führt zu 20-Benzoylamino-17(20)-pregnen-21-säure-methylester-Derivaten 6. Durch Reduktion des Esters und anschließende Hydrolyse sind Produkte mit Corticosteron-Seitenkette sowie ein neuartiges Ringschluß-Produkt zugänglich.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
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  • 97
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 161-162 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: From the root bark of Capparis decidua (Capparidaceae), a new spermidine alkaloid, capparisinine was isolated. The structure 1 of the alkaloid was determined by means of spectral studies and correlation with other known alkaloids of similar structures. Capparisinine is a positional isomer of capparidisine which is known already as a constituent of this plant.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 98
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 175-178 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of β,γ-Unsaturated Ketones and γ-Hydoxy Carbonyl Compounds from Methyl 2-SiloxycyclopropanecarboxylatesSeveral methyl 2-siloxycyclopropanecarboxylates 5 are smoothly transformed into isomerically pure β,γ-unsaturated carbonyl compounds 10 by reduction with LiAlH4 or by addition of methyllithium followed by ring cleavage with acid. The method fails with bicyclic and phenyl-substituted starting materials. The intermediates obtained by reduction can also be treated with base affording γ-hydroxy carbonyl compounds 12 regioselectively.
    Notes: Einige 2-Siloxycyclopropancarbonsäure-methylester 5 werden durch Reduktion mit LiAlH4 oder Addition von Methyllithium sowie anschließende Ringöffnung im sauren Bereich glatt in isomerenreine β,γ-ungesättigte Carbonylverbindungen 10 übergeführt. Bei bicyclischen und phenylsubstituierten Ausgangsmaterialien versagt die Methode. Basische Ringöffnung der durch Reduktion erhaltenen Zwischenprodukte liefert regioselektiv γ-Hydroxycarbonylverbindungen 12.
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 215-219 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Diastereoselektive Addition von Crotylboronsäureestern an OximeAddition der E-sowie Z-Crotylboronsäureester 8, 9 an Aldoxime ließ sich unter 4-9 kbar Druck in guten Ausbeuten realisieren. Dabei resultierte eine der Richtung nach überraschende Diastereoselektivität: E-8 ergab bevorzugt die anti-, Z-9 die syn-N-(β-Methylalkyl)hydroxylamine 10, 11.
    Notes: The addition of E-and Z-crotylboronates 8, 9 to aldoximes has been realized in good yields by running the reaction under 4-9 kbar pressure. The direction of the attendant diastereoselectivity was surprising: E-8 led preferentially to the anti-, Z-9 to the syn-N-(β-methylalkyl)hydroxylamines 10, 11.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 100
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Studien über die Bestandteile von Jateorhiza palmata Miers (Colombo-Wurzel), II. - Isolierung und Struktur von sechs neuen Furanoid-Diterpen-Glucosiden: Palmatosid B, C, D, E, F und GSechs neue als Palmatosid B(1), C(2), D(3) E(4), F(5) und G(6) bezeichnete Furanoid-Diterpen-Glucoside wurden aus der getrockneten Wurzel von Jateorhiza palmata Miers (Colombo-Wurzel) isoliert. Auf Grund von chemischen und spektroskopischen Beweisen wurden die Strukturen von 1, 2, 3, 4, 5 und 6 als 4-O-(β-D-Glucopyranosyl)chasmanthin, 4-O-(β-D-Glucopyranosyl)columbin, 4-O-(β-D-Glucopyranosyl)isocolumbin, 4-O-(β-D-Glucopyranosyl)isojateorin, 4-O-(β-D-Glucopyranosyl)jateorin, und [2S-(2α,4aα,6aβ,10aβ,10bα)]-2-(3-Furanyl)-6a-(β-D-glucopyranosyloxymethyl)-1,2,4a,5,6,6a,7,10,10a,10b-decahydro-10b-methyl-4H-naphtho[2,1-c]pyran-4,7-dion ermittelt.
    Notes: Six new furanoid diterpene glucosides, named palmatoside B(1), C(2), D(3), E(4), F(5), and G(6) were isolated from the dried roots of Jateorhiza palmata Miers (Colombo root). The structures were elucidated by chemical and spectroscopic evidence to be 4-O-(β-D-glucopyranosyl)chasmanthin, 4-O-(β-D-glucopyranosyl)columbin, 4-O-(β-D-glucopyranosyl)isocolumbin, 4-O-(β-D-glucopyranosyl)isojateorin, 4-O-(β-D-glucopyranosyl)jateorin, and [2S-(2α,4aα,6aβ,10bα,10bα)]-2-(3-furanyl)-6a-(β-D-glucopyranosyloxymethyl)-1,2,4a,5,6,6a,7,10,10a,10b-decahydro-10b-methyl-4H-naphtho[2,1-c]pyran-4,7-dione, respectively.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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