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  • 1975-1979  (47)
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  • 1
    Electronic Resource
    Electronic Resource
    Säurekatalysierte Umlagerung von 7-Hydroxy-royleanon in ein 20(10→9) abeo-Abietan-Derivat und zwei Phenalenone (1975)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 58 (1975), S. 1934-1939 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acid-catalyzed rearrangement of 7-hydroxyroyleanone into a 20(10→9) abeo-abietane derivative and two phenalenonesShort treatment of either horminone (1b), taxoquinone (1a), 6,7-dehydroroyleanone (3) or 6β-hydroxyroyleanone (1c) with 80% H2SO4 at 0° leads to a mixture of rearranged products. Two of the structures, determined by X-ray-cristallography, were found to be (9R, 10R)-20(10→9)-abeo-12-hydroxy-5,7, 12-abietatriene-11,14-dione (4) and 9-isopropyl-2,2,5-trimethyl-8H-phenaleno[1,9-bc]furan-8-one (5), and the third compound, isolated in very small amounts, has been provisionally identified as 3-hydroxy-9-isopropyl-2,2,5-trimethyl-8H-phenaleno[1,9-bc]furan-8-one (6) from the spectroscopic data.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19750580708
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  • 2
    Electronic Resource
    Electronic Resource
    Strukturbestimmung von O-Methylazafrinmethylester durch 13C-NMR.-Spektroskopie (1975)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 58 (1975), S. 2044-2049 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structure Determination of Azafrin Methyl Ester 5-O-Monomethyl Ether by 13C-NMR.-Specta.The structure of the monomethyl ether (2) of azafrin methyl ester (1) was determined by a partial analysis of the 13C-NMR.-spectra. Assignments of quaternary carbon atoms and methyl groups in the cyclohexane ring were achieved using vicinal 13C-, 1H-spin coupling. Substituent effects on methyl and methylene carbon atoms in 2 are discussed with respect to the conformation of the methoxy group. The spectra prove C(5)—OH as the site of methylation. Therefore C(5)—OH is less hindered than C(6)—OH.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19750580719
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  • 3
    Electronic Resource
    Electronic Resource
    Reinvestigation of Original Taraxanthin SamplesNo. 10 in the Trondheim series Carotenoids of higher plants. No. 9: Phytochemistry 14, 797 (1975). (1976)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 59 (1976), S. 1360-1364 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Überprüfung einiger Originalpräparate von Taraxanthin.Das von R. Kuhn & E. Lederer 1931 entdeckte und seither in zahlreichen höheren Pflanzen nachgewiesene Taraxanthin wird anhand von Originalpräparaten aus Impatiens nolitangere L., Ranunculus acer L. sowie durch erneute Isolierung aus Taraxacum officinale L. mit modernen Methoden untersucht. Taraxanthin erweist sich als Gemisch von Xanthophyll-epoxid (= Lutein-epoxid; 2) oder dessen Umlagerungsprodukten und O4-Carotinoiden bekannter Struktur. Das aus Taraxacum erhaltene Präparat setzt sich aus 2 (73%), Flavoxanthin (4, 13%) und Chrysanthemaxanthin (4 (C(8)-Epimer), 14%) zusammen. Nicht identifizierte Carotinoide in den untersuchten Präparaten betragen weniger als 3,5%. Ein in kleiner Menge in R. acer nachgewiesenes Carotinoid ist wahrscheinlich 5,6-Dihydroxy-5,6-dihydrolutein (6).Der Name Taraxanthin als Bezeichnung für ein einheitliches Carotinoid soll aufgegeben werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19760590440
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  • 4
    Electronic Resource
    Electronic Resource
    Die Carotinoide der Blüten von Rosa foetida (1977)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 1754-1757 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carotenoids in petals of Rosa foetidaThe petals of Rosa foetida, HERRM., a species of prime importance in the history of breeding true yellow garden roses, have been analysed for carotenoids for the first time. The following components were identified: β-carotene (1, 4,5%), lutein (2, 8%), zeaxanthin (3, 17,4%), auroxanthin (4, 30,8%), luteoxanthin (5, 21,9%), violaxanthin (6, 9,2%) and neochrome (7, 4,1%). Not identified carotenoids (4,1%) contained probably mutatoxanthin, antheraxanthin and apocarotenals. Thus the brillant yellow colour of R. foetida flowers is due mainly to carotenoid epoxides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19770600530
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  • 5
    Electronic Resource
    Electronic Resource
    Diterpenoide Drüsenfarbstoffe aus Labiaten: Coleone U, V, W und 14-O-Formyl-coleon-V sowie 2 Royleanone aus Plectranthus myrianthus BRIQ.; cis- und trans-A/B-6, 7-Dioxoroyleanon (1977)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 2770-2779 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Leaf-gland Pigments: Coleons U, V, W, 14-O-Formyl-coleon-V, and two Royleanones from Plectranthus myrianthus BRIQ.; cis- and trans-A/B-6,7-DioxoroyleanonesFrom leaf-glands of the South-African P. myrianthus (Labiatae) the following diterpenoids have been isolated and their structures established: coleon U, C20H26O5 (6, 11, 12, 14-tetrahydroxy-abieta-5, 8, 11, 13-tetraene-7-one, 2a); coleon V, C20H26O5 (11, 12, 14-trihydroxy-abieta-8, 11, 13-triene-6, 7-dione, 4a); coleon W, C22H28O8 (16(or 17)-acetoxy-6, 11, 12, 14, 17 (or 16)-pentahydroxy-abieta-5, 8, 11, 13-tetraene-7-one, 6); 14-O-formyl-coleon-V, C21H26O6 (14-formyloxy-11, 12-dihydroxy-abieta-8, 11, 13-triene-6, 7-dione, 4b); 7α-formyloxy-6β-hydroxyroyleanone, C21H28O6 (7α-formyloxy-6β, 12-dihydroxy-abieta-8, 12-diene-11, 14-dione, 1a); the already known 6β, 7α-dihydroxyroyleanone (1c) and a dimeric abietane derivative whose structure is not yet elucidated. This is the first record of a co-occurrence of coleons and royleanones in the same plant. In the course of chemical investigations of 4a and 4b the highly oxidized trans- and cis-A/B-6,7-dioxoroyleanones (5a and 5b) were obtained.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19770600830
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  • 6
    Electronic Resource
    Electronic Resource
    3,4-Dimethoxyfuran: Eigenschaften, Berechnungen und SubstitutionsreaktionenIn memoriam Prof. H. Labhart (1978)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 61 (1978), S. 430-443 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3,4-Dimethoxyfuran: Properties, Calculations and some Substitution Reactions3,4-Dimethoxyfuran (3,4-DF) is much more reactive than furan itself. We present experimental details for the synthesis of this useful compound in 50-100 g batches. 3-4-Dibenzyloxyfuran has also been prepared. Quantum mechanical calculations by PPP-and CNDO-methods analogous to furan itself gave the following information (compared with furan): enhanced negative partial charge at C(2) and C(5), higher acidity at α-position, a stronger and at the same time inverted dipol moment. In accordance with the calculations, 3,4-DF can easily be substituted by weak electrophilic reagents, e.g. in a typical Mannich reaction. The bis-amino compound 8 is produced in good yields. Lithiation by butyl-Li leads to mono- or di-substituted products. The mono- and di-Li-3,4-DF have been used for the preparation of various acylated and alkylated 3,4-DF derivatives.By acid hydrolysis of 3,4-DF crystalline 4-methoxy-3 (2H)-furanone has been prepared.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19780610138
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  • 7
    Electronic Resource
    Electronic Resource
    Synthese und Chiralität von (5S, 6R)-5,6-Epoxy-5,6-dihydro-β,β-carotin und (5R, 6R)-5,6-Dihydro-β,β-carotin-5,6-diol, einem Carotinoid mit ungewöhnlichen Eigenschaften (1978)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 61 (1978), S. 822-831 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Chirality of (5S,6R)-5,6-Epoxy-5,6-dihydro-β,β-carotene and (5R,6R)-5,6-Dihydro-β,β-carotene-5,6-diol, a Compound with Unexpected Solubility CharacteristicsWittig-condensation of azafrinal (1e) with the phosphorane derived from 7 leads to a (1:3)-mixture of (E)-9′- and (Z)-9′-β,β-carotene-diol 3, from which pure and optically active 3 ((5R,6R)-5,6-dihydro-β,β-carotene-5,6-diol) has been isolated as bright violet leaflets, m.p. 168°. Due to the trans-configuration of the diol moiety and to severe steric hindrance, hydrogen bonding is reduced to such an extent, that 3 behaves much more as a hydrocarbon than as a diol. There is good evidence that the so-called ‘β-oxycarotin’ obtained by Kuhn & Brockmann [15] by chromic acid oxidation of β, β-carotene is the corresponding racemic cis-diol. 3 has been converted into (5S, 6R)-5,6-epoxy-5.6-dihydro-β,β-carotene (4), m.p. 156°. This transformation establishes for the first time the chirality of a caroteneepoxide (without other O-functions).Full spectral and chiroptical data including a complete assignement of 13C-chemical shifts for azafrin methyl ester and 3 are presented.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19780610229
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  • 8
    Electronic Resource
    Electronic Resource
    Abbau von Palustrin zu (-)-Dihydropalustraminsäure ((2R, 6S, 1′S)-[6-(1′-Hydroxypropyl)-2-piperidyl]essigsäure) und Struktur von Palustrin und Palustridin. Mitteilung über Schachtelhalmalkaloide13. und 14. Mitt. s. [1a][1b].Aus der Diss. von C.M.[1c]. (1978)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 61 (1978), S. 905-921 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Degradation of palustrin to (-)-dihydropalustramic acid ((2R,6S,1′S)-[6-(1′-hydroxypropyl)-2-piperidyl]acetic acid), and the structure of palustrin and palustridinThe structure of the macrocyclic alkaloid palustrin is shown to be 1a. Its piperidine unit can be obtained as (-)-dihydropalustramic acid (6a) by the following sequence of degradation reactions (Scheme 1): catalytic hydrogenation of 1a followed by methylation and Hofmann degradation provides the allyl base 4. the regioselectivity of the Hofmann elimination is explained by intramolecular proton abstraction at C(3) by C(18)-O-. Catalytic reduction of 4 and subsequent acidic hydrolysis yielded 6a and N, N-dimethylputrescine (=N,N-dimethyl-1,4-butanediamine; 7). Loss of the N-alkyl group in the formation of 6a occurs during the catalytic hydrogenation step. This interpretation is supported by the results of model experiments. The position of the double bond in 1a is deduced from the IR. spectrum of the bromo-δ-lactone 19 prepared by treatment of 1a with N-bromosuccinimide at pH 4 (Scheme 3). Some of our previously published results on the degradation of dihydropalustrin (2a) are obviously at variance with the newly proposed structure for palustrin (1a). They can easily be explained by assuming a partial hydrogenolysis of the C(17)-N(1) bond during the preparation of dihydropalustrin from palustrin. Periodate cleavage of dihydropalustramic acid methyl ester (6b) liberates propionaldehyde, which can be trapped by working at pH 7.5 (Scheme 2); at lower pH values it condenses rapidly with the simultaneously generated 3,4,5,6-tetrahydropyridine derivative 15. The structure of the condensation product is proposed to be 16 on the basis of the isolation of its hydrogenation product, an isomeric dihydropalustramic acid (17).
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19780610238
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  • 9
    Electronic Resource
    Electronic Resource
    Rhodium (I)-katalysierte Reaktionen der [2+4]-Cycloaddukte aus 3,4-Dimethoxyfuran und Acetylendicarbonsäure-estern (1978)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 61 (1978), S. 1134-1138 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [2+4]-Cycloaddition Products of 3,4-Dimethoxyfuran with Acetylenedicarboxylates and Their Transformations under the Influence of Rhodium(I) Catalysts3,4-Dimethoxyfuran (1) readily reacts with acetylenedicarboxylates (2) at room temperature in a [2+4]-cycloaddition to give a mono-(3) and several di-addition products. 90% of the latter consists of the endo-exo compound 4. Under the influence of catalytic amounts of [Rh(CO)2Cl]2 the mixture of mono- and di-adducts in methanolic solution is smoothly transformed into endo-5,5,6-trimethoxy-7-oxabicyclo [2.2.1]hept-2-ene-2,3-dicarboxylateAlle Verbindungen sind racemisch. Die Formeln stellen jeweils nur ein Enantiomeres dar. (5) , 3-hydroxy-4,5-dimethoxyphthalate ( 6) and (I R*, 2 S*, 4 R*, 5 R*, 7 R*, 11 R*, 12 R*) -5,8,8,9,12-pentamethoxy-3,6-dioxatetracyclo [5.3.1.1 2,5 . 0 4,11]dodec-9-ene-1,11-dicarboxylate ( 7).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19780610327
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  • 10
    Electronic Resource
    Electronic Resource
    Absolute Konfiguration von α-Doradexanthin und von Fritschiellaxanthin, einem neuen Carotinoid aus Fritschiella tuberosa IYENG (1978)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 61 (1978), S. 1962-1968 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Absolute Configuration of α-Doradexanthin and of Fritschiellaxanthin, a New Carotenoid from Fritschiella tuberosa IYENG.Fritschiellaxanthin, a new oxocarotenoid produced by the green alga Fritschiella tuberosa, in a nitrogen-deficient medium is now shown to be (3 S, 3′ R, 6′ R)-3, 3′-dihydroxy-β, ∊-caroten-4-one (4b). It is not identical with α-Doradexanthin (5b) previously found in goldfish (Carassius auratus) and to which we assign the (3 S, 3′ S, 6′ R)-chirality. Consequently, fritschiellaxanthin and α-Doradexanthin are C(3′)-epimers of lutein-4-on. Furthermore, the so-called ′lutein′ from goldfish has now been found to be identical with 3′-epilutein (3). Therefore, fritschiellaxanthin is probably biogenetically derived from lutein (2), whereas α-Doradexanthin is formed from 3′-epilutein (3) with 3, O-didehydrolutein (=(3R, 6′R)-3-hydroxy-β, ∊-caroten-3′-one10) as a precursor. For comparison, optically active 10 and 3 have been prepared from lutein (2) and are fully characterised.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19780610603
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