Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Isolierung und Struktur von langkettigen Alkylphenolen und -pyrocatecholen aus Plectranthus albidus (Labiatae) (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 1890-1900 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isolation and Structure of Long-Chain Alkylphenols and -catechols from Plectranthus albidus (Labiatae)From the title plant, a series of even-numbered long-chain, phenol- or pyrocatechol-derived 1-arylalkan-5-ones was isolated by classical chromatography and preparative reversed phase HPLC. By chemical and spectroscopic methods, including coupled chromatographic techniques (GC/MS/FT-IR, HPLC/MS), their structures were established to be 1-(4′-hydroxyphenyl)tetradecan-5-one (2a), 1-(4′-hydroxyphenyl)hexadecan-5-one (2b), 1-(4′-hydroxyphenyl)octadecan-5-one (2c), and (Z)-1-(4′-hydroxyphenyl)octadec-13-en-5-one (2d); (E,E)-1-(3′,4′-dihydroxyphenyl)deca-1,3-dien-5-one (1a), 1-(3′,4′-dihydroxyphenyl)dodecan-5-one (3a), 1-(3′,4′-dihydroxyphenyl)-tetradecan-5-one (3b), 1-(3′,4′-dihydroxyphenyl)hexadecan-5-one (3c), 1-(3′,4′-dihydroxyphenyl)octadecan-5-one (3d), 1-(3′,4′-dihydroxyphenyl)icosan-5-one (3e), and (Z)-1-(3′,4′-dihydroxyphenyl)octadec-13-en-5-one (3f). In vitro, the compounds show significant antioxidant activity, the inhibitory concentration of the most potent one, 1a, being slightly lower than for 2-(tert-butyl)-4-methoxyphenol (BHA) and 2,6-di(tert-butyl)-4-methylphenol (BHT) in the Fe2+-catalysed autooxidation of linoleic acid, whereas the acitivities of phenols 2a-d are in the same order of magnitude as α-tocopherol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760508
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Struktur und Partialsynthese von dimerem Coleon F (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1638-1641 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structure and Partial Synthesis of Dimeric Coleon FColeon F (1a), on standing in solution, slowly dimerizes to the labile C(7)-epimeric spiro-dihydrofuranes 2a/2b whose structures were elucidated by spectroscopic methods. Oxydative addition of 1a to another molecule of 1a in the presence of Fétizon's reagent rapidly yields 2a/2b, thus confirming their structures as (4bS,9RS,10′aS)4,4a,10′,10′a-tetrahydro-1′,6-dihydroxy-1,2,4a,7′,8′,10′a-hexamethyl-3′,7-bis(2-propenyl)-spiro[3H,9H-phenanthren-9,5′-5′H-phenanthro[1,10-bc]furan]-2,3,5,8,9′-pentone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710708
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Stereochemistry of the Inhibition of δ-Chymotrypsin with Optically Active Bicyclic Organophosphates: 31P-NMR studies (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 421-435 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The inhibition of δ-chymotrypsin with optically active, axially and equatorially substituted trans-3-(2,4-dini-trophenoxy)-2,4-dioxa-3λ5-phospbubicyclo[4.4.0]decan-3-ones ( = hexahydro-4H-1,3,2-benzodioxaphosphorin 3-oxides) was investigated. Their inhibitory power was determined by kinetic measurements, and the stereochemical course of the reaction of stoichiometric amounts of the enzyme and inhibitor was monitored with 31P-NMR spectroscopy at pH 7.8. The irreversible inhibitors show significant enantioselectivity (the (Sp)-enantiomer reacting faster) and yield diastereoisomeric, covalently phosphorylated derivatives of δ-chymotrypsin.31P-NMR Spectroscopic studies of the inhibition by the axially substituted inhibitor revealed for the racemic (±)-2a first a resonance at -4.4 ppm and later, while inhibition proceeded, a second one at -4.5 ppm. The reaction with optically active (+)-2a showed only one signal at -4.4 ppm and its enantiomer (-)-2a only one signal at -4.5 ppm. Using the equatorially substituted racemic epimer (±)-2b, we observed the main resonance at -5.3 ppm and two minor ones at -4.4 and -4.5 ppm. The optically active compound (+)-2b showed two peaks at -4.5 and -5.3 ppm, whereas its antipode (-)-2b revealed two signals at -4.4 and -5.3 ppm.Comparing the 31P chemical shifts of the corresponding covalent phosphoserine derivatives 4a (-5.7 ppm, axial) and 4b (-4.5 ppm, equatorial) shows the inhibition with the axial compounds 2a to proceed via neat inversion of the configuration at the P-atom, whereas the equatorial epimers 2b with a higher conformational flexibility seem to follow a different stereochemical pathway which results in both inversion and retention.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800208
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Isolation, Structure, and Biological Activities of Long-Chain Catechols of Plectranthus sylvestris (Labiatae) (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 436-448 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Antioxidant activity guided fractionation of extracts of the aerial parts of the title plant and HPLC separation yielded a series of oxygenated long-chain alkylcatechols. Their structures were inferred by spectroscopic methods and chemical transformations to be the novel 4-[(2S,4R,6S)-4-(acetyloxy)tetrahydro-6-pentyl-2H-pyran-2-yl]benzene-1,2diol (1a), 4-[(2S,4R6S)-tetrahydro-4-hydroxy-6-pentyl-2H-pyran-2-yl]benzene-1,2-diol (1b), 4-[(3S,5S)-5-(acetyloxy)-3-hydroxydecyl]benzene-1,2-diol (2a), 4-[(3S,5S)3-(acetyloxy)-5-hydroxydecyl]benzene-1,2-diol (2b), (3S,13Z)-1-(3,4-dihydroxyphenyl)-3-hydroxydocos-13-en-5-one (3a), (Z)-1-(3,4-dihydroxyphenyl)docos-13-en-5-one (4), besides the known l-(3,4-dihydroxyphenyl)icosan-5-one (5). The absolute configurations of the optically active compounds which are structurally related to the [n]-gingerols (6) and -diols (7) were established by the high-field 1H-NMR application of Mosher's method. All compounds are in vitro potent antioxidants, inhibiting the Fe2+-catalysed autoxidation of linoleic acid in the same order of magnitude as the commercial antioxidant 2,6-di(tert-butyl)-4-methylphenol (BHT). The dose-dependent inhibitory effects on soybean-lipoxygenase are in the μmol range, that of the most effective compound (3a) in the nmol range, hence being significantly more potent than the Known anti-inflammatory and analgesic drugs indomethacin and nordihydroguaiaretic acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800209
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Stereochemistry of the Inhibition of δ-Chymotrypsin with Optically Active cis-Decaline-Type Organophosphates: 31P-NMR studies (1998)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 81 (1998), S. 1127-1138 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Investigation of the inhibition of δ-chymotrypsin with the four novel, optically active, axially and equatorially substituted cis-3-(2,4-dinitrophenoxy)-2,4-dioxa-3λ5-phosphabicyclo[4.4.0]decan-3-ones (= 3-(2,4-dinitrophenoxy)hexahydro-4H-1,3,2-benzodioxaphosphorin 2-oxides) showed only the equatorially substituted enantiomer (-)-4b to be an irreversible inhibitor of the enzyme, and (-)-4b at pH 7.8 revealed a quickly rising resonance at -2.49 ppm assigned to the hydrolysis product 8 and later, while inhibition proceeded, a second one at -4.08 ppm. attributed to the δ-chymotrypsin adduct 7 (Scheme 3). Comparision of the latter signal with the 31P-NMR chemical shifts of the covalent phosphoserine model compounds (-)-6a (-5.67 ppm, axial substitution) and (+)-6b (-4.02 ppm, equatorial substitution) suggests that the inhibition proceeded via neat retention of the configuration at the P-atom of (-)-4b yielding the equatorially substituted covalent Ser195 adduct 7.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19980810526
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Der Sterische Verlauf der nucleophilen Cyclopropanöffnung an den vier im Spiro(methylcyclopropan)-Ring Diastereoisomeren Lanugonen J (Spirocoleonen) (1986)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 456-466 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Stereochemistry of the Nucleophilie Opening of the Cyclopropane Ring in the four Diastereoisomeric Lanugons J (Spirocoleons)Methanolysis of the spiro(methylcyclopropane) moiety in the four diastereoisomeric lanugons J 3 (13S, 15R), 4 (13R,15R), 5 (13S,15S), and 6 (13R,15S) is shown to proceed stereospecifically with inversion of the configuration at the attacked C-atom (C(15)). The resulting epimeric 2-methoxypropyl-substituted hydroxy-1,4-benzoquinones (royleanones) 7a/8a (monomethoxy derivatives) and 7b/8b (dimethoxy derivatives) could be separated by HPLC using the recently described ‘Non-Aqueous Cation Exchange System’. Respective pairs of 1H-NMR spectra exhibit minute but significant differences in the ABMX3 part of the 2-methoxypropyl group. The final structure assignment is based on a single-crystal X-ray analysis of the dimethoxyroyleanone 7b, whose absolute configuration was established by chiroptical correlation with known abietanoids. Thus, methanolysis of 3 and 4 ((R)-configuration at the reaction centre) yielded the royleanones 7a and 7b with (S)-configuration, whereas analogous treatment of 5 and 6 ((S)-configuration at the reaction centre) led to the corresponding derivatives 8a and 8b both having the (R)-configuration in the 2-methoxypropyl side chain.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19860690227
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Synthese von Alkylphenolen und -pyrocatecholen aus Plectranthus albidus (Labiatae) (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 1901-1915 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Alkylphenols and -catechols from Plectranthus albidus (Labiatae)In the preceding paper, we described the isolation and structure elucidation of a series of even-numbered phenol- or pyrocatechol-derived 1-arylalkane-5-ones. To establish the assigned structures unambiguously and to have larger quantities available for physiological testing, the following compounds were prepared: in the alkylphenol series, 1-(4′-hydroxyphenyl)tetradecan-5-one (2a), 1-(4′-hydroxyphenyl)hexadecan-5-one (2b), and 1-(4′-hydroxyphenyl)octadecan-5-one (2c); in the alkylcatechol series, 1-(3′,4′-dihydroxyphenyl)decan-5-one (3a; not isolated as a natural compound), 1-(3′,4′-dihydroxyphenyl)dodecan-5-one (3b), 1-(3′,4′-dihydroxyphenyl)tetradecan-5-one (3c), 1-(3′,4′-dihydroxyphenyl)hexadecan-5-one (3d), 1-(3′,4′-dihydroxyphenyl)octadecan-5-one (3e), and 1-(3′,4′-dihydroxyphenyl)icosan-5-one (3f); in the alkenylphenol series, (Z)-1-(4′-hydroxyphenyl)octadec-13-en-5-one (4a) and (E)-1-(4′-hydroxyphenyl)octadec-13-en-5-one (4b); in the alkenylcatechol series, (E,E)-1-(3′,4′-dihydroxyphenyl)deca-1,3-dien-5-one (1) and (Z)-1-(3′,4′-dihydroxyphenyl)octadec-13-en-5-one (5). All compounds proved to be identical with the previously assigned structures. Compound 1 was synthesized by regioselective aldol condensation of heptan-2-one with (E)-1-(3′,4′-dimethoxyphenyl)prop-2-enal (6d; Scheme 1), the phenols 2a-c and the catechols 3a-f by addition of the corresponding alkyl Grignard reagent to 5-(4′-methoxyphenyl)- or 5-(3′,4′-dimethoxyphenyl)pentanal (17c and 18c, resp.; Scheme 4), and the olefins 4a, 4b and 5 from 17c or 18c via the 9-O-silyl-protected 13-(4′-methoxyphenyl)- or 13-(3′,4′-dimethoxyphenyl)tridecanals (26 and 27, resp.) and Wittig olefination as the key steps (Scheme 5).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760509
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Plectranthone A, B, C und D. Diterpenoide Phenanthren-1,4-dione aus Blattdrüsen einer Plectranthuus sp. (Labiatae) (1984)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 1003-1011 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Plectranthons A, B, C, and D. Diterpenoid Phenanthrene-1,4-diones from Leaf-glands a Plectranthus sp. (Labiatae)The following structures of four new 1,4-phenanthraquionones, isolated in minute amounts from the coloured leaf-glands of a Plectranthus sp. obtained from the borders of Lake Kiwu2, Rwanda, are proposed: plectranthon A (1; 3-hydroxy-5, 7,8-trimethyl-2-(2-propenyl)phenanthrene-1, 4-dione), plectranthon B (2; 2-(2ξ-acetoxypropyl)-3-hydroxy-5,7,8-trimethylphenanthrene-1,4-dione), plextranthon C (3; 3-hydroxy- 7,8-diemethyl-2-(2-propenyl)phenanthrene-1,4-dione), and plectranthon D (4; 3-hydroxy-7,8,10-trimethyl-2-(2-propenyl)phenanthrene-1,4-dione). 2-(2ξ-Hydroxypropyl)-3,6-dihydroxy-5,7,8-trimethylphenanthrene-1,4-dione (11), a compound very similar to 1-4, was prepared by a Wagner-Meerwein, rearrangement of coleon E (5). Biogenetically, the plectranthons are derived from abietanoic precursors. The compounds 1, 2 and 4 are the first natural C20-phenanthrenes of diterpenoid origin.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19840670412
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    14-Hydroxytaxodion: Partialsynthese und Reaktionen (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 2219-2226 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hitherto unknown diterpenoid 14-hydroxytaxodione (10a) has been prepared by oxidation of 6β-hydroxyroyleanone. Its solutions exhibit a dynamic structural behaviour (UV./VIS/. and NMR.) and lead to an equilibrium mixture of the 11, 14- and the 6, 12-dioxo forms. By methylation and acetylation the 6, 12-dioxo form can be isolated. Chloroform solutions of 14-hydroxytaxodione slowly set up a mixture of coleon V (2a), coleon U (3) and dimeric products (later established as grandidone C, grandidone D and 7-epigrandidone D). Therefore, coleon V (2a) owing to its strong intramolecular H-bond is more stable than 7, 14-dihydroxy-taxodione (2b).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640728
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...