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  • 1
    Digitale Medien
    Digitale Medien
    Radikalische Cyclisierung von Dienen, III Radikalische Cyclisierung von (R)-(-)-Carvon - Über den Einfluß von Charge-Transfer-Wechselwirkung auf den spezifischen Drehwert (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 901-905 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Radical-type cyclisation / Bicyclo[3.2.]octan-3-one, enantiomerically pure / Charge-transfer interactions ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Radical-Type Cyclisation of Dienes, 111. - Radical-Type Cyclisation of (R)-( - )-Carvone - On the Influence of Charge- Transfer Interactions on the Optical RotationUnder the conditions of radical cyclisation, a 1:1 diastereomeric mixture of (1R,2S,5R,R)-(+)- (2a) and (1R.2S,5R,6S)-(+)-6-methoxy-2,6-dimethylbicyclo[3.2.1]octan-3-ones (2b) is obtained from (R)-(-)-carvone in 70% yield. the configuration fo 2a and 2b were confirmed by X-ray structure analyses of their hydrazones 2d and 2e. The regio- and stereoselectivity of the radical cyclisation of 1 to 2a and 2b are discussed. The high value of the specific rotation [-555] of 2d is traced back to charge-transfer interactions between the endo-standing methoxy group at C-6 as electron donor and the dinitrophenyl-hydrazone group as electron acceptor.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230441
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  • 2
    Digitale Medien
    Digitale Medien
    Radikalische Cyclisierung von Dienen, VIII. Über die regioselektive Herstellung von ungesättigten Cyclopenta[b]furan-2-onen aus (S)-(+)-Carvon  -  Bausteine zur Synthese von enantiomerenreinen Triquinanen (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 549-550 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Radicals ; Cyclization ; Triquinanes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Radical-Type Cyclization of Dienes, VIII[1].  -  On the Regioselective Synthesis of Unsaturated Cyclopenta[b]furan-2-ones from (S)-(+)-Carvone  -  Building Blocks for the Synthesis of Enantiomerically Pure TriquinanesThe diastereomeric products 2a and 2b, which were synthesized from (S)-(+)-carvone (1), are converted to (3aS,5S,6aS)-(-)-5-acetoxyhexahydro-6a-methyl-2H-cyclopenta[b]furan-2-one (4) in ca. 50% yield. 4 is regioselectively converted to (3aR,6aS)-(-)-3,3a,6,6a-tetrahydro-6a-methyl- (8a) and (3aS,6aR)-(+)-3,3a,4,6a-tetrahydro-6a-methyl-2H-cyclopenta[b]-furan-2-one (8b). These are used at the 10-g scale for the synthesis of enantiomerically pure triquinanes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19941270314
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  • 3
    Digitale Medien
    Digitale Medien
    Radikalische Cyclisierung von Dienen, IX. Über die Stereoselektivität der radikalischen 4-exo-trig-Cyclisierung von optisch aktiven (2E)-6-Oxohex-2-ensäureestern mit Samarium(II)-iodid (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1305-1309 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Radicals ; Cyclobutanes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Radical-Type Cyclization of Dienes, IX. - On the Stereoselectivity of the Radical 4-exo-trig-Cyclization of Optically Active Ethyl (2E)-6-Oxohex-2-enoates with Samarium(II) IodideEthyl (5R, 2E)-5-(benzyloxy)-4,4-dimethyl-6-oxohex-2-enoate (9) was prepared from (R)-(-)-pantolactone (3) by a series of straightforward reactions. The reaction of 9 with samarium(II) iodide produces enantiomerically pure ethyl (1S,3R,4R)-(-)-[3-(benzyloxy)-4-hydroxy-2,2-dimethylcyclo-butyl]acetate (10) in 60% yield. The absolute configuration at C-1 and C-3 was confirmed by the conversion of 10 to the crystalline 15a, whose absolute configuration is known from its synthesis from (1S,5S)-( + )-α-pinene (12). The configuration of the hydroxy group at C-4 in 10 was determined from NOE studies on the epimiric 17. The radical 4-exo-trig-cyclization of optically active (2E)-6-oxohex-2-enoates with samarium(II) iodide opens a new pathway to enantiomerically pure cyclobutanol and cyclobutanone derivatives, which are of interest as building blocks in natural products synthesis.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19941270720
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  • 4
    Digitale Medien
    Digitale Medien
    Preparation of Kingiside from Aucubin (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1623-1626 
    Details
    ISSN: 1434-193X
    Schlagwort(e): Iridoid glucoside ; (8S)-Kingiside ; (8S)-Loganin ; (8S)-7-Ketologanin ; Asymmetric synthesis ; Natural products ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The tetraacetyl derivative 8 of the naturally occurring kingiside (8a) was prepared from aucubin (1). Intermediates in the synthesis were (8S)-tetraacetyl loganin (6) and (8S)-tetraacetyl-7-ketologanin (7), whose free (8R)-epimers occur in many different plants (Caprifoliaceae, Loganiaceae). The 13C NMR spectrum allows the structure to be unequivocally identified.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Chemie und Stereochemie der Iridoide, XV. Eine effiziente Synthese enantiomerenreiner (-)-Specionin-Analoga aus peracetylierten Iridoidglucosiden Kristall- und Molekülstruktur von (-)-3′-Methoxyspecionin (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 477-480 
    Details
    ISSN: 0170-2041
    Schlagwort(e): Specionin analogs ; (-)-3′-Methoxyspecionin ; Iridoid glucosides, peracetylated ; Cleavage of the glucoside bond, selective ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chemistry and Stereochemistry of Iridoids XV. - An Efficient Synthesis of Enantiomerically Pure (-)-Specionin Analogs from Peracetylated Iridoid Glucosides. - Crystal and Molecular Structure of (-)-3′-MethoxyspecioninWhen peracetylated iridoid glucosides are submitted to hydroxymercuration and reduction with zinc the glucoside bond is cleaved exclusively. The aglycones can be regio- and stereoselectively transformed into specionin analogs. An example is the preparation of crystalline (-)-3′-methoxyspecionin (3b) from hexaacetyl-6-O-vanilloylcatalpol (1d), which is readily available in larger quantities. The stereochemistry of 3b was determined by X-ray crystallographic analysis.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.199119910186
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  • 6
    Digitale Medien
    Digitale Medien
    Chemie und Stereochemie der Iridoide, XIV. Aucubin und Scandosid aus Catalpol (1990)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 715-717 
    Details
    ISSN: 0170-2041
    Schlagwort(e): Aucubin ; Scandoside ; Catalpol ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chemistry and Stereochemistry of Iridoids, XIV.  -  Aucubin and Scandoside from CatalpolAucubin (9), scandoside (10), and its methyl ester [“feretoside” (11)] were obtained, in good yields, from catalpol (1). The absolute configurations of 9-11 were established by correlation to catalpol, whose X-ray crystal structure has previously been determined.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.1990199001137
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  • 7
    Digitale Medien
    Digitale Medien
    Chemie und Stereochemie der Iridoide, XIII. Synthese von enantiomerenreinem (1R,2S,2″Z)-(+)-Methyljasmonat aus Catalpol (1990)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 751-754 
    Details
    ISSN: 0170-2041
    Schlagwort(e): Jasmine oil, fragrance of ; (+)-epi-Jasmonate, methyl, enantiomerically pure ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chemistry and Stereochemistry of Iridoids, XIII.  -  Synthesis of Enantiomerically Pure Methyl (1R,2S,2″Z)-(+)-Jasmonate Starting from CatalpolEnantiomerically pure methyl (1R,2S,2″Z)-(+)-jasmonate (2), which was recognized as a component of the fragrance of the jasmine flower oil, was synthesized starting from catalpol (3). 2 is easily epimerized to 1. Thus, it is necessary to use very mild conditions in the course of the synthesis and purification. These results raise the question whether 2 exists as a natural product in the flower of jasmine and 1 arises during the isolation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.1990199001141
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  • 8
    Digitale Medien
    Digitale Medien
    Chemie und Stereochemie der Iridoide, XVI. EPC-Synthese von (-)-Hypnophilin (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 893-902 
    Details
    ISSN: 0170-2041
    Schlagwort(e): (-)-Hypnophilin, enantiomerically pure ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chemistry and Stereochemistry of Iridoids, XVI. - EPC-Synthesis of (-)-HypnophilinThe synthesis of enantiomerically pure (-)-hypnophilin (27) from (6R,7R)-(-)-7-hydroxy-3-oxabicyclo[4.3.0]non-1-en-9-one (1) is described. 1 was obtained in 93% yield from catalpol, which is readily available from the aqueous sodium carbonate extract of Picrorhiza kurrooa (Scrophulariaceae). The specific rotation, MS, 1H- and 13C-NMR data of synthetic (-)-hypnophilin were identical with those of the natural product.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.1991199101154
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  • 9
    Digitale Medien
    Digitale Medien
    Chemie und Stereochemie der Iridoide, XVII. Palladium-katalysierte Substitution an Hexaacetylaucubin (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 1109-1111 
    Details
    ISSN: 0170-2041
    Schlagwort(e): Hexaacetylaucubin ; Palladium-catalysed substitution ; Iridoidglucosides, N-containing ; Carbohydrates ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chemistry and Stereochemistry of Iridoids, XVII. - Palladium-Catalysed Substitution of HexaacetylacubinAcetoxy groups, in allylic position, can be replaced by nucleophiles in a palladium-catalysed reaction. The reaction of hexaacetylaucubin (2) with piperidine or benzylamine regioselectively gives the crystalline, N-containing iridoidglucosides 3 and 4. With the anion of diemethyl malonate, 5 was obtained along with the byproduct 7. Adding triethylammonium formate as a hydride donor, then the reaction gives 6; a reaction mechanism is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.1991199101194
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  • 10
    Digitale Medien
    Digitale Medien
    Isolierung und NMR-spektroskopische Untersuchungen von (-)-1-O-Benzyl-β-D-primverosid aus grünen Früchten von Prunus laurocerasus (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 703-705 
    Details
    ISSN: 0170-2041
    Schlagwort(e): Primveroside, 1-O-benzyl-β-D- ; Primverose ; Prunus laurocerasus L. ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Isolation and NMR-Spectroscopic Investigations of (-)-1-O-Benzyl-β-D-primveroside from Green Fruits of Prunus laurocerasusThe TLC of the acetylated aqueous extracts of the green fruits of Prunus laurocerasus reveals two spots corresponding to pentaacetyl-glucopyranose and hexaacetyl-1-O-benzyl-β-D-primveroside (2), which can be quantitatively separated by flash chromatography. Saponification of 2 yields the free 1-O-benzyl-β-D-primveroside (1) which affords D-primverose (3) upon hydrogenolysis. The direct hydrogenolysis of 2 yields hexaacetyl-β-D-primverose (4). The structures of compounds 1-4 have been verified by NMR spectroscopy.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jlac.1991199101124
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