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  • 1
    Electronic Resource
    Electronic Resource
    Radikalische Cyclisierung von Dienen, V. Substratkontrollierte asymmetrische Synthese von (-)-Hirsuten und (-)-3-Hydroxyhirsuten aus (R)-(-)-Carvon (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 403-411 
    Details
    ISSN: 0170-2041
    Keywords: Hirsutene derivatives ; Cyclopenta[a]pentalenes ; Radicals ; Cyclizations ; Triquinanes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical-Type Cyclization of Dienes, V. - Substrate-Controlled Asymmetric Synthesis of (-)-Hirsutene and (-)-3-Hydroxyhirsutene from (R)-(-)-Carvone(3aR,6aR)-(-)-6a-Methyl-3,3a,4,6a-tetrahydro-2H-cyclopenta- [b]furan-2-one (6) and (1R,4S)-(-)-3-[4-(but-3-inyl)-3-methyl-cyclopent-2-enyl]-2,2-dimethylpropan-1-ol (11) are key compounds in the synthesis reported in this paper. Enantiomerically pure 6 was obtained in five straightforward steps from the inexpensive precursor (R)-(-)-carvone (1). Compound 11 was prepared from 6 via an SN2′ reaction, by analogy with the synthesis reported by Curran et al. The linear triquinanes 13 and 15 were obtained in gram quantities in two additional steps. The utilisation of (S)-(+)-carvone (ent-1) allows access to the other enantiomeric forms. X-ray analysis of 15a confirmed the structure of 15 and, by correlation, that of 13.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199319930166
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  • 2
    Electronic Resource
    Electronic Resource
    Chemie und Stereochemie der Iridoide, XIX. Zwei einfache EPC-Synthesen mit chemischem Beweis der absoluten Konfiguration von (+)-Mitsugashiwa-Lacton aus (S)-(-)-Citronellol und Aucubin (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 1029-1031 
    Details
    ISSN: 0170-2041
    Keywords: (+)-Mitsugashiwa-lactone ; (4aR,7aR,7S)-(+)-7-Methylhexahydrocyclopenta[c]pyran-1-one ; Iridoids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemistry and Stereochemistry of Iridoids, XIX. - Two Straightforward EPC Syntheses with Chemical Evidence of Absolute Configuration of (+)-Mitsugashiwa Lactone from (S)-(-)-Citronellol and AucubinEnantiomerically pure (+)-Mitsugashiwa lactone (9) was prepared in eight steps from (S)-(-)-citronellol (1), whereas only four steps were required for the conversion of hexaacetylaucubin (10) into 9. Both starting materials are readily available in large quantities. The synthesis of 9 from 1 establishes the absolute configuration at C-7 in 9. Conversely, the synthesis of 9 from 10 confirms the absolute configuration at C-4a and C-7a in 9.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1993199301163
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  • 3
    Electronic Resource
    Electronic Resource
    Chemistry of the Ginkgolides, V. On the Preparation of the Ginkgolide Skeleton (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 287-291 
    Details
    ISSN: 0170-2041
    Keywords: Ginkgolide derivatives ; 14-Epiginkgolide derivatives ; Ginkgo biloba L. ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3,14-Didehydro-10-hydroxyginkgolideOn the nomenclature: The skeleton of the ginkgolides A, B, C, M and J with the natural configuration is called “ginkgolide” since the systematic IUPAC nomenclature is too complicated. According to our nomenclature ginkgolide “A” is 3,10-dihydroxyginkgolide, ginkgolide “B” is 1,3,10-trihydroxyginkgolide etc. The numbering of the C atoms (formula 1) and the indexing of the H atoms (formula 2) are those proposed by Nakanishi[2]. (1) was prepared by reaction of 3,10-dihydroxyginkgolide (3) (ginkgolide “A”) by reaction with phosphoryl chloride in pyridine. Catalytic hydrogenation of 1 leads to 10-hydroxy-14-epiginkgolide (2a), which was epimerized with 4-(dimethylamino)pyridine (DMAP) in acetonitrile to give 10-hydroxyginkgolide (3a). 14-Epiginkgolide (2d) and ginkgolide (3d) were obtained from 2a and 3a via the 10-O-phenylthiocarbonyl derivatives 2c and 3c by means of a free-radical reduction with tri-n-butyltin hydride/α,α′-azobis(isobutyronitrile) (AIBN). By heating the 14-epiginkgolides 2a and 2b and the ginkgolides 3a and 3b in acetonitrile with DMAP an equilibrium on the side of the ginkgolides was established. The constitution and configuration of the compounds were proven by their 1H- and 13C-NMR spectra.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199319930149
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  • 4
    Electronic Resource
    Electronic Resource
    Radikalische Cyclisierung von Dienen, VI. Totalsynthese von (-)-Coriolin und (-)-Epicoriolin aus (S)-(+)-Carvon (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 1133-1140 
    Details
    ISSN: 0170-2041
    Keywords: (-)-Coriolin ; (-)-Epicoriolin ; Radicals ; Cyclization ; Triquinans ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical-Type Cyclization of Dines, VI. - Total Synthesis of (-)-Coriolin and (-)-Epicoriolin from (S)-(+)-Carvone(3aR,4S,6aS)-(+)-4-(4-Methoxybenzyloxy)-6a-methyl-3,3a,4,6a-tetrahydro-2H-cyclopenta[b]furan-2-one (10) and (3aR,3bR,4R,6aS,7S,7aS)-(-)-decahydro-4,7-dihydroxy-3a,5,5-trimethyl-3-methylene-2H-cyclopenta[a]pentalen-2-one (21) are the key intermediates in the synthesis of the title compounds 1 and 1a. Enantiomerically pure 10 is produced from (S)-(+)-carvone (4) in seven straightforward reactions. Compound 21 is produced from 10 by analogy with the method developed for the synthesis of (-)-hirsutene. Through the introduction of the double bond into 21 via the silylenolether 23 one arrives at precoriolin 25, which is converted into (-)-coriolin (1) and the C-3 epimer (-)-epicoriolin (1a) (63:37) with hydrogen peroxide. The structures of 1 and 1a were confirmed via X-ray crystallography.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1993199301181
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  • 5
    Electronic Resource
    Electronic Resource
    Radikalische Cyclisierung von Dienen, VI. Substratkontrollierte asymmetrische Synthese von (3aS,6aR)-(+)-3,3a,6,6a-Tetrahydro-2H-cyclopenta[b]furan-2-on (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 811-814 
    Details
    ISSN: 0170-2041
    Keywords: Cyclopenta[b]furan-2-one, (3aS,6aR)-(+)-3,3a,6,6a-tetrahydro-2H- ; Radicals ; Cyclization ; Carvone ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical-Type Cyclization of Dienes, VI. - Substrate-Controlled Asymmetric Synthesis of (3aS,6aR)-(+)-3,3a,6,6a-Tetrahydro-2H-cyclopenta[b]furan-2-one(R)-(-)-Carvone (1) was converted via straightforward reactions into 10-hydroxycarvone (4) which was cyclized to 5 via the mercury-mediated free-radical method. Periodate cleavage of 5 yields the bicyclic dione 6. Regio- and stereoselective reduction of 6 with lithium tri(tert-butyloxy)hydridoaluminate results in 7 (80% yield). 7 was directly converted into γ-lactone 8 via Baeyer-Villiger oxidation. Saponification of 8 to 9, mesylation of 9 to 10 followed by elimination of methanesulfonic acid yield enantiomerically pure (3aS,6aR)-(+)-3,3a,6,6a-Tetrahydro-2H-cyclopenta[b]furan-2-one (11). The synthesis can be carried out with readily available, and economical, (S)-(+)-carvone to yield ent-11.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1993199301128
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  • 6
    Electronic Resource
    Electronic Resource
    Chemie der Ginkgolide, VI. Herstellung von 1,10-Dihydroxy- und 1,7,10-Trihydroxyginkgolid aus 1,3,7,10-Tetrahydroxyginkgolid (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 1023-1027 
    Details
    ISSN: 0170-2041
    Keywords: 1,10-Dihydroxyginkgolide ; 7-Deoxyginkgolide M ; 3-Deoxyginkgolide B ; 1,7,10-Trihydroxyginkgolide ; Ginkgolide M ; 14-Epiginkgolide ; Ginkgo biloba L. ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemistry of the Ginkgolides, VI. - Preparation of 1,10-Dihydroxy- and 1,7,10-Trihydroxyginkgolide from 1,3,7,10-Tetrahydroxyginkgolide1,3,7,10-Tetrahydroxyginkgolide (“ginkgolide C”, 1) which can be isolated in large quantities from the terpene fraction of Ginkgo leaves, can be converted into 1-(tert-butyldiphenylsilyloxy)-3,7,10-trihydroxyginkgolide (2) in 95% yield. 2 was converted via straightforward reactions into 1,7,10-trihydroxyginkgolide (“ginkgolide M”, 9) and into the until now unknown 1,10-dihydroxyginkgolide (15). 15 can also be obtained from 1,3,10-trihydroxyginkgolide (“ginkgolide B”, 10). The intermediate products 14-epiginkgolides 8 and 14 were epimerized to the ginkgolides with natural configuration at C-14 by reaction with 4-(dimethylamino)pyridine in acetonitrile. The title compounds are of interest for their possible activity as antagonists of the platelet activating factor (PAF).
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1993199301162
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