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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 1636-1642 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The revised structure of the indole alkaloid aristolasicone (2) was confirmed through a convergent total synthesis of the racemic form of this metabolite. The key step involves a one-pot condensation/cyclization reaction between 1-(4-methoxyphenylsulfonyl)-1H-indole-2-acetaldehyde (9) and (±)-trans-5-(2,6-difluorobenzyloxy)-p-menth-l-en-8-amine ((±)-7). The resulting allohobartine derivative (±)-13, obtained in 84% yield, was deprotected and oxidized to (±)-alloscrratenone ((±)-15) which cyclized smoothly to the target molecule (±)-2 upon exposure to BF3 · Et2O.
    Type of Medium: Electronic Resource
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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 oxidative transformation of synthetic (+)-aristoteline ((+)-6) into other metabolites which had been isolated from Aristotelia species was investigated. Thus, treatment of (+)-6 with I2 as the single oxidant furnished the naturally occurring indole alkaloids (+)-makonine ((+)-9),(+)-aristotelinone ((+)-11), or (+)-11, 12-didehydroaristoteline ((+)-7) in good yields, the selectivity of the oxidation process depending on the chosen reaction conditions.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidative transformation of (+)-aristoteline ((+)-5) into its metabolites, the recently synthesized indole alkaloids (-)-serratoline ((-)-6), (+)-aristotelone ((+)-2), and (-)-alloaristoteline ((-)-22), was investigated in more detail. It was demonstrated that the diastereoface selectivity of the reaction of (+)-5 with 3-chloroperbenzoic acid can be altered by variation of the solvent as well as by addition of CF3COOH. The chemoselectivity of the 1,2-rearrangement of the intermediate 3H-indol-3-ol derivatives could be controlled as follows: treatment of 3H-indol-3-ols with aqueous polyphosphoric acid led to the pseudoindoxyl ( = 1,2-dihydro-3H-indol-3-one) derivatives, whereas an analogous treatment of the corresponding O-benzoates furnished exclusively the corresponding, constitutionally isomeric 2-oxindole ( = 1,3-dihydro-2H-indol-2-one) products. Exploitation of these and related findings led to efficient total syntheses of the Aristotelia alkaloid (-)-tasmanine ((-)-1) and of the corresponding unnatural epimer (+)-12, as well as of the two pseudoindoxyls (+)-aristotelone ((+)-2) and (-)-2-epiaristotelone ((-)-11). All these transformations were carried out with synthetic (+)-aristoteline ((+)-5) as the single indole alkaloid precursor.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 1643-1652 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The probably most straightforward plan to synthesize the indole alkaloid alloaristoteline (5) failed, because- in marked contrast to the regular Aristotelia series-electrophilic reagents attack with preference C(3) of the indole moiety in the key intermediate allohobartine ((-)-12), instead of C(18). The only product that could be isolated when (-)-12 was treated with mineral acid was isomer (+)-15 of 5 (Scheme 2). As a consequence, the crucial electrophilic site at C(17) was created by taking recourse to the preparation of the stabilized allylic cation VI. Gratifyingly, this alleged intermediate, obtained from precursor (±)-18, cyclized smoothly to protected (±)-18,19-didehydroalloaristoteline (±)-17, which was transformed in two high-yield steps into the racemic form of the target molecule 5 (Scheme 4). This successful alternative provides unambiguous evidence that the recently revised structure of 5 is indeed correct.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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