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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 113 (1980), S. 2994-3009 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthetic Anthracyclinones, XV. Regio- and Stereoselective Synthesis of α-, β-, and γ-Rhodomycinones via Intramolecular Marschalk-CyclisationSelective protection of the phenolic functions at C-1 and C-5 of 1,4,5-trihydroxy-9,10-anthraquinone (7a) can be effected via the boroacetate III to yield the monoacetate 7b followed by methylation to 7d and saponification to 7e. The hydroxymethylation of 7e, chain elongation and demethylation gives the keton 10c, which reacts with lithiated 1,3-dithiane to yield the α-hydroxydithioacetal 11a. The α-hydroxyaldehyde 11e is obtained via the sulfoxides 11b/11c and the dimethylacetal 11d and can be cyclized after dithionite reduction to yield 61% of γ-rhodomycinone (13a) and 24% of 10-epi-γ-rhodomycinone (14a). A third hydroxy group is introduced stereoselectivly at C-7 by treatment of the bromide V with aqueous alkali to give 80% of β-rhodomycinone (15), epimerization of which at C-7 leads to α-rhodomycinone (16).
    Notes: Der selektive Schutz der Phenolgruppen an C-1 und C-5 des 1,4,5-Trihydroxy-9,10-anthrachinons (7a) kann über das Boroacetat III erreicht werden und liefert das Monoacetat 7b, gefolgt von Methylierung zu 7d und Verseifung zu 7e. Die Hydroxymethylierung von 7e, Kettenverlängerung und Entmethylierung ergibt das Keton 10c, das mit lithiiertem 1,3-Dithian zum α-Hydroxydithioacetal 11a reagiert. Der α-Hydroxyaldehyd 11e wird über die Sulfoxide 11b/11c und das Dimethylacetal 11d erhalten und kann nach Dithionit-Reduktion in 61proz. Ausbeute zum γ-Rhodomycinon (13a) und in 24proz. Ausbeute zum 10-Epi-γ-rhodomycinon (14a) cyclisiert werden. Eine dritte Hydroxygruppe an C-7 wird stereoselektiv durch Behandlung des Bromids V mit wäßrigem Alkali eingeführt und liefert mit 80% β-Rhodomycinon (15), das an C-7 zum α-Rhodomycinon (16) epimerisiert werden kann.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1983 (1983), S. 1818-1838 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthetic Anthracyclinones, XXII. - Rhodmycinones of Type A with methyl, ethyl, and n-Propyl Side ChainThe anthraquinone derivatives 7, 8, 37, 39, and 40 are prepared by addition of dichloromethyllithium to the corresponding ketones 4, 5, 32b, 34b, and 36b. They can be hydrolized to intermediate aldehydes, which cyclize after reduction to anthracyclinones of Type A with methyl group (11, 12a, 13a, 45, 46a, 47a), ethyl group (15a, 16a, 48, 49, 50a), and n-propyl side chain (51a, 52a). The cis/trans ratio of the 7,8-Diols is approximately 1 : 3. The hydroxy groups at C-10 are introduced stereoselectively to the 8,10-cis-diols 20b, 24, 25a, 53, 54, and 55 via bromination and hydrolysis of the bromides.
    Notes: Die Anthrachinonderivate 7, 8, 37, 39 und 40 werden durch Addition von Dichlormethyllithium an die entsprechenden Ketone 4, 5, 32b, 34b und 36b hergestellt. Sie lassen sich zu intermediären Aldehyden hydrolysieren, die nach Reduktion zu Anthracyclinonen vom Typ A mit Methylgruppe (11, 12a, 13a, 45, 46a, 47a), Ethylgruppe (15a, 16a, 48, 49, 50a) und n-Propylseitenkette (51a, 52a) cyclisieren. Das cis/trans-Verhältnis der 7,8-Diole beträgt etwa 1:3. Die Hydroxygruppen an C-10 werden stereoselektiv zu den 8,10-cis-Diolen 20b, 24, 25a, 53, 54 und 55 über Bromierung und Hydrolyse der Bromide eingeführt.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1979 (1979), S. 2011-2017 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthetic Anthracyclinones, XI.  -  Synthesis of 4-Deoxy-β1-rhodomycinone by Intramolecular Marschalk ReactionThe intramolecular Marschalk reaction of the aldehyde 6 yields 4-deoxy-β1-rhodomycinone (7a) and the corresponding cis-diol 8a in high yield.
    Notes: Die intramolekulare Marschalk-Reaktion des Aldehyds 6 liefert in hohen Ausbeuten 4-Desoxy-β1-rhodomycinon (7a) und das entsprechende cis-Diol 8a.
    Type of Medium: Electronic Resource
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