A facile synthesis of benz[a]anthracene-7,12-diones

Tomaszewski, Joseph E.; Manning, Wayne B.; Muschik, Gary M.

doi:10.1016/s0040-4039(01)92805-9

Cited by 8 publications

(1 citation statement)

References 19 publications

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“…In fact, this kind of disconnection between the rings B and C thereby forming ring B is the most frequently applied in angucydine syntheses using the Diels-Alder reaction. Related reactions of naphthoquinone (40) with styrene (43) as the diene component to yield the fully aromatized benzo[a]anthraquinone (44) are much more difficult and require long reaction times at elevated temperatures, as shown in Scheme 12 [51] (compare with [52]). …”

Section: Diels-alder Reactionsmentioning

confidence: 99%

Angucyclines: Total syntheses, new structures, and biosynthetic studies of an emerging new class of antibiotics

Krohn

Rohr

1997

Topics in Current Chemistry

182

148

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General and recent aspects of chemical syntheses on angucyclinones and selected related natural products are summarized here. In the first part of this review on angucyclines, the chemical reaction used as a key step for the construction of the angucyclinone frame is discussed. In the second part, new members of the angucycline group of antibiotics, their bioactivity and recent biosynthetic studies including modern aspects of molecular biology (genetics) are reviewed.

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Section: Diels-alder Reactionsmentioning

confidence: 99%

Angucyclines: Total syntheses, new structures, and biosynthetic studies of an emerging new class of antibiotics

Krohn

Rohr

1997

Topics in Current Chemistry

182

148

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ChemInform Abstract: A FACILE SYNTHESIS OF BENZ(A)ANTHRACENE‐7,12‐DIONES

Tomaszewski¹,

Manning²,

Muschik³

1977

Chemischer Informationsdienst

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Total synthesis of angucyclinones, 6. Synthesis of naturally (MM 47755; X‐14881 E) and non‐naturally occurring aromatic angucyclinones

1995

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The Diels-Alder reactions of the naphthoquinones 1-4 with 1 he dienes Sa-? were investigated. The regioisomeric outcome of the adducts lOa-lOg, 16, and 23 is in agreement with theoretical predictions from frontier orbital calculations. The adduct 10a was further converted to the non-natural 1e.g. 15) and the adduct 16 to the natural angucyclinones MM 47755 (19a) and X-14881 E (22) by silicon-oxygen exchange and photooxygenation. The addition of naphtoquinones 2 and 4 to dienes 6 and 7 afford the Diels-Alder adducts 16 and 23, respectively, which are valuable intermediates for further transformation into non-aromatic angucyclinones.The angucyclinones are an emerging type of quinone antibiotic that have recently attracted much attention"]. They can be divided into two large groups depending on 1 he presence or absence of a C-glycosidic moiety [']. Among {he non-C-glycosidic compounds the tetrangomycin type with aromatic ring B represents the more simple antibiotics. We have recently described the synthesis of racemic rabelo1nycin[~1 and tetrang~rnycin[~] using a Diels-Alder reaction lor the construction of the angular skeleton (for related work using a Diels-Alder approach see r e f~. [~-~l .The problem of the introduction of the labile tertiary hydroxy group at C-3 was solved by the use of silylated diene building blocks and the angular carbonyl group was introduced by a terminal photooxidation step. We now describe a further extension of our method with particular emphasis on the investigation of the regiochemistry of the Diels-Alder step, the possibility of extension to non-aromatic angucyclinones Thus, the Wittig-Horner reaction of the ketone 8L31 with tert-butyl (diethoxyphosphory1)acetate afforded the unsaturated ester 9a (E/Z mixture, 69%) that was converted to the vinyl ketene acetal5b in the usual manner by deprotonation with LDA and treatment with trimethylsilyl chloride (92%) (Scheme 1). The silyloxydiene 6 was prepared by starting from the ethyl ester 9b, which was reduced with LAH in toluene to the allylic alcohol 9d31. PCC oxidation to the unsaturated aldehyde 9d proceeded in good yield (85%). The crude reaction product could be converted to the ( H Z ) mixture of the silylvinyl ether by treatment with zinc chloride/triethylamine in toluene in the presence of trimethylsilyl chloride.The Diels-Alder reactions of the naphthoquinones 1-3 with the vinyl ketene acetal 5a were studied first (Scheme 2). Not surprisingly, the unsubstituted 1 ,4-naphthoquinone 1 was much less reactive than juglone (2) or the halogenated derivative 3, and the reaction mixture had to be refluxed in toluene for several hours to afford the adducts 10a and 10b (8-deoxyangucyclinones). The reactivity and the regiochemical outcome of the reaction of the quinones 2 and 3 are in perfect agreement with previous experimental observations [20,21] and the frontier orbital considerations of Houk et a1.[221. Overlap of the frontier orbitals with the larger coefficients of diene and dienophile is energetically favored and dominates the regio...

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A facile synthesis of benz[a]anthracene-7,12-diones

Cited by 8 publications

References 19 publications

Angucyclines: Total syntheses, new structures, and biosynthetic studies of an emerging new class of antibiotics

Angucyclines: Total syntheses, new structures, and biosynthetic studies of an emerging new class of antibiotics

ChemInform Abstract: A FACILE SYNTHESIS OF BENZ(A)ANTHRACENE‐7,12‐DIONES

Total synthesis of angucyclinones, 6. Synthesis of naturally (MM 47755; X‐14881 E) and non‐naturally occurring aromatic angucyclinones

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