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  Total Synthesis of Myxovirescin A1

Fürstner, A., Bonnekessel, M., Blank, J. T., Radkowski, K., Seidel, G., Lacombe, F., et al. (2007). Total Synthesis of Myxovirescin A1. Chemistry – A European Journal, 13(31), 8762-8783. doi:10.1002/chem.200700926.

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 Urheber:
Fürstner, Alois1, Autor           
Bonnekessel, Melanie1, Autor           
Blank, Jarred T.1, Autor           
Radkowski, Karin1, Autor           
Seidel, Günter1, Autor           
Lacombe, Fabrice1, Autor           
Gabor, Barbara2, Autor           
Mynott, Richard2, Autor           
Affiliations:
1Research Department Fürstner, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445584              
2Service Department Mynott (NMR), Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445627              

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Schlagwörter: alkynes; antibiotics; macrocyclization; metathesis; natural products
 Zusammenfassung: A convergent total synthesis of the antibiotic macrolide myxovirescin A1 (1) is described that is largely based on reagent- and catalyst-controlled transformations. This includes a highly regioselective Negishi reaction of dibromo-alkene 48 with an alkynylzinc reagent, and a palladium catalyzed alkyl-Suzuki coupling of the resulting enyne derivative 12 with the 9-BBN-adduct derived from alkene 61. The latter was obtained via an asymmetric hydrogenation of the chlorinated β-ketoester 49 and an anti-selective oxyallylation of the functionalized aldehyde 53 as the key steps. The preparation of the bis-borylated allyl-donor 57 used in the oxyallylation step, however, required careful optimization and led to important insights into the nature of the classical hydroborating agent “di(isopinocampheyl)borane (Ipc2BH)”. It was unambiguously shown by X-ray crystallography that in the solid state this compound is dimeric, but it is prone to undergo an essentially quantitative mono-deborylation when dissolved in CH2Cl2 or benzene; its composition in ethereal solvents is even more complex as evident from 11B NMR data. Product 71 derived from 12 and 61 was elaborated into the enyne–yne derivative 75, which served as the substrate for an exquisitely selective ring closing alkyne metathesis reaction (RCAM) catalyzed by the molybdenum tris-amido complex 20 activated in situ with CH2Cl2. The resulting cyclic enyne 76 was subjected to a ruthenium catalyzed trans-hydrosilylation/proto-desilylation tandem. Although [Cp*Ru(MeCN)6]PF1 had previously been recommended as catalyst of choice for trans-hydrosilylation reactions of internal alkynes, this complex failed to afford the desired product, whereas its sterically less hindered congener [CpRu(MeCN)3]PF6 permitted the reaction to be performed in appreciable yield, but at the expense of a lower stereoselectivity. AgF-mediated proto-desilylation of the isomeric silanes 79 and 80 followed by cleavage of the remaining acetal protecting groups afforded myxovirescin A1 and its hitherto unknown 14Z-isomer 81, respectively.

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Sprache(n): eng - English
 Datum: 2007-06-182007-09-042007-10-26
 Publikationsstatus: Erschienen
 Seiten: 22
 Ort, Verlag, Ausgabe: -
 Inhaltsverzeichnis: -
 Art der Begutachtung: Expertenbegutachtung
 Identifikatoren: DOI: 10.1002/chem.200700926
 Art des Abschluß: -

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Titel: Chemistry – A European Journal
  Andere : Chem. – Eur. J.
  Andere : Chem. Eur. J.
Genre der Quelle: Zeitschrift
 Urheber:
Affiliations:
Ort, Verlag, Ausgabe: Weinheim, Germany : VCH Verlagsgesellschaft
Seiten: - Band / Heft: 13 (31) Artikelnummer: - Start- / Endseite: 8762 - 8783 Identifikator: ISSN: 0947-6539
CoNE: https://pure.mpg.de/cone/journals/resource/954926979058