Synthetic and biosynthetic studies of the brevianamides
Date
2000
Authors
Halligan, Kathleen Marie, author
Williams, Robert M., advisor
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Journal ISSN
Volume Title
Abstract
The preparation of a pinacol-type rearrangement precursor towards the total synthesis of target indoxyl 8 is presented. The route contains three key steps. These include a photooxidation reaction that installs a hydroxy group in the required stereospecific position, a pinacol-type rearrangement to provide the indoxyl core structure and a Strecker reaction to extend the carbon chain to the aminonitrile derivative. Though several other routes to hydroxyindolenines were pursued, this particular pathway shows the most promise for the completion of indoxyl 8 since the crucial pinacol rearrangement was successful. This route is also amenable to 13C-labeled synthesis of indoxyl 8 and azadiene 29. The biomimetic synthesis of brevianamide B is described. Brevianamide B and epibrevianamide A were synthesized from deoxybrevianamide E in six steps. A Diels-Alder precursor was formed via oxidation of the diketopiperazine moiety and praline ring followed by rearrangement to the azadiene. A [4 + 2] cycloaddition reaction took place to provide two hexacyclic adducts. Oxidation at the 3-position of the indole supplied the hydroxyindolenines. A pinacol-type rearrangement of the respective hydroxy derivatives furnished brevianamide B and epibrevianamide A.
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Subject
Metabolites
Biosynthesis
Diels-Alder reaction