Towards the Core Structure of Strychnos Alkaloids Using Samarium Diiodide‐Induced Reactions of Indole Derivatives |
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Authors: | Dr. Christine Beemelmanns Dr. Steffen Gross Prof. Dr. Hans‐Ulrich Reissig |
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Affiliation: | 1. Institut für Chemie und Biochemie, Freie Universit?t Berlin, Takustr. 3, 14195 Berlin (Germany);2. BCMP, Harvard Medical School, Harvard University, Longwood Avenue 240, 02115 Boston, MA (USA);3. BASF AG, GVA/ID‐B009, 67056 Ludwigshafen (Germany) |
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Abstract: | This report describes the development of a first and second generation approach towards the synthesis of the ABCEG pentacyclic core structure of Strychnos alkaloids. First, we discuss a sequential approach applying a series of functional group transformations to prepare suitable precursors for cyclization reactions. These include attempts of samarium diiodide‐induced cyclizations or a Barbier‐type reaction of a transient lithium organyl, which successfully led to a tetracyclic key building block earlier used for the synthesis of strychnine. Secondly, we account our first steps towards the development of an atom‐economical samarium diiodide‐induced cascade reaction using “dimeric” indolyl ketones as cyclization precursors. In this context, we discuss plausible mechanisms for the samarium diiodide‐induced cascade reaction as well as transformations of the obtained tetracyclic dihydroindoline derivatives. |
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Keywords: | alkaloids Barbier reaction cascade reaction indole samarium diiodide |
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