A Gram‐Scale Batch and Flow Total Synthesis of Perhydrohistrionicotoxin |
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Authors: | Dr. Malte Brasholz Dr. James M. Macdonald Dr. Simon Saubern Dr. John H. Ryan Prof. Dr. Andrew B. Holmes |
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Affiliation: | 1. CSIRO Molecular and Health Technologies, Bayview Avenue, Clayton, VIC 3168 (Australia), Fax: (+61)?3‐9545‐2446;2. Prof.?Dr. A. B. Holmes, Bio 21 Institute, School of Chemistry, University of Melbourne, Flemington Road, Parkville, VIC 3010 (Australia) |
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Abstract: | The total synthesis of the spiropiperidine alkaloid (?)‐perhydrohistrionicotoxin (perhydro‐HTX) 2 has been accomplished on a gram scale by employing both conventional batch chemistry as well as microreactor techniques. (S)‐(?)‐6‐Pentyltetrahydro‐pyran‐2‐one 8 underwent nucleophilic ring opening to afford the alcohol 10 , which was elaborated to the nitrone 13 . Protection of the nitrone as the 1,3‐adduct of styrene and side‐chain extension to the unsaturated nitrile afforded a precursor 17 , which underwent dipolar cycloreversion and 1,3‐dipolar cycloaddition to give the core spirocyclic precursor 18 that was converted into perhydro‐HTX 2 . The principal steps to the spirocycle 18 have successfully been transferred into flow mode by using different types of microreactors and in a telescoped fashion, allowing for a more rapid access to the histrionicotoxins and their analogues by continuous processing. |
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Keywords: | alkaloids cycloaddition flow chemistry olefination total synthesis |
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