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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 

First total synthesis of ent-gelsedine via a novel iodide-promoted allene N-acyliminium ion cyclization.

The first total synthesis of the oxindole alkaloid gelsedine (1) starting from (S)-malic acid is described. The key step is a novel iodide-promoted intramolecular reaction of an allene with an N-acyliminium ion intermediate which provided in a single step the bicyclic vinyl iodide 11. Other important steps are the highly stereoselective Pd-catalyzed Heck cyclization of N-methylanilide 23a which led to the desired spiro-oxindole 24a, the fully regioselective intramolecular oxymercuration of 25a to the desired cyclic ether, and the remarkable oxindole N-demethylation of 29 via a radical mechanism by using dibenzoyl peroxide. The total synthesis was concluded by the stereoselective introduction of the ethyl group from the bis-Boc compound 41 followed by methoxylation of the oxindole nitrogen. This total synthesis leads to the unnatural (+)-enantiomer of gelsedine in 21 steps and 0.10% overall yield.[1]

References

  1. First total synthesis of ent-gelsedine via a novel iodide-promoted allene N-acyliminium ion cyclization. Beyersbergen van Henegouwen, W.G., Fieseler, R.M., Rutjes, F.P., Hiemstra, H. J. Org. Chem. (2000) [Pubmed]
 
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