A novel iodide-promoted, allene-terminated cyclization of an N-acyliminium ion, a stereoselective Heck spirocyclization, and a chemoselective demethylation at the nitrogen atom of an oxindole are the key transformations in the first total synthesis of the indole alkaloid (+)-gelsedine (1). This dextrorotatory form of natural gelsedine was formed as a single enantiomer in 21 steps from (S)-malic acid
First Total Synthesis of <i>e</i><i>nt</i>-Gelsedine via a Novel Iodide-Promoted Allene <i>N</i>-Acyliminium Ion Cyclization
作者:Winfred G. Beyersbergen van Henegouwen、Rutger M. Fieseler、Floris P. J. T. Rutjes、Henk Hiemstra
DOI:10.1021/jo001119t
日期:2000.12.1
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