Total Synthesis of (-)-14-Hydroxygelsenicine and Six Biogenetically Related Gelsemium Alkaloids.

The first concise and collective asymmetric total synthesis of six 14-hydroxygelsenicine-related Gelsemium alkaloids, i.e., 14-hydroxygelsedilam, 14-acetoxygelsedilam, gelsefuranidine, gelsemolenine A, and gelselegandines B and C, was accomplished via the facile construction of a 7-azabicyclo[4.2.1]nonane skeleton by intramolecular aza-Michael addition, the preparation of an oxabicyclo[3.2.2]nonane ring core with a secondary hydroxy group at C14 by an intramolecular oxymercuration-hydroxylation strategy, and divergent transformations of 14-hydroxygelsenicine into biogenetically related alkaloids.