Synthesis and Assignment of Absolute Configuration of the Iridoid 9-Deoxygelsemide
journal contributionposted on 05.02.2010, 00:00 by Alessandro D’Alfonso, Maurizio Pasi, Alessio Porta, Giuseppe Zanoni, Giovanni Vidari
The first enantioselective synthesis of 9-deoxygelsemide, belonging to a rare group of iridoids isolated from Gelsemium plants, is described. The key synthetic steps are a variant of the Woodward−Prevost reaction to install the characteristic cis-α-1,2-dioxygenated system at C-6 and C-7 with complete diastereoselectivity. Construction of the dihydropyran ring was achieved via formylation of lactone I, followed by dehydration of the corresponding lactol. The synthesis allowed assignment of absolute configuration to 9-deoxygelsemide and related iridoids.