Journal of the American Chemical Society, Vol.130, No.41, 13778-13789, 2008
The lyconadins: Enantioselective total syntheses of (+)-lyconadin A and (-)-lyconadin B
A full account of the enantioselective total syntheses of (+)-lyconadin A (1) and (-)-lyconadin B (2) is presented. Central to this venture was recognition and deployment of a key strategy-level intramolecular aldol/conjugate addition cascade that led, in a single operation, to two new carbon-carbon sigma-bonds, three new stereogenic centers, and two new rings, albeit with the incorrect stereogenicity at C(12) for the lyconadins. Correction of the C(12) stereogenicity was achieved via innovative use of a protonated intramolecular aminal. An aminoiodo olefin cyclization, in conjunction with a-pyridinone and 3,4-dihydropyridinone annulation protocols, permitted completion of the syntheses of (+)-lyconadin A (1) and (-)-lyconadin B (2), respectively.