Stereoselective Total Syntheses of Three Lycopodium Alkaloids, (-)-Magellanine, (+)-Magellaninone, and (+)-Paniculatine, Based on Two Pauson-Khand Reactions

摘要

The total syntheses of (—)-magellanine, (+)-magellaninone, and (+)-paniculatine were completed from diethyl L-tartrate via the common intermediate in a stereoselective manner. The crucial steps in these syntheses involved two intramolecular Pauson—Khand reactions of enynes: the first Pauson—Khand reaction constructed the bicyclo[4.3.0] carbon framework, the corresponding A and B rings of these alkaloids in a highly stereoselective manner, whereas the second Pauson—Khand reaction stereoselectively produced the bicyclo[3.3.0]skeleton, which could be converted into the C and D rings of the target natural products.