An Expeditious Route to Both Enantiomers of All Carbon Quaternary Stereocenters at C-3 Carbon of Lactams via [3,3]-Sigmatropic Rearrangement: Total Synthesis of (−)-Physostigmine

摘要: A diastereoselective route to all carbon quaternary stereocenters at the C-3 position of cyclic lactams has been developed via Johnson–Claisen rearrangement γ-hydroxy-α, β-unsaturated lactams. It observed that olefin geometry plays an important role in development absolute stereochemistry product. The dependence product configuration on is explained by postulating probable transition states. success this method shown for multigram scale synthesis these substituted from commercially available cheap starting materials. synthetic usefulness also demonstrated carrying out total (−)-physostigmine.