Synthetic approaches to racemic porantheridine and 8-epihalosaline via a nitroso diels-alder cycloaddition/ring-rearrangement metathesis sequence

摘要

The application of a sequence involving a nitroso Diels-Alder cycloaddition and a ring-rearrangement metathesis to the total synthesis of (±)-8-epihalosaline and the formal synthesis of (±)-porantheridine is described. The formation of the 2,6-trans-disubstituted piperidine backbone of porantheridine has been accomplished by addition of a Grignard reagent onto an N-benzylpiperidone followed by a highly diastereoselective reduction of the imminium intermediate in one pot.