Synthetic Approaches to Racemic Porantheridine and 8-Epihalosaline via a Nitroso Diels−Alder Cycloaddition/Ring-Rearrangement Metathesis Sequence
作者:Pierre Sancibrao、Delphine Karila、Cyrille Kouklovsky、Guillaume Vincent
DOI:10.1021/jo100768d
日期:2010.6.18
Diels−Alder cycloaddition and a ring-rearrangementmetathesis 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
stereoselective synthesis of 2‐(2‐hydroxyalkyl)piperidinealkaloids by ring‐rearrangement metathesis of nitroso Diels–Alder cycloadducts is reported. The approach is illustrated by the formal synthesis of porantheridine and the total synthesis of andrachcinidine through a diastereodivergent allylation of an N‐alkoxy bicyclic lactam. The asymmetric synthesis of the latter alkaloid provides new insights into the configurational
control! N‐alkoxybicyclolactams derived from the ring‐rearrangement metathesis of nitroso Diels–Alder cycloadducts were subjected to the successive addition of two nucleophiles to yield substituted piperidine or pyrrolidine precursors with good to excellent stereoselectivity. The relative configuration of the newly formed stereocenter can be controlled by the order of addition of the two nucleophiles.