Synthetic evaluation of an enantiopure tetrahydropyridine N-oxide. Synthesis of (+)-febrifugine

A study into the synthesis and synthetic utility of (S)-3-benzyloxy-3,4,5,6-tetrahydropyridine N-oxide is described. This nitrone is readily accessed from l-glutamic acid and the regio- and stereoselectivity of cycloaddition of this compound with a range of alkenes has been probed. Reductive cleavage of the major cycloadducts provides access to a diverse range of trans-2,3-disubstituted piperidines. The synthetic scope of this nitrone is further illustrated by the use of this compound as a key intermediate in a concise synthesis of the anti-malarial agent (+)-febrifugine.