Sterically biased 3,3-sigmatropic rearrangement of chiral allylic azides: application to the total syntheses of alkaloids

A tandem Mitsunobu/3,3-sigmatropic rearrangement of allylic azides on a chiral auxiliary system that favors one regioisomer is described. The sequence is completed by the oxidative cleavage of the auxiliary or by a ring-closing metathesis reaction that has produced a carbo- or heterocycle directly and a recyclable form of the chiral auxiliary.