A facile synthesis of (−)- and (+)-Geissman–Waiss lactone via intramolecular Rh(II)-carbenoid mediated C–H insertion reaction: synthesis of (1R,7R,8R)-turneforcidine

The intramolecular C–H insertion reaction in chiral non-racemic diazoacetates (−)-6 and (+)-8 catalyzed by chiral Rh2(MPPIM)4 proceeded efficiently, with excellent regioselectivity and cis-diastereoselectivity, to give (−)- and (+)-Geissman–Waiss lactone, 4b, respectively. Bicyclic lactone (−)-4b was used in the synthesis of the necine base (−)-turneforcidine 3.