Total synthesis of (-)-stemoamide.

A stereocontrolled total synthesis of (-)-stemoamide (1) is presented. The synthesis starts from commercially available (S)-pyroglutaminol (4). A chemoselective iodoboration of 5 was used to access key intermediate 3. The beta,gamma-unsaturated azepine derivative 2 was obtained via a Pd(0)-catalyzed sp(2)-sp(3) Negishi cross-coupling using a Reformatsky nucleophile followed by a ring-closing metathesis reaction. The required C8-C9 trans-stereochemistry of 1 was accessed through a stereoselective bromolactonization/1,4-reduction sequence.