Synthetic studies on (-)-lemonomycin: stereocontrolled construction of the 3,8-diazabicyclo[3.2.1] skeleton.
Stereoselective synthesis of the pentacyclic key intermediate 22 for (-)-lemonomycin (1) has been accomplished using the Ugi 4-CC reaction with our novel isocyanide 8, a cross-metathesis of 13 and allylsilane and a subsequent intramolecular Hosomi-Sakurai type reaction.