From macrocycle dipeptide lactams to azabicyclo[X.Y.0]alkanone amino acids: a transannular cyclization route for peptide mimic synthesis.

[reaction: see text] Macrocyclic and fused bicyclic dipeptides are complementary motifs for mimicry of different types of beta-turn geometry. Macrocyclic dipeptide mimics have served as precursors for the synthesis of their bicyclic counterparts using electrophilic transannular cyclizations of 9- and 10-membered ring lactams 9-12 to form azabicyclo[4.3.0]- and -[5.3.0]alkanone amino esters 13-16.