Synthesis of Bicyclic Pyroglutamic Acid Featuring the Ugi Reaction and a Unique Stereoisomerization at the Angular Position by Grob Fragmentation Followed by a Transannular Ketene [2+2] Cycloaddition Reaction - Vamos, Mitchell; Ozboya, Kerem; Kobayashi, Yoshihisa (Synlett, 2007)