A number of dual domain acyclic and macrocyclic pipecolyl a-ketoamide derivatives were prepared which possess the elements of previously described high-affinity FKBP binding domains as well as simplified mimics of the FK506 effector domain, a critical feature for immunosuppressive activity of the FKBP12-FK506 complex. Compounds of this study exhibited a range of FKBP cis-tram peptidyl-pmlyl isomerase inhibitory activities but no activity in a splenocyte mitogenesis assay for immunosuppmsslon.