Conformationally constrained compounds that mimic the secondary structure of reverse-turn regions of biologically active peptides and proteins as well as their prodrugs are disclosed. Such reverse-turn mimetic structures and prodrugs have utility over a wide range of fields, including use as diagnostic and therapeutic agents. Libraries containing the reverse-turn mimetic structures of this invention are also disclosed as well as methods for screening the same to identify biologically active members. The invention also relates to the use of such compounds and prodrugs for inhibiting or treating disorders modulated by Wnt-signaling pathway, such as cancer, especially colorectal cancer, restenosis associated with angioplasty, polycystic kidney disease, aberrant angiogenesis disease, rheumatoid arthritis disease, tuberous sclerosis complex, Alzheimer's disease, excess hair growth or loss, or ulcerative colitis.