New Templates for Syntheses of Ring-Fused, C<SUP>10</SUP> β-Turn Peptidomimetics Leading to the First Reported Small-Molecule Mimic of Neurotrophin-3

β-Turn peptidomimetics <BO>1</BO> were designed to mimic hot spots of neurotrophin-3 (NT-3) and others. Solid-phase syntheses of these were developed, though limitations were encountered with scale-up. Consequently, an alternative design with <BO>2</BO> was investigated. <BO>1</BO> and <BO>2</BO> favored distorted type I β-turn conformations in solution. It was found that peptidomimetic <BO>2b</BO> has NT-3-like neurotrophic activity in cell survival assays, selectively binds the NT-3 receptor TrkC, and induces the tyrosine phosphorylation of the TrkC receptor.