Analysis of the structures of pre-miR-377 and pre-miR-421 identified a 5'G_G/3'CAC bulge adjacent to pre-miR-377's Dicer site, not found in pre-miR-421 (Fig. ). Mining Inforna identified compound C2 (Fig. ) that bound selectively to this site over a mutated base paired control with a Kd of 4 μM (Fig. ). Thus, linking TGP-377/421 and C2 with appropriate spacing could provide a ligand selective for pre-miR-377 (Figs. and). To provide compounds that can be linked together to allow for modular assembly, derivatives of each of these two modules were synthesized; a carboxylic acid was added to TGP-377/421 (C1-COOH) and an alkyne moiety was added to C2 (C2-Ak). C1-COOEt and C2-Ak bound selectively to their respective RNA targets with Kd's of 0.8 and 1.6 M, respectively, with no measurable affinity to a mutant base paired RNA control (Fig. and). Binding was measured with the acylated acid to mimic the dimerized compound.