Enaminone-based mimics of extended and hydrophilic α-helices

The pursuit of structural and functional mimics of α-helices has been a fruitful area of research over the past decade. The evolution of scaffold design has led to the progression from molecules that are difficult to synthesize, solubilize, and derivatize to structural motifs that can be easily assembled, elongated, and diversified. Other important elongated helices include leucine zippers, structural motifs in the DNA-binding region of transcription factor proteins. A major goal in the field of helix mimicry is the development of scaffolds that can be easily elongated and functionalized for use in probing the nature of these important biological molecules. The enaminone synthetic route is also amenable to ready elongation. The first series of extended mimics was based on an amide-terminated scaffold. Complementary packing of the isopropyl side groups is evident in the crystal structure of compound 17, which contains two enaminone molecules in each asymmetric unit.