Synthesis of Three-Dimensional (Di)Azatricyclododecene Scaffold and Its Application to Peptidomimetics

A novel sp³ carbon-rich tricyclic 3D scaffold-based peptide mimetic compound library was constructed to target protein-protein interactions. Tricyclic framework 7 was synthesized from 9-azabicyclo[3,3,1]nonan-3-one (11) via a gold(I)-catalyzed Conia-ene reaction. The electron-donating group on the pendant alkyne of cyclization precursor 12 b-e was the key to forming 6-endo-dig cyclized product 7 with complete regioselectivity. Using the synthetic strategy for regioselective construction of bridged tricyclic framework 7, a diazatricyclododecene 3D-scaffold 8 a, which enables the introduction of substituents into the scaffold to mimic amino acid side chains, was designed and synthesized. The peptide mimetics 21 a-u were synthesized via step-by-step installation of three substituents on diazatricyclododecene scaffold 8 a. Compounds 21 a-h were synthesized as α-helix peptide mimics of hydrophobic ZZxxZ and ZxxZZ sequences (Z=Leu or Phe) and subjected to cell-based assays: antiproliferative activity, HIF-1 transcriptional activity which is considered to affect cancer malignancy, and antiviral activity against rabies virus. Compound 21 a showed the strongest inhibitory activity of HIF-1 transcriptional activity (IC₅₀ =4.1±0.8 μM), whereas compounds 21 a-g showed antiviral activity with IC₅₀ values of 4.2-12.4 μM, suggesting that the 3D-scaffold 8 a has potential as a versatile peptide mimic skeleton.