N -Alkyl Carbamoylimidazoles as Versatile Synthons for the Synthesis of Urea-Based PSMA Inhibitors.

We describe N -alkyl carbamoylimidazoles as readily available and highly versatile synthons for synthesizing urea-based prostate-specific membrane antigen (PSMA) inhibitors. Urea formation proceeded in high yields (>80%) at room temperature under aqueous conditions. All novel compounds were tested for their PSMA inhibitory potency in a cell-based radiometric binding assay. Compound 17 was identified as a novel high-affinity PSMA inhibitor (IC 50 = 0.013 μM) suitable for developing an 18 F-labeled radioligand for PET imaging of PSMA in prostate cancer.