A series of phenylpiperazine derivatives were synthesized and evaluated for their neuropeptide Y (NPY) Y5 receptor antagonistic activities. The benzindane portion of 2 was replaced by 1-phenylpiperazine, resulting in novel urea derivative 3f. Subsequent optimization of the phenylpiperazine template by substitution of the phenyl moiety resulted in a series of (2-methanesulfonamidephenyl) piperazine derivatives that showed potent ...