Photoactivatable analogues of a Substance P non-peptidic antagonist, for probing the antagonist binding site of the NK1 receptor

(+)-(2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine (CP-99,994) binds with high affinity (pKi 9.6) to the human NK1 receptor. Racemic analogues of CP-99,994 containing either benzoyl or diazirinyl moieties also bind with high affinity (pKi 9.4 and 9.1 respectively). These analogues are of tremendous potential for mapping the antagonist binding site of the NK1 receptor.