Tritiation of nonpeptide substance P antagonist CP-96,345 and its azido analogue. Synthetic and characterization details

CP-96,345 (1) was the first nonpeptide antagonist discovered for the SP receptor and [3H] CP-96,345 was required to study the mechanism of receptor action. The radioligand was prepared at high specific activity by catalytic dehalogenation of a dibrominated precursor and this same approach was also used to prepare a photoaffinity analogue.