Synthesis and characterization of optically pure [ 3 H](+)azidophenazocine ([ 3 H](+)‐AZPH), a novel photoaffinity label for sigma receptors

[ 3 H](+)‐cis‐N‐(2‐(4‐Azidophenyl)ethyl) ‐2′‐hydroxy‐2,6‐dimethyl‐6,7‐benzomorphan ([ 3 H] 1 ) ([ 3 H](+)‐AZPH), a novel high affinity and high selectivity benzomorphan based photoaffinity label for sigma receptors was synthesized in 4 steps starting with optically pure (+)‐normetazocine and 2‐( p ‐azidophenyl)ethyl methanesulfonate ester. Condensation of these compounds in DMF in the presence of NaHCO 3 afforded 1 in 77% yield. The tritiation precursor (+)‐cis‐N‐(2‐(4‐azidophenyl)ethyl)‐2′‐hydroxy‐1′,3′‐dibromo‐2,6‐dimethyl‐6,7‐ benzomorphan ( 4 ) for medium specific activity [ 3 H] 1 was obtained in 96% yield by bromination of 1 with 2 equivalents of bromine. The sequence of catalytic tritiation of 4 , treatment of the resulting aniline ([ 3 H] 5 ) (13.5% radiochemical yield, specific activity 22.9 Ci/mmol) with nitrous acid followed by sodium azide afforded the target compound in 78% chemical yield.