Preparation of [7,8,19,20 - 3H] naloxone of high specific activity

The preparation of [7,8,19,10 - 3H] naloxone (3c) is described starting from noroxymorphone 2. After saturation of the 7,8 double bond with tritium gas (using PdO catalyst) the resulting compound was propargylated under very mild conditions for a short time with propargyl bromide to give N-propargyl, [7,8,-3H] dihydro-noroxymorphone at 925 GBq:nmole (25,1 Ci/nmole) specific activity. This material was tritiated again in the presence of Lindlar catalyst in dimethylformamide (DMF) under carefully controlled conditions. Pure, tritiated naloxone with a specific activity of 3,09 TBq/nmole (83,7 Ci/nmole) was isolated from the reaction mixture by TLC in one dimension using a two-step developing system. (author)