A non‐exchange synthesis of tritium‐labelled tetrahydrocannabinols

Tritium‐labelled (‐) ‐Δ1 (6) and (‐) ‐Δ1 ‐tetrahy irocannabinols at a specific activity of 607 mCi/mmole were synthesized by a non‐exchange method. The tritium was introduced by the catalytic reduction with tritium gas of an unsaturated precursor of dimethyl olivetol in hexafluorobenzene as a non‐exchanging solvent. Specifically labelled olivetol was subsequently used in the synthesis of (‐) ‐Δ1 ‐tetrahydrocannabinol by an established method. The radiochemical purity of the product was shown to be greater than 98% by TLC, GLC, liquid scintillation counting and bioassay.