Novel synthesis of (-)-trans-Δ9,11-tetrahydrocannabinol

Article abstract of DOI:10.1002/jhet.5570250324

Addition of hydrogen chloride gas to a solution of Δ⁸-tetrahydrocannabinol in dry dichloromethane at -60° in the presence of zinc chloride results in the formation of a higher concentration of 9-α-chlorohexahydrocannabinol (75%) than the thermodynamically more stable 9-β-chlorohexahydrocannabinol (25%). The two isomers can be separated by reverse-phase hplc. Elimination of hydrogen chloride from 9-α-chlorohexahydrocannabinol using potassium t-amylate under anhydrous conditions gives exclusively Δ^9,11-tetrahydrocannabinol in overall yield of 65%.