Cannabinoid metabolites have been reported to be more potent than the parent compounds. Among them, Ajulemic acid (AJA) is a synthetic analogue of Δ9-THC-11-oic which will be a good template structure for discovery of more potent analogues. Herein, we optimized the key allylic oxidation step to introduce the C-11 hydroxy group with high yield. And a series of compounds were prepared with this condition applied including HU-210, 11-Nor-Δ8-Tetrahydrocannabinol-9-carboxylic acid and Δ9-THC-COOH.