Haschisch‐Inhaltsstoffe. 7. Mitteilung . Synthese von (−)‐11‐Hydroxy‐Δ 8 ‐6a, 10a‐ trans ‐Tetrahydrocannabinol

When (−)‐Δ 8 ‐6a, 10a‐ trans ‐THC (THC = Tetrahydrocannabinol), in the form of its diacetate, was irradiated in the presence of oxygen and a sensitizer, followed by reduction with NaBH 4 , three allylic alcohols were formed: (−)‐8α‐and (−)‐8β‐hydroxy‐Δ 9,11 ‐THC (proportion 3:1) and (−)‐9α‐hydroxy‐Δ 7,8 ‐THC. Acetylation of the epimeric 8‐hydroxy‐compounds with Ac 2 O/pyridine gave the corresponding diacetates. When (−)‐Δ 8 ‐6a, 10a‐ trans ‐THC, in the form of its tetrahydropyranyl derivative, was heated with m ‐chloroperbenzoic acid, the two epimeric 8,9‐epoxides were formed in equal amounts. These compounds, on treatment with butyllithium, afforded (−)‐8α‐ and (−)‐8β‐hydroxy‐Δ 9,11 ‐ 6a, 10a‐ trans ‐THC‐tetrahydropyranylether. After removing the protecting group and treatment with Ac 2 O/pyridine the same diacetates, as formed by photooxygenation of (−)‐Δ 8 ‐THC‐acetate, were obtained as a 1:1‐mixture. On heating these epimeric diacetates to 290° they underwent allylic rearrangement to (−)‐11‐acetoxy‐Δ 8 ‐THC‐acetate. From this (−)‐11‐hydroxy‐Δ 8 ‐6a, 10a‐ trans ‐THC was obtained by treatment with LiAlH 4 .