Bronsted Acid Catalyzed Asymmetric Synthesis of cis-Tetrahydrocannabinoids

We report herein the catalytic asymmetric cyclization of 1-aryl terpenols to afford enantiomerically highly enriched Delta(9)-cis-tetrahydrocannabinoid scaffolds in a single step. As powerful chiral catalysts strongly acidic imidodiphosphorimidates (IDPis) have been identified which furnish the products with good yields and excellent enantioselectivity. Upon MOM-deprotection some naturally occurring cannabimimetica such as (-)-cis-Delta(9)-tetrahydrocannabinol and (-)-perrottetinene as well as some unnatural analogues were made accessible along a merely 3-step biomimetic sequence (MOM=methoxymethyl).