Synthetic Strategies for Rare Cannabinoids Derived from Cannabis sativa

Efficient syntheses of eight key cannabinoids were established and optimized. Predominant cannabinoids such as cannabigerol (CBG-C5) and cannabidiol (CBD-C5) were prepared from olivetol via regioselective condensation. Further treatments of CBD led to Δ9-tetrahydrocannabinol (THC-C5), Δ8-iso-tetrahydrocannabinol (iso-THC-C5), and cannabinol (CBN-C5). Alternatively, a [3 + 3] annulation between olivetol and citral yielded the minor cannabinoid cannabichromene (CBC-C5), which was converted into two very rare polycycles, cannabicyclol (CBL-C5) and cannabicitran (CBT-C5), in a one-pot reaction. Finally, all eight syntheses were extended by utilizing resorcinol and two phenolic analogues, achieving a cannabinoid group with more than 30 compounds through a facile synthesis strategy.