Synthetic approaches to cis-THC, a promising scaffold in medicinal chemistry

The chemistry of phytocannabinoids has witnessed renewed interest these last decades as a consequence of reduced restrictions, research on the endocannabinoid system and the development of approved therapeutic treatments based on cannabinoids. The medicinal cannabinoid market constitutes a prolific scenario in current medicine. Most studies, however, have focused on only two major components of Cannabis sativa L., namely, cannabidiol (CBD, 2) and (−)-Δ9-trans-tetrahydrocannabinol (Δ9-trans-THC, 6a), the latter being the main psychoactive compound of this plant. The cis-diastereoisomer of Δ9-trans-THC, Δ9-cis-THC, although also present in the same plant, has been less investigated in terms of biological, medicinal and synthetic perspectives. Interestingly, the cis-fused tetrahydrobenzo [c]chromene motif present in Δ9-cis-THC is embedded in many other natural products which also exhibit interesting biological activities such as anticancer, antifungal, and antiparasitic. This review discloses synthetic approaches that have been established towards the cis-fused tetrahydroisochromene system of Δ9-cis-THC.