Computational Evidence for Tunneling and a in the Biosynthesis of Tetrahydrocannabinol.

Quantum tunneling is computed for a reaction sequence that models the conversion of the -quinone methide of cannabigerolic acid to the decarboxylated product (-)--Δ-tetrahydrocannabinol (THC, ). This calculation is the first to evaluate multidimensional tunneling in this sequence. Computations were carried out with POLYRATE and GAUSSRATE using B3LYP/6-31G(d,p) to examine the mechanism of THC formation.