O-Methyl Phytocannabinoids: Semi-synthesis, Analysis in Cannabis Flowerheads, and Biological Activity

A general protocol for the selective mono-O-methylation of resorcinyl phytocannabinoids was developed. The availability of semisynthetic monomethyl analogues of cannabigerol, cannabidiol, and cannabidivarin (1a-3a, respectively) made it possible to quantify these minor phytocannabinoids in about 40 different chemotypes of fiber hemp. No chemotype significantly accumulated mono-O-methyl cannabidiol (2b) or its lower homologue (3b), while at least three chemotypes containing consistent amounts (≥ 400 mg/kg) of O-methylcannabigerol (1b) were identified. O-Methylation of alkyl phytocannabinoids (1b-3b) does not significantly change the activity on peroxisome proliferator-activated receptors in contrast to what was reported for phenethyl analogues.