Synthesis and optical rotation of the (-)-cannabidiols

N, N-Dimethylformamide-dineopentylacetal mediates the direct formation of (-)-cannabidiol from (+)-trans- or (+)-cis-p-menthadiene-(2,8)-ol-(1) and olivetol. This reaction provides a simple synthetic entry into the series of optically active constituents of haschisch and defines at the same time the chirality of these compounds.