Summary The synthesis of a new ( -)-ds-6a, 10s-tvans-tetrahydrocannabinol analogue, containing a N-mcthyl-3-propyl-pyrrol1din-3-yl side-chain, is reported.

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.

Acids, such as p‐toluenesulfonic acid, mediate the direct formation of optically active (−)‐Δ6,1‐3,4‐trans‐tetrahydrocannabinol from (+)‐cis‐or (+)‐trans‐p‐menthadiene‐(2,8)‐ol‐(1) and olivetol.

Successive treatment of (−)‐Δ6,1‐3,4‐trans‐tetrahydrocannabinol with hydrochloric acid/zinc chloride and potassium‐t‐amylate gives (−)‐Δ1,2‐3,4‐trans‐tetrahydrocannabinol in quantitative yield.

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