High-pressure Diels-Alder cycloadditions between benzylideneacetones and 1,3-butadienes: application to the synthesis of (R,R)-(-)- and (S,S)-(+)-[[DELTA].sup.8]-tetrahydrocannabinol

High-pressure Diels-Alder reactions of various alkoxy/alkyl-substituted benzylideneacetones with methyl-1,3-butadienes are described. The application to the synthesis of [[DELTA].sup.8]-trans-THC in both enantiomeric pure forms is based on the resolution of selected cycloadduct by the SAMP-hydrazone method.