High-pressure Diels-Alder reactions of 1, 3, 3-trimethyl-2-vinyl-l-cyclohexenes 3a, b, i with substituted 1, 4-benzoquinones afford, in good yield, highly functionalized tricyclic ring systems which are found in many classes of naturally occurring terpenes. Notably, the reactions of 3a are highly regio-and stereoselective. Efficient, formal syntheses of the antitumor diterpenes (*)-taxodione and (*)-royleanone are reported, which demonstrate ...
