Scheme 12.
(A) Synthesis of phyllocladanol (21) features a Lewis acid-catalyzed formal intramolecular [3 + 2] cross-cycloaddition of cyclopropane 1,1-diesters with alkenes [68]. (B) (5,6-Dihydro-1,4-dithiin-2-yl)methanol 151 used as a versatile allyl-cation equivalent in [3 + 2] cycloaddition in the synthesis of (±)-cuparene (13) [69].
