Total synthesis of the revised structures of α- and β-diversonolic esters (4 and 5). Reagents and conditions: a) MeLi (1.6 M in ether, 1.1 equiv), ether, −78 °C, 15 min; then tBuLi (1.7 M in pentane, 2.2 equiv), −78 °C, 15 min; then 20 (1.5 equiv), −78→ −40 °C, 40 min; b) IBX (2.0 equiv), DMSO, 23°C, 1 h, 45 % over two steps; c) 1.0 M HClO4 aq./THF (1:1), 50 °C, 2 h, 80 %, 4:5 ca. 1:3 dr.