Scheme 1.

Formation of the Allo-Cedrane Skeleton^a

^aReagents and conditions: (a) CuSO₄•5H₂O (10 mol%), PhH, 80 °C, 4 h; (b) PhI(OAc)₂ (3.0 equiv), tert-butyl hydroperoxide (70 wt% in H₂O, 4.0 equiv), EtOAc, –20 °C, 12 h, 43% (two steps); (c) SeO₂ (2.2 equiv), 1,4-dioxane, 120 °C, 14 h; (d) NaClO₂ (10.0 equiv), NaH₂PO₄•H₂O (8.0 equiv), 2-methyl-2-butene (25 equiv), t-BuOH:H₂O (1:1), 19 h, 73% (two steps); (e) H₂O₂ (50 wt% in H₂O, 10.0 equiv), NaOH (3.0 M, 4.0 equiv), MeOH, 0 → 23 °C, 7 h, 16% (81% BRSM); (f) TiCl₄ (1.2 equiv), DCE, 50 °C, 4 h, 14%.