Scheme 2. Total synthesis of spiroviolene (4) starting from known intermediate 18: (a) pyridine (1.2 equiv.), CH₂Cl₂, then SOCl₂ (1.1 equiv.), 0 °C to 40 °C, 12 h, 98%; (b) LiAlH₄ (2.0 equiv.), Et₂O, 0 °C, then 17, Et₂O, 0 °C to 23 °C, 30 min; (c) Ph₃P (1.2 equiv.), imidazole (1.5 equiv.), CH₂Cl₂, 23 °C, 5 min, then I₂ (1.2 equiv.), 0 °C to 23 °C, 1 h, 79% over 2 steps; (d) H₂NNMe₂ (5.0 equiv.), 23 °C, 12 h, 96%; (e) LDA (1.3 equiv.), THF, −78 °C, 15 min, then 18, THF, 0 °C, 2 h, then HMPA (1.3 equiv.), −78 °C, 10 min, then 15 (1.2 equiv.), THF, −78 °C to 23 °C, 15 h, then 1 M HCl/THF (1 : 1), 23 °C, 12 h, 65%; (f) KHMDS (1.3 equiv.), THF, −78 °C to 0 °C, 2 h, then Comins' reagent (1.1 equiv.), THF, −78 °C, 1 h, 87%; (g) Pd(OAc)₂ (10 mol%), Ph₃P (20 mol%), toluene, 23 °C, then Et₃N (2.0 equiv.), 90 °C, 20 h, 88%; (h) H₂ (balloon pressure), Pd/C (10 wt%), EtOH, 23 °C, 30 min, >99%.