Scheme 10.

Completion of the total synthesis of (–)-spinosyn A (1). a, DDQ, CH₂Cl₂/pH 7 buffer, 0°C, 4 h, quantitative; b, 30 (2.1 eq), trimethylsilytrifluoromethanesulfonate (30 mol %), CH₂Cl₂, -78°C, 1h, 90–97%; c, guanidinium nitrate, NaOMe, MeOH, CH₂Cl₂, 2 h, 95%; d, SnCl₂, PhSH, Et₃N, THF, 15 min, 92%; e, NaBH₃CN, CH₂O, MeOH, HOAc, NaOAc, 87%; f, thiocarbonyldiimidazole, DMAP, Ph—CH₃, 65°C, 2 h; g, Bu₃SnH (25 eq), AIBN, dioxane, 100°C, 20 min, ≈35% of 1, ≈10% of 39 after HPLC.