Scheme 11.

Completion of the synthesis of trilobolide, nortrilobolide, and thapsivillosin F. a, 1: NaBH₄, MeOH, O°C, 86%, d.r. = 4:1; 2: angelic acid, Et₃N, 2,4,6-trichlorobenzoyl chloride, toluene, 80°C, 76%. b, Tetrabutylammonium fluoride, THF, RT, quantitative c, 1: Isopropenyl acetate, polymer-supported-TsOH, CH₂Cl₂, RT, 68%; 2: HCl (aqueous), MeOH, 40°C. d, (S)-2-Methylbutyric anhydride, DMAP, CH₂Cl₂, RT, 78% over two steps. e, Butyric anhydride, DMAP, CH₂Cl₂, RT, 72% over two steps. f, Senecioic anhydride, DMAP, CH₂Cl₂, RT, 73% over two steps.