Abstract
The thesis consists of two parts: the first part describes the total syntheses of eremophilanoid natural products: (±)-eremopetasidione (8), (±)-3β-angeloyloxyfuranoeremophilane (25) and (±)-3β-methacryloyl- oxyfuranoeremophilane (26). In the second part describes the total syntheses of sesterpenoid acids: 102 and 103. The cis-decalin 79 was obtained from 2-methoxy-4-methylphenol (77) via a sequence of reactions involving intermolecular Diels-Alder reaction of masked o-benzoquinone derived from 77 and ethyl vinyl ketone, silyl enol ether formation and Cope rearrangement. Hydrolysis of compound 79 with 10% aqueous oxalic acid followed by reduction and deketalization furnished key intermediate 73. Selective α-acetylation of compound 73 and DDQ oxidation accomplished the total synthesis of (±)-eremopetasidione (8). Aldol reaction of compound 73 with acetonyl tetrahydropyranyl ether (68) followed by treatment with acidic aqueous tetrahydrofuran provided 3β-hydroxyfuranoeremophilane (93). Finally, esterification of furan 93 was effected with angeloyl chloride and methacryloyl chloride to accomplish the total syntheses of (±)-3β-angeloyloxyfuranoeremophilane (25) and (±)-3β-methacryloyl- oxyfuranoeremophilane (26), respectively. The tricyclic compound 172 was obtained via intramolecular Diels-Alder reaction of masked o-benzoquinone, produced in situ from oxidation of 2-methoxy-4-methylphenol (77) with DAIB in the presence of allyl alcohol, followed by addition and anionic oxy-Cope rearrangement. Hydrogenation of compound 172 and deketalization furnished cis-decalin 176. Transformation of compound 176 into compound 181 was achieved in 4 steps. Finally, the total synthesis of sesterpenoid acid 102 was accomplished by means of Horner-Emmons reaction and saponification. Compound 102 was isomerized into 103 when treated with p-toluenesulfonic acid in dichloromethane. However, our 1H and 13C NMR spectra of 102 and 103 are found to be somewhat different from those of natural products.