1978 年 26 巻 12 号 p. 3704-3714
Total syntheses of (±)-furanoeremophilane (34), (±)-furanoligularane (37), (±)-9, 10-dehydrofuranoeremophilane (32), (±)-ligularone (1), (±)-3β-hydroxyfuranoeremophilane (25), and (±)-3β-furanoligularanol (31) are described. Reduction of cis-annulated 6, 9-dioxo-3-ketal (9) with NaBH4 gave ketols (10a and 11a). 11a was desketalized and subjected to selective reduction with P-I2 to give 3, 6-diketone (13), which was already converted into (±)-1. Reduction of 3, 9-dioxo-6α-ol (14), derived from 10a, with P-I2 afforded a mixture of 17-20. Both 3, 9-diketones (18 and 19) were converted into 3, 9-diol acetates (24b and 30b), respectively. The Birch reductions were effected for deacetoxylation of α'-acetoxy-α-substituted furan, e.g. (26) and the results are shown in Table I. Reductive deacetoxylation of 24b and 30b by the Birch procedure gave (±)-25 and (±)-31, respectively. (±)-Hydroxyfuranoeremophilane (6), derived from 18, was treated with POCL3-pyridine to give (±)-32. Reductive deacetoxylation of acetate (33) by the Birch procedure gave (±)-34. trans-Annulated 3, 9-diketone (19) was derived to the acetate (36b), which was converted by the Birch procedure into (±)-37.
