Studies on the Terpenoids and Related Alicyclic Compounds. XXIII. Total Syntheses of (±)-Phomenone, (±)-3-Epiphomenone, (±)-Ligularenolide, and (±)-Furanoligularanone
作者:KOJI YAMAKAWA、MASATO KOBAYASHI、SHOTARO HINATA、TSUYOSHI SATOH
DOI:10.1248/cpb.28.3265
日期:——
Total syntheses of (±)-phomenone (5a), (±)-3-epiphomenone (12), (±)-ligularenolide (27), and (±)-furanoligularanone (34) are described. Dehydration of 6 followed by epoxidation gave the epoxide (8), which was treated with lithium diethylamide to afford the alcohol (9). Epoxidation of 9 gave the α-epoxide (10), which was deketalized to give the diketone (11) Reduction of 11 with NaBH4 gave (±)-3-epiphomenone (12) as a major product. Stereoselective synthesis of (±)-5a starting from 7 was examined. Deketalization of 7 gave the triene-dione (13) which was reduced with NaBH4 to afford the alcohols 14a and 14b. Epoxidation of 3α-ol (14a) gave the epoxide (15), which was treated with lithium diethylamide to afford the diol (16). Epoxidation of 16 with hydrogen peroxide gave (±)-phomenone (5a) regio- and stereoselectively. Treatment of 17 with lithium diisopropylamide followed by condensation with methyl pyruvate gave the hydroxy ester (19), which was treated with acetic acid to give the ketone (24). 24 was thioketalized to give 25, which was treated with p-toluenesulfonic acid to afford the unsaturated lactone (26). 26 was transformed to (±)-ligularenolide (27) and (±)-tetrahydroligularenolide (28) in good yield. Condensation of 17 with acetol pyranyl ether followed by catalytic hydrogenation gave 33. Treatment of 33 with p-toluenesulfonic acid gave (±)-furanoligularanone (34), which was transformed to (±)-3β-furanoligularanol (36).
描述了 (±)-phomenone (5a)、(±)-3-epiphomenone (12)、(±)-ligularenolide (27) 和 (±)-furanoligularanone (34) 的全合成。 6脱水,然后环氧化,得到环氧化物(8),将其用二乙基氨基锂处理,得到醇(9)。 9的环氧化得到α-环氧化物(10),将其去缩酮化得到二酮(11)。用NaBH 4 还原11得到(±)-3-epiphomenone(12)作为主要产物。检查了从7开始的(±)-5a的立体选择性合成。 7的脱缩酮得到三烯二酮(13),将其用NaBH 4 还原得到醇14a和14b。 3α-醇(14a)的环氧化得到环氧化物(15),将其用二乙基氨基锂处理得到二醇(16)。 16 用过氧化氢进行环氧化,区域选择性和立体选择性地生成 (±)-佛蒙酮 (5a)。用二异丙基氨基锂处理17,然后与丙酮酸甲酯缩合,得到羟基酯(19),将其用乙酸处理,得到酮(24)。将24硫酮化得到25,将其用对甲苯磺酸处理得到不饱和内酯(26)。 26以良好的产率转化为(±)-木瓜烯内酯(27)和(±)-四氢木瓜烯内酯(28)。 17与丙酮醇吡喃基醚缩合,随后催化氢化,得到33。用对甲苯磺酸处理33,得到(±)-呋喃寡糖酮(34),将其转化为(±)-3β-呋喃寡糖醇(36)。