The chemical transformations of α-santonin (1), a C-6 lactonized eudesmanolide, into C-8 lactonized eudesmanolides, telekin (4) and pinnatifidin (5), are described. Desulfurization of the thio-ketal (8), derived from tetrahydroyomogin (7), with Raney Ni gave the 4-ene (10), which was converted into the α-epoxide (12). Ring-opening of the epoxy ring with LiNEt2 afforded the allyl alcohol (13). Phenylselenenylation of 13 gave the selenide (14), and oxidative elimination then gave telekin (4). Bromination of 3-oxoeudesman-8, 13-olide (18) gave the 2α-bromo-3-ketone (19). Reduction of 19 with NaBH4 gave bromohydrins (20 and 21), which were treated with Zn dust to afford the olefin (22). Treatment of 22 with N-bromosuccinimide afforded the 2-hydroxy-3-bromide (24), which was oxidized to give the 2-oxo-3-bromide (25). Dehydrobromination of 25 afforded the 2-oxo-3-ene (26). Pinnatifidin (5) was synthesized from 26 by phenylselenenylation and deselenoxylation procedures.
描述了α-santonin(1),一种C-6
乳酸化的eudesmanolide,转化为C-8
乳酸化的eudesmanolides,telekin(4)和pinnatifidin(5)的
化学转变。从四氢yomogin(7)衍生的
硫酮(8)经过Raney
镍的脱
硫反应得到4-烯(10),进一步转化为α-
环氧化物(12)。用LiNEt2开环环氧环得到烯醇(13)。对13进行苯基
硒化得到
硒化物(14),随后通过氧化消除反应得到telekin(4)。对3-氧代eudesman-8, 13-内酯(18)进行
溴化反应得到2α-
溴-3-酮(19)。用NaBH4还原19得到
溴醇(20和21),再用
锌粉处理得到烯烃(22)。对22进行N-
溴琥珀
酰亚胺处理得到2-羟基-3-
溴化物(24),接着氧化得到2-氧-3-
溴化物(25)。对25进行脱
溴化反应得到2-氧-3-烯(26)。通过苯基
硒化和去
硒醇化过程合成pinnatifidin(5)。