Various approaches to the total synthesis of the unusual diterpenoid tropone
(2), discovered in the yew species
Cephalotaxus harringtonia and
C. hainanensis, are described. The rhodium-catalysed
intramolecular cyclopropanation reaction of an aryl ring by means of the
transition metal catalysed reaction of a diazoacetyl function was used to
assemble the 5/7 ring system and to provide a cycloheptatrienyl precursor
to the tropone moiety, e.g.(28)→(29) and (38) →(39). In the most
promising approach, the carbocyclic system was assembled by means of the aldol
reaction (42) →(43) with the newly formed α-hydroxyl being employed
subsequently in the formation of the δ-lactone function of (44). The
tropone ring may be formed from the methoxycycloheptatriene moiety simply by
treatment with mercuric nitrate. Tropone (45) was formed from (44) in this
way, but attempts to convert it into harringtonolide by means of transannular
oxidation based on the 4-hypoiodite failed. The crystal structure of an
intermediate is reported.
从紫杉树种中发现的不同寻常的二萜类化合物 tropone (2) 的全合成方法
(2) 的各种方法。
Cephalotaxus harringtonia 和
C. hainanensis 中发现的。铑催化的
的分子内环丙烷化反应。
过渡金属催化的重氮乙酰官能团分子内环丙烷化反应被用于
通过过渡金属催化重氮乙酰基官能团的分子内环丙烷化反应,组装出 5/7 环系统,并为托品酮分子提供环庚三烯基前体。
例如,(28)→(29) 和 (38) →(39)。在最
在最有前途的方法中,碳环系统是通过醛醇反应(42
反应 (42) →(43) 来组装碳环系统,新形成的 α- 羟基被用于
随后在形成 (44) 的 δ-内酯官能团时使用。内酯
通过硝酸汞处理,甲氧基环庚三烯就可以形成托品酮环。
硝酸汞处理。托品酮(45)就是用这种方法由(44)形成的。
但试图通过基于 4-羟基-4-环氧化反应的跨annular 氧化反应将其转化为 harringtonolide 的尝试并不成功。
氧化法将其转化为哈灵内酯的尝试失败了。报告了一种
中间体的晶体结构。