The synthesis of polyethers 32 and 33 from tricyclic bis-spiroacetal aldehyde 27 and E-bromide 7 are described. A key step in the synthetic strategy involved the oxidative cyclisation of a bicyclic hydroxyspiroacetal 22a,b to a cis bis-spiroacetal unit, which resulted in preferential formation of cis aldehyde 27. A Barbier reaction of bromide 7 and tricyclic aldehyde 27 then afforded erythro alcohol 28 which after epoxidation and acid catalysed cyclisation completed the synthesis of polyethers 32 and 33 providing an effective framework on which to synthesise the B,C,D and E rings of antibiotic CP44,161 1.
描述了由
三环双螺
缩醛27和E-
溴化物7合成聚醚32和33。合成策略的关键步骤涉及双环羟基螺
缩醛 22a,b
氧化环化为顺式双螺
缩醛单元,从而优先形成顺式醛 27。
溴化物 7 和
三环醛 27 发生巴比耶反应,得到赤醇28 在环
氧化和酸催化环化后完成了聚醚 32 和 33 的合成,为合成
抗生素 CP44,161 1 的 B、C、D 和 E 环提供了有效的框架。