A Total Synthesis of Galbonolide B

An ester enolate rearrangement/silicon mediated fragmentation cascade was used to convert 7 and 8 into the alcohol 9.
The alcohol 9 was converted into the allylic alcohol 12 and
then to the ester 14. A further ester enolate rearrangement
furnished the stereochemical identity of galbonolide B 1.
Base mediated macrocyclization of the acetate ester 16
followed by base mediated alkylation and acetal deprotection
gave galbonolide B 1.

本研究采用酯烯醇重排（ester enolate rearrangement）/硅介导碎裂级联反应，将化合物7与8转化为醇9。将醇9依次转化为烯丙醇（allylic alcohol）12，随后得到酯14。进一步的酯烯醇重排反应确立了黑没药内酯B（galbonolide B）1的立体化学结构。乙酸酯16经碱介导的大环化（macrocyclization）反应，再经碱介导的烷基化与缩醛脱保护（acetal deprotection）步骤，最终得到黑没药内酯B 1。