(17% yield) with 93% overall ds starting from the ethyl ketone (S)-10. Key steps are the boron-mediated aldol followed by anti selective reduction, giving the C6C10 stereochemistry, the two direction chain extending double titanium aldol coupling, 16 + 20 → 19, and the TFA promoted double cyclisation/dehydration giving an isomer of Membrenone-C, 21 → 4.
以8个步骤(产率为17%)制备了Membrenone-C的异构体,其总ds为93%,起始于乙基酮(S)-10。关键步骤是
硼介导的醛醇缩合,随后抗选择性还原,给了C 6 C 10立体
化学,所述两个方向扩链双
钛醇醛偶联,16 + 20→19,和TFA促进双环化/脱
水得到的异构体Membrenone-C,21→4。