The enantioselective synthesis of mono-TBS protected, double allylic alcohols 5 (ee = 90-94%) employing the SAMP/RAMP-hydrazone methodology is reported. Acetonide protected, α-substituted ketodiols 2 were synthesized from SAMP-hydrazone 1 which were converted to exocyclic olefins 3 by a racemization-free Wittig reaction. Acidic acetal cleavage to 4 followed by selective TBS protection furnished title compounds 5 in very good overall yields and enantiomeric excesses.
报告采用
SAMP/
RAMP- 酰腙方法,对映选择性地合成了单-TBS 保护的双
烯丙醇 5(ee = 90-94%)。 由
SAMP 酰腙 1 合成了受乙酮保护的δ-取代酮二醇 2,并通过无外消旋化的 Wittig 反应将其转化为外环烯烃 3。 酸性
乙缩醛裂解成 4,然后选择性 TBS 保护,得到了标题化合物 5,总产率和对映体过量率都非常高。