Efficient Asymmetric Synthesis of Long-Chain Polyketides Containing up to Ten Contiguous Stereogenic Centres by Double Chain Elongation
作者:Maris Turks、Kelly A. Fairweather、Rosario Scopelliti、Pierre Vogel
DOI:10.1002/ejoc.201100196
日期:2011.6
containing six contiguous stereogenic centres) in which the (Z)-enol isobutyrate units remained intact were obtained. After suitable protection, these were converted into their corresponding lithium (Z)-enolates, which could react with isopropylidene D-glyceraldehyde [(+)-9] to give aldol products that were reduced to various stereodecads (polyketides with ten contiguous stereogenic centres). The disclosed chemistry
2,3-anti-3,4-syn-stereotriad (1Z,2S,3R,4S)-1-ethylidene-2,4-dimethyl-3-[(1S)-1-phenylethoxy]-5-oxopent- 1-基异丁酸酯(-)-8,在一锅操作中由衍生自pentan-3-one和(1E,3Z)-1[(1S)-苯基乙氧基]-的三甲基甲硅烷基(Z)-烯醇醚获得2-methylpenta-1,3-dien-3-ylisobutyrate 通过 SO2 umpolung} 含有乙酮部分,该部分与乙醛发生非对映选择性交叉羟醛反应。在随后的还原之后,获得了(Z)-烯醇异丁酸酯单元保持完整的各种非对映立体六联体(包含六个连续立体中心的聚丙酸酯片段)。经过适当的保护,它们被转化为相应的锂(Z)-烯醇化物,其可与异亚丙基 D-甘油醛 [(+)-9] 反应生成被还原为各种立体异构体(具有十个连续立体中心的聚