Chiral Auxiliaries for Asymmetric Radical Cyclization Reactions: Application to the Enantioselective Synthesis of (+)-Triptocallol
作者:Dan Yang、Ming Xu、Mai-Ying Bian
DOI:10.1021/ol0068243
日期:2001.1.1
[figure: see text] A series of epimeric 8-aryl menthyl derivatives 5a-d and 6a-l, prepared from the same chiral source (R)-pulegone, were employed as chiral auxiliaries in the asymmetric radical cyclization reactions of beta-keto esters mediated by Mn(OAc)3. Chiral precursors 8c and 8d provided the cyclization products 10c and 10d, respectively, as single isomers (dr > 99:1), whereas the cyclization
[图:见正文]由相同的手性来源(R)-普勒高尼制备的一系列差向异构的8-芳基薄荷基衍生物5a-d和6a-1被用作β-酮的不对称自由基环化反应中的手性助剂。由Mn(OAc)3介导的酯。手性前体8c和8d分别提供了环化产物10c和10d,为单一异构体(dr> 99:1),而前体9k的环化得到13k具有良好的立体选择性(dr = 24:1)。非对映异构体13e被用作90%ee中对(+)-雷公藤酚的对映选择性合成的关键中间体。