Intramolecular nitrone dipolar cycloadditions: control of regioselectivity and synthesis of naturally-occurring spirocyclic alkaloids
作者:Alastair J. Hodges、Joseph P. Adams、Andrew D. Bond、Andrew B. Holmes、Neil J. Press、Stephen D. Roughley、John H. Ryan、Simon Saubern、Catherine J. Smith、Michael D. Turnbull、Annabella F. Newton
DOI:10.1039/c2ob26333e
日期:——
The intramolecular nitrone dipolar cycloaddition of in situ-generated nitrones such as compound 26 has been used for the synthesis of cyclic isoxazolidines 27 and 29. The regioselectivity of the intramolecular cycloaddition depends on the nature of the terminal substituent on the dipolarophile. The influence of the substituent on the regioselectivity of the cycloaddition has been examined using several
原位生成的硝酮如化合物26的分子内硝基偶极环加成已用于合成环状异恶唑烷27和29。分子内环加成的区域选择性取决于亲双亲物上末端取代基的性质。已经使用几种模型系统和两种形成硝酮的方法研究了取代基对环加成反应的区域选择性的影响。这些研究表明,在热力学控制的条件下,氰基取代基在促进6,6,5-环稠合加合物27的形成中起特殊作用。该环加成物的效用57(见方案12)作为天然存在的histrionicotoxins的前体是由合成所示的三个“非对称的”(即,与每个侧链带有不同官能基团)的histrionicotoxin家族HTX-259A,HTX-285C和HTX-285E(成员2,3和4)。