Enantioselective Total Synthesis of (−)-Triptolide, (−)-Triptonide, (+)-Triptophenolide, and (+)-Triptoquinonide
作者:Dan Yang、Xiang-Yang Ye、Ming Xu
DOI:10.1021/jo9919613
日期:2000.4.1
The first enantioselective total synthesis of (-)-triptolide (1), (-)-triptonide (2), (+)-triptophenolide (3), and (+)-triptoquinonide (4) was completed. The key step involves lanthanide triflate-catalyzed oxidative radical cyclization of (+)-8-phenylmenthyl ester 30 mediated by Mn(OAc)3, providing intermediate 31 with good chemical yield (77%) and excellent diastereoselectivity (dr 38:1). (+)-Triptophenolide
(-)-雷公藤甲素(1),(-)-雷公藤酮(2),(+)-雷公藤酚(3)和(+)-雷公醌(4)的第一对映选择性全合成完成。关键步骤涉及镧系元素三氟甲磺酸盐催化由Mn(OAc)3介导的(+)-8-苯基薄荷基酯30的氧化自由基环化,为中间体31提供了良好的化学收率(77%)和出色的非对映选择性(dr 38:1)。然后以> 99%对映体过量(> 99%ee)制备(+)-三苯酚甲醚(5),并容易地转化为天然产物1-4。此外,提出了过渡态模型来解释在手性β-酮酯17(无α-取代基)和17a(有α-氯取代基)的氧化自由基环化反应中观察到的相反的手性诱导作用。