The first enantioselective approach to 13a-methyl-14-hydroxyphenanthroindolizidine alkaloids was achieved in six linear steps from phenanthryl alcohol and features a highly substrate-dependent Parham cycloacylation and Seebach's enantioselective alkylation as the key steps. The route is concise, protecting-group free, provides access to all stereoisomers, and works on a gram scale. In addition to the putative structure of hypoestestatin 2, the other three stereoisomers and two structurally related analogues were synthesized, none of which shows identical NMR spectra to those reported for natural hypoestestatin 2, which indicates that further structure revision is required.

中文翻译：

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13a-Methyl-14-hydroxyphenanthroindolizidine 生物碱的第一种对映选择性方法 - Hypoestestatin 2 的合成研究

第一个对 1​​3a-甲基-14-羟基菲并吲哚里西啶生物碱的对映选择性方法是从菲醇的六个线性步骤中实现的，并以高度依赖底物的 Parham 环酰化和 Seebach 的对映选择性烷基化为关键步骤。该路线简洁、无保护基团、提供对所有立体异构体的访问，并且在克级规模上起作用。除了hypoestatin 2的推定结构外，还合成了其他三种立体异构体和两种结构相关的类似物，没有一个显示与天然hypoestatin 2报道的核磁共振谱相同，这表明需要进一步的结构修正。