Asymmetric, stereocontrolled total synthesis of (+) and (−)-spirotryprostatin B via a diastereoselective azomethine ylide [1,3]-dipolar cycloaddition reaction
作者:Paul R Sebahar、Hiroyuki Osada、Takeo Usui、Robert M Williams
DOI:10.1016/s0040-4020(02)00630-0
日期:2002.8
The asymmetric, stereocontrolled total syntheses of (+) and (−)-spirotryprostatin B (2) are described. Formation of the core pyrrolidine ring was accomplished via a diastereoselective asymmetric [1,3]-dipolar cycloaddition reaction. Addition of 3-methoxy-3-methylbutanal to (5R,6S)-2,3,5,6-tetrahydro-5,6-diphenyl-1,4-oxazin-2-one generated an azomethine ylide that reacted with ethyl oxindolylidene acetate
描述了(+)和(-)-螺旋前列腺素B(2)的不对称,立体控制的总合成。核心吡咯烷环的形成是通过非对映选择性不对称[1,3]-偶极环加成反应完成的。在(5 R,6 S)-2,3,5,6-四氢-5,6-二苯基-1,4-恶嗪-2-one中添加3-甲氧基-3-甲基丁醛可生成与乙氧基二亚甲基乙酸乙烯酯可提供所需的环加合物(11),该环加合物具有天然螺菌素前列腺素B的正确相对和绝对立体化学。关键的偶极环加成反应设置了四个连续的立体中心。恶嗪酮的还原裂解生成螺-羟吲哚吡咯烷(19),它与d-脯氨酸苄基酯偶联并环化成五环二酮哌嗪22。Barton修改的Hunsdiecker规程实现了氧化脱羧反应,生成了12- Epi- spirotryprostatin B(30)。d-脯氨酸立体异构中心与甲醇钠的热力学差向异构化产生螺环前列腺素B作为主要产物。天然产物对映体前列腺素B的对映体由(5 S,6 R)-2,3