Stereoselective synthesis of (−)‐cytoxazone and its unnatural congener (+)‐5‐
<i>epi</i>
‐cytoxazone
作者:Izabel Luzia Miranda、Pedro Henrique Costa Santos、Markus Kohlhoff、Gislaine Aparecida Purgato、Marisa Alves Nogueira Diaz、Gaspar Diaz‐Muñoz
DOI:10.1002/chir.23334
日期:2021.8
respectively, is described. The stereoselective addition of cyanide to an N-Boc protected aminoaldehyde (tert-butyl ((R)-1-(4-methoxyphenyl)-2-oxoethyl)carbamate) (5) constitutes the key step in this approach, producing a mixture of cyanohydrins 6a and b (1,2-anti and 1,2-syn tert-butyl (2-cyano-2-hydroxy-1-(4-methoxyphenyl)ethyl)carbamate) in 89% yield, with reasonable stereoselectivity (1.0:1.8) in favor
描述了从d -4-羟基苯基甘氨酸以 10% 和 16% 的总产率立体选择性合成 (-)-cytoxazone 及其非天然立体异构体 (+)-5- epi -cytoxazone 的有趣方案。氰化物立体选择性加成到N- Boc 保护的氨基醛(叔丁基((R)-1-(4-甲氧基苯基)-2-氧乙基)氨基甲酸酯)(5)构成了该方法的关键步骤,产生了混合物氰醇6a和b(1,2-反和 1,2-合成-丁基(2-氰基-2-羟基-1-(4-甲氧基苯基)乙基)氨基甲酸酯),产率为 89%,具有合理的立体选择性(1.0:1.8),有利于抗Felkin 产物(1,2- syn) . 由该混合物的三个连续步骤的一锅序列产生恶唑烷酮异构体9a和b ((4 R ,5 R )- 和 (4 R ,5 S )-4-(4-甲氧基苯基)-2-氧恶唑烷-5 -羧酸盐)。色谱柱分离和两种前体的酯功能降低导致 (-)-胞嘧啶和 (+)-5-