Enantioselective synthesis of non-proteinogenic amino acids via metallated bis-lactim ethers of 2,5-diketopiperazines
作者:Ulrich Schöllkopf
DOI:10.1016/s0040-4020(01)91926-x
日期:1983.1
excess = asymmetric induction) of the adduct exceeds 95%. On hydrolysis the adducts are cleaved liberating the chiral auxiliary (used to build up the bis-lactim ether 1) and the target molecules, the optically active amino acid methyl esters of type 8,19,25 or 36. The two amino acid esters are separable either by fractional distillation or (eventually after further hydrolysis to amino acids) by chromatography
2,5-二酮哌嗪的双-内酯醚1包含一个手性诱导中心,一个酸性CH键和两个易于水解的位点。他们用BuLi反应以得到类型的锂化合物4,15,19或32,其具有前手性的C原子。他们很容易添加亲电试剂(例如烷基化剂或羰基化合物),具有非同寻常的非对映异构性。在许多情况下,加合物的减值(de =非对映异构体过量=不对称诱导)超过95%。水解时,加合物被裂解释放出手性助剂(用于构建双内酰胺醚1)和目标分子,即8型旋光氨基酸甲基酯,19,25或36。两种氨基酸酯可通过分馏或(最终在进一步水解成氨基酸后)通过色谱法分离。讨论了过渡状态模型,该模型可以解释异常高的不对称诱导和诱导构型的可预测性。