Trading N and O. Part 2: Exploiting aziridinium intermediates for the synthesis of β-hydroxy-α-amino acids
作者:Stephen G. Davies、Ai M. Fletcher、Aileen B. Frost、Paul M. Roberts、James E. Thomson
DOI:10.1016/j.tet.2014.06.057
日期:2014.9
The β-hydroxy-α-amino acids (S,S)-allo-threonine, (S,S)-β-hydroxyleucine and a range of aryl substituted (S,S)-β-hydroxyphenylalanines were prepared from the corresponding enantiopure anti-α-hydroxy-β-amino esters via a rearrangement protocol, which proceeds via the intermediacy of the corresponding aziridinium ions. The starting anti-α-hydroxy-β-amino esters were prepared in >99:1 dr using our diastereoselective
β型羟基-α氨基酸(小号,小号) -同种异体-苏氨酸,(小号,小号)-β-hydroxyleucine和取代的(一系列芳基的小号,小号)-β-hydroxyphenylalanines从相应的对映纯的制备抗-α-羟基-β-氨基酯通过重排方案,其通过相应的叠氮鎓离子的中间进行。使用我们的非对映选择性氨基羟基化方法,以> 99:1 dr制备起始的抗-α-羟基-β-氨基酯,从而共轭添加锂(R)-N-苄基-N-(α-甲基苄基)酰胺成α,β-不饱和酯,然后用(-)-樟脑磺酰基氧氮丙啶氧化所得的烯醇化物。随后的抗-α-羟基-β-氨基酯中的羟基的活化促进了叠氮鎓离子的形成[其随着C(2)处构型的反转而进行),以及中间叠氮鎓离子与H 2 O的区域选择性开环[其在C(3)处进行构型转化]给出了相应的抗-β-羟基-α-氨基酯,为单一非对映异构体(> 99:1 dr)。通过顺序的氢解和酯水解对这些底物进行脱保护