The Nonchiral Bislactim Diethoxy Ether as a Highly Stereo-Inducing Synthon for Sterically Hindered,γ-Branchedα-Amino Acids: A Practical, Large-Scale Route to an Intermediate of the Novel Renin Inhibitor Aliskiren
作者:Richard Göschke、Stefan Stutz、Walter Heinzelmann、Jürgen Maibaum
DOI:10.1002/hlca.200390235
日期:2003.8
The diastereoselective synthesis of the sterically hindered, γ-branched α-amino acid derivative (2S,4S)-24a and its N-[(tert-butoxy)carbonyl](Boc)-protected alcohol (2S,4S)-19, both key intermediates of a novel class of nonpeptide renin inhibitors such as aliskiren (1), is described. Initially, the analogous methyl ester (2S,4S)-17 was obtained by alkylation of the chiral Schöllkopf dihydropyrazine
位阻γ-支链α-氨基酸衍生物(2 S,4 S)-24a及其受N -[(叔丁氧基)羰基](Boc)保护的醇(2 S,4 S)的非对映选择性合成- 19,一类新的非肽肾素抑制剂,例如阿利吉仑(均为关键中间体1中所述)。最初,类似的甲基酯(2小号,4小号) - 17由手性烷基化得到Schöllkopf二氢吡嗪([R )- 12A与二烷氧基取代的烷基溴([R )- 11A,其与显式高diastereofacial选择性(进行DS ≥98%),得到(2小号,5 - [R,2'小号) - 13A(方案4),其次是温和的酸水解和N- Boc保护(方案5)。相反,建议除了(i)预期的屏蔽作用外,对于(R)-11a与对映异构体(S)-12b的反应,完全缺乏立体控制且收率很低。所述MeOC(6)和的大残基(间的辅助,空间排斥的PR基的C(2)- [R )- 11A在所提出的过渡状态,这将强烈不利于两者的Si和