Asymmetric Synthesis of<b><i>β</i></b>-Amino Acids by Addition of Chiral Enolates to Nitrones via<b><i>N</i></b>-Acyloxyiminium Ions
作者:Toru Kawakami、Hiroaki Ohtake、Hiroaki Arakawa、Takahiro Okachi、Yasushi Imada、Shun-Ichi Murahashi
DOI:10.1246/bcsj.73.2423
日期:2000.11
both boron and titanium(IV) enolates bearing chiral auxiliaries. Reversal of diastereoselectivity was observed by the reactions of the boron and titanium(IV) enolates. Using these reactions, all of the four stereoisomers of α-methyl-β-phenylalanines, for example, can be prepared highly diastereoselectively. Cyclic N-acyloxyiminium ions are useful for the asymmetric synthesis of pyrrolidine and piperidine
N-Acyloxyiminium 离子是由硝酮与酰卤反应生成的,是高活性物质,可与多种亲核试剂发生轻松反应,如烯酮甲硅烷基缩醛、钛 (IV) 和硼烯醇化物、氢化和烯丙基锡 (IV) ) 试剂和炔基钛 (IV) 试剂,得到 α-取代的胺衍生物。光学活性 β-氨基酸可以通过 N-酰氧基亚胺鎓离子与带有手性助剂的硼和钛 (IV) 烯醇反应制备。通过硼和钛 (IV) 烯醇化物的反应观察到非对映选择性的逆转。例如,使用这些反应,可以高度非对映选择性地制备 α-甲基-β-苯丙氨酸的所有四种立体异构体。环状 N-酰氧基亚胺离子可用于吡咯烷和哌啶生物碱的不对称合成;