Sequential enolate alkylations of (S)-N(1)-methyl-5-methoxy-6-isopropyl-3,6-dihydropyrazin-2-one and (S)-N(1)-p-methoxybenzyl-5-methoxy-6-isopropyl-3,6-dihydropyrazin-2-one proceed with excellent levels of diastereoselectivity (>90% de) affording quaternary α-amino acids in high enantiomeric excess (>98% ee) after deprotection and hydrolysis.
(S)-N(1)-甲基-5-甲氧基-6-异丙基-3,6-二氢
吡嗪-2-酮和(S)-N(1)-对甲氧基苄基-5-甲氧基-6-异丙基-3,6-二氢
吡嗪-2-酮的顺序对映体烷基化反应以极好的非对映选择性(>90% de)进行,以高对映体过量(>90% de)得到季δ-
氨基酸、6- 二氢嗪-2-酮的非对映选择性极佳(de>90%),在脱保护和
水解后可得到对映体过量(ee>98%)的季δ-
氨基酸。