Enantioselective synthesis of β-amino acids. Part 11: Diastereoselective alkylation of chiral derivatives of β-aminopropionic acid containing the α-phenethyl group
作者:Vı́ctor Manuel Gutiérrez-Garcı́a、Heraclio López-Ruiz、Gloria Reyes-Rangel、Eusebio Juaristi
DOI:10.1016/s0040-4020(01)00540-3
日期:2001.7
particular, the diastereoselectivity of alkylation of (R,R)-2-Li enolate showed substantial stereoinduction by the bis[α-phenylethyl]amide auxiliary, leading to 80% ds in the methylation reaction. No appreciable effect upon diastereoselectivity was observed by the presence of additives (LiCl, HMPA, DMPU) in the reaction. On the other hand, stereoinduction by the α-phenylethylamino group in the methylation
研究了β-氨基丙酸的几种新颖的手性衍生物,它们是对映纯α-取代的β-氨基酸的潜在有用的前体。特别地,(R,R)-2- Li烯醇盐的烷基化的非对映选择性显示了双[α-苯基乙基]酰胺助剂的大量立体诱导,导致甲基化反应中的ds为80%。通过在反应中存在添加剂(LiCl,HMPA,DMPU),未观察到对非对映选择性的明显影响。另一方面,α-苯基乙基氨基在烯醇酯(S)-3的甲基化中的立体诱导-Li在标准条件下(THF,-78°C)较低(65%ds),但在3当量的存在下提高到81%ds。HMPA作为助溶剂。“匹配的”和“不匹配的”衍生物(R,R,S)-11和(R,R,R)-11分别通过其相应的烯醇锂被甲基化。观察到的非对映选择性通常遵循基于双立体诱导的预期趋势。因此,在匹配的异构体(R,R,S)-11 -Li的甲基化中,非对映选择性达到89%ds 。