AbstractN‐Boc‐protected α‐amino acids are synthesized in two steps from linear or branched carboxylic acid feedstocks. In the first step, the carboxylic acid is coupled with tert‐butyl aminocarbonate (BocNHOH) to generate azanyl ester (acyloxycarbamate) RCO2NHBoc. In the second step, this azanyl ester undergoes a stereocontrolled iron‐catalyzed 1,3‐nitrogen migration to generate the N‐Boc‐protected non‐racemic α‐amino acid. This straightforward protocol is applicable to the catalytic asymmetric synthesis of α‐monosubstituted α‐amino acids with aryl, alkenyl, and alkyl side chains. Furthermore, α,α‐disubstituted α‐amino acids are accessible in an enantioconvergent fashion from racemic carboxylic acids. The new method is also advantageous for the synthesis of α‐deuterated α‐amino acids. N‐Boc‐protected α‐amino acids synthesized using this two‐step protocol are ready‐to‐use building blocks.
摘要N-叔丁氧羰基保护的α-氨基酸由线性或支链羧酸原料分两步合成。第一步,羧酸与氨基甲酸叔丁酯(BocNHOH)偶联生成偶氮酯(酰氧基氨基甲酸酯)RCO2NHBoc。在第二步中,该氮杂环戊烯酯经过立体控制的铁催化 1,3 氮迁移,生成 N-Boc 保护的非亲和 α-氨基酸。这种直接的方案适用于催化不对称合成带有芳基、烯基和烷基侧链的 α-单取代 α-氨基酸。此外,α,α-二取代的α-氨基酸可以从外消旋羧酸中以对映转化的方式获得。这种新方法还有利于合成α-氚代α-氨基酸。采用这种两步法合成的 N-Boc 保护的 α- 氨基酸是即用型构筑模块。