Catalytic asymmetric Tsuji–Trost α−benzylation reaction of N-unprotected amino acids and benzyl alcohol derivatives

• Published in: Nature communications Vol. 13; no. 1; pp. 2509 - 11
• Main Authors: Liu, Jian-Hua, Wen, Wei, Liao, Jian, Shen, Qi-Wen, Lin, Yao, Wu, Zhu-Lian, Cai, Tian, Guo, Qi-Xiang
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06.05.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 639/638/403/933; 639/638/77/883; Alcohol; Alcohols; Aldehydes; Amino Acids; Asymmetry; Benzyl Alcohol; Benzyl Alcohols - chemistry; Catalysis; Catalysts; Esters; Humanities and Social Sciences; Lewis acid; multidisciplinary; Natural products; Nucleophiles; Optical activity; Palladium; Palladium - chemistry; Reagents; Science; Science (multidisciplinary); Somatostatin; Stereoselectivity
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-30277-9

Catalytic asymmetric Tsuji–Trost benzylation is a promising strategy for the preparation of chiral benzylic compounds. However, only a few such transformations with both good yields and enantioselectivities have been achieved since this reaction was first reported in 1992, and its use in current organic synthesis is restricted. In this work, we use N-unprotected amino acid esters as nucleophiles in reactions with benzyl alcohol derivatives. A ternary catalyst comprising a chiral aldehyde, a palladium species, and a Lewis acid is used to promote the reaction. Both mono- and polycyclic benzyl alcohols are excellent benzylation reagents. Various unnatural optically active α-benzyl amino acids are produced in good-to-excellent yields and with good-to-excellent enantioselectivities. This catalytic asymmetric method is used for the formal synthesis of two somatostatin mimetics and the proposed structure of natural product hypoestestatin 1. A mechanism that plausibly explains the stereoselective control is proposed. The catalytic asymmetric benzylations of prochiral nucleophiles are very limited. Here, the authors disclose an asymmetric α−benzylation of N-unprotected amino acids with benzyl alcohol derivatives by a chiral aldehyde-involved catalytic system.