Natural amino acids are essential for construction of peptides and proteins, control of vital function and basis of life-support. On the other hand, unnatural amino acids are used as intermediates of medicine and chiral building blocks, and sometimes possess physiological activities by themselves. Various synthetic methods for the synthesis of unnatural amino acids have been reported such as Strecker reaction and phase-transfer catalytic reaction but there are a lot of amino acids which have not been reported or are difficult to synthesize. We have comprehensively studied iridium catalyzed C-H bond activation and rhodium catalyzed [2+2+2] cycloaddition for the construction of various practical skeletons. In particular, we focused 4-substituted tryptophan (Trp) derivatives and aminoindan carboxylic acid (Aic) derivatives as α-amino acids, and 4-substituted γ-amino acids. Here, we report new approaches to the synthesis of their amino acids using our originally developed reaction. We achieved the synthesis of 4-substituted Trp derivatives via Ir-catalyzed sp2 C-H bond activation (Eq. 1), the enantioselective synthesis of Aic derivatives via Rh-catalyzed [2+2+2] cycloadition (Eq. 2), and the enantioselective synthesis of 4-substituted γ-amino acids via Ir-catalyzed sp3 C-H bond activation (Eq. 3). In addition, we also achieved natural product synthesis by these reactions as synthetic applications.

Transition metal-catalyzed synthesis of chiral amino acids and their synthetic applications

251st National Meeting (2016)

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