Efficient synthetic methods for α,β-dehydroamino acids as useful and environmentally benign building blocks in biological and materials science

Both natural and unnatural amino acids, peptides, and proteins are widely recognized as green and sustainable organic chemicals, not only in the field of biological sciences but also in materials science. It has been discovered that artificially designed unnatural peptides and proteins exhibit advanced properties in medical and materials science. In this context, the development of precise chemical modification methods for amino acids and peptides is acknowledged as an important research project in the field of organic synthesis. While a wide variety of modification methods for amino acid residues have been developed to artificially modify peptides and proteins, the representative methods for modifying amino acid residues have traditionally relied on the nucleophilic properties of the functionalities on the residues. In this context, the development of different modification methods using an umpolung-like approach by utilizing the electrophilic nature of amino acid derivatives appears to be very attractive. One of the promising electrophilic amino acid compounds for realizing important modification methods of amino acid derivatives is α,β-dehydroamino acids, which possess an α,β-unsaturated carbonyl structure. This review article summarizes methods for the preparation of α,β-dehydroamino acids derived from natural and unnatural amino acid derivatives. The utilities of α,β-dehydroamino acid derivatives, including peptides and proteins containing dehydroalanine units, in bioconjugations are also discussed.