The synthesis of constrained aziridine-2-carboxylic acid derivatives and azetidine-3-carboxylic acid derivatives is of great importance in agricultural and medicinal chemistry. This research concerns the development of syntheses of new functionalized derivatives of aziridine-2-carboxylic acid and azetidine-3-carboxylic acid. The study of their further transformations and ring opening reactions towards potentially physiologically active amino acid derivatives, and their application in the synthesis of peptides are also performed in this research.