Diels–Alder cycloadditions of 3-phenylamino-5-bromo-2-pyrone for the synthesis of constrained α-amino acid derivatives

3-Phenylamino-5-bromo-2-pyrone undergoes facile Diels–Alder cycloadditions with various electron deficient dienophiles to afford an array of functionally rich and stereochemically defined cycloadducts in good to excellent isolated yields. Due to the electron donacity of the amine group, it only proceeds in normal electron demand D–A cycloadditions. Subsequent ring openings with NaOMe provided constrained α-amino acid derivatives.