A photochemical approach to phenylalanines and related compounds by alkylation of glycine

Phenylalanines can be prepared on UV photolysis of protected glycines in the presence of di-tert-butyl peroxide, substituted toluenes and the photosensitiser benzophenone. These reactions, which lead to highly selective mono-alkylation at the α-position of glycines, involve coupling of captodative α-glycine radicals with benzyl radicals. This method can be used to selectively alkylate a variety of glycine derivatives using a range of substituted toluenes under neutral reaction conditions.