Intramolecular photodecarboxylation reactions of potassium ω-phthalimido carboxylates in water or mixtures of water and organic solvents (acetone, acetonitrile) were investigated using an incoherent XeCl excimer radiation source emitting at 308 nm. Electron transfer induced intermolecular addition of alkyl carboxylates to phthalimides likewise proceeded efficiently under these conditions. The reactions can be performed in multigram (i.e. 10–30 g product) quantities using easiliy available substrates such as glutamic acid (for the synthesis of 3), leucine (for 8, 9) or simple alkyl carboxylates (for 11). The advantages of this methodology are: clean and high-yielding reactions, solvent and waste minimization, water-based processes and efficient utilization of photons of defined energy.