We describe a general method for the unimolecular photochemical generation of tyrosyl radicals from adiaryl oxalate ester platform on the nanosecond time scale.Symmetric and asymmetric tyrosine oxalate esters havebeen prepared in gram quantities. Direct photocleavage ofthe oxalate linkage by laser flash photolysis affords tyrosylradicals within 50 ns. This approach provides unnaturalcaged amino acids that may be incorporated into model andbiological systems for the study of proton-coupled electrontransfer in enzymatic catalysis.