A photolabile protecting group for the phenolic hydroxyl function of tyrosine.

The ortho-nitrobenzyl group (ONBzl) was utilized to protect the phenolic function of the side chain of tyrosine. Optimal conditions for its mild photolytic removal were established. This paper describes the preparation and properties of some (O-ONBzl)-tyrosine derivatives of potential value in the synthesis of tyrosine-containing peptides. Their use in the synthesis of the dipeptide, N-benzyloxycarbonyl-L-tyrosyl-glycine ethyl ester is presented as an example.