The (Z) group is another carbamate-type amine protecting group, discovered by Leonidas Zervas in the early 1930s and usually added via reaction with benzyl chloroformate.
It is removed under harsh conditions using HBr in acetic acid, or milder conditions of catalytic hydrogenation.
This methodology was first used in the synthesis of oligopeptides by Zervas and Max Bergmann in 1932. Hence, this became known as the Bergmann-Zervas synthesis, which was characterised "epoch-making" and helped establish synthetic peptide chemistry as a distinct field. It constituted the first useful lab method for controlled peptide synthesis, enabling the synthesis of previously unattainable peptides with reactive side-chains, while Z-protected amino acids are also prevented form undergoing racemization.
The use of the Bergmann-Zervas method remained the standard practice in peptide chemistry for two full decades after its publication, superseded by newer methods (such as the Boc protecting group) in the early 1950s. Nowadays, while it has been used periodically for α-amine protection, it is much more commonly used for side chain protection.