H-D-Ser(tBu)-OH is a protected derivative of the unnatural D-serine amino acid, used in peptide synthesis to enable the controlled assembly of peptides by protecting the serine side chain hydroxyl group from unwanted reactions. It is commonly employed in the production of pharmaceuticals, bioactive peptides, and research compounds, ensuring the integrity and specificity of the peptide sequence during synthesis. The tert-butyl (tBu) protecting group provides stability under acidic conditions typically used in solid-phase peptide synthesis (SPPS) and other complex peptide construction methods.