N-Boc-L-(+)-Penicillamine is a protected derivative of the non-proteinogenic amino acid L-penicillamine. Its chemical structure features a tert-butoxycarbonyl (Boc) group protecting the amine functionality, along with a thiol group and two methyl groups attached to the beta-carbon, forming a characteristic tertiary thiol moiety. This compound is a chiral building block with the (R)-configuration. This derivative is primarily employed as a key chiral intermediate in the synthesis of complex molecules, particularly in pharmaceutical research. The Boc-protected amine group allows for selective deprotection under mild acidic conditions, facilitating its incorporation into peptide chains or other molecular frameworks. Its main application lies in the preparation of peptide-based drugs and bioactive compounds where the penicillamine unit is required, often utilized in the synthesis of enzyme inhibitors or as a metal-chelating component in drug design. As a derivative of a sulfur-containing amino acid, it serves as a valuable reagent in medicinal chemistry and biochemistry research. It must be handled with care, typically under inert atmosphere and stored at low temperatures to preserve the reactivity of the thiol group and prevent racemization.