D-Valine N-carboxy anhydride (D-Val NCA), also known as (R)-4-isopropyl-2,5-oxazolidinedione, is a heterocyclic organic compound with the CAS number 43089-05-0. It is a derivative of the amino acid D-valine, where the amino group has been converted into a cyclic anhydride structure. This compound is a white to off-white crystalline solid and is sensitive to moisture. The primary and most significant application of D-Val NCA is as a key monomer in the solid-phase peptide synthesis (SPPS) of polypeptides and proteins. It serves as an activated form of D-valine, enabling efficient and controlled ring-opening polymerization to form peptide bonds without racemization. This makes it an essential building block for producing peptides with specific sequences and chiral purity, which are crucial in pharmaceutical research and development, particularly for creating peptide-based drugs and bioactive compounds. While its dominant use is in peptide synthesis as a specialized intermediate, its well-defined heterocyclic structure also qualifies it as a valuable organic synthesis building block in a broader chemical context. It must be stored under inert conditions to prevent hydrolysis and degradation.