L-Aspartic acid di-tert-butyl ester hydrochloride is primarily used in peptide synthesis as a protecting group for the carboxyl function of aspartic acid. This compound helps prevent unwanted side reactions during the formation of peptide bonds, ensuring higher purity and yield of the final peptide product. It is particularly valuable in solid-phase peptide synthesis (SPPS), where selective deprotection is required. Additionally, it finds application in the synthesis of complex organic molecules and pharmaceuticals, where precise control over reactivity is essential. Its stability under various reaction conditions makes it a reliable choice in organic and medicinal chemistry research.