H-D-Ala-Gln-OH is primarily used in peptide synthesis and research applications. It serves as a building block for creating more complex peptides, particularly in studies involving protein structure and function. This dipeptide is also utilized in the development of peptide-based drugs, where it can enhance stability and bioavailability. Additionally, it finds application in nutritional science, as it can be a component of specialized diets or supplements aimed at supporting gut health and immune function. Its role in cell culture media is another key application, where it helps in promoting cell growth and maintaining cellular health.