6-Hydroxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid is primarily used in pharmaceutical research and development. It serves as a key intermediate in the synthesis of various bioactive compounds, particularly those targeting neurological disorders. Its structure is often utilized in the design of molecules that interact with neurotransmitter systems, making it valuable for creating potential treatments for conditions like Parkinson's disease, depression, and anxiety. Additionally, it is explored in the development of enzyme inhibitors and receptor modulators due to its unique chemical framework. Researchers also investigate its potential in designing novel drugs with improved efficacy and reduced side effects.