Phenylmalonic acid is primarily used in organic synthesis as a building block for more complex chemical compounds. It serves as a key intermediate in the production of pharmaceuticals, particularly in the synthesis of active pharmaceutical ingredients (APIs). Its structure allows for versatile chemical reactions, making it valuable in creating compounds with potential therapeutic properties. Additionally, it is employed in research and development for studying enzyme mechanisms and biochemical pathways, particularly those involving malonic acid derivatives. In material science, it can be utilized in the preparation of polymers and coatings, contributing to the development of advanced materials with specific properties.