Used primarily as a key intermediate in the synthesis of pharmaceuticals, especially in the production of certain antibiotics and anti-inflammatory agents. It participates in ring-forming reactions to create lactone structures found in bioactive molecules. Also employed in the preparation of specialty polymers and fine chemicals due to its reactivity toward nucleophiles like amines and alcohols. Its anhydride functionality allows for selective acylation under controlled conditions, making it valuable in multi-step organic syntheses.