Chlorotripyrrolidinophosphonium hexafluorophosphate, also known as PyAOP, is a chemical compound commonly used as a coupling reagent in peptide synthesis and other amide bond-forming reactions. This phosphonium-based reagent plays a crucial role in organic synthesis, particularly in peptide chemistry, due to its ability to activate carboxylic acids, forming highly reactive acylating intermediates and facilitating efficient and selective amide bond formation. Its unique structure and reactivity make it valuable in the production of peptides for research, pharmaceutical, and biotechnological applications.