2,2,5,7,8-Pentamethylchroman-6-sulfonyl chloride (Pmc-Cl) is a specialty chemical reagent widely used in organic synthesis, particularly as a protecting group for the indole nitrogen of tryptophan residues in solid-phase peptide synthesis. It reacts with amines to form stable sulfonamide derivatives, which are orthogonally deprotectable under mild acidic conditions (e.g., TFA), making it compatible with Fmoc/tBu protection strategies. This compound is crucial for the synthesis of peptides, proteins, and pharmaceuticals containing tryptophan, preventing side reactions and ensuring high selectivity. Unlike general sulfonyl chlorides, its chroman-based structure provides enhanced stability and specificity in complex biochemical environments.