Solid phase synthesis of the hexapeptide, GPRVVE, which represents the amino terminal six amino acids of the α‐chain of human fibrin, yielded a product that contained a modified glutamic acid. The nature of the modification was established as the Friedel‐Crafts acylation product of the peptide and anisole, the latter reagent employed in the HF deblocking step. The anisoylated peptide selectively enhanced the activation rate of native [Glu1]plasminogen by recombinant tissue plasminogen activator, accelerated clot lysis, and retarded the polymerization of nascent f