Fmoc-3-amino-4-methylbenzoic acid is primarily used in peptide synthesis as a building block. The Fmoc (fluorenylmethyloxycarbonyl) group serves as a protecting group for the amino functionality during the synthesis process, ensuring that the amino group remains intact while other reactions take place. This compound is particularly valuable in solid-phase peptide synthesis (SPPS), where it helps in the stepwise assembly of peptides. Its structure allows for the introduction of specific aromatic and methyl-substituted moieties into peptide chains, which can be crucial for designing peptides with particular biological activities or structural properties. Additionally, it is employed in the development of peptidomimetics and small molecule drugs, where its unique chemical properties can enhance binding affinity or modulate pharmacokinetics.