5-Hydroxy-4-methoxy-2-nitrobenzoic acid ethyl ester

It acts as a structural precursor that is reduced to an amine, subsequently cyclized, chlorinated, and coupled with 3-chloro-4-fluoroaniline to form the core 6,7-disubstituted quinazoline structure of the drug. 5-Hydroxy-4-methoxy-2-nitrobenzoic acid ethyl ester (and its methyl ester analog) serves as a key intermediate in the synthesis of Gefitinib, a tyrosine kinase inhibitor for cancer treatment.