5-Amino-2-hydroxybenzoic acid (I) was protected as the N-Boc derivative (II) by treatment with di-tert-butyl dicarbonate and Et3N. Reaction with triphenylphosphine and carbon tetrabromide in tetrahydrofuran generated the bromobutyl ester (III). After conversion of (III) to the nitroxybutyl ester (IV) by reaction with AgNO3 in refluxing acetonitrile, acid deprotection of the Boc group furnished the title compound.