5-Isoxazolecarbaldehyde is the derivative of 5-Isoxazolecarboxylic Acid, which is used as a reagent in the synthesis of N-(benzo[1,2,3]triazol-1-yl)-N-((benzyl)acetamido)phenyl carboxamides as severe acute respiratory syndrome coronavirus (SARS-CoV) 3CLpro inhibitors. 5-Isoxazolecarboxylic Acid is also used as a reagent in the synthesis of TC-6683, a α4β2 nicotinic acetylcholine receptor agonist for treatment of cognitive disorders.