(4-Hydroxyphenoxy)acetic acid (CAS# 1878-84-8) is used in the design, synthesis and evaluation of postulated transient intermediate and substrate analogues as inhibitors of 4-hyroxyphenylpyruvate dioxygenase. Acts as a reagent in the preparation, anti-HIV and kinesin Eg5 inhibitory activities, QSAR, and modeling studies of triazolothiadiazole and triazolothiadiazine derivatives. Synthesis of thiadiazolotriazin-4-ones and study of their mosquito-larvicidal and antibacterial properties.