The chemistry of isoxazole is associated with the name of Ludwig Claisen who discovered 3-phenyl-5-isoxazolone by carrying out the reaction of benzoyl acetic ester with hydroxylamine. 4-Isoxazolones which are tautomeric with 4-hydroxy-isoxazoles have received little attention. The recognition of the pharmacological activity of some isoxazole derivatives such as Cycliton, a dialkylamide of isoxazole carboxylic acid used as analeptics and Gantrisin a sulfa drug from amino isoxazole5-8, has contributed to the development of isoxazole chemistry. The antibiotic, Cycloserine9,10 (or oxamycin) a simple derivative of 3-isoxazolidone has aroused a new interest in this field.