Direct esterification of a labile alkoxyamine R1R2NOR3, which was previously reported as unsuccessful, is achieved by a Mitsunobu reaction or a nucleophilic substitution. Ester derivatives are obtained under smooth conditions and easily purified. Macrocyclization attempts on ester derivatives were successful for five-membered ring lactones and unsuccessful for 13-membered ring lactones. Moreover, the success of the cyclization was ...