A series of seven spirocyclic compounds bearing the newly synthesized 6,8-diaza-2-oxaspiro[3•5]nonane ring system are reported. Their preparation consists in the condensation of 3,3-bis(aminomethyl)oxetane monohydrate, obtained via pentaerythritol tribromide and, 3,3-bis(bromomethyl)oxetane, with certain amidines and guanidines.