Abstract The title compounds 4 were synthesized via the acid-catalyzed reaction of α- (acylaminooxy) carboxylic acid amides 6 with carbonyl compounds, and controlled catalytic hydrogenation of the resulting 2-benzyloxy-carbonyldihydro-2H-1, 2, 4-oxadiazin-5 (6H)- ones 7 (R 6= PhCH 2 O).
![benzyl 4-oxo-2-oxa-1,5-diazaspiro[5.5]undecane-1-carboxylate Structure](https://image.chemsrc.com/caspic/166/83395-80-6.png)
![2-oxa-1,5-diazaspiro[5.5]undecan-4-one Structure](https://image.chemsrc.com/caspic/258/83396-06-9.png)
