Irradiation of 3-methylene-2,2,4,4-tetramethylcyclobutanone with nitrogen acids such as succinimide, phthalimide, imidazole, 3,5-dimethylpyrazole, purine, and benzimidazole gives 1:1 adducts that were identified as cyclic α-aminoacetals structurally related to nucleosides. Keywords: photochemistry of cyclobutanones, oxacarbene, nucleoside analogs.