ethyl 3-hydroxy-3,4,4,5-tetramethyl-3,4-dihydro-2H-pyrolle-2-carboxylate

ethyl 2,3,3,4-tetramethyl-3H-pyrrole-5-carboxylate

N-(4-hydroxyimino-3,3-dimethylpentan-2-ylidene)hydroxylamine

1,2,3,3-tetramethylcyclopropene

(5-hydroxy-3,4,4,5-tetramethylpyrazol-1-yl)-phenylmethanone