2-formyl-3-[2-(methoxycarbonyl)ethyl]-4-methylpyrrole

3-(2-methoxycarbonylethyl)-4-methyl-5-(p-toluenesulfonyl)-3-pyrrolin-2-one

t-butyl 2,5-dihydro-2-hydroxy-4-(2-methoxycarbonylethyl)-3-methyl-5-oxo-1H-pyrrole-2-carboxylate

2-(2,2-Dimethoxy-1-methylethyliden)pentandisaeure-dimethylester

tert-butyl 5-formyl-3-methyl-4-(2-methoxycarbonylethyl)pyrrole-2-carboxylate