5-tert-Butoxycarbonylmethyl-3-(2-methoxycarbonyl-ethyl)-4-methyl-1H-pyrrole-2-carboxylic acid tert-butyl ester

5-{tert-Butoxycarbonyl-[3-eth-(E)-ylidene-4-methyl-5-oxo-pyrrolidin-(2E)-ylidene]-methyl}-3-(2-methoxycarbonyl-ethyl)-4-methyl-1H-pyrrole-2-carboxylic acid tert-butyl ester

5-{tert-Butoxycarbonyl-[4-ethyl-3-methyl-5-oxo-1,5-dihydro-pyrrol-(2Z)-ylidene]-methyl}-3-(2-methoxycarbonyl-ethyl)-4-methyl-1H-pyrrole-2-carboxylic acid tert-butyl ester