3-{5-[4-Ethyl-3-methyl-5-oxo-1,5-dihydro-pyrrol-(2Z)-ylidenemethyl]-4-methyl-2H-pyrrol-3-yl}-propionic acid methyl ester

5-[Allyloxycarbonyl-(triphenyl-λ5-phosphanylidene)-methyl]-3-(2-methoxycarbonyl-ethyl)-4-methyl-1H-pyrrole-2-carboxylic acid tert-butyl ester