The crystal structure of two chain functionalized pyrroles, methyl 1-benzyl-5-(1-(4-chlorobenzoyloxy)-2-methoxy-2-oxoethyl)-4-(4-chlorophenyl)-1H-pyrrole-2-carboxylate and methyl 1-benzyl-4-(biphenyl-4-yl)-5-(1-(4-biphenylcarbonyloxy)-2-methoxy-2-oxoethyl)-1H-pyrrole-2-carboxylate, which are both important active candidates as antitumoral agents, have been obtained ab initio from synchrotron X-ray powder diffraction data. Both compounds crystallize in the monoclinic system (space group P21/c), with a = 20.2544(3) Å, b = 6.80442(9) Å, c = 21.1981(3) Å, β = 111.6388(9)° and a = 29.7747(6) Å, b = 6.27495(14) Å, c = 18.8525(3) Å, β = 107.053(2)°, respectively. These structures were determined using a direct space approach, by means of Monte Carlo technique, followed by Rietveld refinement.