Gravar-mail: Ethyl 1-(4-chloro­phen­yl)-3-[1-(4-meth­oxy­phen­yl)-4-oxo-3-phenyl­azetidin-2-yl]-2-nitro-2,3,10,10a-tetra­hydro-1H,5H-pyr­rolo[1,2-b]isoquinoline-10a-carboxyl­ate