By cyclocondensation of 3-nitrobenzaldehyde (I) with methyl 3-aminocrotonate (II) and 1-benzyl-3-(acetoacetoxy)pyrrolidine (III) in refluxing isopropanol. The pyrrolidine (III) is obtained as follows: The condensation of 2-hydroxysuccinic acid (IV) with benzylamine (VI), which is reduced with LiAlH4 in dry THF yielding N-benzyl-3-hydroxypyrrolidine (VIII). Finally, this compound is condensed with diketene (VII) by means of sodium acetate at 80 C.