The reaction of (E)-6-(3-aminophenyl)-6-(3-pyridyl)-5-hexenoic acid methyl ester (I) with diphenyl N-cyanocarbinimidate (II) in isopropanol gives the N-cyanoisourea (III), which is condensed with tert-butylamine (IV) in refluxing isopropanol yielding the guanidine derivative (IV). Finally, hydrolysis of the ester group of (IV) with NaOH affords the target compound.