The condensation of N-(tert-butoxycarbonyl)-L-leucine (I) with 1-2,3,4-trimethoxybenzyl)piperazine (II) by means of N-hydroxysuccinimide (HSI) and dicyclohexylcarbodiimide (DCC) in dichloromethane gives the corresponding acylated piperazine (III), which is deprotected with dry HCl in ethyl acetate yielding the leucine derivative (IV). Finally, this compound is condensed with trans-epoxysuccinic acid monoethyl ester (V) by means of DCC and HSI as before and treated with H2SO4.
The reaction of 1-(1-propen-2-yl)-2 benzimidazolinone (I) in hexamethylphosphorus triamide with sodium hydride and 3-benzalamino-3,3-dimethylpropyl chloride (II) and treating the reaction product with hydrochloric acid gives 1-(3 amino-3,3-dimethylpropyl)-2 benzimidazolone (III). The amine (III) is refluxed with 1-(1-naphthyloxy)propylene-(2,3)-oxide (IV) yielding the title compound.