Synthesis and antituberculosis activity of O-aroyl-β-(4-phenylpiperazin-1-yl)propioamidoximes

The search for new tuberculostatics is an important task for medicinal chemistry. A series of new O-aroyl-β-(4-phenylpiperazin-1-yl)propioamidoximes were synthesized and tested in vitro for antituberculosis activity. The synthesis of the target substances consists of 3 – 4 steps. In the first step, β-(4-phenylpiperazin1-yl)propionitrile was obtained in 79% yield; the second step yields β-(4-phenylpiperazin-1-yl)propioamidoxime in 75% yield. Subsequent aroylation of this amidoxime by substituted benzoic acid chlorides in the presence of Et3N leads to the target O-aroyl-β-(4-phenylpiperazin-1-yl)propioamidoximes in 61 – 93% yields. Hydrochlorides of the O-aroylated products were obtained in 72 – 94% yields by the action of ethereal HCl on solutions of the bases. PMR spectra of hydrochlorides of the O-aroylated products show evidence of slow inversion of the heterocycle at the β-position and coordination of HCl at the N1 atom of the 4-phenylpiperazine fragment. Some bases and hydrochlorides of O-aroyl-β-(4-phenylpiperazin-1-yl)propioamidoximes exhibited interesting antituberculosis properties when tested in vitro on sensitive, resistant, and multi-drug resistant strains of M. tuberculosis.