Synthesis and activity of (+)-usnic acid and (−)-usnic acid derivatives containing 1,3-thiazole cycle against Mycobacterium tuberculosis

New usnic acid (UA) derivatives were investigated in vitro to elucidate their potential inhibitory activities on the growth of Mycobacterium smegmatis and Mycobacterium tuberculosis . Seven pairs of enantiomers of thiazole UA derivatives were tested using the M. smegmatis strain mc 2 155 test system, and the “structure–activity” relationship was established. The most active compounds were (+)-3 and (−)-3 , and their kinase inhibitory activities were investigated. The results obtained using the Streptomyces lividans APHVIII+ and M. smegmatis APHVIII+ test systems indicated the significant protein kinase activity of these compounds and revealed the species specificity of the actions of the dextro- and levorotatory isomers. Both isomers, (+)-3 and (−)-3 , possess similar inhibitory activity against M. tuberculosis H37Rv. The action of the isomers on eukaryotic cells was also investigated, and the results demonstrate that the dextrorotatory isomer (+)-3 leads to the lysis of intact macrophages to a degree higher than that obtained spontaneously and significantly higher than that obtained with the levorotatory isomer.