Structure-activity relationships of 2-aminothiazoles effective against Mycobacterium tuberculosis.

Abstract A series of 2-aminothiazoles was synthesized based on a HTS scaffold from a whole-cell screen against Mycobacterium tuberculosis (Mtb) . The SAR shows the central thiazole moiety and the 2-pyridyl moiety at C-4 of the thiazole are intolerant to modification. However, the N-2 position of the aminothiazole exhibits high flexibility and we successfully improved the antitubercular activity of the initial hit by more than 128-fold through introduction of substituted benzoyl groups at this position. N -(3-Chlorobenzoyl)-4-(2-pyridinyl)-1,3-thiazol-2-amine ( 55 ) emerged as one of the most promising analogues with a MIC of 0.024 μM or 0.008 μg/mL in 7H9 media and therapeutic index of nearly ∼300. However, 55 is rapidly metabolized by human liver microsomes ( t 1/2  = 28 min) with metabolism occurring at the invariant aminothiazole moiety and Mtb develops spontaneous low-level resistance with a frequency of ∼10 −5 .