Potent Inhibitors of the Qi Site of the Mitochondrial Respiration Complex III

A series of azole-fused salicylamides were prepared as analogues of antimycin and assayed for activity at complex III of the mitochondrial respiratory chain. The activity of these compounds approached that of antimycin in inhibitory potency and some showed growth reduction of Septoria nodorum in vitro. Compound 8a was shown to bind at the Qi site of complex III by red-shift titration of the bc₁ complex.