Synthesis and Biological Evaluation of Novel 2-Aminonicotinamide Derivatives as Antifungal Agents

Graphical Infections unanchored ! A series of novel 2-aminonicotinamide derivatives were designed, synthesized, and evaluated for in vitro antifungal activity. Compounds 11 g and 11 h have excellent activity against Candida albicans , with MIC 80 values of 0.0313 μg mL −1 , and exhibit broad-spectrum antifungal activity against fluconazole-resistant C. albicans , C. parapsilosis , C. glabrata , and Cryptococcus neoformans , with a MIC 80 range of 0.0313–2.0 μg mL −1 . Further investigation suggested that compound 11 g targets the cell wall and decreases glycosylphosphatidylinositol anchor content on the cell surface of C. albicans . Based on the structures of the reported compounds G884 [ N -(3-(pentan-2-yloxy)phenyl)nicotinamide], E1210 [3-(3-(4-((pyridin-2-yloxy)methyl)benzyl)isoxazol-5-yl)pyridin-2-amine], and 10 b [2-amino- N -((5-(3-fluorophenoxy)thiophen-2-yl)methyl)nicotinamide], which inhibit the biosynthesis of glycosylphosphatidylinositol (GPI)-anchored proteins in fungi, a series of novel 2-aminonicotinamide derivatives were designed, synthesized, and evaluated for in vitro antifungal activity. Most of these compounds were found to exhibit potent in vitro antifungal activity against Candida albicans , with MIC 80 values ranging from 0.0313 to 4.0 μg mL −1 . In particular, compounds 11 g [2-amino- N -((5-(((2-fluorophenyl)amino)methyl)thiophen-2-yl)methyl)nicotinamide] and 11 h [2-amino- N -((5-(((3-fluorophenyl)amino)methyl)thiophen-2-yl)methyl)nicotinamide] displayed excellent activity against C. albicans , with MIC 80 values of 0.0313 μg mL −1 , and exhibited broad-spectrum antifungal activity against fluconazole-resistant C. albicans , C. parapsilosis , C. glabrata , and Cryptococcus neoformans , with a MIC 80 range of 0.0313–2.0 μg mL −1 . Further studies by electron microscopy and laser confocal microscopy indicated that compound 11 g targets the cell wall and decreases GPI anchor content on the cell surface of C. albicans .