Two genotoxic impurities of sulfonate esters in Posaconazole: Synthesis, method validation and mechanism of action

Sulfonate esters are a class of organic impurities that includes highly potent mutagenic substances that typically need to be controlled down to a low ppm level in pharmaceutical development. In this work, two genotoxic impurities of sulfonate esters in Posaconazole, for example, ((3S,5R)‐5‐((1H‐1,2,4‐triazol‐1‐yl)methyl)‐5‐(2,4‐difluorophenyl)tetrahydrofuran‐3‐yl)methyl‐4‐methylbenzenesulfonate and (2S,3S)‐3‐ (4‐(4‐(4‐(4‐(((3R,5R)‐5‐((1H‐1,2,4‐triazol‐1‐yl)methyl)‐5‐(2,4‐difluorophenyl)tetrahydrofuran‐3‐yl)methoxy)phenyl)piperazin‐1‐yl)phenyl)‐5‐oxo‐4,5‐dihydro‐1H‐1,2,4‐triazol‐1‐yl)pentan‐2‐yl‐4‐methylbenzenesulfonate, were synthesized and characterized. The genotoxicity which was evaluated by two (quantitative) structure‐activity relationships prediction methodologies showed positive. Furthermore, a novel high‐performance liquid chromatography‐tandem mass spectrometry limit test method for detecting these two impurities in Posaconazole has been established and validated. The chromatographic separation of analytes was conducted on an ACQUITY BEH C18 column, and performed with 0.05% methanoic acid‐water and 0.05% methanoic acid‐acetonitrile as mobile phases A and B, respectively. Six batches of commercial‐scale Posaconazole samples were detected by the validated method and the results were in accordance with the Food and Drug Administration acceptance criteria for the genotoxic impurities in drug substances. Finally, a tentative mechanism for these two impurities was proposed, they are generally accepted to undergo an SN2‐type reaction, resulting in 7‐methylguanine as the predominant adduct in double‐stranded DNA.