4-Acetoxy-2'',4''-difluorobiphenyl (Diflunisal EP Impurity C) is an impurity of Diflunisal (D445751), which acts as an analgesic agent, used in Alzheimer’s studies (1,2,3) as an anti-inflammatory. As well as in autolytic regulation of human kallikrein -related peptidase 6 (4).