Venetoclax Impurity 20

2- ((1H-pyrrolo[2,3-b]pyridin-5-yl) oxy) -4- (4- ((4'- (4- ((4'-chloro-5,5-dimethyl-3,4,5,6-tetrahydro-[1,1'-biphenyl]-2-yl) methyl) piperazin-1-yl) -5,5-dimethyl-3,4,5,6-tetrahydro-[1,1'-biphenyl]-2-yl) methyl) piperazin-1-yl) benzoic acid