Lopinavir EP Impurity R 

Chemical Name: (2S)-N-[(1S,3S,4S)-1-Benzyl-4-[[2-(2,6-dimethylphenoxy)acetyl]amino]-3-hydroxy-5-phenylpentyl]-2-[3-[2-(2,6dimethylphenoxy)acetyl]-2-oxotetrahydropyrimidin1(2H)-yl]-3-methylbutanamide (as per EP); (S)-N-{(2S,4S,5S)-5-[2-(2,6-Dimethylphenoxy)acetamido]-4-hydroxy-1,6-diphenylhexan-2-yl}-2-{3-[2-(2,6-dimethylphenoxy)acetyl]-2-oxotetrahydropyrimidin-1(2H)-yl}-3-methylbutanamide (as per USP)