passages.id: split_5_test_2125_passage
passages.type: progene_text
passages.text: Two other compounds , 18a (2-acetamido-4-(3-methoxyphenyl)-4-oxobutyric acid ) and 18c (2-butyramido-4-(3-methoxyphenyl)-4-oxobutyric acid ) , that have the same structure as 15a and 15c , except the amino group in R(1) , showed different effects .