The omeprazole molecule consists of three parts, a substituted pyridine ring, a substituted benzimidazole ring and CH2SO chain connecting the 2-positions of these ring systems. All three are essential for the antisecretory effect. In order to maintain a good effect the pyridine ring has to be substituted by alkyl or alkoxy groups, but not in the 6-position. The substituents in the benzimidazole ring are not that important, but substituents with strongly electron withdrawing groups such as NO2 or highly hydrophilic groups such as NHCOCH3 tend to give compounds with low antisecretory effects.