Tetroxoprim can be synthesised by three different routes: 1) 2-Amino-4-hydroxy-5-[3,5-dimethoxy-4-(2-methoxyethoxy)benzyl]pyrimidine can be obtained by conversion of 3,5-dimethoxy-4-(2-methoxyethoxy)hydroxycinnamic acid ethyl ester (I) with the addition of sodium methylate and guanidine hydrochloride (II). With the acid of phosphorousoxychloride (III) can be converted to (IV) and then finally aminolysed to tetroxoprim at 160 C.
2) Using 3,5-dimethoxy-4-(2-methoxyethoxy)benzaldehyde (V) as a starting material, Tetroprim can be obtained by reaction with 3-methoxypropionitrile (VI) in the presence of a basic catalyst and ring closure finally brought about with guanidine hydrochloride (II).
3) 2,4-Diamino-5-(3,5-dimethoxy-4-hydroxybenzyl)pyrimidine (VII) can be etherised after heating under reflux for three hours with p-toluenesulfonic acid-(2-methoxyethyl)ester (IX) in the presence of a basic catalyst.