O-methylisourea hemisulfate was used as a reagent for the preparation of (D,L)-arginine methyl ester analogues with antiarrhythmic activity. It is also used in the synthesis of [6-methyl-2-methoxy-3-Chemicalbook (substituted phenylethanone)-4-(substituted phenyl)]-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid ethyl ester with antibacterial activity has different concentrations of Mycobacterium tuberculosis, Staphylococcus aureus and Bacillus subtilis.