The alkylation of uracil and methyluracil with thiophosphamide or benzotef was carried out in an aqueous medium at pH i0. 0, and of nitrouracil in a neutral medium. The ethyleneimine rings of the reagent were opened, and the N-phosphorylated 2-aminoethyl residue entered into the 3-position of the uracil ring to form the corresponding derivatives. Thus, N, N', N"-tris [B-(3-uracil) ethyl] thiophosphoric acid triamine (Ia), N, N', N"-tris [~-(6-methyl-3-uracil)- ...