Aminomethylation of thiourea with aqueous formaldehyde and simple amino acids (glycine, β-alanine, γ-aminobutyric acid) have resulted in the formation of (4-thioxo-1,3,5-triazinan-1-yl)-substituted acetic, propionic, and butyric acids, respectively. By alkylation of these compounds corresponding S-methyl and S-ethyl iodides were obtained, and by the action of tert-butylamine, the corresponding salts. The same salts were obtained by the reaction of amine exchange between 5-tert-butyl-1,3,5-triazinan-2-thione and these amino acids in water. As a result of neutralization of S-methyl iodides with tert-butylamine in 2-propanol or aqueous 2-propanol zwitterionic [4-(methyl-sulfanyl)-3,6-dihydro-1,3,5-triazin-1(2H)-yl] derivatives of these acids were isolated. From aqueous solutions of S-methyl iodides and tert-butylamine ion associates of the corresponding zwitter-ions and tert-butylammonium iodide have crystallized. The same associates have formed at treating Smethyl iodides with tert-butylamine or diethylamine in the absence of a solvent.It was shown in [1] that 3-tert-butyl-6-(methylsulfanyl)-1,2,3,4-tetrahydro-1,3,5-triazine hydroiodide enters in the amine exchange reaction with glycine and β-alanine. In the case of glycine the final product of the exchange, [4-(methylsulfanyl)-5,6-dihydro-1,3,5-triaz-3-inium-1(2H)-yl] acetate, was isolated from the reaction mixture of transamination in the individual form. In this paper we describe the independent synthesis of this compound and its homologs by aminomethylation of thiourea with aqueous formaldehyde and simple amino acids and the subsequent methylation of thus obtained cyclic Mannich bases with methyl iodide followed by the neutralization of the resulting isothiuronium salts with tert-butylamine.The scientific literature contains no data on the aminomethylation of thiourea (I) with amino acids as the amino component. There are a number of patents [2-6] describing use of cyclic Mannich bases IIa-IIc, the derivatives of thiourea and amino acids, as stabilizers of silver halide emulsion layers of the material for color photography, silver halide solvents for a photographic developer compositions and toners, the components of thermographic and photothermographic materials. The patent [2], which refers to several other patents and the work [7], describes a general method for the preparation of these compounds, but none of these sources does not contain their characteristics.Indeed, as in the case of aminomethylation using simple aliphatic amines [7], thiourea (I) in aqueous formaldehyde easily enters into a similar reaction with the simplest amino acids like glycine, β-alanine, and γ-aminobutyric acid forming well-crystallized Mannich bases IIa-IIc. Probably, this reaction may be used to protect amino groups in peptide synthesis, just as it is suggested to do with the use of urea and formaldehyde [8].In acetone or 2-propanol Mannich bases IIa-IIc readily in nearly quantitative yield are alkylated with simple alkyl halides forming a well-crystallized isothiuronium salts I...