In this paper is presented a theoretical study of chemical reactivity on the formation of four proteinogenic amino acids: cysteine, aspartic acid, asparagine and threonine. According to a theoretical model based on three syntons: methylene, nitrene and carbon monoxide at low temperatures, aziridinone would be formed first. This one, with methylene and carbon monoxide forms further the precursors intermediates of these four proteinogenic amino acids. Finally, the precursors in reaction with water, a key component of the primary atmosphere, lead to amino acids specified above. The study is mainly based on quantum mechanical calculations, B88-LYP DFT. Methylaziridonil, aziridonilacetyl and ethylaziridonil radicals should be formed at low temperature, which finally in reaction with water will form cysteine, aspartic acid, asparagine and threonine.