Many studies on prebiotic chemistry indicate that UV radiation could have played a very important role in the evolution of prebiotic chemistry (e.g Ferris, 1983; Barks, 2010). The surface of the Earth during the Archean period (approximately 3.8 Ga) was exposed to high doses of UVC radiation (200–280 nm) and UVB (280–315 nm) in comparison with the radiation that arrives today (e.g Sagan, 1973; Cockell, 1998) due to lack of layer of ozone, its atmospheric composition, and higher activity of the sun in this wavelength range. In an astrobiological context, it is known that stars have constant UV emissions, particularly dwarf M-type stars. Depending on the atmospheric composition of a potentially habitable hypothetical planet and the spectral type of the star that hosts it, the planet could receive part of the UV radiation emitted by the star. This radiation might change the potential chemical reactivity and synthesis of some organic compounds on the planet. The atmosphere of the Earth 3.8 Ga ago possibly composed of carbon dioxide (CO2). There are no enough experimental works regarding the CO2-rich atmosphere as to establish the role of the UV radiation in the formation/destruction of prebiotic organic molecules. In this work, we use the ATMOS photochemical model to calculate the amount of UV light that would reach the surface of a potentially habitable planet with an atmosphere composed of CO2, N2 and H2O around a young Sun-like star and dwarf-like stars M with different levels of chromospheric activity. For other hand, we analyzed a known route of adenine synthesis from formamide through computational methods, to know how UV radiation affects these molecules of prebiotic importance and if it could have been important for trigger reactions for the production of molecules of prebiotic importance.