General description： Four stable conformers of N4-acetylcytosine, and the one of the stable form containing an intramoleuclar six-membered ring have been reported by theoretical calculations.The infrared and FT-Raman spectra of N4-acetylcytosine in the solid phase has been reported. application： N4-Acetylcytosine may be used in the preparation of cytidine. It may be used in the preparation of 1-(4-azido-4-deoxy-β-D-glucopyranosyl)cytosine.