Hydrolysable chestnut tannins, which contain several hydroxyl groups, were reacted with dimethyl carbonate, and then with hexamethylenediamine. The dried product was analyzed in MALDI-TOF, 13C NMR and FTIR spectrometry. The spectra revealed the presence of urethane functions and their yield was relatively high. This synthesis of polyurethanes is interesting because it does not depend on using isocyanates as reactants while instead utilizing a natural material, hydrolysable chestnut tannin, as their major constituent.