Resumo em inglês We report the synthesis of amino(2-hydroxy-2-(4-methoxyphenyl)ethylamino)methaniminium (14) as a direct precursor of a tubastrine derivative (3-dehydroxy-4-methoxytubastrine). The synthetic steps involved functional group interconversions starting from 1-(4-methoxyphenyl)ethanone to obtain the guanidine-protected derivative 13. Tentative dehydration of 13 with SiOH-adsorbed CuSO4 resulted in guanidine deprotection only. This was an unexpected result, since there are no re (mais) ports of CuSO4.SiOH as Boc-deprotecting of guanidines. The product 14 was obtained in five steps and 5.4 % overall yield, and constitutes a direct precursor of 3-dehydroxy-4-methoxytubastrine.