Display omitted •Carbamates yield other carbamates or amidinoureas without using strong base/catalyst.•Boc/Cbz/Fmoc-protected guanidines react with aliphatic amines to yield amidinoureas.•Protected guanidines react with alcohols interchanging Boc by Cbz & Fmoc/Cbz by Boc.•Boc-protected aniline did not react with alcohols or amines under the conditions used. The reactivity of carbamates to produce other carbamates (by reaction with alcohols) or amidinoureas (by reaction with amines), without the use of strong bases or catalysts, has been studied indicating the suitability/selectivity of the method in achieving differently substituted/protected guanidines. Thus, 4-(4-guanidinophenyloxy)anilines fully protected with the most common amino protecting groups on the guanidino moiety (Boc, Cbz and Fmoc) and Boc-protected on the anilino functionality have been used as starting materials. Reactions with aliphatic amines yielded mono-substitution of one of the guanidino protecting groups producing the corresponding amidinoureas. Reactions with alcohols resulted in the corresponding substitution of both guanidino protecting groups allowing for the interchange of Boc by Cbz and Fmoc and Cbz by Boc. The Boc-protected aniline did not undergo any reaction under the conditions used.