[Structure: see text] Catalyst-free N-tert-butyloxycarbonylation of amines in water is reported. The N-t-Boc derivatives were formed chemoselectively without any isocyanate, urea, N,N-di-t-Boc, and O/S-t-Boc as side products. Chiral amines, esters of alpha-amino acids, and beta-amino alcohol afforded optically pure N-t-Boc derivatives. Amino alcohol and 2-aminophenol afforded the N-t-Boc derivative without oxazolidinone formation. Selectivity was observed during competition of aromatic amine vs aliphatic amine, amine vs amino acid ester, amine vs amino alcohol, and primary amine vs secondary amine.