Gold nanoparticles on a polysaccharide-based support (chitosan) were found to catalyze with very high yields the regioselective hydroamination of alkynes without the need for acid promoters and inert atmosphere. The metal-support interactions were studied by Raman, IR, UV, and NMR spectroscopy. The interaction between gold and the NH and OH groups of chitosan allow good dispersion of the nanocrystals on the biopolymer. The chitosan-silica composite further stabilizes gold nanoparticles against agglomeration or leaching compared with other supports. (c) 2007 Elsevier Inc. All rights reserved.