Chemo- and Site-Selective Alkyl and Aryl Azide Reductions with Heterogeneous Nanoparticle Catalysts

Site-selective modification of bioactive natural products is an effective approach to generating new leads for drug discovery. Herein, we show that heterogeneous nanoparticle catalysts enable site-selective monoreduction of polyazide substrates for the generation of aminoglycoside antibiotic derivatives. The nanoparticle catalysts are highly chemoselective for reduction of alkyl and aryl azides under mild conditions and in the presence of a variety of easily reduced functional groups. High regioselectivity for monoazide reduction is shown to favor reduction of the least sterically hindered azide. We hypothesize that the observed selectivity is derived from the greater ability of less-hindered azide groups to interact with the surface of the nanoparticle catalyst. These results are complementary to previous Staudinger reduction methods that report a preference for selective reduction of electronically activated azides.