Selective Monoreduction of 2,4 Diazido-Dideoxy Hexoses by Hydrogenation over Lindlar Catalyst

A novel, mild and site-selective hydrogenation of equatorial azides in diazido hexoses, achieved using Lindlar catalyst, is reported. Optimization studies on l-β-2,4-dideoxy-diazido rhamnoside revealed exclusive reduction of the equatorial azide while axially positioned azide groups remain untouched, affording the corresponding monoamino sugar in up to 87% yield. The methodology proved reliable across different diverse substitution patterns, consistently favoring equatorial over axial azide reduction while allowing for straightforward purification and scalability.