A chromatography free, four-step strategy has been developed to synthesize reversed N- nucleosides (4A-D) starting from -D-galactopyranose. The triaozle moiety served as heterocyclic part of nucleoside was created via 1,3 dipolar cycloaddition reaction between sugar azide (1,2:3,4-di-O-isopropylidene-6-deoxy-6-azido- -Dgalactopyranoside, 3) and terminal alkyne. Sugar azide 3 was obtained from 1,2:3,4-di-O-isopropylidene-6-tosyl- -Dgalactopyranoside (2). Purification of products was carried out through solvent-solvent extraction and/or crystallization techniques. This is an example of click reaction. Some advantages of click reaction include mild reaction conditions, selectivity, efficiency and high yields.

Uroosa Aslam, Imran Ali Hashmi, Muhammad Naveed Javed, Shoaib Muhammad, Muhammad Nabeel, Ahmed Bari and Firdous Imran Al