A nucleoside consists of two components, i.e., a nitrogenous base (purine or pyramidine)’ and a five-carbon sugar (ribose or deoxyribose). It is obtained when the nitrogenous base is attached, to C1 of sugar by a β – linkage. Thus, in general, a nucleoside may be represented as a base – super. Examples of nucleosides are adenosine, cytidine etc.