A very efficient route to the diastereoselective synthesis of polyhydroxy pyrrolidines, piperidines and azepanes from an aldehyde derivative of ribose is reported. Asymmetric α-amination of aldehydes using proline catalysed hydrazination is the key step in the synthesis. The method utilizes the stereocenters present in ribose and the extra carbon atoms present in the target molecules are incorporated using Wittig reactions. The incorporation of the amino group is carried out asymmetrically to account for additional stereocenters. This synthetic route to iminocyclitols has the potential to be extended for the synthesis of a large class of such compounds starting from other sugar derived aldehydes.