Conversion of vinyl pyranosylamine and vinyl furanosylamines to 2,6- and 2,5-disubstituted pyrrolidine and piperidine iminosugars, respectively, in one pot was developed using Kimura and Tamaru's procedure, where a Pd salt in the presence of Et2Zn was used for the domino reaction. In this procedure, double allylation, which involves nucleophilic allylation-heterocyclization, took place to give desired nitrogen heterocycles. This strategy was further elaborated to synthesize some unnatural deoxycalystegines, hydroxylated pyrrolidines, piperidines, and indolizidine analogues.