The synthesis of a variety of chemically modified oligonucleotides requires the development of a practical synthetic method for its building block, i.e., nucleoside analogs. The one-pot Pummerer-like reaction using hypervalent iodine in combination with 6-chloropurine and an 'armed' 4-selenosugar bearing an electron-donating group at the 2-position gave the desired 4'-seleno-6-chloropurine derivative in higher yield as compared to the previous method using a 'disarmed' 4-selenosugar bearing an electron withdrawing group at the 2-position. In addition, the use of 2,6-dichloropurine as a nucleobase transformable into guanine skeleton enabled an effective Pummerer-like reaction followed by isomerization to the desired N9 isomer under the acidic conditions. This Pummerer-like reaction between chlorinated purine bases and an 'armed' 4-selenosugar is advantageous because it affords 4'-selenopurine nucleosides in one-pot without the need for isolation of the unstable selenoxide derivative. (C) 2016 Elsevier Ltd. All rights reserved.