“…Recently, we have reported a novel synthesis method for ODNs using H -phosphonamidate derivatives as monomers. 9 In this method, H -phosphonamidate monomers having heterocyclic amino groups, such as thiomorpholino, morpholino, and N -methylpiperadino groups, reacted with an alcohol to form an internucleotidic H -phosphonate diester under mild basic conditions without the use of additives ( Scheme 1 ). In the reaction, the heterocyclic amino groups of H -phosphonamidate monomers worked as leaving groups, and one-step formation of the H -phosphonate diester linkage from H -phosphonamidate derivatives was achieved.…”