Synthesis of lariat-DNA via the chemical ligation of a dumbbell complex

[reaction: see text] An efficient synthesis of a medium-sized DNA lariat through the chemical ligation of a Y-shaped dumbbell precursor is described. The methodology requires only commercially available phosphoramidites and reagents and affords regioisomerically pure lariat molecules. Characterization of the lariat by T(m) analysis reveals that the molecule displays markedly enhanced thermal stability and unimolecular association-dissociation kinetics, consistent with DNA dumbbell behavior.