Synthesis of Lariat-DNA via the Chemical Ligation of a Dumbbell Complex

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.