Nucleosides and Nucleotides. 182. Synthesis of Branched Oligodeoxynucleotides with Pentaerythritol at the Branch Point and Their Thermal Stabilization of Triplex Formation<sup>1</sup>
To find an oligodeoxynucleotide (ODN) with tripler stabilization capability, we designed and synthesized novel branched ODNs I and 2 with pentaerythritols at their branch points. Branched ODNs 1 and 2 were synthesized on a solid support using bis(phosphoramidite) 11. The stability of the triplexes, formed by branched ODNs 1 and 2 with (dA)(21) or (dT)(21) was studied by thermal denaturation. Branched ODN 1 formed a stable parallel T.AT-type tripler with (dA)(21) (T-m = 38.9 degrees C) in a buffer of 0.01 M sodium phosphate (pH 7.0) containing 0.5 M NaCl and 0.02 M MgCl2, while branched ODN 2 formed a stable antiparallel A.AT-type tripler with (dT)(21) (T-m = 44.2 degrees C) in the same buffer. The formation of these triplexes was also confirmed by circular dichroism (CD) measurements and a gel retardation assay.