Solid-Phase Synthesis of Phosphate/Boranophosphate Chimeric DNAs Using the H-Phosphonate-H-Boranophosphonate Method

Boranophosphate (PB) DNAs are promising antisense oligonucleotide candidates because of their attractive features, such as high nuclease resistance and low toxicity. However, a full boranophosphate backbone modification to antisense DNAs causes reduced duplex formation with complementary RNAs and reduced antisense activity. In this study, an efficient solid-phase synthesis of phosphate/boranophosphate (PO/PB) chimeric DNA was achieved by the combination of the H-phosphonate and H-boranophosphonate methods. The physiological and biological properties of the synthesized PO/PB chimeric DNAs were also evaluated. The strategy employed herein can facilitate the design and synthesis of PO/PB chimeric DNAs containing site-specific boranophosphate modifications.