Synthesis of oligonucleoside boranophosphates via an H-phosphonate method without nucleobase protection

Short oligonucleoside boranophosphates containing all four nucleosides were synthesized on solid support using base-unprotected nucleoside H-phosphonate monomers. This strategy avoided irreversible base modifications during the boronation procedure. Structures of the boranophosphate oligomers were confirmed by 1H, 31P, 10B NMR and MS analysis as well as by enzymatic hydrolysis.