The prooligonucleotide approach: Synthesis of mixed phosphodiester and SATE phosphotriester prooligonucleotides using H-phosphonate and phosphoramidite chemistries

The synthesis of mixed SATE-phosphotriester and phosphodiester prooligonucl eotides using both phosphoramidite and H-phosphonate chemistries is describ ed. The key step is the selective oxidation of phosphite triester and H-pho sphonate linkages to yield thiono- or oxo-triester SATE and thiono- or oxo- diester Linkages. This approach allows the synthesis of any desired mixed p rooligos bearing either tBu- or Me-SATE enzymolabile protecting groups.