REFERENCES
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- General Procedure for the Sequential Transformation of ribonucleosides to 5′-DMTr- 2′-O-Silylribonucleosides: D-[1′-13C]-3′,5′-O-(Di-tert-butylsilanediyl)-N 6-benzoyladenosine (6a): To a solution of 5a (0.58 g, 1.54 mmol) and AgNO3 (0.78 g, 4.6 mmol) in anhydrous DMF (9 mL) at 0°C was added dropwise di-tert-butyldichlorosilane (0.5 mL, 2.37 mmol) with vigorous stirring. The mixture was warmed to room temperature and subsequently stirred for 15 min. Triethylamine (0.65 mL, 4.64 mmol) was added, and the mixture was stirred for an additional 5 min. The solvent was removed under reduced pressure. Water (15 mL) was added and the resulting solution extracted with CH2Cl2. The organic layer was separated, washed with brine, dried over Na2SO4, and evaporated to dryness under reduced pressure. The residue was purified by silica gel chromatography to give 7a (72%). All NMR analyses were in agreement with the structure. D-[1′-13C]-2′-O-tert-butyldimethylsilyl-3′,5′-O-di-tert-butylsilanediyl-N 6-benzoyladenosine (7a): To a solution of 6a (0.41 g, 0.81 mmol) and catalytic amount of DMAP in anhydrous pyridine (10 mL) was added dropwise tert-butyldimethylsilyl chloride (2 eq, 0.12 g, 0.78 mmol). The mixture was refluxed overnight. After evaporation under reduced pressure, the resulting mixture was diluted with CH2Cl2, and the organic phase washed with brine and dried over Na2SO4. After a column chromatography on silica gel, the desired product 7a was isolated with 74% yield. All NMR analyses were in agreement with the structure. D-[1′-13c]-2′-O-tert-butyldimethylsilyl-N 6-benzoyladenosine (8a): A solution of HF.pyridine (60 μL, 2.34 mmol; commercially available) was carefully diluted with anhydrous pyridine (0.31 mL) and then added dropwise to a solution of 7a (0.36 g, 0.58 mmol) in THF (3 mL) at 0°C. The mixture was warmed to room temperature, stirred for 5 min. and then diluted with pyridine (0.5 mL). Water (5 mL) was added and the extraction was performed with CH2Cl2. The organic layer was collected, washed with 5% NaHCO3 and dried over Na2SO4. After evaporation under reduced pressure, the residue was purified by a column chromatography on silica gel to yield the desired compound 8a with 96% yield
- Sinha , N. D. , Biernat , J. , McManus , J. and Köster , H. 1984 . Nucleic Acid Res. , 12 : 4539
- Milecki , J. , Dembek , P. , Antkowiak , W. Z. , Gdaniec , Z. , Mielewczyk , S. and Adamiak , R. W. 1989 . Nucleosides & Nucleotides , 8 : 463
- All synthesized products have been fully characterized by 1H, 13C NMR and MS