1,3-Dichloro-1,1,3,3-tetraisopropyldisiloxane [Hydroxyl Protecting Agent]

• Uridine [U0020]
• 1,3-Dichloro-1,1,3,3-tetraisopropyldisiloxane (= TIPDSCl₂) [D1608]
• Pyridine

Uridine (1.0 g, 4.10 mmol) was added to pyridine (13.7 mL) at room temperature and stirred, then TIPDSCl₂ (1.42 g, 4.50 mmol) was added and stirred for 7 hours. After ethyl acetate (10 mL) was added to the reaction solution, the organic layer was washed with 0.05 mol/L HCl (10 mL), ion exchanged water (10 mL), and brine (10 mL). The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (dichloromethane:methanol = 10:1) to afford 1 (1.38 g, 69% yield) as a white solid.

The reaction solution was monitored by UPLC.

Compound 1

¹H NMR (400 MHz, CDCl₃); δ 8.45 (s, 1H), 7.66 (d, J = 8.1 Hz, 1H), 5.73(s, 1H), 5.68 (d, J = 7.9 Hz, 1H), 4.39 (m, 1H), 4.21 (m,2H), 4.09 (m, 1H), 4.02 (m, 1H), 2.98 (s, 1H), 1.10 (m, 28H).

• Preparation of Zwitterionic Ribonucleoside Phosphoramidites for Solid-Phase siRNA Synthesis
• R. Smicius, J. Engels, J. Org. Chem. 2008, 73, 4994.