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TCI Practical Example: Construction of the Nucleoside Phosphoramidite Using DCI

We are proud to introduce the phosphoramidite synthesis of 5'-O-benzoylthymidine utilizing DCI as an activator.

Used Chemicals

• 5'-O-Benzoylthymidine (1)
• 2-Cyanoethyl N,N,N',N'-Tetraisopropylphosphordiamidite [C2228]
• 4,5-Dicyanoimidazole (= DCI) [D2026]
• DMF
• Acetonitrile

Procedure

To an acetonitrile (2 mL) solution of 2-cyanoethyl N,N,N',N'-tetraisopropylphosphordiamidite (0.42 g, 1.4 mmol) and DCI (0.14 g, 1.2 mmol) were added a DMF solution of 1 (0.40 g, 1.2 mmol) under nitrogen atmosphere. The reaction mixture was stirred overnight at room temperature, then diluted with TBME and washed with water, DMF:water (1:1) solution, water and brine. The organic layer was concentrated under reduced pressure. The resulting crude product was purified by column chromatography (hexane:ethyl acetate:triethylamine = 1:2:0.03 on silica gel) to give 2 as a white powder (0.45 g, 68% yield).

Experimenter’s Comments

The reaction mixtures were monitored by LCMS.

Analytical Data

Compound 2

¹H NMR (400 MHz, DMSO-d6); δ 11.36 (brs, 1H), 8.05-7.96 (m, 2H), 7.73-7.64 (m, 1H), 7.59-7.51 (m, 2H), 7.45-7.37 (m, 1H), 6.25-6.17 (m, 1H), 4.72-4.62 (m, 1H), 4.62-4.52 (m, 1H), 4.51-4.38 (m, 1H), 4.32-4.15 (m, 1H), 3.84-3.66 (m, 2H), 3.66-3.51 (m, 2H), 2.84-2.73 (m, 2H), 2.47-2.22 (m, 2H), 1.67-1.53 (m, 3H), 1.27-1.03 (m, 12H).

¹³C NMR (101 MHz, DMSO-d6); δ 165.5, 163.6, 150.4, 135.8, 133.7, 129.3 (3C), 128.9 (2C), 119.0, 109.9, 84.1, 82.8, 72.8, 64.9, 58.3 (2C), 42.7, 37.7, 24.3 (4C), 19.8, 11.9.

³¹P NMR (162 MHz, DMSO-d6); δ 147.89.

Lead Reference

• Efficient activation of nucleoside phosphoramidites with 4,5-dicyanoimidazole during oligonucleotide synthesis
  • C. Vargeese, J. Carter, J. Yegge, S. Krivajansky, A. Settle, E. Kropp, K. Peterson, W. Pieken, Nucleic Acids Res. 1998, 26, 1046.