Trifluoroacetic acid → (2R,3R)-1-Benzyloxy-2-((2-amino-1,6-dihydro-6-oxopurin-9-yl)methyl)butan-3-ol

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Reaction Steps

A solution of 24 (4.3 g, 9.03 mmol) in a mixture of TFA (60 ml) and water (20 ml) was kept at room temperature for 2 days until almost no starting 24 was seen by HPLC analysis. The reaction was concentrated, co-evaporated with acetionitrile (3×100 ml) to remove most of TFA and water and re-dissolved in THF (100 ml), triethylamine (2 ml) was added to neutralize residual TFA followed by 12 ml of 1 M tetrabutylammonium fluoride in THF. The reaction was allowed to proceed for 2 hrs (monitored by HPLC), concentrated and treated with water (70 ml) and ethyl acetate. At this point crystallization of 25 started as a gelatinous solid. After being allowed the solid to form for several hours the mixture was filtered to collect the solid, which was washed with 33% ethyl acetate in hexane and dried to afford 1.65 g of 25. The aqueous phase was extracted with ethyl acetate. All ethyl acetate extracts, including the very first one, were combined, concentrated and chromatographed on silica in a gradient of MeOH (10-20%) in dichloromethane to afford 0.75 g of 25 (combined yield—2.4 g, 77%). 1H NMR (DMSO-d6): δ 10.53 (s, 1H), 7.57 (s, 1H), 7.30 (m, 5H), 6.42 (s, 2H), 4.80 (d, J=4.8 Hz, 1H), 4.36 (d, J=1.5 Hz, 2H), 4.11 (m, 1H), 3.99 (m, 1H), 3.67 (m, 1H), 3.32 (m, 2H), 2.10 (m, 1H), 1.09 (d, J=6.3 Hz, 3H).

Provenance & Evidence