反应详情

Starting material was 2′-azido-2′-deoxyuridine prepared according to literature (Verheyden et al., J. Org. Chem 36, 250 (1971)), which was 4,4-dimethoxytritylated at 5′-OH with 4,4-dimethoxytrityl chloride in pyridine and acetylated at 3′-OH with acetic anhydride in a one-pot reaction using standard reaction conditions. With 191 mg (0.71 mmole) 2′-azido-2′-deoxyuridine as starting material, 396 mg (0.65 mmol, 90.8%) 5′-O-(4,4-dimethoxytrityl)3′-O-acetyl-2′-azido-2′-deoxyuridine was obtained after purification via silica gel chromatography. Reduction of the azido group was performed using published conditions (Barta et al, Tetrahedron 46, 587-594 (1990)). Yield of 5′-O-(4,4-dimethoxytrityl)-3′-O-acetyl-2′-amino-2′-deoxyuridine after silica gel chromatography was 288 mg (0.49 mmole; 76%). This protected 2′-amino-2′-deoxyuridine derivative (588 mg, 1.0 mmole) was reacted with 2 equivalents (927 mg, 2.0 mmole) N-Fmoc-glycine pentafluorophenyl ester in 10 ml dry DMF overnight at room temperature in the presence of 1.0 mmole (174 μl) N,N-diisopropylethylamine. Solvents were removed by evaporation in vacuo and the residue purified by silica gel chromatography. Yield was 711 mg (0.71 mmole, 82%). Detritylation was achieved by a one hour treatment with 80% aqueous acetic acid at room temperature. The residue was evaporated to dryness, co-evaporated twice with toluene, suspended in 1 ml dry acetonitrile and 5′-phosphorylated with POCl3 according to literature (Yoshikawa et al, Bull. Chem. Soc. Japan 48, 3505 (1969) and Sowa et al., Bull. Chem. Soc. Japan 48, 2084 (1975)) and directly transformed in a one-pot reaction to the 5′-triphosphate using 3 ml of a 0.5 M solution (1.5 mmole) tetra (tri-n-butylammonium) pyrophosphate in DMF according to literature (e.g. Seela et al., Helvetica Chimica Acta 74, 1048 (1991)). The Fmoc and the 3′-O-acetyl groups were removed by a one-hour treatment with concentrated aqueous ammonia at room temperature and the reaction mixture evaporated and lyophilized. Purification also followed standard procedures by using anion-exchange chromatography on DEAE-Sephadex with a linear gradient of triethylammonium bicarbonate (0.1 M-1.0 M). Triphosphate containing fractions (checked by thin layer chromatography on polyethyleneimine cellulose plates) were collected, evaporated and lyophilized. Yield (by UV-absorbance of the uracil moiety) was 68% (0.48 mmole).

1. customprepared
2. customreaction conditions