Methanesulfonyl chloride → 5'-O-(4,4'-dimethoxytrityl)-3'-O-[(dimethyl-1,1-dimethylethyl)silyl]-4'-(7-methanesulfonyloxy-1-hepten-1-yl)-thymidine

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Reaction Conditions

Reaction Steps

Methanesulfonyl chloride (96 μL, 1.22 mmole) was added dropwise to Compound (4) (250 mg, 0.32 mmole) in dry pyridine (3 mL) at 0° C. under nitrogen. The mixture was stirred at 0° C. for 2 hours and the reaction was quenched by the dropwise addition of methanol (1.5 mL). The yellow solution was poured into water (20 mL) and the layers were separated. The organic phase was washed with brine (20 mL), dried over magnesium sulfate and concentrated to a white solid (0.41 g) under reduced pressure. (Routinely, this crude material was used directly in the next step). The crude product (0.41 g) was purified by column chromatography on silica gel using ethyl acetate/hexane mixtures for elution. 5'-O-(4,4'-dimethoxytrityl)-3'-O-[(dimethyl-1,1-dimethylethyl) silyl]-4'-(7-methanesulfonyloxy-1-hepten-1-yl)-thymidine (241 mg, 87.5%) was obtained as a white solid. Recrystallization from hexane/dichloromethane gave a sample with m.p. 72°-75° C.

Provenance & Evidence