Trimethylsilyl triflate → 4-(4-ethylphenylmethyl)-1-(2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl) pyrazole

Participants

Reaction Conditions

Reaction Steps

To a solution of 4-(4-ethylphenylmethyl)pyrazole 36 (495 mg) in acetonitrile (2.0 ml) was added N,O-bis(trimethylsilyl)acetamide (1.05 ml), and the mixture was stirred under heating at 60° C. for 2.5 hours under argon atmosphere. The reaction mixture was cooled to room temperature, and the solvent was evaporated under reduced pressure to give crude 4-(4-ethylphenylmethyl)-1-trimethylsilylpyrazole 37, which was used in the subsequent reaction without further purification. (2) The above N-silyl compound 37 was dissolved in dichloroethane (7.0 ml), and added thereto were molecular sieve 4A powder (500 mg), 1,2,3,4,6-penta-O-acetyl-β-D-glucopyranose 38 (1.04 g) and trimethylsilyl trifluoromethanesulfonate (0.51 ml). The mixture was stirred under heating at heating at 80° C. for 3 hours under argon atmosphere. The reaction mixture was cooled to room temperature, and insoluble materials were filtered off. Subsequently, the filtrate was poured into a saturated aqueous sodium hydrogen carbonate solution. The mixture was extracted twice with dichloromethane, and dried over sodium sulfate. The solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography (hexane:ethyl acetate=80:20-50:50) to give 4-(4-ethylphenylmethyl)-1-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)pyrazole 39 (610 mg) as a colorless semisolid. APCI-Mass m/Z 517 (M+H). (3) From the above tetraacetate compound 39, the desired 4-(4-ethylphenylmethyl)-1-(β-D-glucopyranosyl)pyrazole 40 was prepared in a manner similar to Example 106-(3) as colorless oil. APCI-Mass m/Z 349 (M+H).

Provenance & Evidence