5-[3-butyl-5-(1,2-dihydroxy-2-phenyl-ethyl)-isoxazol-4-ylmethoxy]-2-methyl-2H-pyrazole-3-carboxylic acid methyl ester → 5-(3-butyl-5-formyl-isoxazol-4-ylmethoxy)-2-methyl-2H-pyrazole-3-carboxylic acid methyl ester

Participants

Reaction Steps

To a solution of 5-[3-butyl-5-(1,2-dihydroxy-2-phenyl-ethyl)-isoxazol-4-ylmethoxy]-2-methyl-2H-pyrazole-3-carboxylic acid methyl ester (440 mg, 1.03 mmol) in benzene (2 mL) was added lead tetraacetate (545 mg, 1.23 mmol) with benzene (2 mL) and the reaction was stirred at room temperature for 1 h and then lead tetraacetate (136 mg, 0.3 mmol) and benzene (1.5 mL) added. After 30 min, the suspension was filtered over Celite® and the filtrate was concentrated to give crude 5-(3-butyl-5-formyl-isoxazol-4-ylmethoxy)-2-methyl-2H-pyrazole-3-carboxylic acid methyl ester as a yellow oil (330 mg). The oil was taken up in methanol (12 mL) and sodium borohydride (97 mg, 2.57 mmol) was added in portions over 3 min. Upon addition, the reaction became a clear light yellow solution containing a black precipitate. After stirring at room temperature for 15 min, the mixture was filtered over Celite® and the filter cake was washed with methanol. The filtrate was concentrated and the residue was portioned between 0.5M aqueous hydrochloric acid and ethyl acetate. The aqueous phase was extracted two times with ethyl acetate and the combined organic phases were washed with brine, dried over sodium sulfate and concentrated to afford a yellow oil. The crude material was purified by chromatography (silica, heptane:ethyl acetate 1:0 to 1:1) to afford the title compound (256 mg, 77%) as a colorless oil. MS: m/e=322.2 [M+H]+.

Provenance & Evidence