Imidazole → 17-Ethyl-1-hydroxy-12-[2'-(4"(tert-butyldimethylsiloxy)-3"-hydroxycyclohexyl)-1'-methylvinyl]-23,25-dimethoxy-13,19,21,27-tetramethyl-11,28-dioxa-4-azatricyclo[22.3.1.04,9]octacos-18-ene-2,3,10,16-tetraone

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To a solution of 17-ethyl-1-hydroxy-12-[2'-(3",4"-dihydroxycyclohexyl)-1'-methylvinyl]-23,25-dimethoxy-13,19,21,27-tetramethyl-11,28-dioxa-4-azatricyclo[22.3.1.04,9 ]octacos-18-ene-2,3,10,16-tetraone (1.04 g) in dry methylene chloride (25 ml) was added an excess of imidazole (280 mg) followed by tert-butyldimethylsilyl chloride (228 mg). After 21 hours of stirring at room temperature, the mixture was quenched by the addition of half-saturated sodium bicarbonate and extracted with ethyl acetate. The combined organics were washed with brine, dried over magnesium sulfate and purified by flash chromatography (ethyl acetate:hexane (1:2)+1% methanol) to give the title compound (370 mg).

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