2-Nitrobenzenesulfonyl chloride → 17-Ethyl-1-hydroxy-12-[2'-(4"-(o-nitrophenylsulfonyloxy)-3"-isopropyloxycyclohexyl)-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'-(4"-hydroxy-3"-isopropyloxycyclohexyl)-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 (158 mg) in dry methylene chloride (3.5 ml) was added an excess of diisopropylethyl amine (82 μl) and o-nitrophenylsulfonyl chloride (87 mg) followed by addition of 4-dimethylaminopyridine (58 mg). The mixture was stirred at room temperature for 23 hours at which time it was diluted with ethyl acetate, extracted from saturated sodium bicarbonate solution and washed with brine. The combined organics were dried over magnesium sulfate and the concentrate purified by flash chromatography on silica gel (ethyl acetate: hexane (1:1)+1% methanol to give the title compound (130 mg).

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