2-Nitrobenzenesulfonyl chloride → 17-Ethyl-1-hydroxy-12-[2'-(4"-(o-nitrophenylsulfonyloxy)-3"-propyloxycyclohexyl)-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"-propyloxycyclohexyl)-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 (130 mg) in dry methylene chloride (1.75 ml) was added an excess of diisopropylethyl amine (67 μl) and o-nitrophenylsulfonyl chloride (72 mg) followed by addition of 4-dimethylaminopyridine (47 mg). The mixture was stirred at room temperature for 16 hours at which time it was diluted with ethyl acetate, extracted from half-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 (1:2)+1% methanol to give the title compound (111 mg).

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