2-Nitrobenzenesulfonyl chloride → 17-Ethyl-1-hydroxy-12-[2'-[3"-(2"'-nitrobenzenesulfonyloxy)-4"-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 (200 mg, Example 38) in dry methylene chloride (20 ml) was added diisopropylethylamine (150 μl) followed by 2-nitrobenzenesulonyl chloride (60 mg), then 4-dimethylaminopyridine (27 mg). The yellow solution was stirred at room temperature under nitrogen atmosphere for 4 h, then quenched with sat'd aqueous sodium bicarbonate solution. The organic layer was washed (water, sat'd NaHCO3, sat'd NaCl), dried (anhydrous Na2SO4) and the solvent was removed in vacuo. Chromatography on silica gel (2:1 ethyl acetate/hexane) gave 70 mg of the title compound A and 60 mg of the title compound B (Mass, 1H and 13C NMR data were consistent with the structures).

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