Trifluoromethanesulfonic acid → 17-Ethyl-1-hydroxy-14-(tert-butyldimethylsiloxy)-12-[2'-(4"-(m-(tert-butyldimethylsiloxymethyl)benzyloxy)-3"-methoxycyclohexyl)-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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Reaction Steps

To a solution of 17-ethyl-1-hydroxy-14-(tert-butyldimethylsiloxy)-12-[2'-(4"-hydroxy-3"-methoxycyclohexyl)-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 (230 mg in 3 ml 33% methylene chloride in cyclohexane) was added m-(tert-butyldimethylsiloxymethyl)-benzyltrichloroacetimidate (198 μl neat) and the reagents allowed to mix for 5 minutes. Trifluoromethanesulfonic acid (4.5 μl neat) was added slowly via syringe and the mixture stirred at room temperature. After 1 hour the reaction was quenched by the addition of saturated sodium bicarbonate and extracted with ethyl acetate (3×8 ml). The combined organics were washed with brine and dried over magnesium sulfate. Purification of the concentrate by preparative TLC on silica gel (ethyl acetate: hexane (1:2)+1% methanol) gave the title compound (165 mg)

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