Trifluoroacetic acid → Ethyl acetate methanol ammonium hydroxide

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N-(Triphenylmethyl)-O-[4-[6-benzyloxy-3-[3-methoxy-4-[(1-pyrrolidinyl)methyl]benzyl]benzo[b]thiophen-2-yl]phenyl]-L-serine methyl ester (165 mg, 0.18 mmol) in dichloromethane (5 mL) was treated with triethylsilane (0.3 mL) and trifluoroacetic acid (0.3 mL) at ambient temperature for 30 min. The solvent and excess reagents were removed under reduced pressure. The residue was dissolved in THF (3 mL) and treated with an aqueous solution of ammonium formate (25%, 2 mL) and palladium on carbon (10%, 50 mg) at ambient temperature for 21 h before filtration through diatomaceous earth with dichloromethane and methanol rinse. The filtrate was extracted with dichloromethane (30 mL×3) which was washed with water (50 mL). The combined organic layers were dried with sodium sulfate and concentrated under reduced pressure. Chromatography with NH4OH:MeOH:EtOAc (3:7:90) afforded the product as a white solid (26 mg, 25%).

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