To a solution of methyl 4′-((S)-2-((S)-2-((tert-butoxycarbonyl)(methyl)amino)propanamido)-3-((R)-3,3-dimethyl-5-(((R)-1,2,3,4-tetrahydronaphthalen-1-yl)carbamoyl)-1,3-azasilolidin-1-yl)-3-oxopropyl)-[1,1′-biphenyl]-4-carboxylate (40 mg, 0.053 mmol) in THF (1 mL) and MeOH (0.5 mL) was added LiOH solution (0.48 mL, 0.95 mmol). The resulting mixture was stirred at rt overnight and acidified (1N HCl) to pH 1. The resulting mixture was extracted with ethyl acetate (2×). The organic layer was separated, dried over MgSO4 and concentrated in vacuo to give the title compound. MS(ESI+) m/z 741.5 (M+H)+.
