C(OC([N:8](C(OC(C)(C)C)=O)[C:9]1[C:10]([C:28]([O:30][CH3:31])=[O:29])=[N:11][C:12]([CH:15]2[CH2:20][CH2:19][N:18](C(OC(C)(C)C)=O)[CH2:17][CH2:16]2)=[CH:13][N:14]=1)=O)(C)(C)C.C(O)(C(F)(F)F)=O>C(Cl)Cl.C(#N)C>[NH2:8][C:9]1[C:10]([C:28]([O:30][CH3:31])=[O:29])=[N:11][C:12]([CH:15]2[CH2:16][CH2:17][NH:18][CH2:19][CH2:20]2)=[CH:13][N:14]=1To a solution of methyl 3-[bis(tert-butoxycarbonyl)amino]-6-(1-tert-butoxycarbonyl-4-piperidyl)pyrazine-2-carboxylate (285 mg) in DCM (7 mL) was added TFA (3 mL) dropwise. The reaction mixture was stirred at room temperature for 1 h, then diluted with acetonitrile and concentrated in vacuo. The reaction mixture was diluted with ethyl acetate, washed with 50% saturated sodium bicarbonate solution (2×20 mL), water, and brine. The product was not able to be extracted from aqueous layer with ethyl acetate, and was taken forward directly to the subsequent acylation step using Schotten-Baumen conditions LC/MS m/z 237.1 [M+H]+.
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