Hydrochloric Acid → HCID 58865792, compound

1-Hydroxy-naphthalene-2-carboxylic acid [4-(2,3-bis-((3R,5S)-3,5-bis-(tert-Butoxycarbonylamino)-piperidin-1-yl)-quinoxalin-6-ylcarbamoyl)-phenyl]-amide (253) (9 mg, 8.5 μmmol) was dissolved in TFA (1 mL) and the mixture was shaken in a Teflon septum capped vial at room temperature for 3 hours. LC-MS indicated complete de-protection at this point. The solution was concentrated to give an orange oil. The oil was dissolved in MeOH (1 mL) and HCl (1 mL, 4.0 M in dioxane) was added and the mixture was vortexed for 20 seconds. A fine suspension was observed. The mixture was concentrated to an orange powder. Ethyl ether (5 mL) was added to the powder and vortexed for 2 minutes. The solid was collected by filtration and dried under high vacuum for 16 hours to give the desired product (254) as a yellow/green powder (5.4 mg, 6.69 μmmol, 78.7% yield, assuming a 4 HCl salt). LC-MS (ESI): (exact mass: 660.33) m/e=661.6 [M+1]+. 1H NMR (400 MHz, D2O): δ 1.70–1.82 (m, 2H), 2.61–2.65 (m, 2H), 2.78–2.94 (m, 2H), 3.57–3.60 (m, 2H), 3.67–3.68 (m, 4H), 3.97 (d, 2H, J=9.6 Hz), 4.23 (d, 2H, J=9.6 Hz), 6.89 (d, 1H, J=8.8 Hz), 7.14 (d, 1H, J=8.4 Hz), 7.18–7.29 (m, 3H), 7.32–7.53 (m, 6H), 7.74 (d, 2H, J=7.6 Hz).