Hydrochloric Acid → HCID 69422026, Verbindung

2,3-Bis-((3R,5S)-3,5-bis-(tert-Butoxycarbonylamino)-piperidin-1-yl)-6-nitro-quinoxaline (245) (0.05 g, 0.135 mmol) was dissolved in TFA (3 mL) and the mixture was shaken at room temperature in a Teflon septum capped vial 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 (255) as an orange powder (0.023 g, 0.042 mmol, 31% yield, assumed 4 HCl salt). LC-MS (ESI): (exact mass: 401.23) m/e=402.2 [M+1]+. 1H NMR (400 MHz, D2O): δ 1.72 (q, 2H, J=12 Hz), 2.49 (d, 2H, J=10 Hz), 2.94 (q, 4H, J=12 Hz), 3.51–3.67 (m, 4H), 4.44 (dd, 2H, J1=12 Hz, J2=4.4 Hz), 4.57 (dd, 2H, J1=12.8 Hz, J2=3.6 Hz), 7.71 (d, 1H, J=9.2 Hz), 8.10 (dd, 1H, J1=9.2 Hz, J2=2.8 Hz), 8.44 (d, 1H, J=2.4 Hz).