[C:1]([O:5][C:6]([N:8]([O:19][CH2:20][CH2:21][NH:22]C(OCC1C=CC=CC=1)=O)[C:9]([NH:11][C:12]([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:13])=[NH:10])=[O:7])([CH3:4])([CH3:3])[CH3:2]>[Pd].C(O)C.O1CCCC1>[C:1]([O:5][C:6]([N:8]([O:19][CH2:20][CH2:21][NH2:22])[C:9]([NH:11][C:12]([O:14][C:15]([CH3:17])([CH3:16])[CH3:18])=[O:13])=[NH:10])=[O:7])([CH3:4])([CH3:3])[CH3:2]A mixture of [N,N′-di(tert-butoxycarbonyl)]2-(benzyloxycarbonylamino) ethoxyguanidine (730 mg, 1.5 mmol), as prepared in the preceding step, 10% palladium on carbon (70 mg) in ethanol (20 mL) and tetrahydrofuran (20 mL) was hydrogenated under hydrogen (balloon) for 30 min. The catalysts were removed by filtration through Celite and the filtrate was concentrated in vacuo. The residue was purified on a Waters Sep-Pak (10 g, 95:5 methylene chloride: methanol saturated with ammonia) to give the title compound as a colorless oil (290 mg, 61%). 1H-NMR (300 MHz, CDCl3) δ 9.08 (br s, 1H), 4.08 (t, J=5.2 Hz, 2H), 2.99 (q, J =5.1 Hz, 2H), 1.50 (s, 9H), 1.48 (s, 9H).
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