[NH2:1][C:2]1[N:3]=[CH:4][C:5]([C:8]#[C:9][CH2:10][C@H:11]([NH:16][C:17]([O:19][C:20]([CH3:23])([CH3:22])[CH3:21])=[O:18])[C:12]([O:14][CH3:15])=[O:13])=[N:6][CH:7]=1.C([O-])=O.[NH4+]>CO.C(OCC)(=O)C.[Pd]>[NH2:1][C:2]1[N:3]=[CH:4][C:5]([CH2:8][CH2:9][CH2:10][C@H:11]([NH:16][C:17]([O:19][C:20]([CH3:23])([CH3:22])[CH3:21])=[O:18])[C:12]([O:14][CH3:15])=[O:13])=[N:6][CH:7]=1A mixture of methyl (S)-5-(5-amino-2-pyrazinyl)-2-[[(1,1-dimethylethoxy)carbonyl]amino]-pent-4-ynoate (10.0 g; 31.2 mmol), ammonium formate (29.7 g; 468.0 mmol) and active 10% palladium-on-charcoal (1.2 g) in methanol (100 ml) is refluxed for 3 hours. The reaction mixture is filtered and concentrated under reduced pressure. The residue obtained is taken up in ethyl acetate (300 ml), washed with brine (2×200 ml), dried over sodium sulphate, filtered and concentrated under reduced pressure. The residue obtained is purified on a column of silica eluted under pressure with a dichloromethane/methanol mixture (96/4). 7.9 g of methyl (S)-5-(5-amino-2-pyrazinyl)-2-[[(1,1-dimethylethoxy)carbonyl]amino]pentanoate are isolated in the form of a viscous oil.
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