Reaction SMILES: C([O-])(=O)C.[NH4+].ClC(Cl)(Cl)C[O:9][C:10]([C@@H:12]1[CH2:17][CH2:16][CH2:15][N:14]([C:18](=[O:50])[C@@H:19]([NH:35][C:36](=[O:49])[C@@H:37]([NH:41][C:42](OC(C)(C)C)=[O:43])[CH:38]([CH3:40])[CH3:39])[CH2:20][C:21]2[CH:26]=[CH:25][CH:24]=[C:23]([O:27][Si:28]([C:31]([CH3:34])([CH3:33])[CH3:32])([CH3:30])[CH3:29])[CH:22]=2)[NH:13]1)=[O:11].O1[CH2:57][CH2:56][CH2:55][CH2:54]1>O.[Zn]>[C:31]([Si:28]([CH3:29])([CH3:30])[O:27][C:23]1[CH:22]=[C:21]([CH2:20][C@H:19]([NH:35][C:36](=[O:49])[C@@H:37]([NH:41][C:42](=[O:43])[CH2:57][CH2:56][CH:55]=[CH2:54])[CH:38]([CH3:40])[CH3:39])[C:18]([N:14]2[CH2:15][CH2:16][CH2:17][C@@H:12]([C:10]([OH:9])=[O:11])[NH:13]2)=[O:50])[CH:26]=[CH:25][CH:24]=1)([CH3:33])([CH3:34])[CH3:32]
Reactant: CC(C)[C@H](NC(=O)OC(C)(C)C)C(=O)N[C@@H](Cc1cccc(O[Si](C)(C)C(C)(C)C)c1)C(=O)N1CCC[C@@H](C(=O)OCC(Cl)(Cl)Cl)N1
Reactant: C1CCOC1
Agent: CC(=O)[O-]
Agent: [NH4+]
Agent: [Zn]
Solvent: O
Product: C=CCCC(=O)N[C@H](C(=O)N[C@@H](Cc1cccc(O[Si](C)(C)C(C)(C)C)c1)C(=O)N1CCC[C@@H](C(=O)O)N1)C(C)C
Temperature: 25 °C
Reaction time: 72 h
Yield: 97 %

Procedure:
Ammonium acetate (548 mg, 7.11 mmol) was added to a mixture of (S)-1-{(S)-2-((S)-2-tert-butoxycarbonylamino-3-methyl-butyrylamino)-3-[3-(tert-butyl-dimethyl-silanyloxy)-phenyl]-propionyl}-hexahydro-pyridazine-3-carboxylic acid 2,2,2-trichloro-ethyl ester (750 mg, 1.016 mmol) and zinc dust (664 mg, 10.16 mmol) in tetrahydrofuran (20 mL) and water (7 mL) and the reaction mixture was stirred for 3 days at room temperature. The mixture was filtered through celite and the residue was washed with ethyl acetate. The organic layer was washed with an aqueous citric acid solution and water, dried over anhydrous sodium sulfate and the solvent evaporated to afford (S)-1-[(S)-3-[3-(tert-butyl-dimethyl-silanyloxy)-phenyl]-2-((S)-3-methyl-2-pent-4-enoylamino-butyrylamino)-propionyl]-hexahydro-pyridazine-3-carboxylic acid (599 mg, 97%) as a colourless foam which was used crude in the next step. N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (265 mg, 1.38 mmol) and 4-dimethylaminopyridine (60 mg, 0.494 mmol) was added to a solution of (S)-1-[(S)-3-[3-(tert-butyl-dimethyl-silanyloxy)-phenyl]-2-((S)-3-methyl-2-pent-4-enoylamino-butyrylamino)-propionyl]-hexahydro-pyridazine-3-carboxylic acid (599 mg, 0.987 mmol) and (4-vinyl-pyridin-2-yl)-methanol (1.34 mmol) in dichloromethane (10 mL) and the reaction mixture was stirred at room temperature for 18 hours. The solution was washed with aqueous citric acid and saturated sodium hydrogen carbonate solution, dried over anhydrous sodium sulfate and the solvent evaporated. The residue was purified by silica gel chromatography using iso-hexanes/ethyl acetate 1:4 to afford the title compound (386 mg, 54%) as a colourless foam. 1H NMR (300 MHz, CDCl3) δ0.20 (s, 6H), 0.88 (d, J=6.9 Hz, 3H), 0.94 (d, J=6.9 Hz, 3H), 0.97 (s, 9H), 1.46 (s, 9H), 1.5-2.2 (m, 7H), 2.6-3.1 (m, 3H), 3.55-3.65 (m, 1H), 3.92-3.98 (m, 1H), 4.25-4.35 (m, 1H), 5.07 (d, J=8.7 Hz, 1H), 5.27-5.31 (m, 2H), 5.57 (d, J=10.9 Hz, 1H), 5.72-5.80 (m, 1H), 6.03 (d, J=17.6 Hz, 1H), 6.50 (d, J=8.0 Hz, 1H), 6.67-6.82 (m, 4H), 7.05-7.10 (m, 1H), 7.37 (s, 1H), 8.56 (d, J=5.1 Hz, 1H). LCMS (m/z) 724 [M+H], Tr=5.75 min.