[C:1]([O:5][C:6]([N:8]1[CH2:12][C@@H:11]([CH2:13][N:14]([CH:31]([CH3:33])[CH3:32])[C:15](=[O:30])[C:16]2[CH:21]=[CH:20][C:19](OC)=[C:18](OCCCOC)[CH:17]=2)[C@H:10]([C:34](C)(C)[O:35][SiH2]C(C)(C)C)[CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].O.[F-].C([N+:47]([CH2:52][CH3:53])([CH2:50][CH3:51])CC)C.O.C[CH2:56][O:57][C:58](C)=O.[CH3:61]C#N>>[C:1]([O:5][C:6]([N:8]1[CH2:12][C@@H:11]([CH2:13][N:14]([CH:31]([CH3:33])[CH3:32])[C:15]([C:16]2[CH:17]=[C:18]3[C:19]([C:53]([CH3:61])=[CH:52][N:47]3[CH2:50][CH2:51][CH2:56][O:57][CH3:58])=[CH:20][CH:21]=2)=[O:30])[C@H:10]([CH2:34][OH:35])[CH2:9]1)=[O:7])([CH3:2])([CH3:3])[CH3:4]To a solution of (3S,4R)-3-(tert-butyl-dimethyl-silanyloxymethyl)-4-({isopropyl-[4-methoxy-3-(3-methoxy-propoxy)-benzoyl]-amino}-methyl)-pyrrolidine-1-carboxylic acid tert-butyl ester (13.8 g, 22 mmol) in MeCN (350 mL) is added tetraethylammonium fluoride hydrate (6.6 g, 44 mmol) under a nitrogen atmosphere. The reaction mixture is refluxed for 3 h. Water and AcOEt are added, the layers are separated and the aqueous one extracted twice with AcOEt. The combined organic extracts are dried (Na2SO4), filtered and the solvent is removed in vacuo. The crude product is purified by flash chromatography on silica gel (eluent: CH2Cl2/MeOH 100:0 to 90:10) to give the title product. TLC, Rf (CH2Cl2/MeOH 95:5)=0.2. MS (LC-MS): 402.2 [M+H-Boc]+; tR (HPLC, Macherey-Nagel Nucleosil C18 column, 10-100% CH3CN/H2O/5 min, 100% CH3CN/3 min, CH3CN and H2O containing 0.1% TFA, flow: 1.5 mL/min): 6.85 min.
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