[P:1](N(C)C)(N(C)C)N(C)C.C(Br)(Br)(F)F.[C:16]([O:20][C:21]([C@@H:23]([N:26]1[C:30](=[O:31])[CH2:29][CH:28]([CH:32]=[O:33])[CH2:27]1)[CH2:24][CH3:25])=[O:22])([CH3:19])([CH3:18])[CH3:17].[PH4+].P(CCCC)(CCCC)CCCC.C(F)(Cl)(Cl)Cl>C1COCC1.CCO.CCCCCC>[C:16]([O:20][C:21]([C@@H:23]([N:26]1[C:30](=[O:31])[CH2:29][CH:28]([CH:32]=[O:33])[CH2:27]1)[CH2:24][CH3:25])=[O:22])([CH3:19])([CH3:17])[CH3:18].[PH3:1]
The synthesis of the two diastereoisomers of (2S)-2-(2-oxo-4-(2,2-difluorovinyl)-1-pyrrolidinyl)butanoic acid 2,2-(dimethyl)ethyl ester 399 is representative. In a three necked flask under argon, (Me2N)3P (89.8 g, 0.55 mol.) is added to a solution of CF2Br2 (58 g, 0.25 mol.) in THF (280 ml) at −78° C. (appearance of a white precipitate) and warmed to room temperature. A solution of the aldehyde 396 as a 1/1 mixture of diastereoisomers (35.2 g, 0.138 mol.) in THF is added dropwise to the preformed phosphonium salt. After 1 h, the reaction mixture is filtered through celite and concentrated in vacuo. The reaction mixture is diluted with hexane, washed with brine, dried over magnesium sulfate and concentrated in vacuo to afford the crude olefin which is purified by column chromatography on silicagel (CH2Cl2/MNeOH 99/01 (v/v)) to afford 34.6 g of a 1/1 diastereoisomeric mixture of (2S)-2-(2-oxo-4-(2,2-difluorovinyl)-1-pyrrolidinyl)butanoic acid 2.2-(dimethyl)ethyl ester 399 (87%): 1H NMR (250 MHz, (CD3)2SO): 0.81-0.91 (m, 3H), 1.44 (s, 9H), 1.50-1.75 (m, 1H), 1.80-1.95 (m, 1H), 2.30-2.40 (m, 2H partially overlapped with solvent), 3.00-3.35 (m, 2H), 3.45-3.55 (m, 1H), 4.20-4.40 (m, 1H), 4.60 (ddd, 1H for one diastereoisomer), 4.75 (ddd, 1H for another diastereoisomer). 6.2.4. By Olefination with (nBu)3P/CCl3F Alternatively to §6.2.3., halovinyl derivatives can be obtained by Wittig olefination of the 1-[(1S)-1-(tertbutoxycarbonyl)propyl]-5-oxo-3-pyrrolidinecarboxaldehyde 396 in the presence of a phosphine and an halogenomethane. For example of 2-(2-oxo-4-(2-(Z)-fluorovinyl)-1-pyrrolidinyl)butanoic acid 2,2-(dimethyl)ethyl ester is obtained from aldehyde 396 by successive reaction with CFCl3 and n-Bu3P followed by dephosphorylation of the intermediate vinylic phosphonium by NaOH. 6.2.5. Synthesis of the 4-cyano-pyrrolidone Alternatively, 4-cyano-pyrrolidone derivatives are obtained by reacting 1-[(1S)-1-(tertbutoxycarbonyl)propyl]-5-oxo-3-pyrrolidinecarboxaldehyde 396 with hydroxylamine followed by SeO2. 6.3. Amination of the 2.2-dimethyl-ethyl Ester 63.1. Deprotection with Trifluoroacetic Acid and Aminolysis The synthesis of the two diastereoisomers of (2S)-2-(2-oxo-4-(2,2-difluorovinyl)-1-pyrrolidinyl)butanamide 213 and 222 is representative:
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