[CH3:1][N:2]([CH3:15])[C:3]([N:5]1[CH2:9][CH:8]2[CH2:10][CH:11]([C:13]#[N:14])[CH2:12][CH:7]2[CH2:6]1)=[O:4].[CH2:16](Cl)[C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1.C[Si](C)(C)[N-][Si](C)(C)C.[Li+]>O1CCCC1>[CH3:1][N:2]([CH3:15])[C:3]([N:5]1[CH2:9][CH:8]2[CH2:10][C:11]([CH2:16][C:17]3[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=3)([C:13]#[N:14])[CH2:12][CH:7]2[CH2:6]1)=[O:4]5-Cyano-hexahydro-cyclopenta[c]pyrrole-2-carboxylic acid dimethylamide 12a (4.0 g, 19.3 mmol) was dissolved in 60 mL of tetrahydrofuran with stirring followed by addition of benzyl chloride (5.4 g, 42.5 mmol) and lithium hexamethyldisilazide (42.5 mL, 42.5 mmol) under nitrogen atmosphere. The reaction mixture was stirred at room temperature for 4 hours. The reaction was monitored by TLC until the disappearance of the starting materials and quenched with 50 mL of water. The mixture was extracted with ethyl acetate. The combined organic extracts were dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain the title compound 5-benzyl-5-cyano-hexahydro-cyclopenta[c]pyrrole-2-carboxylic acid dimethylamide 14a (2.6 g, yield 46%) as a light yellow solid.
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