C([Li])CCC.[CH3:6][P:7](=[O:14])([O:11][CH2:12][CH3:13])[O:8][CH2:9][CH3:10].[C:15]([O:19][C:20]([N:22]1[CH2:26][CH2:25][C@H:24]([C:27](=[O:32])N(OC)C)[CH2:23]1)=[O:21])([CH3:18])([CH3:17])[CH3:16].O>C1COCC1>[CH2:9]([O:8][P:7]([CH2:6][C:27]([CH:24]1[CH2:25][CH2:26][N:22]([C:20]([O:19][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:21])[CH2:23]1)=[O:32])([O:11][CH2:12][CH3:13])=[O:14])[CH3:10]Add butyl lithium (98.0 mL, 157 mmol) dropwise to a solution of diethyl methylphosphonate (23.6 g, 155 mmol) in THF (194 mL) under nitrogen at −78° C. over 15 minutes. Add (S)-3-(methoxy(methyl)carbamoyl)pyrrolidine-1-carboxylic acid tert butyl ester (5.0 g, 19.4 mmol) in THF and stir at −78° C. for about 3.5 hrs. Pour into water and extract with ethyl acetate (3×). Wash the combined organics with water and brine. Dry (MgSO4), filter, and concentrate. Subject the residue to silica gel chromatography, eluting with 0-50% acetone in chloroform followed by another silica gel chromatography eluting with 0-30% acetone in dichloromethane to afford 3.15 g (47%) of the desired compound. MS (m/z)=294.0 (M−55)
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