C(O[C@H]1C[N:8]([C:10]([O:12][C:13]([CH3:16])(C)C)=O)[C@@H](C(O)=O)C1)C=C.COC[C@H]1CCCN1C(C1C=C(C=C(C2OC=CN=2)C=1)C(OC)=O)=O.O1C=CN=C1.C([Li])CCC.[CH2:55]([Sn:59](Cl)([CH2:64][CH2:65][CH2:66][CH3:67])[CH2:60][CH2:61][CH2:62][CH3:63])[CH2:56][CH2:57][CH3:58]>C1COCC1>[CH2:64]([Sn:59]([CH2:55][CH2:56][CH2:57][CH3:58])([CH2:60][CH2:61][CH2:62][CH3:63])[C:10]1[O:12][CH:13]=[CH:16][N:8]=1)[CH2:65][CH2:66][CH3:67]Step H (2): Preparation of methyl 3-((R)-2-(methoxymethyl)pyrrolidine-1-carbonyl)-5-(oxazol-2-yl)benzoate. To a solution of oxazole (2.0 g, 29.0 mmol) in THF (30 mL) was added n-butyl lithium (2.0 M solution in cyclohexanes, 16 mL, 31.9 mmol) at −78° C. slowly. The reaction mixture was stirred at −78° C. for 1.2 h, then tributylstannyl chloride (5.0 g, 15.4 mmol) was added. The reaction mixture was warmed up to rt over 3 h. Hexanes (200 mL) was added and the mixture was washed with H2O, dried over Na2SO4 and concentrated under vacuum to give 5.6 g of the 2-(tributylstannyl)oxazole ready for use.
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