Cl.[CH3:2][O:3][C:4](=[O:10])[C@@H:5]1[CH2:9][CH2:8][CH2:7][NH:6]1.C([N:13](CC)CC)C.[CH2:18]([O:25][C:26]1[CH:34]=[CH:33][C:29]([C:30](O)=[O:31])=[CH:28][CH:27]=1)[C:19]1[CH:24]=[CH:23][CH:22]=[CH:21][CH:20]=1.C1CCC(N=C=NC2CCCCC2)CC1>CN(C=O)C>[CH3:2][O:3][C:4](=[O:10])[C@@H:5]1[CH2:9][CH2:8][CH2:7][N:6]1[NH:13][C:30](=[O:31])[C:29]1[CH:33]=[CH:34][C:26]([O:25][CH2:18][C:19]2[CH:24]=[CH:23][CH:22]=[CH:21][CH:20]=2)=[CH:27][CH:28]=1L-Proline methyl ester hydrochloride (7.2 g, 43.8 mmol) was dissolved in 100 mL of anhydrous DMF at 0° C. To this solution was added triethylamine (4.2 g, 43.8 mmol). After vigorous stirring for 1 hour, the solid triethylamine hydrochloride was removed by filtration. To the filtrate was added 4-benzyloxybenzoic acid (10.0 g, 43.8 mmol) followed by DCC (9.9 g, 48.2 mmol). The reaction mixture was allowed to stir overnight at room temperature. The solid DCU was then removed by filtration, and the filtrated distributed between H2O/ethyl acetate (300 mL ea.). The organic was washed several times with 200 mL portions of H2O to remove DMF. The organic was dried (Na2SO4), and concentrated in vacuo to a solid residue that was chromatographed (SiO2, 15-100% ethyl acetate/hexanes). Isolation provided 5.3 g (35%) of N-(4-benzyloxybenzamido)-L-proline methyl ester as a white solid. MS.
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