C([C:4]1[C:5](=[O:13])[NH:6][C:7]([CH:10]([CH3:12])[CH3:11])=[CH:8][CH:9]=1)(O)=O.C1(P(N=[N+]=[N-])(C2C=CC=CC=2)=[O:21])C=CC=CC=1.C([N:33]([CH2:36]C)CC)C.[CH2:38]([OH:45])[C:39]1[CH:44]=[CH:43][CH:42]=[CH:41][CH:40]=1>O1CCOCC1>[CH2:38]([O:45][C:36]([NH:33][C:4]1[C:5](=[O:13])[NH:6][C:7]([CH:10]([CH3:11])[CH3:12])=[CH:8][CH:9]=1)=[O:21])[C:39]1[CH:44]=[CH:43][CH:42]=[CH:41][CH:40]=13-Carboxy-6-isopropyl-2(1H)-pyridinone (2.82 g, 15.6 mmol), as prepared in the preceding step, diphenylphosphoryl azide (3.50 mL, 16.2 mmol), and triethylamine (2.30 mL, 16.5 mmol) were refluxed in 1,4-dioxane (100 mL) for 16 hours. Benzyl alcohol (1.65 mL, 15.9 mmol) and additional triethylamine (2.40 mL, 17.2 mmol) were added and the reaction refluxed another 24 hours. After concentrating the reaction mixture in vacuo, the residue was dissolved in methylene chloride, washed with pH 1 brine, saturated NaHCO3, and pH 7 brine, dried over MgSO4, and filtered. The evaporated filtrate was then purified by flash column chromatography (gradient elution, 10% to 25% ethyl acetate in methylene chloride) giving the title compound as a light yellow solid (1.10 g, 25%). 1H NMR (300 MHz, CDCl3) δ11.61 (br s, 1H), 8.05 (br d, 1H, J=7.2 Hz), 7.67 (s, 1H), 7.39 (m, 5H), 6.08 (d, 1H, J=7.7 Hz), 5.21 (s, 2H), 2.80 (septet, 1H, J=6.9 Hz), 1.28 (s, 3H), 1.26 (s, 3H).
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