[N+:1]([C:4]1[CH:9]=[CH:8][C:7]([C:10]2[CH:15]=[CH:14][CH:13]=[C:12]([C:16]([OH:18])=[O:17])[CH:11]=2)=[CH:6][CH:5]=1)([O-:3])=[O:2].C(Cl)(=O)C(Cl)=O.[C:25](O)([CH3:28])([CH3:27])[CH3:26].[Li]CCCC>C(Cl)Cl.CN(C=O)C.C1COCC1>[N+:1]([C:4]1[CH:5]=[CH:6][C:7]([C:10]2[CH:15]=[CH:14][CH:13]=[C:12]([C:16]([O:18][C:25]([CH3:28])([CH3:27])[CH3:26])=[O:17])[CH:11]=2)=[CH:8][CH:9]=1)([O-:3])=[O:2]
To a solution of 15 (1.215 g, 5 mmol) in 30 mL of methylene chloride was added oxalyl chloride (0.65 mL, 7.45 mmol) and one drop of DMF. The mixture was stirred until no further bubbling was observed. The clear solution was exaporated to dryness to give the crude acid chloride. To another flask containing 7.0 mL of tert-butanol was added n-BuLi (1.8 M in hexane, 2.8 mL, 5.04 mmol) under a water bath. The turbid solution was stirred for 5 min at room temperature and then the above acid chloride in 20 mL of THF was added through a dropping funnel. The mixture was stirred overnight before the solvents were evaporated. The residue was dissolved into methylene chloride and washed with 0.5 N NaOH. The organic layer was dried over MgSO4 and evaporated. The residue was recrystallized from methanol to give pale yellow crystals (851 mg, 57%). m.p. 110.5-111.0° C. 1H NMR (CDCl3) δ 8.32 (d, 7.8 Hz, 2H), 8.24 (s, 1H), 8.06 (d, 7.7 Hz, 1H), 7.77 (m, 3H), 7.56 (t, 7.7 Hz, 1H), 1.63 (s, 9H). 13C NMR (CDCl3) δ 165.1, 147.1, 146.5, 138.7, 132.8, 131.0, 129.6, 129.0, 128.2, 127.8, 124.0, 81.4, 28.0, LRMS (EI) for C17H17O4N 299 (M+, 20), 243 (70), 266 (30), 152 (25; HRMS (EI) calcd 299.1157, obsd 299.1192. Anal. (C17H17NO4) C, H, N.
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