[O:1]1[CH:5]=[CH:4][CH:3]=[C:2]1[C:6](=[N:10][OH:11])[C:7]([OH:9])=[O:8].Br[C:13]1([C:18]([O:20][C:21]([CH3:24])([CH3:23])[CH3:22])=[O:19])[CH2:17][CH2:16][CH2:15][CH2:14]1>O>[C:21]([O:20][C:18]([C:13]1([O:11][N:10]=[C:6]([C:2]2[O:1][CH:5]=[CH:4][CH:3]=2)[C:7]([OH:9])=[O:8])[CH2:17][CH2:16][CH2:15][CH2:14]1)=[O:19])([CH3:24])([CH3:22])[CH3:23]The dipotassium salt of 2-(fur-2-yl)-2-hydroxyiminoacetic acid (syn isomer) was generated under an atmosphere of dry nitrogen and alkylated with t-butyl 1-bromocyclopentanecarboxylate using the method of Preparation 2. The product was isolated by pouring into water, acidifying and extracting in the conventional manner, thereby yielding the title compound, m.p. 106.8°-107.3°; λmax (pH 6 buffer) 277.5 nm (ε 15,100); τ(d6 -DMSO) values include 8.03, 8.30 (m, cyclopentyl protons) and 8.63 (C(CH3)3).
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