O[C@H:2]([CH2:6][CH2:7][C:8]1[CH:13]=[CH:12][CH:11]=[CH:10][CH:9]=1)[C:3]([O-:5])=[O:4].[N+:14]([C:17]1[CH:25]=[CH:24][C:20]([C:21]([OH:23])=O)=[CH:19][CH:18]=1)([O-:16])=[O:15].[C:26]1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=C[CH:27]=1.N(C(OCC)=O)=NC(OCC)=O>O1CCCC1>[N+:14]([C:17]1[CH:18]=[CH:19][C:20]([C:21]([C@H:2]([CH2:6][CH2:7][C:8]2[CH:13]=[CH:12][CH:11]=[CH:10][CH:9]=2)[C:3]([O:5][CH2:26][CH3:27])=[O:4])=[O:23])=[CH:24][CH:25]=1)([O-:16])=[O:15]To a cold (ice bath) solution of commercially available (R)-2-hydroxy4-phenyl-butyrate, ethyl ester (1.86mL, 9.60 mmole), p-nitrobenzoic acid (6.42 g, 38.4mmole, 4 eq) and triphenylphosphine (10.07 g, 38.4 mmole, 4 eq.) in anhydrous tetrahydrofuran (110 mL) was added diethyl azodicarboxylate (6.05 mL, 38.4 mmole, 4 eq) dropwise over a period of 40 minutes keeping the internal temperature between 4 and 5° C. After stirring for one additional hour at 4-5° C., the ice bath was removed and the solution was allowed to stir at ambient temperature for 5 days. The solvents were removed and the residue was redissolved in a mixture of ether and ethyl acetate (600 mL). Silica gel (200 mL) was added and the solvents removed. The adsorbate was flash chromatographed (gradient (80/20-70/30 petroleum ether/ethyl acetate) to give the title compound as a yellow oil (4.03 g): NMR (CDCl3); δ8.30 (d, J=9 Hz, 2H), 8.18 (d, J=9 Hz, 2H), 7.38-7.18(m, 5H), 5.28 (t, J=2 Hz, 1H), 4.23(q, J=7 Hz, 2H), 2.85 (t, J=8 Hz, 2H), 2.40-2.33 (m, 2H), 1.29 (t, J=7H, 3H); MS [(+) FAB]: [M+H] m/z=358.
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