[CH3:1][O:2][C:3](=[O:19])[CH2:4][O:5][C:6]1[CH:15]=[CH:14][C:13]([S:16]C#N)=[C:12]2[C:7]=1[CH2:8][CH2:9][CH2:10][O:11]2.SC[C@H]([C@@H](CS)O)O.OP([O-])(O)=O.[K+]>CO>[CH3:1][O:2][C:3](=[O:19])[CH2:4][O:5][C:6]1[CH:15]=[CH:14][C:13]([SH:16])=[C:12]2[C:7]=1[CH2:8][CH2:9][CH2:10][O:11]2A solution of (8-thiocyanato-chroman-5-yloxy)-acetic acid methyl ester (1.3 g, 4.6 mmol), dithiothreitol (910 mg, 6 mmol), and KH2PO4 (4.6 mL of a 0.02M solution) in 30 mL MeOH was heated at reflux for 1 hour after which time the reaction was cooled and concentrated in vacuo. Purification by flash column chromatography (gradient elution: 10% EtOAc/hexanes to 35% EtOAc/hexanes) gave the title compound (710 mg, 61%) as a pale yellow solid. 400 MHz 1H NMR (DMSO-d6) δ 6.97 (d, 1H, J=8.5 Hz), 6.31 (d, 1H, J=8.5 Hz), 4.70 (s, 2H), 4.40 (s, 1H), 4.11 (t, 2H, J=5.4 Hz), 3.63 (s, 3H), 2.56 (t, 2H, J=6.3 Hz), 1.84 (m, 2H).; MS m/z 255 (M+1).
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