[SH:1][CH2:2][CH2:3][C:4]([O:6][CH2:7][CH3:8])=[O:5].[C:9]1(=[O:15])[O:14][C:12](=[O:13])[CH2:11][CH2:10]1>CN(C1C=CN=CC=1)C.C(#N)C.N1C=CC=CC=1>[SH:1][CH2:2][CH2:3][C:4]([O:6][CH2:7][CH3:8])=[O:5].[C:9]([OH:14])(=[O:15])[CH2:10][CH2:11][C:12]([OH:5])=[O:13]As shown in FIG. 2, Ethyl 3-mercaptopropionate (2.95 g, 22 mmol) was added under argon to a stirring solution of succinic anhydride (2.0 g, 20 mmol) and DMAP (122 mg, 1 mmol) in 25 ml of acetonitrile-pyridine (9:1). The reaction mixture was stirred at room temperature overnight. The solution was concentrated under reduced pressure and dried in vacuo. The residue was dissolved in 50 ml of EtOAc. The EtOAc solution was washed with 0.1 N HCl aqueous solution 30 ml×3, H2O×3, dried over anhydrous MgSO4. After filtration, the solution was concentrated to dry under reduced pressure and in vacuo. 1H NMR (CDCl3, 500 MHz) δ 10.23 (s, br), 4.14 (2H, q, J=7.0 Hz, —CH2—CH3), 3.13 (2H, t, J=7.0 Hz, —S—CH2—), 2.88 (2H, t, J=7.0 Hz, —S—CO—CH2—), 2.69 (2H, t, J=7.0 Hz, —S—CH2—CH2—), 2.62 (2H, t, J=7.0 Hz, —CH2—COOH), 1.25 (3H, t, J=7.0 Hz, —CH2—CH3).
불러오는 중…