C(N(CC)CC)C.[C:8]([CH2:10][C:11]([C:13]1[CH:22]=[CH:21][C:16]([C:17]([O:19][CH3:20])=[O:18])=[CH:15][CH:14]=1)=[O:12])#[N:9].[S:23]1CC(O)S[CH2:25][CH:24]1O.O>CN(C)C=O.C(O)(=O)C.C(OCC)(=O)C>[NH2:9][C:8]1[S:23][CH:24]=[CH:25][C:10]=1[C:11]([C:13]1[CH:22]=[CH:21][C:16]([C:17]([O:19][CH3:20])=[O:18])=[CH:15][CH:14]=1)=[O:12]
Triethylamine (1.331 mL, 9.55 mmol) was added with stirring to a solution of methyl 4-(2-cyanoacetyl)benzoate (4.85 g, 23.87 mmol) and 1,4-dithiane-2,5-diol (1.817 g, 11.93 mmol) in dimethylformamide (10 mL), to give a yellow solution. After 15 min, the solution was heated to 60° C. for 2 hours and stirred at room temperature overnight. Water (50 mL), ethyl acetate (50 mL), and glacial acetic acid (ca. 1-3 mL) were added to the oily residue until the organic layer became clear. After separation of the organic layer and further extraction of the aqueous layer with ethyl acetate (50 mL), the combined organic layers were washed subsequently with 5% aqueous NaHCO3 and H2O, dried over anhydrous MgSO4. The solvent was removed and the residue was purified via ISCO (0-50% EtOAc/Hexanes; 80 g silica gel column) to afford title compound 491 (3.7 g, 59%) as a yellow solid. MS (m/z): 357.4 (M+H).
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