Br[CH2:2][C:3](=O)[CH:4]([CH3:6])[CH3:5].C(OC(C1O[S:15]C=CC=1)=O)C.[NH3:19].[CH3:20][CH2:21][O:22][C:23]([CH3:25])=[O:24]>C(O)C.O>[CH:4]([C:3]1[N:19]=[C:25]([C:23]([O:22][CH2:21][CH3:20])=[O:24])[S:15][CH:2]=1)([CH3:6])[CH3:5]
A solution of compound 211 (3.5 g, 1.25 eq.) and ethylthioxamate (2.3 g, 1 eq.) in ethanol (40 mL) was heated to 80° C. for 6 hrs, and then cooled to 0° C. The reaction mixture was diluted with water and EtOAc, and then neutralized to pH 7 with NH3 (28%). The aqueous layer was extracted with EtOAc. The combined organic layers were dried over sodium sulfate and then removed under reduced pressure. The residue was purified by chromatography on silica gel to yield compound 212 as yellow oil in quantitative yield. 1H NMR (DMSO-d6, 400 MHz): δ (ppm) 1.25 (d, J=6.73 Hz, 6H), 1.31 (t, J=7.24 Hz, 3H), 3.11 (hep, J=6.73 Hz, 1H), 4.35 (q, J=7.24 Hz, 2H), 7.72 (s, 1H).
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