S(Cl)(Cl)=O.[Br:5][CH2:6][C@@:7]([OH:12])([CH3:11])[C:8](O)=[O:9].[CH3:13][C:14]1[CH:15]=[C:16]([CH:18]=[CH:19][C:20]=1[N+:21]([O-:23])=[O:22])[NH2:17].O>CC(N(C)C)=O>[Br:5][CH2:6][C@@:7]([OH:12])([CH3:11])[C:8]([NH:17][C:16]1[CH:18]=[CH:19][C:20]([N+:21]([O-:23])=[O:22])=[C:14]([CH3:13])[CH:15]=1)=[O:9]Thionyl chloride (0.48 ml, 6.6 mmol) was added dropwise to a solution of (2R)-3-Bromo-2-hydroxy-2-methylpropionic acid (1.0 g, 5.5 mmol) in 10 ml of DMA at −5 to −10° C. The mixture was stirred for 2 h, and a solution of 3-methyl-4-nitroaniline (0.83 g, 5.5 mmol) in 7 ml of DMA was added to the above mixture. The resulting mixture was stirred for 3 h at room temperature and poured into water (250 ml). The aqueous phase was extracted with ethyl acetate (4×50 ml), dried over Na2SO4 and evaporated. The yield of the desired compound was 2.5 g (contains also DMA), and it was used without further purifications. 1H NMR (DMSO-d6): 1.48 (3H, s), 2.53 (3H, s), 3.58 (1H, d, J=10.4 Hz), 3.82 (1H, d, J=10.4 Hz), 6.34 (1H, bs), 7.86 (1H, dd, J=9.0 Hz and 2.2 Hz), 7.91 (1H, d, J=2.2 Hz), 8.04 (1H, d, J=9.0 Hz), 10.09 (1H, bs).
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