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Under an argon atmosphere, 5-(4-acetoxyphenyl)-2-amino-3-benzylpyrazine (c-19) (337 mg, 1.05 mmol) was dissolved in anhydrous dichloromethane (9 mL), and to this was added triethylamine (220 μL, 1.58 mmol) and stirred at room temperature. To this was added methanesulfonyl chloride (245 μL, 3.16 mmol) and stirred for 1.5 h at the same temperature. To this was added 2 M hydrochloric acid to stop the reaction and after separating the aqueous layer and organic layer, the organic layer was washed with saturated aqueous solution of sodium sulfate and dried over anhydrous sodium sulfate. After removing anhydrous sodium sulfate by filtration, the filtrate was concentrated under reduced pressure with a rotary evaporator. The residue was purified by silica gel column chromatography (28 g, n-hexane/ethyl acetate=3/1→3/2) to give 5-(4-acetoxyphenyl)-3-benzyl-2-bis(methanesulfonyl)aminopyrazine (c-39) as a yellow amorphous (241 mg, 48.3%). Rf=0.32 (n-hexane/ethyl acetate=3/2). Mp. 165.5-167° C. UV (MeOH) λmax (log ε) 306 (4.29), 293 (4.25), 259 (4.21). UV (pH PB) λmax (log ε) 336.5 (4.19), 264 (4.09). 1H NMR (400 MHz, DMSO-d6) δ 2.29 (s, 3H), 3.59 (s, 6H), 4.36 (s, 2H), 7.20-7.26 (m, 1H), 7.26-7.35 (m, 6H), 8.11-8.17 (AA′BB′, 2H), 9.14 (s, 1H). 13C NMR (75.5 MHz, DMSO-d6) δ 20.9, 38.5, 43.1 (1C×2), 122.7 (2C), 126.6, 128.3 (2C), 128.6 (2C), 129.5 (2C), 132.1, 137.6, 139.2, 141.5, 151.4, 152.5, 155.6, 169.0. IR (KBr, cm−1) 509, 523, 706, 756, 766, 912, 974, 1015, 1163, 1200, 1321, 1368, 1418, 1435, 1528, 1603, 1755, 3032. HRMS (FAB+) m/z 476.0936 (M+H, C21H22N3O6S2 requires 476.0950).

1. stirringstirred for 1.5 h at the same temperature
2. customthe reaction
3. customafter separating the aqueous layer and organic layer
4. washthe organic layer was washed with saturated aqueous solution of sodium sulfate
5. dry with materialdried over anhydrous sodium sulfate
6. customAfter removing anhydrous sodium sulfate
7. filtrationby filtration
8. concentrationthe filtrate was concentrated under reduced pressure with a rotary evaporator
9. customThe residue was purified by silica gel column chromatography (28 g, n-hexane/ethyl acetate=3/1→3/2)