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0 °C

Under an argon atmosphere, 5-(4-acetoxyphenyl)-2-amino-3-benzylpyrazine (c-19) (303 mg, 949 μmol) was dissolved in pyridine (3 mL) and cooled to 0° C. To this was added benzylsulfonyl chloride (362 mg, 1.90 mmol) and the mixture was stirred for 30 min at the same temperature. To this was further added benzylsulfonyl chloride (89.7 mg, 470 μmol) and the mixture was stirred for 30 min at the same temperature. To this was added saturated aqueous solution of sodium bicarbonate to stop the reaction and extracted 3 times with dichloromethane. The organic layer was washed once with water, once with 2 M hydrochloric acid and once with saturated aqueous solution of sodium sulfate, and then dried over anhydrous sodium sulfate. After removing anhydrous sodium saturation by filtration, the filtrate was concentrated under reduced pressure with a rotary evaporator. The residue was filtered through a Kiriyama funnel and recrystallized from ethyl acetate/methanol (1/1) to give 5-(4-acetoxyphenyl)-3-benzyl-2-(benzylsulfonylamino)pyrazine (c-32) as a colorless solid (124 mg, 27.6%). Rf=0.56 (n-hexane/ethyl acetate=1/1). Mp. 240-241° C. UV (MeOH, 0.3% DMSO) λmax (log ε) 324 (4.06), 286.5 (4.13), 264 (4.19). UV (pH PB, 0.3% DMSO) λmax (log ε) 338.5 (4.01), 290 (4.01), 273.5 (4.02). 1H NMR (400 MHz, DMSO-d6) δ 2.29 (s, 3H), 4.25 (s, 2H), 4.92 (s, 2H), 7.14-7.21 (m, 1H), 7.23-7.28 (m, 6H), 7.35 (s, 5H), 8.03-8.12 (AA′BB′, 2H), 8.93 (s, 1H), 10.55 (s, 1H). IR (KBr, cm−1) 530, 700, 889, 920, 1157, 1179, 1204, 1223, 1325, 1420, 1454, 1748, 3267. HRMS (FAB+) m/z 474.1486 (M+H, C26H24N3O4S requires 474.1488).

1. stirringthe mixture was stirred for 30 min at the same temperature
2. customthe reaction
3. extractionextracted 3 times with dichloromethane
4. washThe organic layer was washed once with water, once with 2 M hydrochloric acid and once with saturated aqueous solution of sodium sulfate
5. dry with materialdried over anhydrous sodium sulfate
6. customAfter removing anhydrous sodium saturation
7. filtrationby filtration
8. concentrationthe filtrate was concentrated under reduced pressure with a rotary evaporator
9. filtrationThe residue was filtered through a Kiriyama funnel
10. customrecrystallized from ethyl acetate/methanol (1/1)