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Under an argon atmosphere, 5-(4-acetoxyphenyl)-2-amino-3-benzylpyrazine (c-19) (194 mg, 607 μmol) was dissolved in pyridine (2 mL) and to this was added 4-(dimethylamino)pyridine (7.8 mg, 64 μmol) and cooled to 0° C. To this was added phenylacetyl chloride (160 μL, 1.21 mmol) and stirred for 2 h after warming to room temperature. To this was added saturated aqueous solution of sodium bicarbonate to stop the reaction and after collecting the precipitate by filtration using a Kiriyama funnel, the residue was dried in vacuo to give 5-(4-acetoxyphenyl)-3-benzyl-2-(phenylacetylamino)pyrazine (c-30) as a colorless solid (53.9 mg, 20.3%). Rf=0.24 (n-hexane/ethyl acetate=3/2). Mp. 228-231° C. UV (MeOH, 0.3% DMSO) λmax (log ε) 318 (4.19), 290 (4.17), 259 (4.24). 1H NMR (400 MHz, DMSO-d6) δ 2.29 (s, 3H), 3.68 (s, 2H), 4.07 (s, 2H), 7.01-7.08 (AA′BB′, 2H), 7.11-7.22 (m, 3H), 7.23-7.29 (m, 3H), 7.31-7.38 (m, 4H), 8.07-8.14 (AA′BB′, 2H), 8.93 (s, 1H), 10.57 (s, 1H). IR (KBr, cm−1) 706, 851, 918, 1157, 1206, 1223, 1346, 1366, 1410, 1449, 1495, 1543, 1576, 1670, 1755, 3248. HRMS (FAB+) m/z 438.1806 (M+H, C27H24N3O3 requires 438.1818).

1. temperatureafter warming to room temperature
2. customthe reaction
3. customafter collecting the precipitate
4. filtrationby filtration
5. customthe residue was dried in vacuo