[CH3:1][CH:2]1[CH2:7][C:6]([C:8]2[N:9]=[CH:10][C:11]([NH2:14])=[N:12][CH:13]=2)=[CH:5][CH2:4][O:3]1>CO.[Pd]>[CH3:1][C@@H:2]1[CH2:7][C@H:6]([C:8]2[N:9]=[CH:10][C:11]([NH2:14])=[N:12][CH:13]=2)[CH2:5][CH2:4][O:3]1.[CH3:1][C@H:2]1[CH2:7][C@@H:6]([C:8]2[N:9]=[CH:10][C:11]([NH2:14])=[N:12][CH:13]=2)[CH2:5][CH2:4][O:3]1To a solution of 5-(2-methyl-3,6-dihydro-2H-pyran-4-yl)pyrazin-2-amine (250 mg, 1.307 mmol) in MeOH (13.100 mL) was added Pd/C (278 mg, 0.261 mmol). The solution was degassed by N2 stream for 10 min. After flushed by H2 gas, hydrogen balloon was equipped. The reaction mixture was stirred for 25 h. After filtered through Celite, the volatile material was removed to give the crude product, which was purified with flash chromatography eluting with 0-10% of MeOH in DCM to provide 180 mg of diastereomers. Then chiral separation (ChiralPak 5mic AD column, 4.6×100 (mm), 5 mL/min, EtOH+0.1% DEA=15%) provided 40 mg of 5-((2R,4R)-2-methyltetrahydro-2H-pyran-4-yl)pyrazin-2-amine (Rt=1.32 min; LCMS (m/z): 194.2 (MH+), 0.44 min) in 22% yield and 30 mg of desired 5-((2S,4S)-2-methyltetrahydro-2H-pyran-4-yl)pyrazin-2-amine (Rt=1.83 min; LCMS (m/z): 194.2 (MH+), 0.44 min) in 16% yield.
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