[CH2:1]([N:5]1[C:13]2[N:12]=[CH:11][N:10]([CH2:14][CH:15]=[CH2:16])[C:9]=2[C:8](=[O:17])[NH:7][C:6]1=[O:18])[CH2:2][CH2:3][CH3:4].C1C(=O)N([Cl:26])C(=O)C1>CN(C=O)C>[CH2:1]([N:5]1[C:13]2[N:12]=[C:11]([Cl:26])[N:10]([CH2:14][CH:15]=[CH2:16])[C:9]=2[C:8](=[O:17])[NH:7][C:6]1=[O:18])[CH2:2][CH2:3][CH3:4]To a solution of 3-butyl-7-(2-propen-1-yl)-3,7-dihydro-1H-purine-2,6-dione (3.34 g, 13.4 mmol) in anhydrous DMF (19 ml) was added NCS (1.97 g, 14.8 mmol) and left to stir at rt under nitrogen for 22 h. The mixture was concentrated in vacuo to give a yellow solid which was filtered and washed with MeOH to provide a first crop. The filtrate was concentrated to a solid and washed with MeOH to provide a second crop and repeated a further two occasions to provide the title compound. On the final wash the filtrate was further purified by SPE (Si, 20 g) cartridge eluting with EtOAc:cyclohexane (1:1). The combined solids were dried under vacuum to afford the title compound (2.42 g, 64%).
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