[Cl:1][C:2]1[C:7]([C:8]([OH:10])=[O:9])=[C:6](Cl)[N:5]=[C:4]([S:12][CH3:13])[N:3]=1.CN(C)[C:16](=[O:18])C.O1CCCC1.[H-].[Na+]>CO>[Cl:1][C:2]1[C:7]([C:8]([OH:10])=[O:9])=[C:6]([O:18][CH3:16])[N:5]=[C:4]([S:12][CH3:13])[N:3]=1A mixture of 4,6-dichloro-5-carboxy-2-methylthiopyrimidine (prepared in Example 320(1)) 5.00 g, N,N-dimethylacetamide 50 ml, tetrahydrofuran 20 ml and sodium hydride (60%) 1.673 g is stirred for 20 minutes on an ice bath. Methanol 5 ml is dropped thereto over a period of 30 minutes and the mixture is stirred for 15 minutes. The reaction mixture is diluted with a 10% aqueous citric solution and extracted with ethyl acetate. The organic layer is washed, dried and concentrated in vacuo. The resulting solid is triturated with hexane in ice to give 4-chloro-5-carboxy-6-methoxy-2-methylthiopyrimidine as a slightly brown crystalline powder, 4.61 g. mp 179-181° C.
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