Benzoic acid, 4-​[[[1,​4-​dihydro-​2-​[[[(3-​methoxyphenyl)​methyl]​amino]​carbonyl]​-​4-​oxothieno[2,​3-​d]​pyrimidin-​5-​yl]​methoxy]​methyl]​-​, sodium salt (1:2)