[CH3:1][C:2]1(O)[C:10]2[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=2[N:4]2[CH2:11][CH2:12][CH2:13][N:14]=[C:3]12.S(=O)(=O)(O)O.O.C(=O)(O)[O-:23].[Na+].[C:27](#[N:29])[CH3:28]>CS(O)(=O)=O>[C:27]([NH:29][C:2]1([CH3:1])[C:10]2[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=2[N:4]2[CH2:11][CH2:12][CH2:13][N:14]=[C:3]12)(=[O:23])[CH3:28]A solution of 2,3,4,10-tetrahydro-10-methylpyrimido [1,2-a]indol-10-ol (0.444 g) in acetonitrile (4 ml) and methanesulphonic acid (10 drops) was adde dropwise over 5 min to stirred sulphuric acid 98% w/w (2.5 ml) at 50°-60°. After 2.5h, the solution was poured into water (100 ml), basified with sat. aqueous sodium bicarbonate, and extracted with chloroform (3×100 ml). The extracts were washed with water (200 ml), dried (MgSO4), and evaporated in vacuo to give the title compound as the free base (0.07 g).
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