200 mg of 2-(10-methyl-5,5-dioxo-5,10-dihydrophenothiazin-2-yl)-3-(tetrahydropyran-4-yl)propionic acid, 74.8 mg of commercially available 2-aminothiazole and 220 μl of N,N-diisopropylethylamine are dissolved in 10 ml of dimethylformamide. 212 mg of TOTU are added, and the mixture is stirred at room temperature overnight. The reaction mixture is then diluted by addition of 50 ml of ethyl acetate and washed five times with in each case 30 ml of saturated sodium bicarbonate solution. The organic phase is dried over MgSO4, and the solvent is then removed under reduced pressure. The residue is purified by RP-HPLC. This gives 141 mg of 2-(10-methyl-5,5-dioxo-5,10-dihydrophenothiazin-2-yl)-3-(tetrahydropyran-4-yl)-N-thiazol-2-ylpropionamide as a colorless lyophilisate.
