Diethyl chlorophosphate → N-(10-methoxymethyl-10H-pyrazino[2,3-b][1,4]benzothiazin-8-ylmethyl)-5-methyl-1,2-oxazole-4-carboxamide

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Reaction Steps

A solution of 520 mg of 5-methyl-1,2-oxazole-4-carboxylic acid and 0.75 ml of triethylamine in tetrahydrofuran (10 ml) was ice-cooled. After adding 0.8 ml of diethyl chlorophosphate, the resulting mixture was stirred at room temperature for 30 minutes. To the reaction mixture was added 5 ml of a solution of 750 mg of 8-aminomethyl-10-methoxymethyl-10H-pyrazino[2,3-b][1,4]-benzothiazine in tetrahydrofuran and the resulting mixture was stirred at room temperature for 1.5 hours. Next, the reaction mixture was distributed into ethyl acetate and an aqueous solution of ammonium chloride. The organic layer was extracted, washed with water and dried over anhydrous sodium sulfate. After distilling off the solvent under reduced pressure, the residue was purified by silica gel column chromatography (eluted with dichloromethane/methanol) to thereby give 520 mg of N-(10-methoxymethyl-10H-pyrazino[2,3-b][1,4]benzothiazin-8-ylmethyl)-5-methyl-1,2-oxazole-4-carboxamide. Further, the product was treated by the same method as the one of Example 434 to thereby give 310 mg of the title compound as yellow crystals.

Provenance & Evidence