| 摘要 |
<p>The invention comprises 2-(C1- 5 alkyl)-6-halo-4H - pyrazino[2,3 - d][1,3]oxazin - 4 - ones and the preparation thereof by heating a 3-amino-6-halopyrazinoic acid with a C2- 6 alkanoic acid anhydride. The example relates to 2-methyl-6-chloro - 4H - pyrazino[2,3 - d][1,3] - oxanin - 4 - one. The starting material, 3-amino-6-chloropyraninoic acid, is made by alkaline hydrolysis of the corresponding methyl ester.</p> |
