A pharmaceutical compound of the formula
 in which R¹ is halo-C₁₋₁₀ alkyl, C₁₋₁₀ alkylthio, halo-C₁₋₁₀ alkylthio or optionally substituted phenylthio, R² is hydrogen or C₁₋₄ alkyl, R³ and R⁴ are each hydrogen or C₁₋₄ alkyl, and X is oxygen or sulphur; and salts thereof.
                            一种药物化合物,其
化学式为
 其中 R¹ 是卤代-₁₋₁₀ 烷基、C₁₋₁₀ 烷
硫基、卤代-₁₋₁₀ 烷
硫基或任选取代的苯
硫基、R² 是氢或 C₁₋₄ 烷基,R³ 和 R⁴ 分别是氢或 C₁₋₄ 烷基,X 是氧或
硫;及其盐类。