| 摘要 |
<p>This invention provides new compounds of formula I, <IMAGE> I wherein R1 is hydrogen, halogen of an atomic number of from 9 to 35, or alkyl of 1 to 4 carbon atoms, R2 is alkyl of 1 to 4 carbon atoms, R4 is alkyl of 1 to 4 carbon atoms, and either I.</p> |
