| 摘要 |
<p>Compounds having the structure , , , and , and the pharmaceutically acceptable salts thereof, wherein R1 is hydrogen, halogen, hydroxy, alkanoyloxy, alkoxy, alkylthio, alkyl or trifluoromethyl; R2 is hydrogen, alkyl or alkenyl; R3 is hydrogen, halogen or alkyl; R4 is formyloxy or alkanoyloxy; m is 1 or 2; and n is 0, 1 or 2; have useful physiological activity.</p> |
