| 摘要 |
A compound having the formula <IMAGE> wherein a is 0 or 1, R1 is hydrogen or lower alkyl, A is lower alkylene or lower alkylidene, and R2 and R3, which can be the same or different, are hydrogen, lower alkyl, cycloalkyl, benzyl or substituted benzyl, or <IMAGE> form a saturated heterocyclic ring, and pharmacologically acceptable acid addition salt thereof, exhibits anti-viral activity and is free from significant effect on the central nervous system.
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