CPC C07D 491/22 (2013.01) | 7 Claims |
1. A compound or a pharmaceutically acceptable salt thereof, wherein the compound has the structure of formula (i):
wherein,
a is 0;
the carbon atoms marked with p1* and p2* each is asymmetric center, and the asymmetric center is S configured, R configured or racemic;
L1 is selected from —CH2— and
R1 is Cl; and
R2 is F.
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