| 摘要 |
The present invention relates to substantially pure piperidine derivative compounds as shown below, wherein R1 is hydrogen or hydroxy; R2 is hydrogen; or R1 and R2 taken together form a second bond between the carbon atoms bearing R1 and R2; R3 is -COOH or -COOH4; R4 is an alkyl with 1 to 6 carbon atoms; A, B, and D are the substituents of their respective rings each of which may be different or the same and are hydrogen, halogens, alkyl, hydroxy, alkoxy, or other substituents. A process of preparing such piperidine derivative compounds in substantially pure form is also disclosed. (see formula I) or (see formula II)
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