✍ Scribed by Zhi-Hao Shi; Yun-Yang Wei; Chuan-Jin Wang; Li Yu
No coin nor oath required. For personal study only.
Endomorphin‐2 (1; H‐Tyr‐Pro‐Phe‐Phe‐NH~2~; EM2) and its novel cyclic asparagine (__cyclo__Asn) analogues, H‐Tyr‐__c__Asn(CHPh)‐Phe‐Phe‐NH~2~ (2) and H‐Tyr‐__c__Asn(CHMe~2~)‐Phe‐Phe‐NH~2~ (3), were synthesized via liquid‐phase synthesis. The structures of the products and intermediates were characterized by IR, ^1^H‐NMR, MS, and HR‐MS analyses. The antinociceptive activity of EM2 and its cyclic asparagine analogues were assessed in AcOH‐induced abdominal constriction tests in mice with i.p. injection. The results show that the antinociceptive activities of EM2 and its cyclic asparagine analogue 2 were higher than those of aspirine and meperidine. Analogue 2 was observed to be a stronger analgesic with dose‐dependence than EM2. The test mice did not show any tendency to be addicted while administrated of analogue 2 repeatedly and regularly.
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