Abstract
A facile synthesis for novel loperamide analogs as potential μ opioid receptors is described. The synthetic procedure for compound 5, which contains two 4-phenyl piperidine scaffolds, was optimized, and this compound was synthesized in excellent yield. We also describe a mild and highly efficient protocol for the synthesis of compounds 6 and 7.
Highlights
Opioid ligand receptors are involved in various physiological activities, including analgesia, miosis, bradycardia, general sedation, hypothermia, insensitivity and depression of the flexor reflexes and have been widely used in medicine, most prominently in the treatment of pain [1,2]
Molecules 2012, 17 agonists and show affinity and selectivity for the cloned μ human opioid receptor, they do not pass through the blood–brain barrier (BBB) [12], they are currently mainly used as antidiarrheal drugs
As a consequence of our interest in MORs containing 4-phenylpiperidine scaffolds, we developed a mild and highly efficient protocol for the synthesis of compounds 5, 6 and 7
Summary
Opioid ligand receptors are involved in various physiological activities, including analgesia, miosis, bradycardia, general sedation, hypothermia, insensitivity and depression of the flexor reflexes and have been widely used in medicine, most prominently in the treatment of pain [1,2]. The desired product 5 was obtained in low yield by coupling 10b with the amine 9b in a reaction catalyzed by TiCl4 in toluene refluxing for 20 h (Scheme 2) [23]. Chromatography of the sample on a silica gel column eluted with ammonium hydroxide (2 M) solution in MeOH-CH2Cl2 (5:95 v/v) gave 13b as a pale-yellow solid (1.58 g, 55% yield).
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