Probes for narcotic receptor mediated phenomena. 26. Synthesis and biological evaluation of diarylmethylpiperazines and diarylmethylpiperidines as novel, nonpeptidic delta opioid receptor ligands.
We recently reported (+)-4-¿(alphaR)-alpha-¿(2S,5R)-4-allyl-2, 5-dimethyl-1-piperazinyl¿-3-methoxybenzyl-N,N-diethylbenzamide (1b, SNC80) as a novel nonpeptidic delta receptor agonist and explored the structure-activity relationships (SAR) of a series of related derivatives. We have found that delta binding activities and selectivity showed little change when the 3-methoxy group in 1b was removed or replaced by the other substituents, whereas the N, N-diethylbenzamide group is important for interaction with the delta receptor. Extensive modification of the piperazine nucleus led to the synthesis of a new series of N, N-diethyl(alpha-piperazinylbenzyl)benzamides (2, 3a-e), N, N-diethyl(alpha-piperidinyl or piperidinylidenebenzyl)benzamides (4a, 5a-c, 6a-b), and related derivatives (4b, 7a-c). Several compounds (2, 3a, 3e, 6a) strongly bound to the delta receptor with K(i) values in the low nanomolar range. On the other hand, the binding affinities of these compounds for the mu and kappa receptors were negligible, indicating excellent delta opioid receptor subtype selectivity. The two nitrogen atoms on the piperazine nucleus showed different SAR in the interaction of this series of compounds at the delta receptor. Nitrogen N(4) appears to be an important structural element and is essential for electrostatic interaction, while N(1) seems to be unnecessary for recognition at the delta receptor.
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Laboratory of Medicinal Chemistry, Building 8, Room B1-23, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
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D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D008813:Mice, Inbred ICR; D015335:Molecular Probes; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D010879:Piperazines / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology*; D011869:Radioligand Assay; D051381:Rats; D017465:Receptors, Opioid, delta / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D013329:Structure-Activity Relationship
D008024:Ligands; D015335:Molecular Probes; D010879:Piperazines; D017465:Receptors, Opioid, delta