Investigation of the Bioactive Conformation of Histamine H3 Receptor Antagonists by the Cyclopropylic Strain-Based Conformational Restriction Strategy
摘要:
We previously identified the highly potent histamine H-3 receptor antagonists (1R,2S)-2-[2-(4-chlorobenzylamino)ethyl]-1-(1H-imidazol-4-yl)cyclopropane (1) and its enantiomer ent-1. Although the conformations of 1 and ent-1 are restricted by the central cyclopropane ring, the 2-(4-chlorobenzylamino)ethyl side chain essential for the H3 receptor binding may somewhat freely rotate. To investigate the bioactive conformation, the 1'-ethyl-substituted derivatives 2a and 2b and their enantiomers ent-2a and ent-2b were designed as side chain conformation-restricted analogues of 1 and ent-1, based on the cyclopropylic strain. These compounds were synthesized, and their analysis by NMR and calculations suggested that the side chain moiety was effectively restricted in a syn-form or an anti-form by the cyclopropylic strain as expected. Pharmacological evaluation and docking simulation showed that the bioactive conformations of 1 and ent-1 appear to be the syn-form and the anti-form, respectively. Thus, the cyclopropylic strain can be effectively used for conformational restriction of the side chain moiety of cyclopropane compounds.
Investigation of the Bioactive Conformation of Histamine H3 Receptor Antagonists by the Cyclopropylic Strain-Based Conformational Restriction Strategy
摘要:
We previously identified the highly potent histamine H-3 receptor antagonists (1R,2S)-2-[2-(4-chlorobenzylamino)ethyl]-1-(1H-imidazol-4-yl)cyclopropane (1) and its enantiomer ent-1. Although the conformations of 1 and ent-1 are restricted by the central cyclopropane ring, the 2-(4-chlorobenzylamino)ethyl side chain essential for the H3 receptor binding may somewhat freely rotate. To investigate the bioactive conformation, the 1'-ethyl-substituted derivatives 2a and 2b and their enantiomers ent-2a and ent-2b were designed as side chain conformation-restricted analogues of 1 and ent-1, based on the cyclopropylic strain. These compounds were synthesized, and their analysis by NMR and calculations suggested that the side chain moiety was effectively restricted in a syn-form or an anti-form by the cyclopropylic strain as expected. Pharmacological evaluation and docking simulation showed that the bioactive conformations of 1 and ent-1 appear to be the syn-form and the anti-form, respectively. Thus, the cyclopropylic strain can be effectively used for conformational restriction of the side chain moiety of cyclopropane compounds.
Investigation of the Bioactive Conformation of Histamine H<sub>3</sub> Receptor Antagonists by the Cyclopropylic Strain-Based Conformational Restriction Strategy
We previously identified the highly potent histamine H-3 receptor antagonists (1R,2S)-2-[2-(4-chlorobenzylamino)ethyl]-1-(1H-imidazol-4-yl)cyclopropane (1) and its enantiomer ent-1. Although the conformations of 1 and ent-1 are restricted by the central cyclopropane ring, the 2-(4-chlorobenzylamino)ethyl side chain essential for the H3 receptor binding may somewhat freely rotate. To investigate the bioactive conformation, the 1'-ethyl-substituted derivatives 2a and 2b and their enantiomers ent-2a and ent-2b were designed as side chain conformation-restricted analogues of 1 and ent-1, based on the cyclopropylic strain. These compounds were synthesized, and their analysis by NMR and calculations suggested that the side chain moiety was effectively restricted in a syn-form or an anti-form by the cyclopropylic strain as expected. Pharmacological evaluation and docking simulation showed that the bioactive conformations of 1 and ent-1 appear to be the syn-form and the anti-form, respectively. Thus, the cyclopropylic strain can be effectively used for conformational restriction of the side chain moiety of cyclopropane compounds.