| Objective: Chronic obstructive pulmonary disease?COPD? is a kind of common and serious diseases. The long-acting muscarinic M3 antagonists are presently the first choice to treat COPD in clinics. But the side effects can't be ignored duo to their lower subtype selectivity?M3/M2?. In this paper, a series of tropane compounds were designed and synthesized based on previous works. Their antagonistic activity and duration to muscarinic M3 receptor, and subtype selectivity?M3/M2? were investigated. The models of quantitative structure activity relationship?QSAR?, quantitative structure-offrate relationship?QSOR? and quantitative structure-selectivity relationship?QSSR? were constructed to guide successive molecular design of long-acting, higher active and selective muscarinic M3 antagonists to improve the druggability. The QSOR studies were firstly reported. In addition, the establishment of chiral separation for enantiomers of 3?-acyloxy-6?-acetoxyltropane compounds could lay a solid foundation for developing optically pure clinical drug.Methods: Some 3?-acyloxytropane compounds?C series? and 3?-acyloxy-6?-acetoxyltropane compounds?E series? including racemates and?3S, 6S?,?3R, 6R?-isomers were synthesized by acylation. The isolated trachea?M3? and left atria?M2? on guinea pigs were selected as testing samples to evaluate their antagonistic activity and duration to muscarinic M3 receptor, and subtype selectivity?M3/M2? with tiotropium bromide taken as the control. The functional antagonistic parameter?p A2?M3??, duration parameter?log?t1/2?offset??? and subtype selectivity?M3/M2? parameter??p A2?M3/M2? [p A2?M3?-p A2?M2?]? of tropane compounds prepared in this paper or former studies were applied tobuild QSAR?M3?, QSOR?M3? and QSSR?M3/M2? models respectively. The three models were used to predict their antagonistic activity and duration to muscarinic M3 receptor, and subtype selectivity?M3/M2? respectively. Besides, the information on structural optimization was also acquired by these models. Furthermore, the enantioseparation of racemic 3?-acyloxy-6?-acetoxyltropane compounds were investigated by high performance liquid chromatograph with amylose-based chiral stationary phase Chiralpak AD or cellulose-based chiral stationary phases Chiralcel OD-H in the normal phase mode, using various mixtures of n-hexane-isopropanol as mobile phases.Results: Thirteen tropane compounds, including seven new ones in which four compounds are optical isomers, were prepared and showed antagonistic activity to muscarinic M3, M2 receptor. The antagonistic activity of C06 was the strongest [p A2?M3? = 8.538] among the targets, but lower than that of tiotropium bromide. Three targets had better antagonistic duration. The acting time of C06 was the longest [t1/2?offset? > 720.0 min] among the targets and similar to that of tiotropium bromide. Seven targets had at least five times subtype selectivity?M3/M2?. C13 elicited the highest subtype selectivity?M3/M2? [?p A2?M3/M2? = 1.883]. The cross-validation coefficient?q2?, non-cross-validation coefficient squared?r2?, standard error?SE? and F value of QSAR?M3? model were 0.730, 0.986, 0.106 and 395.428. Those of QSOR?M3? model were 0.682, 0.990, 0.075 and 241.026, while, QSSR?M3/M2? 0.738, 0.990, 0.093 and 167.113 respectively. All the three models had better predicting ability. The enantiomers of E06 were completely separated on a Chiralpak AD column. While the enantiomers of E03, A14 and A10 got complete, baseline and basic separation respectively on a Chiralcel OD-H column.Conclusion: The results of qualitative research showed the compound with two phenyl rings in the substituent of C-3? position had longer acting time. The compound with three phenyl rings in C-3? position had the highest subtype selectivity?M3/M2?. The introduction of halogen atoms on the phenyl ring in C-3? position was in favor ofimproving the acting time of compounds to muscarinic M3 receptor. Introducing hydroxyl or O atom in the substituent of C-3? position could increase the interactions between compound and M3 receptor by forming extra hydrogen bond. This obviously improved the antagonistic activity and acting time of compound to muscarinic M3 receptor. However, introducing acetoxy in C-6? position was unfavorable to increase the antagonistic activity and acting time to muscarinic M3 receptor, and subtype selectivity?M3/M2?. The QSAR?M3??QSOR?M3? and QSSR?M3/M2? models provided a lot of structural information. It was suggested that increasing the volume of substituted group or electron density in the middle and upper regions near the acyloxy at C-3? position could improve the antagonistic activity to muscarinic M3 receptor. Increasing the bulk of substituted group in the middle and lower regions at C-3? position could improve the acting time and subtype selectivity?M3/M2? respectively. Nevertheless, the size of substituents was too large to extend the acting time. Increasing the volume of substituted group or the positive charge near the phenyl ring in C-3? position would decrease the antagonistic activity but increase the acting time to M3 receptor. Decreasing the volume of substituted group or increasing the positive charge could improve the subtype selectivity?M3/M2? of compounds. The acting time could also be extended by increasing the negative charge in the position around N-methyl. Furthermore, the steric effect of the substituent in C-3? position was the key factor of determining the selective recognition of chiral stationary phase to the enantiomers of 3?-acyloxy-6?-acetoxyltropane compounds. Besides, the molecular interaction, such as ?-? interaction, also exerted great influence to the result of chiral resolution. |
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