Design, Synthesis And Activity Test Of Large-conductance Calcium-activated Potassium Channel Openers

The calcium activated potassium channel is one type of potassium channel that is regulated not only by membrane depolarization but also by the changes in intracellular calcium levels. BK channel (large conductance calcium-activated, voltage-dependent potassium channels, MaxiK) is one type of calcium activated potassium channel. The structure character of BK, the modulation of BK, the function of BK, the modulators of BK were reviewed in this thesis.The openers of BK channels can dampen or stabilize cellular excitability or lower the effectiveness of excitatory inputs. The therapeutical application of BK channel openers is for stroke, bladder over activity, epilepsy, asthma, hypertension and so on. Estradiol and Tamoxifen have nongenomic upregulation of BK channel activity upon the expression of theβ₁ subunit by increasing the NP₀ of BK.Tamoxifen was considered as a good lead for the design of new openers on BK. Eighty-nine compounds were synthesized by the structure modification of Tmoxifen and the structures were confirmed by MS, high-resolution MS and 'H-NMR spectra. Considering the difficulties of synthesis, isolation and identification of Z/E isomer, Symmetric ketone was chosen for the Mcmurry coupling key step reaction to give symmetric compounds. The mechanism of both Mcmurry reaction and the synthesis of benzophenone derivatives from Weinreb amide were also discussed.Based on the test method of BK channel modulators, fluorescence method and patch clamp method were applied. A fluorescence assay with DiBAC₄(3) to semi-quantitatively test the channel opening activity of the target compounds on the BK channel expressed in HEKBK293 cell was carried out by choosing tamoxifen as the control. And primary SARs were summarized from the fluorescence results. Sixteen compounds were tested by inside-out patch clamp method while five of them show BK opening activities.