1,1-二氧化苯駢[1.3.2]二噻唑亞烷衍生物作為第二型環氧化酶 與第五型脂氧合酶雙效抑制劑之設計、合成與活性評估

Abstract

新穎的第二型環氧化酶（COX-2）與第五型脂氧合酶（5-LOX）雙效抑制劑具有重大的發展潛力，所以本研究之初步結果以化合物6為基礎，合成了一系列1,1-二氧化苯駢[1.3.2]二噻唑亞烷衍生物。在製備這類化合物的過程中，合成雙芳香基硫化物的耦合反應以及最後的環化反應是所有最終產物的必經步驟，而本研究中也固定以這些方法當作標準合成程序。 本研究初期曾針對COX-2的結構進行虛擬篩選，並挑中化合物7以作為預設標的物，不料後續研究卻間接確認化合物6才具有抑制COX-2的活性，而且發現化合物6也能夠抑制5-LOX。根據化合物6與COX-2活性區的對接模型﹙docking model﹚所顯示，對化合物6進行優化時應保留化合物與酵素活性區之間的重要作用力，所以研究中針對NO2、SO2NH2、SO2CH3以及羧酸衍生物等多種位於第5或第6位的氫鍵接受體加以探討，並依序觀察不同芳香性基團接在第3位硫原子上的差異；研究中發現，若是要對第二型環氧化酶與第五型脂氧合酶產生抑制作用，6-NO2基團是必要的取代基。在這些化合物之中，具有COX-2/5-LOX雙效抑制能力的化合物都有相同的特徵：3-芳香性基團上的取代基屬於中等體積的親脂性基團，其中含有3-(4-三級丁基苯基)取代基的化合物具有最強效的COX-2抑制能力（IC50 = 0.27 μM），而含有3-(4-聯苯基)取代基的化合物則具有最強效的5-LOX抑制能力（IC50 = 0.15 μM）。但是，與化合物7類似的化合物8則無法對COX-2或5-LOX產生抑制作用。 除了酵素抑制活性之外，在動物實驗中以100 mg/kg的劑量採取腹腔注射給藥之後可以發現，同時帶有3-(4-三級丁基苯基)與6-硝基取代基的1,1-二氧化苯駢[1.3.2]二噻唑亞烷能夠產生顯著的快速消炎作用。根據本研究的結果顯示，在開發第二型環氧化酶與第五型脂氧合酶雙效型抑制劑的時候，可以採用1,1-二氧化苯駢[1.3.2]二噻唑亞烷衍生物作為新穎的架構，並以這類雙效型抑制劑作為開發抗發炎藥物時的參考。 藉由微波加速反應與縮短反應時間的特性，可以進一步提升合成雙芳香基硫化物的效能，並且簡化反應後的處理程序；因為雙芳香基硫化物是1,1-二氧化苯駢[1.3.2]二噻唑亞烷的前驅物，所以微波加熱有助於改善本系列化合物的產率。跟傳統的加熱方法比較起來，只要使用微波輔助的耦合反應，就可以在溫和的條件下合成出多樣化的雙芳香基硫化物，而且產率都能達到94%以上。在合成各種1,1-二氧化苯駢[1.3.2]二噻唑亞烷衍生物的過程中，必須要使用反應性較低的分子以及高極性的試劑，而微波加熱方式讓這些反應得以順利進行。

According to our preliminary discovery of compound 6, a series of benzo[1.3.2]dithiazolium ylide 1,1-dioxide derivatives were designed and synthesized for the development of new prototype dual inhibitors of cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX). To synthesize these derivatives, cross-coupling of diaryl sulfides and ring closure reaction were taken as fundamental and standardized steps. Compound 7 was initially believed as a virtual hit through the COX-2 structure-based virtual screening, however, compound 6 was indirectely identified as a selective COX-2 inhibitor, which also exhibited 5-LOX inhibition. With an attempt to optimize compound 6, docking model of compound 6 in the active site of COX-2 was considered. To maintain these important interactions between compound 6 and COX-2, versatile hydrogen bonding acceptors such as NO2, SO2NH2, SO2CH3 and certain carboxylic acid derivatives at the 5- or 6- position of benzo[1.3.2]dithiazolium ylide scaffold together with different aryl moieties on the sulfur atom at the 3-position were stepwisely investigated. Meanwhile, the 6-NO2 group was revealed to play an essential role in the inhibition of COX-2 and 5-LOX. Regard to the overall efficacy among them, compounds with lipophilic groups of proper bulkiness on the 3-aryl moiety provided evident dual COX-2/5-LOX inhibitory activity. The compound with 3-(4-tbutylphenyl) substituent was illustrated to be the most potent COX-2 inhibitor (IC50 = 0.27 μM), and the compound with 3-(4-biphenyl) substituent, was the most potent 5-LOX inhibitor (IC50 = 0.15 μM). Unfortunately, compound 8 analogous to 7 was inactive in inhibiting neither COX-2 nor 5-LOX. In addition to enzyme-inhibiting studies, intraperitoneal administration of 3-(4-tert-butylphenyl)-6-nitrobenzo[1.3.2]dithiazolium ylide 1,1-dioxide at 100 mg/kg gave significant acute anti-inflammatory activity. Benzo[1.3.2]dithiazolium ylide 1,1-dioxide derivatives herein represented a novel scaffold for the exploitation of dual COX-2/5-LOX inhibitors, which may be useful in the construction of new anti-inflammatory agents. With the assistance of microwave irradiation on the improvement of reaction yields, the synthesis of diaryl sulfides as precursors of benzo[1.3.2]dithiazolium ylide 1,1-dioxide became more feasible in shortening the reaction time and simplifying the post-treatment of reactions. Compared to a conventional heating system, microwave-assisted cross-coupling helped a variety of diaryl sulfides be prepared in a mild condition and in excellent yields, greater than 94%. The application of microwave-assisted synthesis to deactivated reagents and polar systems facilitated the construction of miscellaneous benzo[1.3.2]dithiazolium ylide 1,1-dioxide derivatives.