Structure-activity relationships of (E)-3-(1,4-benzoquinonyl)-2-[(3-pyridyl)-alkyl]-2-propenoic acid derivatives that inhibit both 5-lipoxygenase and thromboxane A2 synthetase

As part of our research for the development of novel antiinflammatory drug candidates, we have designed and synthesized a series of (E)-3-(1,4-benzoquinonyl)-2-[(3-pyridyl)alkyl]-2-propenoic acid derivatives as dual inhibitors of 5-lipoxygenase (5-LO) and thromboxane (TX) A2 synthetase. In order to increase the absorption after oral administration, we introduced a carboxylic acid moiety into the 1,4-benzoquinone skeleton, which has 5-LO-inhibitory character. Introduction of a 3-pyridylalkyl group at the double bond of the 1,4-benzoquinonyl propenoic acid moiety afforded good to moderate inhibitory activities against the production of leukotriene (LT) B4 and TXA2 while not significantly inhibiting that of prostaglandin E2 by glycogen-induced peritoneal cells of rat (in vitro). The length of the methylene chain of the 3-pyridylalkyl group influenced the inhibition of LTB4 and TXB2 production. An increase of lipophilicity by introducing a more lipophilic alkoxy group did not markedly increase the inhibitory activity on LTB4 production. The position of alkoxy group on the 1,4-benzoquinone skeleton played an important role in TXA2 synthetase inhibition. Compounds such as 20c (E6700) with an appropriate alkoxy group and proper length of methylene side chain, together with a polar substituent (carboxylic acid), showed good inhibition of both 5-LO and TXA2 synthetase and possess a variety of pharmacologically beneficial effects.