Structure-Activity Relationships of 2-Aminothiazole Derivatives as Inducible Nitric Oxide Synthase Inhibitor
作者:Shigeo Ueda、Hideo Terauchi、Motoji Kawasaki、Akihiro Yano、Motoharu Ido
DOI:10.1248/cpb.52.634
日期:——
Nitric oxide synthase (NOS) has been divided into two major sub-enzymes, i.e. inducible NOS (iNOS) and constitutive NOS (cNOS). Although nitric oxide (NO) plays an important role as host defense mediator, excessive production of NO by iNOS has been involved in the pathology of many inflammatory diseases. Recently, we reported that the 2-imino-1,3-oxazolidine (1a) weakly inhibits iNOS and that introduction of an alkyl moiety on the oxazolidine ring of 1a enhances the inhibitory activity and selectivity for iNOS. In our search for better iNOS inhibitors, we focused our efforts on the 2-aminothiazole scaffold 3 as it possesses a ring similar to that of 1a. In this study, we evaluated the inhibitory activity of a series of 2-aminothiazole derivatives against both iNOS and neuronal NOS (nNOS). Our results show that introduction of appropriately-sized substituents at the 4- and 5-position of the 2-aminothiazole ring improves the inhibitory activity and selectivity for iNOS. We also found that the selectivity of 5a [5-(1-methyl)ethyl-4-methylthiazol-2-ylamine] and 5b [5-(1,1-dimethyl)ethyl-4-methylthiazol-2-ylamine] for iNOS was similar to that of oxazolidine derivative 1b (4-methyl-5-propyl-2-imino-1,3-oxazolidine) and much higher than that of L-NAME. However, we could not enhance the inhibitory activity against iNOS by introducing an alkyl substituent into the 2-aminothiazole ring as we could in the case of oxazolidine one. On the other hand, introduction of bulky or hydrophilic substituent at any position of the 2-aminothiazole ring remarkably decreased or even abolished the inhibitory activity against NOS.
一氧化氮合酶(NOS)被分为两种主要的亚酶,即可诱导型一氧化氮合酶(iNOS)和构成型一氧化氮合酶(cNOS)。虽然一氧化氮(NO)在宿主防御中发挥重要作用,但iNOS过量产生NO已涉及许多炎症疾病的病理。最近,我们报告了2-亚氨基-1,3-噁唑烷(1a)对iNOS的抑制作用较弱,并且在1a的噁唑烷环上引入烷基基团可以增强对iNOS的抑制活性和选择性。在寻找更好的iNOS抑制剂时,我们将精力集中在2-氨基噻唑骨架3上,因为它具有类似于1a的环状结构。在本研究中,我们评估了一系列2-氨基噻唑衍生物对iNOS和神经型一氧化氮合酶(nNOS)的抑制活性。结果表明,在2-氨基噻唑环的4位和5位引入适当大小的取代基能显著提高对iNOS的抑制活性和选择性。我们还发现,5a [5-(1-甲基)乙基-4-甲基噻唑-2-胺]和5b [5-(1,1-二甲基)乙基-4-甲基噻唑-2-胺]对iNOS的选择性与噁唑烷衍生物1b(4-甲基-5-丙基-2-亚氨基-1,3-噁唑烷)相似,并且远高于 -NAME。然而,我们未能通过在2-氨基噻唑环上引入烷基取代基来增强对iNOS的抑制活性,正如在噁唑烷的情况下所实现的那样。另一方面,在2-氨基噻唑环的任何位置引入笨重或亲水性取代基显著降低甚至完全消除了对NOS的抑制活性。