Novel Tetracyclic Imidazole Derivatives: Synthesis, Dynamic NMR Study, and Anti-Inflammatory Evaluation Renata Rupc ˇic ´,* Marina Modric ´, Antun Hutinec, Ana C ˇ ikos ˇ, Barbara Stanic ´, Milan Mesic ´, Dijana Pes ˇic ´, and Mladen Merc ´ep GlaxoSmithKline Research Centre Zagreb, Prilaz baruna Filipovic ´a 29, Zagreb HR-10000, Croatia *E-mail: renata.q.rupcic@gsk.com Received September 23, 2009 DOI 10.1002/jhet.376 Published online 3 May 2010 in Wiley InterScience (www.interscience.wiley.com). A series of tetracyclic imidazole derivatives 9a–9v and 10a–10h are prepared by multistep route start- ing from the known tricyclic diketones 2a–2d. Intermediary dibenzooxepin[4,5-d]imidazoles (3a, 3c) and dibenzothiepin[4,5-d]imidazoles (3b, 3d) are N-protected to 4e, 4f and to the isomeric compounds 5a, 5b and 6a, 6b. The isomeric compounds 5 and 6 are separated. Compounds 4, 5, and 6 are formy- lated at C(2) to afford 7a–7j. In the last steps, aldehyde group is reduced, then alkylated to the two sets of isomeric x-dimethylaminoalkyl derivatives 9a–9v. N-deprotection of 9i–9v led to the compounds 10a–10h. Assignment of the syn/anti structure to 5a and 6a was supported by 1D selective ROESY NMR spectra, whereas conformational mobility for the selected representatives 8a and 8b is studied by dynamic NMR. Activation energies (energy barriers for interconversion) are determined to be 11.5 and 16.2 kcal/mol, respectively. A series of derivatives 9 and 10 were tested in vitro for their anti- inflammatory activity. J. Heterocyclic Chem., 47, 640 (2010). INTRODUCTION In our continuing efforts toward the development of disease modifying treatments for rheumatoid arthritis (RA), we are targeting inhibition of overproduction of tumor necrosis factor alpha cytokine (TNF-a) that is recognized as a key cytokine in RA progression. A small molecule inhibitor of TNF-a would be a novel potent anti-inflammatory drug having this distinguished mechanism of action. In the frame of our project aimed toward synthesis, structure determination of tetracyclic imidazoles, and screening of their activity on the selected biological targets, we entered the study of a large series of dibenzo-oxepin- and dibenzo-thiepin im- idazole derivatives. In our previous articles we have reported on the synthesis, properties, and preliminary bi- ological results of oxa-, aza-, and thia-dibenzoazulenes, characterized by the annulated furane I [2], pyrrole II, III [3], and thiophene IV, V [4] ring (Fig. 1). Prelimi- nary results have revealed activity of these polycyclic systems in the in vitro anti-inflammatory test in lipo- polysaccharide (LPS) induced TNF-a production in human peripheral blood mononuclear cells (hPBMCs) that encouraged us to extend our effort on other five membered heterocyclic systems [5,6]. Generally, structural complexity of this specific class of recently studied non-steroidal anti-inflammatory com- pounds increases from diaryl-substituted heterocycles general formulae VI, to polycondensed heterocyclic structures VII. Representatives of the former are vici- naly substituted polycyclic aryl/pyridine-4-yls, potent inhibitors of p38 MAP kinase (p38) [7,8], while 2-sub- stituted-4,5-diarylimidazoles VIII are claimed as in vivo anti-inflammatory active structures (Fig. 2) [9–14]. Moreover, polycondensed heterocycles with non-aro- matic dibenzoazulene core and annelated 5-membered het- erocycles are repeatedly claimed as anti-inflammatory active compounds. Among them are 2-substituted-1H-phe- nanthro[9,10-d]imidazoles IX [15], 2-substituted diben- zo[2,3:6,7]thiepino[4,5-d]imidazoles X [16–20], 2-substi- tuted dibenzo[2,3:6,7]oxepino[4,5-d]imidazoles, and their corresponding sulfoxides and sulfones XI (Fig. 3) [21]. V C 2010 HeteroCorporation 640 Vol 47