N-[1-Aryl-2-(1-imidazolo)ethyl]-guanidine derivatives as potent inhibitors of the bovine mitochondrial F 1 F 0 ATP hydrolase Karnail S. Atwal, a, * Saleem Ahmad, a Charles Z. Ding, a,y Philip D. Stein, a John Lloyd, a Lawrence G. Hamann, a David W. Green, b,{ Francis N. Ferrara, a Paulina Wang, b W. Lynn Rogers, b Lidia M. Doweyko, a Arthur V. Miller, a Sharon N. Bisaha, a Joan B. Schmidt, a Ling Li, a Kenneth J. Yost, a Hsi-Jung Lan c and Cort S. Madsen b, * a Department of Discovery Chemistry, Bristol-Myers Squibb, Pharmaceutical Research Institute, PO Box 5400, Princeton, NJ 08543-5400, USA b Department of Cardiovascular Biology, Bristol-Myers Squibb, Pharmaceutical Research Institute, PO Box 5400, Princeton, NJ 08543-5400, USA c Department of Metabolism and Pharmacokinetics, Bristol-Myers Squibb, Pharmaceutical Research Institute, PO Box 5400, Princeton, NJ 08543-5400, USA Received 21 July 2003; accepted 14 November 2003 Abstract—A series of substituted guanidine derivatives were prepared and evaluated as potent and selective inhibitors of mitochondrial F 1 F 0 ATP hydrolase. The initial thiourethane derived lead molecules possessed intriguing in vitro pharmacological profiles, though contained moieties considered non-drug-like. Analogue synthesis efforts led to compounds with maintained potency and superior physical properties. Small molecules in this series which potently and selectivity inhibit ATP hydrolase and not ATP synthase may have utility as cardioprotective agents. # 2003 Elsevier Ltd. All rights reserved. The mitochondrial F 1 F 0 ATPase is responsible for the majority of ATP synthesis in mammalian cells. How- ever, it can also hydrolyze ATP during cellular anoxia so the direction of this enzymes catalytic activity can have a profound effect on cellular metabolism. 1 During anoxia this electrochemical gradient collapses, and mitochondrial F 1 F 0 ATPase switches to its hydrolytic state. 2 This hydrolysis of ATP serves no useful purpose and depletes the ischemic tissue of ATP leading to cell death. 3 The mitochondrial F 1 F 0 ATP synthase activities in vesicles from ischemic muscle are substantially (  50– 80%) less than those of control muscle. A naturally occurring inhibitor, IF 1 protein (IF 1 ), may be bound to the F 1 unit under ischemic conditions to inhibit the mitochondrial F 1 F 0 ATP hydrolase activity of the enzyme. However, the activity of IF 1 is highly pH dependent and in severe conditions it can only provide modest control. 4 The conversion of mitochondrial F 1 F 0 ATP synthase to hydrolase is reversible, since addition of oxygen to the mitochondria of ischemic muscle can reactivate the mitochondrial F 1 F 0 ATPase and the ATP levels can return to control. Several inhibitors of F 1 F 0 ATPase have been described, including efrapeptin, 5 oligomycin, 6 aurovertin B, 7 and azide. 8 Oligomycin targets F 0 and reportedly postpones cell injury by preventing ATP loss during ischemia. 9 Prior to our recent disclosure of benzopyran derivatives related to compound 1, 10 the known inhibitors of mito- chondrial F 1 F 0 ATPase have all been large molecules, and consequently not orally bioavailable. Through sub- sequent directed screening efforts, a second small mole- cule template was discovered, as represented by thiourethanes such as 2. In this paper, we describe structural modifications within this series which led to cyano- and acyl-guanidine derivatives which posses potent and selective inhibitory activity against 0960-894X/$ - see front matter # 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmcl.2003.11.077 Bioorganic & Medicinal Chemistry Letters 14 (2004) 1027–1030 * Corresponding authors. Tel.: +1-609-818-3550 (L.G.H.); tel: +1-609-818-5238 (C.S.M.); e-mail: lawrence.hamann@bms.com; cort.madsen@bms.com y Current address: Cumbre, Inc., 1502 Viceroy Drive, Dallas, TX 75235-2304, USA. { Current Address: Abbott Bioresearch Center, 100 Research Drive, Worcester, MA 01605-5314, USA.