Angiogenesis inhibitor TX-1898: syntheses of the enantiomers of sterically diverse haloacetylcarbamoyl-2-nitroimidazole hypoxic cell radiosensitizers Cheng-Zhe Jin, a,f Hideko Nagasawa, a Mariko Shimamura, b Yoshihiro Uto, a Seiichi Inayama, c Yoshio Takeuchi, d Kenneth L. Kirk e and Hitoshi Hori a, * a Department of Biological Science and Technology, Faculty of Engineering, University of Tokushima, Tokushima 770-8506, Japan b Medical Research and Development Center, The Tokyo Metropolitan Institute of Medical Science, 3-18-22 Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan c Institute of Oriental Medical Sciences, 2-6-3 Ebisunishi, Shibuya-ku, Tokyo 155-0021, Japan d Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Sugitani 2630, Toyama 930-0194, Japan e Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Health, DHHS, Bethesda, MD 20892, USA f Pharmaceutical School of the University of Yanbian, Yanji 133000, China Received 14 June 2004; revised 28 June 2004; accepted 28 June 2004 Available online 27 July 2004 Abstract—(R)-and(S)-Epichlorohydrins were used to prepare the enantiomers of sterically diverse haloacetylcarbamoyl-2-nitroim- idazoles that function as hypoxic cell radiosensitizers. The synthetic design allowed for introduction of a side chain of varying bulk that permitted an examination of the steric effects on enantio-discrimination in biological assay systems. The single stereocenter also connected the two pharmacophores––a 2-nitroimidazole moiety critical to hypoxic cell radiosensitization, and a halo- acetylcarbamoyl group to function as an anti-angiogenesis pharmacophore. In the chick embryo chorioallantoic membrane (CAM) assay, the R-enantiomers possessing the bulky p-tert-butylphenyl group showed higher anti-angiogenic activity than the cor- responding S-enantiomers, while there were no differences in the activity between the enantiomers containing the less bulky methyl and tert-butyl groups. Among the compounds we report, R-p-tert-butylphenyl-bromoacetylcarbamoyl-2-nitroimidazole, TX-1898, was found to be the most promising candidate for further development of as anti-angiogenic hypoxic cell radiosensitizer. Ó 2004 Elsevier Ltd. All rights reserved. 1. Introduction Angiogenesis is required for tumor growth and meta- stasis and, therefore, represents an exciting target for cancer treatment. Angiogenesis is a complex process involving a number of distinct steps, such as endothelial cell migration, proliferation, formation of capillary tubes in endothelial cells, their invasion, and metastasis. These steps are tightly regulated by pro- and anti-angio- genic factors. 1–3 Tumor-related angiogenesis is a multi- step process that is initiated through the activity of various pro-angiogenic factors, such as vascular endo- thelial growth factor (VEGF), basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), insulin-like growth factor (IGF), and interleukin-8 (IL- 8). Many enzymes are involved, including such as the matrix metalloproteinases (MMPs), thrombin and methionine aminopeptidase-2 (MetAP-2), urokinase- type plasminogen activator (uPA), and others. Various anti-angiogenic drugs have been developed that target several related growth factor receptors such as VEGF receptors (VEGFR-1 and VEGFR-2), bFGF receptor, and PDGF receptor. Indeed, some of these agents, such as SU5416, 4 ZD6474, 5 SU6668, 6 are now in clinical tri- als as anti-angiogenic drugs. Our own interest in this area is focused on small molecule anti-angiogenic agents related to the naturally-occurring angiogenic inhibitor fumagillin, and its semi-synthetic analog TNP-470, one of the first substances to be recognized to as having an anti-angiogenic effect. 7–10 0968-0896/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmc.2004.06.039 Keywords: Angiogenesis inhibitor; Hypoxic cell radiosensitizer; Halo- acetylcarbamoyl-2-nitroimidazole; Enantiomers. * Corresponding author. Tel.: +81-88-656-7514; fax: +81-88-656- 9164; e-mail: hori@bio.tokushima-u.ac.jp Bioorganic & Medicinal Chemistry 12 (2004) 4917–4927