Synthesis of N 2 -(substituted benzyl)-3-(4-methylphenyl)indazoles as novel anti-angiogenic agents Li-Jiau Huang, a Mei-Ling Shih, a Hua-Sin Chen, a Shiow-Lin Pan, b Che-Ming Teng, b Fang-Yu Lee c and Sheng-Chu Kuo a, * a Graduate Institute of Pharmaceutical Chemistry, China Medical University, Taichung, Taiwan b Pharmacological Institute, College of Medicine, National Taiwan University, Taiwan c Yung-Shin Pharmaceutical Industry Co., Ltd. Tachia, Taichung, Taiwan Received 10 June 2005; revised 16 August 2005; accepted 17 August 2005 Available online 3 October 2005 Abstract—To search for novel compounds with potent anti-angiogenic activity, a series of N 1 -(substituted benzyl)-3-(4-methylphe- nyl)-1H-indazoles (16, 18, 20, 22, 24, 26, 28, 30, 32) and N 2 -(substituted benzyl)-3-(4-methylphenyl)-2H-indazoles (17, 19, 21, 23, 25, 27, 29, 31, and 33) were synthesized. The structures of these regioisomers were established by IR, UV, and NMR spectral data. 3-(4- Methylphenyl)-1H-indazole (6) and the N 2 -substituted derivatives (17, 19, 21, 23, 25, 29, 31, 33) were evaluated for their anti-an- giogenic activity. Most of them showed more prominent activity than ethyl 4-(1-benzyl-1H-indazol-3-yl)benzoate (YD-3). Among these tested compounds, 2-(4-chlorobenzyl)-3-(4-methylphenyl)-2H-indazole (19), 2-(4-methylbenzyl)-3-(4-methylphenyl)-2H-inda- zole (25), and 2-(4-methoxybenzyl)-3-(4-methylphenyl)-2H-indazole (31) showed significant anti-angiogenic activity and are worthy of further investigation. Ó 2005 Elsevier Ltd. All rights reserved. 1. Introduction Angiogenesis, the formation of new capillaries from pre- existing blood vessel, is essential in physiologic and pathologic processes. 1 The first hypothesis that angio- genesis is essential for tumor growth and metastasis was made by Folkman about 30 years ago. 2 Since then, the research activity in the field of angiogenesis has in- creased immensely. A number of angiogenic agents are currently under advanced stage clinical trials for the treatment of cancer. Among them, bevacizumab (Ava- stin), 3 in combination with chemotherapy, was ap- proved by the FDA in 2004. Recently, a series of N 1 -(substituted benzyl)-3-(substi- tuted aryl)indazoles were evaluated for their anti-angio- genic activity. Among these tested compounds, ethyl 4-(1-benzyl-1H-indazol-3-yl)benzoate (YD-3) exhibited significant anti-angiogenic activity. 4 In this work, the previously unknown N 2 -regioisomers of indazole derivatives were synthesized and their anti- angiogenic activities were examined. 2. Results and discussion 2.1. Chemistry The synthesis of N 1 - and N 2 -(substituted benzyl)-3-(4- methylphenyl)indazoles (16–33) is illustrated in Scheme 1. In the beginning, 1-(N-morpholino)cyclohex- ene (1) was treated with 4-methylbenzoyl chloride (2) in the presence of Et 3 N to produce 4-[2-(4-methyl- benzoyl)cyclohexylidene]morpholin-4-ium (3) which was then acidified with 20% HCl and heated to yield 2-oxocyclohexyl-4-methyl phenyl ketone (4). 5 Next, the condensation of compound 4 with hydrazine hydrate afforded 3-(4-methylphenyl)-4,5,6,7-tetrahydro-1H-in- dazole (5). 6 Subsequent dehydrogenation of compound 5 over Pd/C, under elevated temperature, yielded the key intermediate, 3-(4-methylphenyl)-1H-indazole (6). 7 Afterwards, compound 6 was subjected to alkylation by treating with various substituted benzyl chlorides in the presence of EtONa, to yield the corresponding N 1 - and N 2 -regioisomers (16–33). To avoid the 0968-0896/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmc.2005.08.032 Keywords: Anti-angiogenic agents; N 2 -(Substituted benzyl)-3-(4-methyl- phenyl)-indazoles. * Corresponding author. Tel.: +886 4 2205 3366 1006; fax: +886 4 2203 0760; e-mail: sckuo@mail.cmu.edu.tw Bioorganic & Medicinal Chemistry 14 (2006) 528–536