Synthesis of new heteroaryl and heteroannulated indoles from dehydrophenylalanines: Antitumor evaluation

The growth inhibitory effect of three of the new compounds prepared was evaluated on the in vitro growth of three human tumor cell lines. A 3-(dibenzothien-4-yl)indole and a phenylbenzothienoindole or a 3-(dibenzofur-4-yl)indole and a phenylbenzofuroindole were prepared by a metal-assisted C–N intramolecular cyclization of the methyl esters of N-Boc-( E) or ( Z)-β-dibenzothien-4-yl or β-dibenzofur-4-yl dehydrophenylalanines. The latter were obtained by Suzuki cross-coupling of the methyl esters of N-Boc-( E) or ( Z)-β-bromodehydrophenylalanines with dibenzothien-4-yl or dibenzofur-4-yl boronic acids, in high yields. The intramolecular cyclization from E or Z pure Suzuki-coupling products gave the corresponding heteroaryl and heteroannulated indoles, in different ratios, by either direct cyclization or cyclization after isomerisation. Three of the cyclized compounds, the two heteroarylindoles and the phenylbenzothienoindole, were evaluated for their capacity to inhibit the in vitro growth of three human tumor cell lines, MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer), and SF-268 (CNS cancer). The methyl 3-(dibenzothien-4-yl)indole-2-carboxylate was the most potent compound with GI 50 values ranging from 11 to 17 μM.