Focused library development of 2-phenylacrylamides as broad spectrum cytotoxic agents
2013
Tarleton, Mark | Dyson, Lauren | Gilbert, Jayne | Sakoff, Jennette A. | McCluskey, Adam
With our lead compound (E)-3-(4-chlorophenyl)-2-(1H-pyrrole-2-carbonyl)acrylonitrile (1) inducing 50% growth inhibition of 11 cancer cell lines at 27–61μM, potency enhancements were rapidly established through the synthesis of a series of focused compound libraries. Six highly focused libraries (46 compounds in total) were synthesised. Each library allowed the identification of a new lead compound, viz Library A identified (E)-3-(pentafluorophenyl)-2-(1H-pyrrole-2-carbonyl)acrylonitrile (11) and (E)-3-(1H-indol-3-yl)-2-(1H-pyrrole-2-carbonyl)acrylonitrile (13) as inhibitors with improved cytotoxicity. Synthesis of discrete libraries of amidoacrylamide analogues (Ar–CC(CN)–Ar✠Ar–CC(CN)–C(O)NH)–Ar) resulted in a series of analogues significantly more potent that the lead, 1. Three furan three analogues: (E)-3-(5-chlorofuran-2-yl)-2-cyano-N-(4-methoxybenzyl)acrylamide (33), (E)-3-(5-bromofuran-2-yl)-2-cyano-N-(4-methoxybenzyl)acrylamide (34) and (E)-2-cyano-3-(furan-3-yl)-N-(4-methoxybenzyl)acrylamide (37) returned broad spectrum growth inhibition (GI₅₀ values of 5–16μM). Replacement of the furan moiety with simple aromatics gave an additional three analogues: (E)-2-cyano-N-(4-methoxybenzyl)-3-phenylacrylamide (39), (E)-3-(4-chlorophenyl)-2-cyano-N-(4-methoxybenzyl)acrylamide (41) and (E)-2-cyano-N-(4-methoxyphenyl)-3-(naphthalen-1-yl)acrylamide (45) with GI₅₀ values of 7–24μM. The final library retained the aromatic substituents but introduced a 3,4-dichlorbenzylamine moiety to afford the 1-naphthyl substituted 52, which was the most potent broad spectrum cytotoxic analogue produced here in with an average GI₅₀=8.6μM. This represents a fivefold potency enhancement relative to 1 and a new cytotoxic scaffold suitable for further development.
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