A focused library synthesis and cytotoxicity of quinones derived from the natural product bolinaquinone

Bolinaquinone is a natural product that is a structurally complex, cytotoxic sesquiterpene quinone. A scaffold simplification and focused library approach using a microwave-assisted Suzuki coupling gave 32 bolinaquinone analogues with good-to-excellent cytotoxicity profiles. Mono-arylbenzoquinones, Library A, were preferentially toxic towards BE2-C (neuroblastoma) cells with growth inhibition (GI(50)) values of 4-12 mu M; only the 3,4-dimethoxyphenyl 23 and 3-biphenyl 28 variants were broad-spectrum active-HT29 (colon carcinoma), U87 and SJ-G2 (glioblastoma), MCF-7 (breast carcinoma), A2780 (ovarian carcinoma), H460 (lung carcinoma), A431 (skin carcinoma), Du145 (prostate carcinoma), BE2-C (neuroblastoma), MIA (pancreatic carcinoma) and SMA (spontaneous murine astrocytoma). Library B with a second aryl moiety exhibited broad-spectrum cytotoxicity with MCF-7 cells' GI(50) values of 5.6 +/- 0.7 and 5.1 +/- 0.5 mu M for 2,5-dimethoxy-3-(naphthalene-1-yl)-6-(naphthalene-3-yl) 33 and 2,5-dimethoxy-3-(biaryl-2-yl)-6-(naphthalene-3-yl) 36, respectively. Similar potencies were also noted with 2,5-dimethoxy-3,6-diphenyl 30 against A2780 (GI(50) = 5.9 +/- 0.0 mu M) and with 2,5-dimethoxy-3-(biaryl-3-yl)-6-(naphthalene-3-yl) 37 against HT29 (GI(50) = 5.4 +/- 0.4 mu M), while the 3,4-dimethoxy mono-aryl analogue 23 exhibited good levels of activity against A2780 (GI(50) = 3.8 +/- 0.75 mu M), the neuroblastoma cell line BE2-C (GI(50) = 3 +/- 0.35 mu M) and SMA (GI(50) = 3.9 +/- 0.54 mu M). Introduction of the amino-substituted Library C gave 2(naphthalen-1-yl)-5-(naphthalen-3-yl)-3,6-bis(propylamino) 43, with excellent activity against HT29 (0.08 +/- 0.0 mu M), MCF-7 (0.17 +/- 0.1 mu M), A2780 (0.14 +/- 0.1 mu M), A431 (0.11 +/- 0.0 mu M), Du145 (0.16 +/- 0.1 mu M), BE2-C (0.08 +/- 0.0 mu M) and MIA (0.1 +/- 0.0 mu M).