Polymethylcarborane as a novel bioactive moiety: derivatives with potent retinoid antagonistic activity

4-[(Deca-B-methyl-1,12-dicarba-closo-dodecaboran-1-yl)carbamoyl]benzoic acid and its congeners showed potent antagonistic activity at concentrations of 10−7–10−8 M on the differentiation-inducing action of retinoids towards human promyelocytic leukemia HL-60 cells. This is the first example of derivatives of polymethylcarborane, which resembles C60 in size, with biological activity.