Alkylation of phenols with 1,3-cyclohexadiene (1) has been conducted and a series of cyclohexen-2-yl- and cyclohexyl-substituted phenols and quinones were screened against the proliferation of HUVEC and cancer cells. Phenol type as well as the size and occupied position of the substitute are important for the alkylating reaction and the inhibitory activity and selectivity of a compound. 2,5-di(cyclohexen-2-yl)benzene-1,4-diol (25) bearing two cyclohexen-2-yl groups and 2-tert-butyl-5-(cyclohexen-2-yl)benzene-1,4-diol (30) bearing cyclohexen-2-yl and tert-butyl groups exhibited good selectivity against HUVEC proliferation (IC50s of 2.0 and 1.4 microM, respectively) with relatively low toxicity to ccc-HPF-1.