We recently reported the anti-cancer and anti-cytomegalovirus (CMV) activity of artemisinin-derived trioxane diphenylphosphate dimer 838. To probe the relationship between chemical structure and anti-CMV and anti-cancer activities, we now report synthesis and evaluation of a series of eight new dimer phosphate ester analogs of 838. This series of novel molecules was screened against human foreskin fibroblasts (HFFs) infected with CMV and against the human Jurkat T cell acute lymphoblastic leukemia cell line. This SAR study confirms the very high anti-CMV and anti-cancer potencies of dimer diphenyl phosphate ester 838 without its being toxic to normal cells.