A series of novel 4-hydroxybenzaldehyde derivatives were synthesized and their inhibitory effects on the diphenolase activity of mushroom tyrosinase were investigated. Most of target compounds had more potent inhibitory activities than the parent compound 4- hydroxybenzaldehyde (IC50= 1.22 mM). Interestingly, compound 3c bearing a dimethoxyl phosphate was found to be the most potent inhibitor with IC50 value of 0.059 mM. The ...