The cytotoxicity of EGCG against U266 cells is mediated with 67LR. The U266 cells were incubated with 18 and 19 and (-)-EGCG 1 (0, 5.0, 10, 25 or 50 µM) for 120 h at 37 o C. The relative number of viable cells was estimated using an ATPlite assay. The IC50 cytotoxicity value of the 8-and 6subsituted EGCGs 18 and 19 against U266 cells were almost comparable to that of natural (-)-EGCG 1. These results indicated that the absolute configuration of the trans-flavan-3-ol gallates 3 was not important to the biological activity. Finally, we examined synthesis of the 18 F-labeled EGCG [ In conclusion, we successfully developed a method for direct modification of EGCG via a gold-catalyzed electrophilic aromatic substitution with an N-(2-alkynylbezoyloxyl)methyl amide. This amide generated N-acyl imine in the presence of (Ph3P)AuOTf and provided a mixture of Nacylaminomethyl substituted EGCG at 6 and 8 positions. This unique selectivity could be due to the nature of N-acyl imine as an electrophile. Using the method, we prepared the EGCGs 20a and 21a possessing a (2,2-dimethyl-1,3-dioxan-5-yl)methyl sulfonoylxoyl group from the O-protected EGCG by a single step. 18 F-Fluorination of the sulfonates 20a and 21a provided the 18 F-labeled-EGCG 30 and 31. After separation of the isomers, removal of the O-protecting group of [ 18 F]30 provided the 18 Flabaled EGCG [ 18 F]18 using a neopentyl labeling unit. It should be noted that it is the first report on the synthesis of 18 F-labeled EGCG without a significant loss of its binding affinity to 67LR. Current efforts are focused on improving the radiochemical yields of the 18 F-labeled EGCG to evaluate its biological distribution.