However, these chemical probes required tedious multi-step synthesis to introduce the functional moiety at the A ring. On the other hand, electrophilic substitution allows one to site-selective reaction of EGCG at the A ring. Treatment of EGCG with an excess amount of thiol and form aldehyde under acdic conditions provided 6,8-bis(octylthiomethyl) substituted EGCG. We have reported on the electrophilic substitution of EGCG 1 with 6-azido-6-deoxy-L-idose in the presence of Sc(OTf)3 at 70 o C to produce the 8-substituted EGCG 2 with an azido group, without significantly compromising its anticancer effects. The azido-functionalized EGCG was employed as a chemical probe for analyzing EGCG-protein interactions. These direct site-selective modification of EGCG at the A ring would become an efficient and alternative method of synthesizing biologically active EGCG derivatives.