Intramolecular base‐catalysis in the radical‐scavenging reaction by vitamin E derivatives bearing a pyridine moiety

In order to develop effective radioprotectors, we recently synthesized three vitamin E derivatives bearing a pyridine moiety with a linkage of different spacers. All the vitamin E derivatives efficiently scavenged 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH • ) in deaerated methanol at 25 °C. The second‐order rate constant for DPPH • ‐scavenging by one of the vitamin E derivatives determined by the stopped‐flow technique is about 3‐fold larger than that by 2,2,5,7,8‐pentamethylchroman‐6‐ol (PMC), a vitamin E model. This suggests that the pyridine moiety may accelerate the reaction by stabilizing the radical cation generated in the electron transfer from the vitamin E derivative to DPPH • .