Substitution of the flavin chromophore with lipophilic side chains: A novel membrane redox label

The synthesis of “amphiphilic” flavins substituted with C18-hydrocarbon sidechains in positions 3, 5, 7, 8 and 10 is described. 3-, 7-, and 10-amphiflavins were obtained by new total syntheses. Furthermore, 3-amphiflavin was obtained by C18-alkylation of natural flavin in the oxidized state, whereas 5-amphi(dihydro)flavin was obtained by alkylation under reducing conditions.