On mechanistic aspects of 5-deazaflavin dependent dehydrogenation of alcohol

The reaction of 5-deazaflavins with alcoholates was investigated and the direct hydride equivalent transfer from C1 of alcoholates to C5 of 5-deazaflavins was confirmed by chemical methods. 5-Alkoxy-10-butyl-3-methyl-5-deazaflavins were synthesized by treatment of 10-butyl-5-chloro-3-methyl-5-deazaflavin with the corresponding alcoholates. The 5-alkoxy-5-deazaflavins were reduced by sodium borodeuteride or sodium hydro-sulfite in deuterium oxide or monodeuteriomethanol to give 10-butyl-3-methyl-1,5-dihydro-5-deazaflavin-5,5-D2 exclusively. 3,10-Dimethyl-5-deazaflavin radical anion was detected by esr technique on treatment of 3,10-dimethyl-5-deazaflavin with potassium in DMF. From the above reactions, a mechanism of 5-deazaflavin dependent dehydrogenation of alcoholate was proposed.