Acid-catalysed reduction of flavin analogues by an NADH model compound, 10-methyl-9,10-dihydroacridine and cis-dialkylcobalt(III) complexes

Shunichi Fukuzumi, Sadaki Kuroda, Tatsushi Goto, Kunio Ishikawa, Toshio Tanaka

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Abstract

An acid-stable NADH model compound, 10-methyl-9,10-dihydroacridine (AcrH2) (3), and cis-dialkylcobalt(III) complexes, cis-[R 2Co(bipy)2]+ (R = Me, Et; bipy = 2,2′-bipyridine), can reduce flavin analogues {Fl: 3-methyl-10- phenylbenzo[g]pteridine-2(1H),4(3H)-dione (1) and riboflavin (2)}, efficiently in the presence of perchloric acid (HClO4) in acetonitrile (MeCN) at 298 K to yield the corresponding dihydroflavin radical cations (FlH 2+.). Essentially, no reaction occurs in the absence of HClO4 under the same conditions. The radical cations (FlH 2+.) formed are very stable to oxygen in the presence of HClO4 in MeCN. Large primary kinetic isotope effects [k H/kD 9.6 ± 0.8 and 9.9 ± 0.8 for (1) and (2), respectively] have been observed for the formation of FlH2 +., indicating that hydride transfer from AcrH2 to the protonated flavins (FlH+) to give the dihydroflavins (FlH 2) is followed by fast comproportionation between FlH2 and FlH+ to yield FlH2+. in the presence of HClO4 in MeCN. The reaction mechanisms of hydride transfer from AcrH2 to FlH+ are compared with the acid-catalysed electron-transfer reactions from cis-[R2Co(bipy)2] + to FlH+.

Original languageEnglish
Pages (from-to)1047-1053
Number of pages7
JournalJournal of the Chemical Society, Perkin Transactions 2
Issue number8
Publication statusPublished - Dec 1 1989
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Chemistry(all)

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