79075-95-9Relevant academic research and scientific papers
The Chemistry of 1-Carba-1-deaza-N5-ethyl-N3-methyllumiflavins. Influense of the N1 upon the Reactivity of Flavin 4a-Hydroperoxides
Ball, Sheldon,Bruice, Thomas C.
, p. 5494 - 5503 (2007/10/02)
N5-ethyl-N3-methyl-1,5-dihydro-1-deazalumiflavin (C1-FlEtH) has been synthetized and characterized.In aqueous solution (pH 3) C1-FlEtH reacts with 1 eqiv of 3O2 to provide N5-ethyl-N3-methyl-1-deazalumiflavinium cation (C1-Flox+Et).C1-Flox+Et may be reduced to C1-FlEtH by ascorbate, dithionite, or H2/Pd.C1-Flox+Et is not photoreducible by EDTA as is Flox+Et.This is due to direct photolysis of C1-Flox+Et with the accompanying loss of the N5-ethyl substituent as acetaldehyde.The spectral properties of C1-FlEtH2+, C1-FlEtH, and C1-FlEt- and associated pKa's have been determined and compared to the analogous constants for FlEtH2+, FlEtH, and FlEt-.A comparison of the spectral properties of Flox+Et and C1-Flox+Et has been made.The pKa values and the pH dependences of the rate constants for the formation and dissociation of the pseudobases (i.e.C1-4a-FlEtOH and 4a-FlEtOH) of Flox+Et and C1-Flox+Et have also been determined as have the rate constants (pH 3.0) for addition of β-mercaptoethanol to the 4a-position of Flox+Et and C1-Flox+Et (providing 4a-FlEt-SCH2CH2OH and C1-4a-FlEt-SCH2CH2OH).Partial oxidation of C1-FlEtH by 3O2 in H2O produces the radical C1-FlEt. through comproportionation of C1-Flox+Et and C1-FlEtH.Evidence is presented, suggesting that the radical C1-FlEt. possesses a higher free-energy content than does FlMe..The oxidation of C1-FlEtH in H2O or t-BuOH with excess 3O2 is autocatalytic in nature.The initial rate for reaction of C1-FlEtH with 3O2 is substantially greater than the initial rate for reaction of FlMeH with 3O2.This observation is discussed in terms of the mechanism of reaction of FlRH with O2.In DMF, C1-FlEtH reacts with 3O2 to form a 4a-hydroperoxide (i.e.C1-4a-FlEtOOH) which is quite stable.The rate constants for solvolysis of C1-4a-FlEtOOH and 4a-FlEtOOH in DMF have been compared.The second-order rate constants for the (a) oxidation of I- in 95percent EtOH/DMF, (b) N-oxidation of N,N-dimethylbenzylamine, N-methylbenzylamine, and morpholine in DMF, and (c) the S-oxidation of thioxane in DMF by C1-4a-FlEtOOH and α-FlEtOOH have been determined.The flavin products for the N- and S-oxygenation reactions are the pseudobases C1-4a-FlEtOH and 4a-FlEtOH.These reactions are quantitative.Comparison of the various rate constants indicates that C1-4a-FlEtOOH is from 3- to 17-fold a poorer oxidizing agent than is 4a-FlEtOOH.This can be explained by the somewhat less electronegative character of the 4a-position of the 1-deazaflavin hydroperoxide.The equilibrium constants for 4a-additions and retroadditions to C1-Flox+Et and Flox+Et are comparable, and this leads to the conclusion that the difference in free-energy contents of C1-Flox+Et and Flox+Et (starting states) and C1-4a-FlEtX and 4a-FlEtX (products) is the same.Due to this feature, the decrease in ΔG* for 4a additions to Flox+Et, as compared to C1-Flox+Et ...
