Electrochemical oxidation of 5-hydroxytryptophol. I: Studies in acid solution.
The oxidation chemistry of the endogenous central nervous system indole 5-hydroxytryptophol (5-HTOL) has been studied at pH 2 using electrochemical methods. The first voltammetric oxidation peak (I) appears to involve an initial one-electron abstraction giving a transient radical cation that, in the rate-controlling step, deprotonates to give a neutral radical. A radical-substrate reaction then occurs to give a dimer radical which is further oxidized to yield three simple dimers (4,4'-,4,6'-, and 2,4'-linked). The neutral radical can be further oxidized (1e) to a quinone imine that, as a result of very fast follow-up chemistry and electrochemistry, yields tryptophol-4,5-dione (B) which has been isolated in pure form. Reactions between intermediate species also result in three dimers containing residues of 5-HTOL and B and an unusual oxygen-bridged trimer.
Cheng
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Department of Chemistry and Biochemistry, University of Oklahoma, Norman 73019.
Dryhurst
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D006916:5-Hydroxytryptophan / Q000032:analysis; D004563:Electrochemistry; D006917:Hydroxytryptophol / Q000032:analysis*; D007211:Indoles / Q000032:analysis*; D010084:Oxidation-Reduction; D012701:Serotonin / Q000032:analysis; D012996:Solutions
D007211:Indoles; D012996:Solutions; D006917:Hydroxytryptophol; D012701:Serotonin; D006916:5-Hydroxytryptophan