These authors contributed equally to this work.
Mass spectrometric studies shed light on unusual oxidative transformations of 1,2-dehydro-N-acetyldopa
Article first published online: 30 JUN 2013
Copyright © 2013 John Wiley & Sons, Ltd.
Rapid Communications in Mass Spectrometry
Volume 27, Issue 15, pages 1785–1793, 15 August 2013
How to Cite
Abebe, A., Kuang, Q. F., Evans, J. J. and Sugumaran, M. (2013), Mass spectrometric studies shed light on unusual oxidative transformations of 1,2-dehydro-N-acetyldopa. Rapid Commun. Mass Spectrom., 27: 1785–1793. doi: 10.1002/rcm.6630
- Issue published online: 20 JUN 2013
- Article first published online: 30 JUN 2013
- Manuscript Accepted: 19 MAY 2013
- Manuscript Revised: 15 MAY 2013
- Manuscript Received: 14 FEB 2013
Lamellarins are a group of over 70 plus bioactive marine natural compounds possessing a 6,7-dihydroxycoumarin moiety. Although they appear to derive from 3,4-dihydroxyphenylalanine (dopa), practically nothing is known about the metabolic fate of these compounds. Biochemical considerations indicate that they could arise from a N-acetyl-1,2-dehydrodopa precursor through oxidative cyclization reaction.
To assess the above hypothesis, we synthesized N-acetyl-1,2-dehydrodopa and conducted oxidation studies with commercially available mushroom tyrosinase and evaluated the course of the reaction with reversed-phase liquid chromatography/mass spectrometry (LC/MS).
Mushroom tyrosinase readily oxidized N-acetyl-1,2-dehydrodopa – not to the normally expected quinone – but to an unstable quinone methide isomer, which rapidly cyclized to produce the dihydroxycoumarin product, 3-aminoacetyl esculetin. Interestingly, 3-aminoacetyl esculetin was further oxidized to a second quinone methide derivative that exhibited an addition reaction with the parent dihydroxycoumarin generating dimeric and other oligomeric products in the reaction mixture.
LC/MS analysis of the N-acetyl-1,2-dehydrodopa oxidation reaction reveals not only a possible novel oxidative cyclization route for the biosynthesis of coumarin-type dehydrodopa compounds in marine organisms, but also unusual oxidative transformations of dehydro dopa derivatives. Copyright © 2013 John Wiley & Sons, Ltd.