Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/16/2011
Publication Date: 3/27/2012
Citation: Zeller, W.E. 2012. Synthesis of (+) and (-)-phaselic acid [abstract]. American Chemical Society. Paper No. AGFD 168.
Technical Abstract: (2S)-Phaselic acid (2S-O-caffeoylmalate) is a common plant metabolite belonging to the o-diphenol subclass of phenolic secondary metabolites. Our interest in this metabolite stems from previous studies showing that the presence of (2S)-phaselic acid in red clover is crucial to the preservation of utilizable protein in this forage during the ensiling process. We required reasonable quantities of (2S)-phaselic acid, both as a reference standard and for a variety of studies directed at elucidating the biological pathway of specific secondary phenolic metabolites. The synthesis of both enantiomers of phaselic acid (2-O-caffeoylmalate) is described. The previously unreported acetate-protected caffeic acid anhydride, prepared through triphosgene-mediated coupling of caffeic acid diacetate, was used with appropriately protected malic acid derivatives as coupling partners to provide fully protected phaselic acid. Sequential unmasking of the protecting groups afforded phaselic acid in an acceptable overall yield. The synthetic sequence described here should be applicable to preparation of additional members of this important class of secondary metabolites.