Synthesis and spectroscopic characterization of [1′-14C]ubiquinone-2, [1′-14C]-5-demethoxy-5-hydroxyubiquinone-2, and [1′-14C]-5-demethoxyubiquinone-2

[1'-C-14]Ubiquinone-2, [1'-C-14]-5-demethoxy-5-hydroxyubiquinone-2, and [1'-C-14]-5-demethoxyubiquinone-2 have been synthesised from [1-C-14]acetic acid. A common feature of these benzoquinones is the isoprenoid chain, and the C-14-label has therefore been incorporated in this isoprenoid. The coupling of the different quinone head groups and the isoprenoid chain is the last step in the total synthesis, to prevent unnecessary loss of the labelled material during synthesis. The products have been characterised by mass spectrometry, H-1 NMR and C-13 NMR.