Abstract The synthesis of [4-14 C]-pelargonidin chloride and [4-14 C]-delphinidin chloride via [formyl-14 C]-2-(benzoyloxy)-4, 6-dihydroxybenzaldehyde, ω, 4-diacetoxyacetophenone and ω, 3, 4, 5-tetraacetoxyacetophenone is described. The first step comprised labelling of the carbonyl group of 2-(benzoyloxy)-4, 6-dihydroxybenzaldehyde, verifying that the coupling with ω, 4-diacetoxyacetophenone or ω, 3, 4, 5-tetraacetoxyacetophenone under ...