Racemic 4-[13C]catechin 14 has been synthesized in ten steps starting frompotassium [13C]cyanide. The intermediate chalcone 9 was formed by acylation of the benzylated phloroglucinol 7 with the caffeic acid synthon 6, using the trifluoroacetic mixed anhydride. The flavonoid skeleton was then obtained by previously described reactions such as the reduction of chalcone 9 and dihydroxylation of flavene