A novel route for the synthesis of naturally occurring furan fatty acids with particular emphasis on labeling with14C is described. Methyl [2-14C] 9-(5-pentyl-3,4-dimethyl-2-furyl)nonanoate was synthesized from 3,4-dimethyl-2-pentylfuran by a new route. [3-14C]11-(5-Pentyl-3-methyl-2-furyl)undecanoate and [2-14C] 9-(5-pentyl-2-furyl)nonanoate were prepared from their lower homologs. The label was introduced in all cases by means of the Arndt-Eistert method for chain elongation, using14CH2N2. Comparisons of yields show that, with increasing number of substituents on the ring, the furan compounds are increasingly subject to uncontrollable side reactions.