Biosynthesis of anacardic acids from acetate in Ginkgo biloba

Anacardic acids synthesized from [1‐ 14 C] and [2‐ 14 C] acetates by Ginkgo biloba were subjected to chemical degradation to locate the 14 C in the molecules. Radioactivity in the carboxyl group was determined by decarboxylation and counting the resulting CO 2 ; in the aliphatic chian, by oxidation of anacardol from which three homologous fatty acids are obtained; and in ring C‐6, chain C‐1 and chain C‐2 by decarboxylation of these fatty acids where the carboxyl groups represent these respective C atoms. Distribution of 14 C in the anacardic acids indicates that synthesis of the chain and of the ring are separate processes. According to its radioactivity, ring C‐6 originates from the chain. A polyketide mechanism appears likely for the ring synthesis, although considerable randomization of 1‐ 14 C and of 2‐ 14 C from the acetates had occurred in the plants.