Biosynthesis of Mycophenolic Acid1

Comparative incorporation experiments with (1′-14C)-orsellinic acid (2) and (1′-14C)-4,6-dihydroxy-2,3-dimethylbenzoic acid (3) suggest that only the latter compound is a specific precursor of mycophenolic acid; the implication of this result in terms of the early stages of the biosynthetic sequence is noted.