Electrocyclic processes in aromatic biosynthesis: A biomimetic study of pseudorubrenoic acid A

The possible involvement of 6π electrocyclic ring closures, mediated by electrocyclase enzymes, of polyunsaturated acyclic polyketide intermediates in the biosynthesis of certain o-dialkyl-substituted benzenoid natural products is discussed. The feasibility of the process is illustrated by the electrocyclic ring closure of 7E,9Z,11E,13Z-1-t-butyldimethylsilyloxy-hexadeca-7,9,11,13-tetraene (12a) to the cyclohexadiene 13 followed by dehydrogenation to the analogue 14 of the o-dialkyl-substituted aromatic metabolite pseudorubrenoic acid A (1).