Aromatic origin of cyclopentenoid metabolites

Oxidative cleavage of aromatic compounds is often part of a degradative process and is widely observed in nature. The immediate catabolic products can sometimes cyclize or rearrange to new secondary metabolites. The enzymatic contraction of a dehydroisocoumarin to yield cyclopentenoid metabolites in Cryptosporiopsis sp. is reported. The label distribution of (+) cryptosporiopsin, a chlorinated cyclopentenone, was determined by analysis of the [¹³C]nmr of [1-¹³C] and [2-¹³C]acetate enriched-cryptosporiopsin. The putative aromatic precursor of cyclopentenoid metabolites, 2,3-dihydro-6,8-dihydroxy-2-methylisocoumarin (6), was isolated from Aspergillus terreus. This metabolite (6) was prepared doubly labeled ($\text{T}{}^{14}\text{C}$). The aromatic origin of the Cryptosporiopsis chlorinated cyclopentenoid metabolites was rigorously proven from feeding experiments with doubly labeled compound 6. A related but nonchlorinated metabolite, terrein, was isolated from A. terreus and was also shown to be derived from [$\text{T}{}^{14}\text{C}\text{]-2,3-dihydro-6,8-dihydroxy-2-methylisocoumarin}$.