Identification of amphilectosins as key intermediates in pseudopterosin biosynthesis

Amphilectosins A and B have been identified from the organic extract of Pseudopterogorgia elisabethae collected in the Florida Keys, along with seco-pseudopterosins and pseudopterosins. The structures of the amphilectosins, "C-12-C-13 dehydro seco-pseudopterosins", suggested that these metabolites provide the biosynthetic link between the seco-pseudopterosins (serrulatane diterpenes) and pseudopterosins (amphilectane diterpenes). This biosynthetic relationship was confirmed through various radiolabeling experiments. Incubation studies with the amphilectosins revealed the selective transformation of amphilectosin A to pseudopterosin Y and the transformation of amphilectosin B to pseudopterosin F, which suggests that the alpha/beta stereochemistry for the isobutenyl group in the pseudopterosins arises from the selective ring closure of the cis- and trans-amphilectosins.