抄録
Biosynthesis of okadaic acid, a potent inhibitor of protein phosphatase 2A, and prorocentrolide, a macrolide having an unprecedented 26-membered carbocyclic ring and a partially hydrated isoquinoline in the molecule, was investigated by feeding experiments. First, the 13C NMR signals of okadaic acid were assigned by analyses of 2D NMR spectra. Feeding experimente were carried out by adding (1-13C), (2-13C), or [1,2-13C] sodium acetate to cultures of Prorocentrum lima. 13C NMR spectra (JEOL, 400MHz, CDC13/CD3OD 2:1) of labeled compounds showed 15 folds enhancement of signal intensities of labeled carbons. Out of 44 carbons of okadaic acid 39 were labeled, but carbons at the two termini could not be labeled with acetic acid. Out of 55 carbons of prorocentrolide 49 carbons were labeled. Three carbons consisting the isoquinoline ring could not be labeled. Two carbons were labeled with both [1-13C] and [2-13C] acetates. The labeling patterns suggested a type of mixed polyketides, involving building blocks formed via malonate, succinate, and 3-hydroxy1-3-methylglutarate.
