Synthesis in the plakortone series:plakortone e

摘要

A Pd(II)-mediated hydroxycyclisation-carbonylation-lactonisation sequence has operated efficiently with racemic enediol (8) to furnish (four)separable diastereomers of the bicyclic lactone system assigned to the sponge-derived,bioactive plakortone E.all four are cis ring-fused,and one is identical,on the basis of ~1H and ~13C nmr spectroscopic comparisons,with plakortone E,thus confirming its constitution and relative stereochemistry about the bicyclic lactone core.This syntheitic approach,when applied to stereoisomer (13),will establish the absolute stereochemistry of plakortone E,like to be that shown for (14).