Bicyclic alpha ,[Omega]-dicarboxylic acid derivatives from a colonial tunicate of the family Polyclinidae

In the course of our search for bioactive metabolites from a colonial tunicate of the family Polyclinidae, six new ( 1- 6) cyclic fatty acid derivatives were isolated. Their planar structures were established on the basis of NMR and MS spectroscopic analyses. The relative configuration was determined by NOESY experiment. Compounds 1- 6 represent a fused bicyclic skeleton possibly derived from alpha ,[Omega]- dicarboxylic acids such as eicosanedioic acid or docosanedioic acid via a Diels-Alder type of cyclization. Compounds 1- 4 and 6 showed mild cytotoxicity against a panel of five human solid tumor cell lines.