Cladocoran A and B: Two Novel g-Hydroxybutenolide Sesterterpenes from the Mediterranean Coral Cladocora cespitosa

The novel terpenoids, cladocoran A (1) and B (2), showing a ç-hydroxybutenolide end group, have been isolated from the Mediterranean Anthozoan Cladocora cespitosa. The unprecedented skeleton of cladocoran was elucidated by spectroscopic methods and chemical conversion. The absolute stereochemistry of the secondary alcohol at C-18 was assigned by the advanced Mosher's method applied to an oxidized derivative of 1.