Structures and absolute stereochemistry of isocyanide and isothiocyanate amphilectenes from the Caribbean sponge Cribochalina sp.

Three new diterpenes (5-7), based on amphilectene skeleton, were isolated f rom the Caribbean sponge Cribochalina sp.. AII contain isocyanide and isoth iocyanate functions and are epimers at C-7 of previously characterized dite rpenoids. The structures of 5-7 were established by spectroscopic technique s. The sponge extract also showed the presence of the known metabolite 4, t ogether with the new bicyclic diterpene 8, potential precursor of the co-oc curring amphilectenes. For the first time, the absolute configuration of th e amphilectene skeleton has been assigned by applying the modified Mosher's method on a derivative of the main compound 4. The isocyanide 4 reduced th e proliferation of lymphocytes T and B under various stimuli. (C) 1999 Publ ished by Elsevier Science Ltd. All rights reserved.