Cespitulins A-D, novel diterpenoids from Taiwanese Cespitularia taeniata

Four novel diterpenoids, designated cespitulins A-D (1-4) were isolated and characterized from the Taiwanese soft coral Cespitularia taeniata. Their structures were determined by extensive spectroscopic analyses (1H-1H COSY, HMQC, HMBC, NOESY). Compounds 1-4 possess an unprecedented bond cleavage between C-9 and C-10 with a hemiacetalic lactone ring rather than a verticillane skeleton.