Abstract
Two novel insecticidal metabolites, calyculin E (1) and F (2), which had insecticial activity against the German cockroach and mosquito larvae, were isolated from a Japanese marine sponge, Discodermia sp. By an extensive examination of the NMR spectra, the isolates were elucidated to be stereoisomers of calyculin A (3) and B (4), respectively. The molecular shape of calyculin E in solution was deduced to be in a folded conformation by using NMR parameters such as NOE values and coupling constants in conjunction with NOE-restricted energy minimization and computer-assisted molecular modeling.
