Four Diterpene Isonitriles from the Sponge Cymbastela hooperi

The low-temperature X-ray structures of four isomeric diterpene isonitriles, C₂₁H₃₁N, obtained from the sponge Cymbastela hooperi, are reported. These are the tetracyclic compounds, (1S*,3S*,4R*,7S*,8S*,12S*,13S*)-7-isocyanocycloamphilect-11(20)-ene (alternative name: 1,4,7,7-tetramethyl-1,2,3,3a,4,5,5a,6,7,9,10,10a,10b,10c-tetradecahydropyrenyl 1-isocyanide) and (1S*,3S*,4R*,7S*,8S*,11R*,12R*,13S*,20S*)-7-isocyanoisocycloamphilect-14-ene (alternative name: 1,4,7,8-tetramethyl-1,2,3,3a,4,5,5a,8,8a,9,10,10a,10b,10c-tetradecahydropyrenyl 1-isocyanide), and the tricyclic compounds, (1S*,3S*,4R*,7S*,8S*,12S*,13S*)-7-isocyanoamphilecta-11(20), 15-diene [alternative name: 1,4-dimethyl-7-methylene-6-(2-methyl-2-propenyl)perhydro-1H-phenalenyl 1-isocyanide] and (1R*,3S*,4R*,7S*,8S*,13R*)-7-isocyanoamphilecta-11,14-diene [alternative name: 1,4,7-trimethyl-6-(2-methyl-1-propenyl)-2,3,3a,4,5,6,8,9,9a,9b-decahydro- 1H-phenalenyl 1-isocyanide]. All of the structures exhibit trans-fused ring systems.

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