A Sesterterpene Lactone from Petrosaspongia nigra sp. nov.

A sponge from the new genus Petrosaspongia has yielded two new isomeric sesterterpene lactones. We report here the structure of one of these lactones, [4aS(4a[alpha],4 b[beta],6a[alpha],7[beta],8a[alpha],11a[beta],12[beta],13a[beta],13b[alpha],15a[beta])]-12-acetoxyoctadecahydro- 1,1,4a,13b-tetramethyl-7,11a-epoxy- 2H-furo[2,3-b]phenanthro[1,2-f]oxocin-10(11H)-one, C₂₇H₄₀O₆.

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