Crinipellins, the First Natural Products with a Tetraquinane Skeleton

The range of cyclopentanoid natural products that exhibit antibiotic activity is expanded by the isolation of the crinipellins, for example, crinipellin A 1a and its O-acetyl derivative 1b. These diterpenoids, which contain an α-methylene ketone group, are produced by cultures of the fungus Crinipellis stipitaria.