New Metabolites Isolated from a Laurencia obtusa Population Collected in Corsica

The chemical investigation of an ethyl acetate extract (EtOAc) obtained from Laurencia obtusa, collected in Corsica, allowed for the identification of three new compounds (1, 2, and 4) and six known compounds. Compounds 1 to 4 were isolated and fully characterized by a detailed spectroscopic analysis. Compounds 1 and 2 are two C₁₅-acetogenins sharing the same ring system: a tetrahydropyran linked by a methylene to a tetrahydrofuran ring. Compound 1 exhibits a bromoallene unit whereas compound 2 possesses an uncommon α-bromo-α,β-unsaturated aldehyde terminal unit. Compound 4 is the first diterpene exhibiting a 19(4 → 3)abeo-labdane skeleton isolated from a Laurencia species. Isolation of concinndiol (compound 3) together with compound 4 suggests a common biosynthetic origin. Additionally, five known compounds, namely sagonenyne, laurene, α-bromocuparene, microcladallene A, and β-snyderol were identified in chromatographic fractions by NMR analysis using a computerized method that was developed in our laboratory.