Macrocarpane-Type Sesquiterpenes from Laurencia microcladia

Seven undescribed sesquiterpenes featuring an uncommon macrocarpane skeleton, laurocarpanes A–G (1–7), were isolated from specimens of Laurencia microcladia collected in Fuerteventura, the Canary Islands. The identification of these macrocarpane-type metabolites is of particular interest from both chemical and chemotaxonomic perspectives, as it highlights distinctive biosynthetic capabilities within the studied species and further expands current knowledge regarding the distribution of this uncommon structural class in marine organisms. Their structures and configurational assignments were determined by a comprehensive NMR study, high-resolution mass spectrometry, and coupling constant evaluations. A biosynthetic model was proposed linking the assembly of the macrocarpane skeleton directly to an (S)-β-bisabolene monocyclic precursor, with the process mediated by vanadium-dependent bromoperoxidase (V-BPO). The plausibility of the proposed biogenetic formation of laurocarpanes A–G (1–7) was assessed through Density Functional Theory (DFT) calculations.