Pimarane diterpenes: Natural source, stereochemical configuration, and biological activity

Plants and fungi are seemingly inexhaustible sources of interesting natural products with remarkable structural and biological diversity. One of the most important groups is the terpenes, ubiquitous natural products that are generated by 2 now well-established biosynthetic pathways: the older mevalonate and the more recently discovered 1-deoxyxylulose-5-phosphate. Among the diterpenes, the pimarane diterpenes are a very representative subgroup with several and interesting biological activities resulting from different functional group modifications. In this review, we outline the method of their structure determination, mainly spectroscopic results, their absolute configuration, and structure-activity relationships, were reported, as well as the mode of action for selected examples from plants, marine organisms, and fungi. The pimarane, isopimarane, and ent-pimarane diterpenes covered in this review have a wide range of biological activities including antimicrobial, antifungal, antiviral, phytotoxic, phytoalexin, cytotoxicity, and antispasmodic and relaxant effects.