First trans-eunicellane terpene synthase in bacteria

Terpenoids are the largest family of natural products, but prokaryotes are vastly underrepresented in this chemical space. However, genomics supports vast untapped biosynthetic potential for terpenoids in bacteria. We discovered the first trans-eunicellane terpene synthase (TS), AlbS from Streptomyces albireticuli NRRL B-1670, in nature. Mutagenesis, deuterium labeling studies, and quantum chemical calculations provided extensive support for its cyclization mechanism. In addition, parallel stereospecific labeling studies with Bnd4, a cis-eunicellane TS, revealed a key mechanistic distinction between these two enzymes. AlbS highlights bacteria as a valuable source of novel terpenoids, expands our understanding of the eunicellane family of natural products and the enzymes that biosynthesize them, and provides a model system to address fundamental questions about the chemistry of 6,10-bicyclic ring systems.

Bio-inspired synthesis of xishacorenes A, B, and C, and a new congener from fuscol

In this manuscript, we describe the conversion of fuscol, a natural product isolated in 1978, to xishacorenes A, B, and C, isolated in 2017, as well as a previously unreported congener, which we have named xishacorene D.

The xishacorene natural products are structurally unique apolar diterpenoids that feature a bicyclo[3.3.1] framework. These secondary metabolites likely arise from the well-studied, structurally related diterpenoid fuscol. In this manuscript, we describe the conversion of fuscol to xishacorenes A, B, and C, as well as a previously unreported congener, which we have named xishacorene D. In addition, we describe immunomodulatory activity studies of the xishacorenes, a structurally related analogue, and fuscol. These studies were aided by an accurate determination of the physical properties (e.g., molar extinction coefficient) of the highly apolar xishacorenes.

Eunicidiol, an anti-inflammatory dilophol diterpene from Eunicea fusca

A new dilophol diterpene, eunicidiol (1), has been isolated from the crude extract of Eunicea fusca, a gorgonian coral collected from Hillsboro Ledge, Florida. This compound was purified, along with fuscol (2) and eunicol (3), using a combination of normal- and reversed-phase chromatography methods. The structure of eunicidiol (1) was elucidated by 1D and 2D NMR spectroscopic analysis, and the absolute configuration was assigned using Mosher's method. The anti-inflammatory activity of 1-3 was evaluated by measuring their ability to reduce phorbol myristate acetate (PMA)-induced edema in a mouse ear model. Topical application of a 100 μg/ear dose of diterpenes 1-3 significantly reduced edema by 44%, 46%, and 54%, respectively. This activity was superior to indomethacin, a known anti-inflammatory used as a control.

Marine natural products

Covering: 2010. Previous review: Nat. Prod. Rep., 2011, 28, 196. This review covers the literature published in 2010 for marine natural products, with 895 citations (590 for the period January to December 2010) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1003 for 2010), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Marine diterpene glycosides

Marine diterpene glycosides (MDGs) respresent a small but highly significant group of the much larger class of marine diterpenes. The three well-studied examples of MDGs are eleutherobins, pseudopterosins and fuscosides, all of which exhibit extremely promising biological activity. The eleutherobins are potent anti-mitotic agents, and the pseudopterosins and fuscosides are potent anti-inflammatory agents. This review discusses the structures and biological activities of these compounds, as well as their biosynthesis and synthesis.