Bond reactivity indices approach analysis of the [2+2] cycloaddition of jatrophane skeleton diterpenoids from Euphorbia gaditana Coss to tetracyclic gaditanone

[2 + 2]-Cycloaddition-derived cyclobutane natural products: structural diversity, sources, bioactivities, and biomimetic syntheses

This review summarizes the structural diversity, bioactivities, and biomimetic synthesis of [2 + 2]-type cyclobutane natural products, along with discussion of their biosynthesis, stereochemical analysis, racemic occurrence, and biomimetic synthesis.

Unprecedented diterpene skeletons isolated from vascular plants in the last twenty years (2001-2021)

Every year there are hundreds of reports about the isolation of undescribed terpenoids based on novel functionalizations of known carbocyclic skeletons series. However, on some occasions the compounds obtained have a carbocyclic skeleton that does not correspond with the series established, in these peculiar opportunities, in addition to finding an undescribed natural product, is obtained an unprecedented carbocyclic skeleton, whose biogenesis must necessarily involve other additional steps that explain its formation. This review accounts for the reports of seventy-nine unprecedented diterpene skeletons (corresponding to one-hundred-three undescribed diterpenoids) isolated from vascular plants in the last two decades. According to the genus, Euphorbia and Salvia are the most prolific in reports of unprecedented diterpene skeletons with a total of twenty, and nine skeletons, respectively. If the findings are expressed in terms of the family, Euphorbiaceae and Lamiaceae have the highest number of reports of undescribed diterpene skeletons, with twenty-seven and twenty-two, respectively. Finally, fifty-three skeletons are derived from higher diterpenoids (2-12, 68, 69, 86, 104-109, 158-161, 186, 189, 222, 250-255, 285-298, 403-404, 415, 416, and 436), twenty are derived from lower diterpenoids (135, 136, 192-194, 225-229, 363-370, 397, and 425), and six (96, 97, 147, 148, 205, and 206) are derived from skeletons whose biogenesis has not yet been established, or at least, cannot be formally included within the groups mentioned above. This article comprehensively highlights the hypothetical biosynthetic pathway for each of the one-hundred-three undescribed compounds with unprecedented diterpene skeletons and summarizes their most significant biological activities.

Euphorbia diterpenoids: isolation, structure, bioactivity, biosynthesis, and synthesis (2013-2021)

Covering: 2013 to 2021As the characteristic metabolites of Euphorbia plants, Euphorbia diterpenoids have always been a hot topic in related science communities due to their intriguing structures and broad bioactivities. In this review, we intent to provide an in-depth and extensive coverage of Euphorbia diterpenoids reported from 2013 to the end of 2021, including 997 new Euphorbia diterpenoids and 78 known ones with latest progress. Multiple aspects will be summarized, including their occurrences, chemical structures, bioactivities, and syntheses, in which the structure-activity relationship and biosynthesis of this class will be discussed for the first time.

Diterpenoids with Rearranged 9(10→11)-abeo-10,12-Cyclojatrophane Skeleton and the First (15S)-Jatrophane from Euphorbia helioscopia: Structural Elucidation, Biomimetic Conversion, and Their Immunosuppressive Effects

Two novel diterpenoids, one with a rearranged trans,trans-fused tricyclo[10.3.0.0^4,6]pentadecane framework (1) and the other with an unprecedented 15S configuration (2), were isolated from Euphorbia helioscopia. Their structures were elucidated by extensive analysis of HR-ESI-MS, NMR, quantum-chemical calculation, and X-ray crystallographic data. Biosynthetically, 1 has a unique "cyclopropane-shift-like" biogenesis involving an oxa-di-π-methane (ODPM) rearrangement, which inspired us to accomplish the biomimetic conversion of 3 to 1. Moreover, compound 1 displayed a potent immunosuppressive effect by inhibiting Kv1.3 voltage-gated channels.