The ophiobolin sesterterpenes are notable plant pathogens which have recently elicited significant chemical and biological attention because of their intriguing carbogenic frameworks, reactive functionalities, and emerging anticancer profiles. Reported herein is a total synthesis of (+)‐6‐epi‐ophiobolin A in 14 steps, a task which addresses construction of the synthetically challenging spirocyclic tetrahydrofuran motif as well as several other key stereochemical problems. This work demonstrates a streamlined synthetic platform to complex ophiobolins leveraging disparate termination modes of a radical polycyclization cascade for divergent elaboration and functionalization. 相似文献
Vibralactone is isolated from the basidiomycete fungus Boreostereum vibrans as one of the strongest lipase inhibitors. Its unusual β‐lactone‐fused bicycle is derived from an aryl ring moiety by an oxidative ring‐expansion prior to an intramolecular cyclization. Herein, we report the discovery of the cyclase VibC which belongs to the α/β‐hydrolase superfamily and is involved in the vibralactone biosynthesis. Biochemical and crystal studies suggest that VibC may catalyze an aldol or an electrocyclic reaction initiated by the Ser‐His‐Asp catalytic triad. For the aldol and pericyclic chemistry in living cells, VibC is a unique hydrolase performing the carbocycle formation of an oxepinone to a fused bicyclic β‐lactone. This presents a naturally occurring, new enzymatic reaction in both aldol and hydrolase (bio)chemistry that will guide future exploitation of these enzymes in synthetic biology for chemical‐diversity expansion of natural products. 相似文献
Starting from equisetin, the asymmetric synthesis of (+)-fusarisetin?A has been accomplished in a one-pot transformation including a biomimetic oxidation and an intramolecular Diels-Alder/Roskamp reaction. Peroxyfusarisetin is proposed as a plausible biosynthetic intermediate based on studies of the oxidation of equisetin. 相似文献
The first total synthesis of diaporthichalasin has been successfully achieved and complete structure elucidation, including the absolute configuration, was also accomplished. The intramolecular Diels–Alder (IMDA) reaction between the diene side chain on the decalin skeleton and α,β‐unsaturated γ‐hydroxy‐γ‐lactam in aqueous media was effectively employed as the key step. From this synthetic study, we found that α,β‐unsaturated γ‐hydroxy‐γ‐lactam is an essential precursor for the construction of the diaporthichalasin‐type pentacyclic skeleton. This important finding strongly suggests that this route is involved in the biosynthetic pathway for diaporthichalasin. 相似文献
The first bioinspired total syntheses of (?) kravanhins A and C were accomplished from a labdane diterpenoid derivative. The key reactions involve a photooxidation and a one‐pot sequential aldol cyclization and lactonization, which provide a new plausible biosynthetic pathway for the kravanhins and other symbiotic members. 相似文献
The total synthesis of the cyclic diterpene ent-tonantzitlolone (ent-1) is presented. Key steps for assembling the macrocyclic core structure of 1 are a highly selective aldol reaction and an E selective ring-closing metathesis reaction. A detailed investigation of these two steps and the final transformations towards the completion of the synthesis is disclosed. 相似文献
Vinigrol, a diterpene natural product, has been a fascinating target for total synthesis for over two decades. This minireview describes recent synthetic studies that have ultimately allowed access to the coveted vinigrol scaffold. Barriault’s synthesis of the vinigrol core is described, in addition to the elegant strategies disclosed by Njar?arson and Hanna. The first total synthesis of vinigrol, reported by Baran in 2009, is also highlighted. This review showcases the fundamental role that natural products play in spawning innovations in synthetic chemistry. 相似文献
In the realm of natural product chemistry, few isolates have risen to the level of fame justifiably accorded to Taxol ( 1 ) and its chemical siblings. This report describes the most concise route to date for accessing the highly oxidized members of this family. As representative members of taxanes containing five oxygen atoms, decinnamoyltaxinine E ( 2 ) and taxabaccatin III ( 3 ), have succumbed to enantioselective total synthesis for the first time in only 18 steps from a simple olefin starting material. The strategy holistically mimics nature's approach (two‐phase synthesis) and features a carefully choreographed sequence of stereoselective oxidations and a remarkable redox‐isomerization to set the key trans‐diol present in 2 and 3 . This work lays the critical groundwork necessary to access even higher oxidized taxanes such as 1 in a more practical fashion, thus empowering a medicinal chemistry campaign that is not wedded to semi‐synthesis. 相似文献
A ten‐step, enantiospecific synthesis of the highly challenging core skeleton of sesterterpenoid astellatol has been achieved. Key transformations of this strategy include a facile, convergent construction of the tricyclic motif and a SmI2‐induced reductive radical cyclization that forms the pivotal cyclobutane ring. 相似文献
Herein, we report the first enantioselective synthesis of dichrocephones A and B, which are cytotoxic triquinane sesquiterpenes with a dense array of stereogenic centers within a strained polycyclic environment. Key features include the application of a catalytic asymmetric Wittig reaction, followed by stereoselective functionalization of the propellane core into a pentacyclic intermediate. Double reductive ring cleavage yielded the proposed structure of dichrocephone A. Mismatched spectroscopic data for our synthetic material compared to the natural isolate led us to revise the previously proposed configuration based on biosynthetic considerations and NMR calculations. Implementation of these findings culminated in the synthesis of dichrocephones A and B. 相似文献
Similar, but different : Possessing almost the same but not identical structures, the recently discovered natural products hopeahainol A ( 1 ) and hopeanol ( 2 ) exhibit important but differing biological properties (see structures). Their first total synthesis has now been achieved through a series of novel cascade reactions and skeletal rearrangements.
