The Total Synthesis of Hyperfirin via a Cyclooctadiene Strategy

Polycyclic polyprenylated acylphloroglucinols (PPAPs) combine compelling structural complexity with effective biological activity. The total synthesis of Hyperfirin is reported as one linear sequence. Key to this novel modular strategy is to access the bicyclo[3.3.1]nonane-2,4,9-trione framework via transannular acylation of a decorated eight-membered ring, followed by late stage bridgehead substitution. The described route adds flexibility to PPAP construction and broadens the scope of eight-membered ring chemistry.

Enantioselective Total Synthesis of (+)-Garsubellin A

Garsubellin A is a meroterpene capable of enhancing the enzyme choline acetyltransferase whose decreased level is believed to play a central role in the symptoms of Alzheimer's disease. Due to the potentially useful biological activity together with the novel bridged and fused cyclic molecular architecture, garsubellin A has garnered substantial synthetic interest, but its absolute stereostructure has been undetermined. We report here the first enantioselective total synthesis of (+)‐garsubellin A. Our synthesis relies on stereoselective fashioning of a cyclohexanone framework and double conjugate addition of 1,2‐ethanedithiol that promotes aldol cyclization to build the bicyclic [3.3.1] skeleton. The twelve‐step, protecting group‐free synthetic route has enabled the syntheses of both the natural (−)‐garsubellin A and its unnatural (+)‐antipode for biological evaluations.

Enantioselective Total Synthesis of Berkeleyone A and Preaustinoids

Herein we report the first enantioselective total synthesis of 3,5-dimethylorsellinic acid-derived meroterpenoids (-)-berkeleyone A and its five congeners ((-)-preaustinoids A, A1, B, B1, and B2) in 12-15 steps, starting from commercially available 2,4,6-trihydroxybenzoic acid hydrate. Based upon the recognition of latent symmetry within D-ring, our convergent synthesis features two critical reactions: 1) a symmetry-breaking, diastereoselective dearomative alkylation to assemble the entire carbon core, and 2) a Sc(OTf)₃ -mediated sequential Krapcho dealkoxycarbonylation/carbonyl α-tert-alkylation to forge the intricate bicyclo[3.3.1]nonane framework. We also conducted our preliminary biomimetic investigations and uncovered a series of rearrangements (α-ketol, α-hydroxyl-β-diketone, etc.) responsible for the biomimetic diversification of (-)-berkeleyone A into its five preaustinoid congeners.

Synthesis and Multiplexed Activity Profiling of Synthetic Acylphloroglucinol Scaffolds

Reported here are novel formic-acid-mediated rearrangements of dearomatized acylphloroglucinols to access a structurally diverse group of synthetic acylphloroglucinol scaffolds (SASs). Density-functional theory (DFT) optimized orbital and stereochemical analyses shed light on the mechanism of these rearrangements. Products were evaluated by multiplexed activity profiling (MAP), an unbiased platform which assays multiple biological readouts simultaneously at single-cell resolution for markers of cell signaling, and can aid in distinguishing genuine activity from assay interference. MAP identified a number of SASs that suppressed pS6 (Ser235/236), a marker for activation of the mTOR and ERK signaling pathways. These results illustrate how biomimetic synthesis and multiplexed activity profiling can reveal the pharmacological potential of novel chemotypes by diversity-oriented synthesis.

Biomimetic Synthesis of Meroterpenoids by Dearomatization-Driven Polycyclization

A biomimetic route to farnesyl pyrophosphate and dimethyl orsellinic acid (DMOA)-derived meroterpenoid scaffolds has yet to be reported despite great interest from the chemistry and biomedical research communities. A concise synthetic route with the potential to access DMOA-derived meroterpenoids is highly desirable to create a library of related compounds. Herein, we report novel dearomatization methodology followed by polyene cyclization to access DMOA-derived meroterpenoid frameworks in six steps from commercially available starting materials. Furthermore, several farnesyl alkene substrates were used to generate structurally novel, DMOA-derived meroterpenoid derivatives. DFT calculations combined with experimentation provided a rationale for the observed thermodynamic distribution of polycyclization products.

Norsampsone E, an unprecedented decarbonyl polycyclic polyprenylated acylphloroglucinol with a homoadamantyl core from Hypericum sampsonii

Norsampsone E, an unprecedented polycyclic polyprenylated acylphloroglucinol from Hypericum sampsonii, featured a homoadamantyl skeleton with the loss of the C-4 carbonyl.

Asymmetric Dearomatization/Cyclization Enables Access to Polycyclic Chemotypes

Enantioenriched, polycyclic compounds were obtained from a simple acylphloroglucinol scaffold. Highly enantioselective dearomatization was accomplished using a Trost ligand-palladium(0) complex. A computational DFT model was developed to rationalize observed enantioselectivities and revealed a key reactant-ligand hydrogen bonding interaction. Dearomatized products were used in visible light-mediated photocycloadditions and oxidative free radical cyclizations to obtain novel polycyclic chemotypes including tricyclo[4.3.1.0^1,4]decan-10-ones, bicyclo[3.2.1]octan-8-ones and highly-substituted cycloheptanones.

Hypersampsones S–W, new polycyclic polyprenylated acylphloroglucinols from Hypericum sampsonii

Five new polycyclic polyprenylated acylphloroglucinols (1–5) with a bicyclo[3.3.1]nonane skeleton, along with five known analogues (6–10), were isolated from the aerial parts of Hypericum sampsonii.