The total synthesis of hyperpapuanone, hyperibone L, epi-clusianone and oblongifolin A

Antimicrobial Evaluation of Two Polycyclic Polyprenylated Acylphloroglucinol Compounds: PPAP23 and PPAP53

Polycyclic polyprenylated acylphloroglucinols (PPAPs) comprise a large group of compounds of mostly plant origin. The best-known compound is hyperforin from St. John's wort with its antidepressant, antitumor and antimicrobial properties. The chemical synthesis of PPAP variants allows the generation of compounds with improved activity and compatibility. Here, we studied the antimicrobial activity of two synthetic PPAP-derivatives, the water-insoluble PPAP23 and the water-soluble sodium salt PPAP53. In vitro, both compounds exhibited good activity against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium. Both compounds had no adverse effects on Galleria mellonella wax moth larvae. However, they were unable to protect the larvae from infection with S. aureus because components of the larval coelom neutralized the antimicrobial activity; a similar effect was also seen with serum albumin. In silico docking studies with PPAP53 revealed that it binds to the F1 pocket of human serum albumin with a binding energy of -7.5 kcal/mol. In an infection model of septic arthritis, PPAP23 decreased the formation of abscesses and S. aureus load in kidneys; in a mouse skin abscess model, topical treatment with PPAP53 reduced S. aureus counts. Both PPAPs were active against anaerobic Gram-positive gut bacteria such as neurotransmitter-producing Clostridium, Enterococcus or Ruminococcus species. Based on these results, we foresee possible applications in the decolonization of pathogens.

Total Synthesis of Hypersampsone M

We report the first total synthesis of hypersampsone M, an archetypal member of the homoadamantane polycyclic polyprenylated acylphloroglucinols (PPAPs). Commencing from cyclohexenone, a key cyclopentene annulation followed by ring-expansion results in an elusive hydrazulene that undergoes a series of unexpected late-stage transformations, ultimately enabling completion of the synthesis. The route detailed herein represents a potentially general strategy for the synthesis of related homoadamantane PPAPs.

Regiodivergent biosynthesis of bridged bicyclononanes

Medicinal compounds from plants include bicyclo[3.3.1]nonane derivatives, the majority of which are polycyclic polyprenylated acylphloroglucinols (PPAPs). Prototype molecules are hyperforin, the antidepressant constituent of St. John's wort, and garcinol, a potential anticancer compound. Their complex structures have inspired innovative chemical syntheses, however, their biosynthesis in plants is still enigmatic. PPAPs are divided into two subclasses, named type A and B. Here we identify both types in Hypericum sampsonii plants and isolate two enzymes that regiodivergently convert a common precursor to pivotal type A and B products. Molecular modelling and substrate docking studies reveal inverted substrate binding modes in the two active site cavities. We identify amino acids that stabilize these alternative binding scenarios and use reciprocal mutagenesis to interconvert the enzymatic activities. Our studies elucidate the unique biochemistry that yields type A and B bicyclo[3.3.1]nonane cores in plants, thereby providing key building blocks for biotechnological efforts to sustainably produce these complex compounds for preclinical development.

Sequential Dieckmann cyclization enables the total synthesis of 7-epi-clusianone and 18-hydroxy-7-epi-clusianone

A unified approach for the construction of the bicyclo[3.3.1]nonane-2,4,9-trione core of polycyclic polyprenylated acylphloroglucinols (PPAPs) was reported. This approach involves a sequential process of two distinct Dieckmann condensation reactions from the linear precursor. Using this method, the divergent total synthesis of the natural products 7-epi-clusianone and 18-hydroxy-7-epi-clusianone and the formal synthesis of sampsonione P were achieved. Additionally, other key steps to realize this strategy include RuCl3-catalyzed oxidative olefin cleavage and Pd-catalyzed Tsuji-Trost decarboxylative allylation. The synthesis indicated that bicyclo[3.3.1]nonane-2,4,9-triones could also be constructed via 6-membered intermediates.

Selective Activation of a TRPC6 Ion Channel Over TRPC3 by Metalated Type-B Polycyclic Polyprenylated Acylphloroglucinols

Selective modulation of TRPC6 ion channels is a promising therapeutic approach for neurodegenerative diseases and depression. A significant advancement showcases the selective activation of TRPC6 through metalated type-B PPAP, termed PPAP53. This success stems from PPAP53's 1,3-diketone motif facilitating metal coordination. PPAP53 is water-soluble and as potent as hyperforin, the gold standard in this field. In contrast to type-A, type-B PPAPs offer advantages such as gram-scale synthesis, easy derivatization, and long-term stability. Our investigations reveal PPAP53 selectively binding to the C-terminus of TRPC6. Although cryoelectron microscopy has resolved the majority of the TRPC6 structure, the binding site in the C-terminus remained unresolved. To address this issue, we employed state-of-the-art artificial-intelligence-based protein structure prediction algorithms to predict the missing region. Our computational results, validated against experimental data, indicate that PPAP53 binds to the 777LLKL780-region of the C-terminus, thus providing critical insights into the binding mechanism of PPAP53.

Unnatural Endotype B PPAPs as Novel Compounds with Activity against Mycobacterium tuberculosis

Pre-SARS-CoV-2, tuberculosis was the leading cause of death by a single pathogen. Repetitive exposure of Mycobacterium tuberculosis(Mtb) supported the development of multidrug- and extensively drug-resistant strains, demanding novel drugs. Hyperforin, a natural type A polyprenylated polycyclic acylphloroglucinol from St. John's wort, exhibits antidepressant and antibacterial effects also against Mtb. Yet, Hyperforin's instability limits the utility in clinical practice. Here, we present photo- and bench-stable type B PPAPs with enhanced antimycobacterial efficacy. PPAP22 emerged as a lead compound, further improved as the sodium salt PPAP53, drastically enhancing solubility. PPAP53 inhibits the growth of virulent extracellular and intracellular Mtb without harming primary human macrophages. Importantly, PPAP53 is active against drug-resistant strains of Mtb. Furthermore, we analyzed the in vitro properties of PPAP53 in terms of CYP induction and the PXR interaction. Taken together, we introduce type PPAPs as a new class of antimycobacterial compounds, with remarkable antibacterial activity and favorable biophysical properties.

Different routes for the construction of biologically active diversely functionalized bicyclo[3.3.1]nonanes: an exploration of new perspectives for anticancer chemotherapeutics

Cancer is the second most high-morbidity disease throughout the world. From ancient days, natural products have been known to possess several biological activities, and research on natural products is one of the most enticing areas where scientists are engrossed in the extraction of valuable compounds from various plants to isolate many life-saving medicines, along with their other applications. It has been noticed that the bicyclo[3.3.1]nonane moiety is predominant in most biologically active natural products owing to its exceptional characteristics compared to others. Many derivatives of bicyclo[3.3.1]nonane are attractive to researchers for use in asymmetric catalysis or as potent anticancer entities along with their successful applications as ion receptors, metallocycles, and molecular tweezers. Therefore, this review article discusses several miscellaneous synthetic routes for the construction of bicyclo[3.3.1]nonanes and their heteroanalogues in association with the delineation of their anticancer activities with few selective compounds.

Total synthesis and structural reassignment of garcinielliptone FC, a polycyclic polyprenylated acylphloroglucinol with diverse bioactivity

Garcinielliptone FC (GFC) was assigned to be a type A polycyclic polyprenylated acylphloroglucinol (PPAP) and was found to exhibit diverse biological activities. Now we revise the structure of GFC to xanthochymol, a type B PPAP, via NMR and total synthesis methods. The total syntheses of (±)-xanthochymol and (±)-cycloxanthochymol were accomplished in 12 and 13 steps, respectively.

Dearomative logic in natural product total synthesis

Covering: 2011 to 2022The natural world is a prolific source of some of the most interesting, rare, and complex molecules known, harnessing sophisticated biosynthetic machinery evolved over billions of years for their production. Many of these natural products represent high-value targets of total synthesis, either for their desirable biological activities or for their beautiful structures outright; yet, the high sp3-character often present in nature's molecules imparts significant topological complexity that pushes the limits of contemporary synthetic technology. Dearomatization is a foundational strategy for generating such intricacy from simple materials that has undergone considerable maturation in recent years. This review highlights the recent achievements in the field of dearomative methodology, with a focus on natural product total synthesis and retrosynthetic analysis. Disconnection guidelines and a three-phase dearomative logic are described, and a spotlight is given to nature's use of dearomatization in the biosynthesis of various classes of natural products. Synthetic studies from 2011 to 2021 are reviewed, and 425 references are cited.

Ni-Catalyzed Reductive Fluoroalkylacylation of Alkynes for the Steroselective Synthesis of Fluoroalkylated Enones

A Ni-catalyzed three-component reductive fluoroalkylacylation of alkynes with fluoroalkyl halides and acyl chlorides is presented. This dicarbofunctionalization provides an efficient method for the synthesis of fluoroalkyl-incorporated enones under mild conditions with high yields and excellent regioselectivity and stereoselectivity.

Total Synthesis of a PPAP, Nemorosonol, Using a Tandem Michael Addition-Intramolecular Aldol Reaction

A strategy for constructing a tricyclo[4.3.1.0^3,7]decane skeleton, which is common to many polycyclic polyprenylated acylphloroglucinols, has been established. The key step was a tandem Michael addition-intramolecular aldol reaction with 3-ethoxy-1-phenyl-2-proyn-1-one, which affords a tricyclo[4.3.1.0^3,7]decane skeleton having a benzoyl group at the C8 position and an appropriate oxygen functional group at the C9 position. This synthetic strategy led to the total synthesis of nemorosonol, which was accomplished in 12 steps from 2-methyl-2-cyclopenten-1-one.

Recent advances in the synthesis of natural products containing the phloroglucinol motif

Covering: June 2009 to 2021Natural products containing a phloroglucinol motif include simple and oligomeric phloroglucinols, polycyclic polyprenylated acylphloroglucinols, phloroglucinol-terpenes, xanthones, flavonoids, and coumarins. These compounds represent a major class of secondary metabolites which exhibit a wide range of biological activities such as antimicrobial, anti-inflammatory, antioxidant and hypoglycaemic properties. A number of these compounds have been authorized for therapeutic use or are currently being studied in clinical trials. Their structural diversity and utility in both traditional and conventional medicine have made them popular synthetic targets over the years. In this review, we compile and summarise the recent synthetic approaches to the natural products bearing a phloroglucinol motif. Focus has been given on ingenious strategies to functionalize the phloroglucinol moiety at multiple positions. The isolation and bioactivities of the compounds are also provided.

Synthesis of 3-epi-Hypatulin B Featuring a Late-Stage Photo-Oxidation in Flow

A synthesis of 3-epi-hypatulin B, a highly oxygenated and densely functionalized bicyclic scaffold, is reported. The carbon skeleton was prepared by functionalization of a cyclopentanone and an intramolecular Mukaiyama aldol reaction. Highlights include a late-stage photo-oxidation of a methoxyallene to provide an ester group. The problems encountered in the batch process were solved by translation into a flow protocol. Our synthesis highlights the value of flow chemistry to enable challenging late-stage transformations in natural product synthesis.

Anticancer Properties and Mechanism of Action of Oblongifolin C, Guttiferone K and Related Polyprenylated Acylphloroglucinols

Polyprenylated acylphloroglucinols represent an important class of natural products found in many plants. Among them, the two related products oblongifolin C (Ob-C) and guttiferone K (Gt-K) isolated from Garcinia species (notably from edible fruits), have attracted attention due to their marked anticancer properties. The two compounds only differ by the nature of the C-6 side chain, prenyl (Gt-K) or geranyl (Ob-C) on the phloroglucinol core. Their origin, method of extraction and biological properties are presented here, with a focus on the targets and pathways implicated in their anticancer activities. Both compounds markedly reduce cancer cell proliferation in vitro, as well as tumor growth and metastasis in vivo. They are both potent inducer of tumor cell apoptosis, and regulation of autophagy flux is a hallmark of their mode of action. The distinct mechanism leading to autophagosome accumulation in cells and the implicated molecular targets are discussed. The specific role of the chaperone protein HSPA8, known to interact with Ob-C, is addressed. Molecular models of Gt-K and Ob-C bound to HSPA8 provide a structural basis to their common HSPA8-binding recognition capacity. The review shed light on the mechanism of action of these compounds, to encourage their studies and potential development.

Pd-Catalyzed Enantioselective Dearomative Allylic Annulation to Access PPAPs Analogues

Polycyclic polyprenylated acylphloroglucinols (PPAPs) share a common bicyclo[3.3.1]alkenone core structure and attract numerous attention from synthetic organic chemists due to their fascinating biological properties and associated synthetic challenges. We present herein that Pd-phosphoramidite catalysts promote the enantioselective dearomative allylic annulation reaction between allyl desoxyhumulones and allylic dicarbonates, affording PPAPs analogues in good yields and enantioselectivities. The reaction likely proceeds through two-step dearomative allylation by Pd, and the C-allylation pathway is the dominant mechanistic model.

Characteristic metabolites of Hypericum plants: their chemical structures and biological activities

Plants belonging to the genus Hypericum (Hypericaceae) are recognized as an abundant source of natural products with interesting chemical structures and intriguing biological activities. In the course of our continuing study on constituents of Hypericum plants, aiming at searching natural product-based lead compounds for therapeutic agents, we have isolated more than 100 new characteristic metabolites classified as prenylated acylphloroglucinols, meroterpenes, ketides, dibenzo-1,4-dioxane derivatives, and xanthones including prenylated xanthones, phenylxanthones, and xanthonolignoids from 11 Hypericum plants and one Triadenum plant collected in Japan, China, and Uzbekistan or cultivated in Japan. This review summarizes their chemical structures and biological activities.

Stereodivergent Strategy in Structural Determination: Asymmetric Total Synthesis of Garcinol, Cambogin, and Related Analogues

The asymmetric total synthesis of five biologically significant polycyclic polyprenylated acylphloroglucinols (PPAPs), including garcinol and cambogin, was achieved through a highly diastereoselective and stereodivergent strategy. Along the way, an efficient cascade Dieckmann cyclization was employed to construct the bicyclo[3.3.1]nonane core in one step. The synthesis provided a general approach toward the chiral endo-type B PPAPs and their C-30 diastereomers in a single sequence, which resolved the challenges of the absolute configuration determination/structural revision of PPAPs bearing exocyclic stereocenters.

Hypermoins A-D: Rearranged Nor-Polyprenylated Acylphloroglucinols from the Flowers of Hypericum monogynum

Hypermonins A-D (1-4), four rearranged nor-polycyclic polyprenylated acylphloroglucinols (PPAPs) with unprecedented skeletons, together with two new biosynthesis related PPAPs (5 and 6) were isolated and identified from the flowers of Hypericum monogynum. Hypermoins A-D represented the first examples of highly modified norPPAPs characterized by a rare 7/6/6/5-tetracyclic system. From the biogenic synthesis pathway analysis, all isolates shared the same biosynthetic intermediate, and the addition of two methyls or one methyl to this intermediate through methyltranferase could generate different types of PPAPs (1-7). Their planner structures as well as absolute configuration were confirmed via spectroscopic analysis, ECD calculation, and X-ray crystallography. All isolates potentially reversed multidrug resistance (MDR) activity in both two cancer cells, HepG2/ADR and MCF-7/ADR. Specifically, hypermoin E (5) and hyperielliptone HA (7) were found to be the best MDR modulators with the reversal fold ranging from 41 to 236, which is higher than the positive control verapamil.

Biomimetic Dearomatization Strategies in the Total Synthesis of Meroterpenoid Natural Products

Natural products are biosynthesized from a limited pool of starting materials via pathways that obey the same chemical logic as textbook organic reactions. Given the structure of a natural product, it is therefore often possible to predict its likely biosynthesis. Although biosynthesis mainly occurs in the highly specific chemical environments of enzymes, the field of biomimetic total synthesis attempts to replicate predisposed pathways using chemical reagents.We have followed several guidelines in our biomimetic approach to total synthesis. The overarching aim is to construct the same skeletal C-C and C-heteroatom bonds and in the same order as our biosynthetic hypothesis. In order to explore the innate reactivity of (bio)synthetic intermediates, the use of protecting groups is avoided or at least minimized. The key step, which is usually a cascade reaction, should be predisposed to selectively generate molecular complexity under substrate control (e.g., cycloadditions, radical cyclizations, carbocation rearrangements). In general, simple reagents and mild conditions are used; many of the total syntheses presented in this Account could be achieved using pre-1980s methodology. We have focused almost exclusively on the synthesis of meroterpenoids, that is, natural products of mixed terpene and aromatic polyketide origin, using commercially available terpenes and electron-rich aromatic compounds as starting materials. Finally, all of the syntheses in this Account involve a dearomatization step as a means to trigger a cascade reaction or to construct stereochemical complexity from a planar, aromatic intermediate.A biomimetic strategy can offer several advantages to a total synthesis project. Most obviously, successful biomimetic syntheses are usually concise and efficient, naturally adhering to the atom, step, and redox economies of synthesis. For example, in this Account, we describe a four-step synthesis of garcibracteatone and a three-step synthesis of nyingchinoid A. It is difficult to imagine shorter, non-biomimetic syntheses of these intricate molecules. Furthermore, biomimetic synthesis gives insight into biosynthesis by revealing the chemical relationships between biosynthetic intermediates. Access to these natural substrates allows collaboration with biochemists to help uncover the function of newly discovered enzymes and elucidate biosynthetic pathways, as demonstrated in our work on the napyradiomycin family. Third, by making biosynthetic connections between natural products, we can sometimes highlight incorrect structural assignments, and herein we discuss structure revisions of siphonodictyal B, rasumatranin D, and furoerioaustralasine. Last, biomimetic synthesis motivates the prediction of "undiscovered natural products" (i.e., missing links in biosynthesis), which inspired the isolation of prenylbruceol A and isobruceol.

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.

Strategies towards endo-type B polycyclic polyprenylated acylphloroglucinols: total synthesis of regio-hyperibone L and (+)-epi-clusianone

The first and general method for the total synthesis of regio-hyperibone L and (+)-epi-clusianone via domino Dieckmann cyclization was developed.

Programmable meroterpene synthesis

The bicyclo[3.3.1]nonane architecture is a privileged structural motif found in over 1000 natural products with relevance to neurodegenerative disease, bacterial and parasitic infection, and cancer among others. Despite disparate biosynthetic machinery, alkaloid, terpene, and polyketide-producing organisms have all evolved pathways to incorporate this carbocyclic ring system. Natural products of mixed polyketide/terpenoid origins (meroterpenes) are a particularly rich and important source of biologically active bicyclo[3.3.1]nonane-containing molecules. Herein we detail a fully synthetic strategy toward this broad family of targets based on an abiotic annulation/rearrangement strategy resulting in a 10-step total synthesis of garsubellin A, an enhancer of choline acetyltransferase and member of the large family of polycyclic polyprenylated acylphloroglucinols. This work solidifies a strategy for making multiple, diverse meroterpene chemotypes in a programmable assembly process involving a minimal number of chemical transformations.

Me2AlSEt-Promoted Domino Dieckmann Cyclization Enables the Total Synthesis of Polycyclic Polyprenylated Acylphloroglucinols

A bioinspired, Me₂AlSEt-promoted domino Dieckmann cyclization via an 8-membered ring intermediate to construct bicyclo[3.3.1]nonanes was developed, and the divergent syntheses of nine complex polycyclic polyprenylated acylphloroglucinols were achieved. This novel domino cyclization tolerates a series of congested substrates, providing a very efficient way to construct diverse polycyclic structures. The selectivity and the advantages of the domino cyclization were studied. Moreover, the structure-activity relationship study leads to the identification of three simplified potent antitumor agents.

A Cyanide-Free Synthesis of Acylcyanides through Ru-Catalyzed C(sp3)-H-Oxidation of Benzylic Nitriles

A practical method for generation of acylcyanides devoid of any external cyanide sources is presented that relies on a mild Ru‐catalyzed selective C−H‐oxidation of benzylic nitriles. The starting materials are smoothly generated through condensation of the corresponding carboxylic acid amides using silanes. The obtained acylcyanides can be employed in a plethora of transformation as exemplified to some larger extend in the sequence of C−H‐oxidation‐Tischenko‐rearrangement for the generation of structurally diverse benzoyloxycyanohydrines.

Aroyl and acyl cyanides as orthogonal protecting groups or as building blocks for the synthesis of heterocycles

α-Cyanoketones represent a synthetically attractive scaffold possessing bifunctional reactivity which enabled synthesis of a diversity of products. This involves reaction of nucleophiles with electrophilic carbonyl carbon performing an efficient and regioselective way to acylation reaction, cycloaddition of activated cyano function with dipolarophiles, metal-catalyzed cross-dehydrogenative coupling carbocyanation across C-C multiple bonds as well as hydrocyanation. This review provides the recent developments in the chemistry of α-cyanoketones which will be beneficial for researchers and scientists in such field.

The Polycyclic Polyprenylated Acylphloroglucinol Antibiotic PPAP 23 Targets the Membrane and Iron Metabolism in Staphylococcus aureus

Recently, a series of endo-type B polycyclic polyprenylated acylphloroglucinols (PPAP) derivatives with high antimicrobial activities were chemically synthesized. One of the derivatives, PPAP 23, which showed high antimicrobial activity and low cytotoxicity, was chosen for further investigation of its bactericidal profiles and mode of action. PPAP 23 showed a better efficacy in killing methicillin resistant Staphylococcus aureus (MRSA) and decreasing the metabolic activity of 5-day-old biofilm cells than vancomycin. Moreover, S. aureus did not appear to develop resistance against PPAP 23. The antimicrobial mechanism of PPAP 23 was investigated by RNA-seq combined with phenotypic and biochemical approaches. RNA-seq suggested that PPAP 23 signaled iron overload to the bacterial cells because genes involved in iron transport were downregulated and iron storage gene was upregulated by PPAP 23. PPAP 23 affected the membrane integrity but did not induce pore formation; it inhibited bacterial respiration. PPAP 23 preferentially inhibited Fe–S cluster enzymes; it has a mild iron chelating activity and supplementation of exogenous iron attenuated its antimicrobial activity. PPAP 23 was more effective in inhibiting the growth of S. aureus under iron-restricted condition. The crystal structure of a benzylated analog of PPAP 23 showed a highly defined octahedral coordination of three PPAP ligands around a Fe (3+) core. This suggests that PPAPs are generally capable of iron chelation and are able to form defined stable complexes. PPAP 23 was found to induce reactive oxygen species (ROS) and oxidative stress. Fluorescence microscopic analysis showed that PPAP 23 caused an enlargement of the bacterial cells, perturbed the membrane, and dislocated the nucleoid. Taken together, we postulate that PPAP 23 interacts with the cytoplasmic membrane with its hydrophobic pocket and interferes with the iron metabolism to exert its antimicrobial activity in Staphylococcus aureus.

Total Synthesis of Norsampsones A and B, Garcinielliptones N and O, and Hyperscabrin A

The asymmetric total synthesis of five decarbonyl polycyclic polyprenylated acylphloroglucinols norsampsnes A (3) and B (4), garcinielliptones O (5) and N (6), and hyperscabrin A (7) is described. The synthesis to construct the core substituted cyclohexanone ring of these natural products was achieved by a key Dieckmann condensation. The chirality of the molecules was introduced by the stereoselective alkylation with Evans' oxazolidinones. The synthesis could be run on grams scale, and the Dieckmann condensation was investigated through the DFT calculations to help improve the yield of garcinielliptone O (5). Determination of the absolute configuration of garcinielliptones O (5) and N (6) was also achieved.

Modular Total Syntheses of Hyperforin, Papuaforins A, B, and C via Gold(I)-Catalyzed Carbocyclization

The remarkable biological activities of polyprenylated polycyclic acylphloroglucinols (PPAPs) combined with their highly oxygenated and densely functionalized frameworks have stimulated the interest of synthetic organic chemists over the past decade. Herein, we report the concise total syntheses of four natural products PPAPs, of which some have antibacterial properties, notably hyperforin and papuaforin A. The salient features of this strategy are the short and gram-scalable synthesis of densely substituted PPAPs scaffolds via a Au(I)-catalyzed carbocyclization and the late-stage functionalization for a unified access to a wide variety of PPAPs.

Research Progress of Polycyclic Polyprenylated Acylphloroglucinols

Polycyclic polyprenylated acylphloroglucinols (PPAPs) are a class of hybrid natural products sharing the mevalonate/methylerythritol phosphate and polyketide biosynthetic pathways and showing considerable structure and bioactivity diversity. This review discusses the progress of research into the chemistry and biological activity of 421 natural PPAPs in the past 11 years as well as in-depth studies of biological activities and total synthesis of some PPAPs isolated before 2006. We created an online database of all PPAPs known to date at http://www.chem.uky.edu/research/grossman/PPAPs . Two subclasses of biosynthetically related metabolites, spirocyclic PPAPs with octahydrospiro[cyclohexan-1,5'-indene]-2,4,6-trione core and complicated PPAPs produced by intramolecular [4 + 2] cycloadditions of MPAPs, are brought into the PPAP family. Some PPAPs' relative or absolute configurations are reassigned or critically discussed, and the confusing trivial names in PPAPs investigations are clarified. Pharmacologic studies have revealed a new molecular mechanism whereby hyperforin and its derivatives regulate neurotransmitter levels by activating TRPC6 as well as the antitumor mechanism of garcinol and its analogues. The antineoplastic potential of some type B PPAPs such as oblongifolin C and guttiferone K has increased significantly. As a result of the recent appearances of innovative synthetic methods and strategies, the total syntheses of 22 natural PPAPs including hyperforin, garcinol, and plukenetione A have been accomplished.

Hypermonins A and B, two 6-norpolyprenylated acylphloroglucinols with unprecedented skeletons from Hypericum monogynum

Hypermonins A and B, two novel 6-norpolycyclic polyprenylated acylphloroglucinols (PPAPs), were isolated from the leaves and twigs of Hypericum monogynum.

Directing Stem Cell Fate: The Synthetic Natural Product Connection

Stem cells possess remarkable potential for the treatment of a broad array of diseases including many that lack therapeutic options. However, the use of cell-based products derived from stem cells as therapeutics has limitations including rejection, sufficient availability, and lack of appropriate engraftment. Chemical control of stem cells provides potential solutions for overcoming many of the current limitations in cell-based therapeutics. The development of exogenous molecules to control stem cell self-renewal or differentiation has arrived at natural product-based agents as an important class of modulators. The ex vivo production of cryopreserved cellular products for use in tissue repair is a relatively new area of medicine in which the conventional hurdles to implementing chemicals to effect human health are changed. Translational challenges centered on chemistry, such as pharmacokinetics, are reduced. Importantly, in many cases the desired human tissues can be evaluated against new chemicals, and approaches to cellular regulation can be validated in the clinically applicable system. As a result linking new and existing laboratory syntheses of natural products with findings of the compounds' unique abilities to regulate stem cell fate provides opportunities for developing improved methods for tissue manufacture, accessing probe compounds, and generating new leads that yield manufactured cells with improved properties. This review provides a summary of natural products that have shown promise in controlling stem cell fate and which have also been fully synthesized thereby providing chemistry platforms for further development.

Skeleton Reassignment of Type C Polycyclic Polyprenylated Acylphloroglucinols

The previous assignment of the type C skeleton of polycyclic polyprenylated acylphloroglucinols (PPAPs) was controversial and proved to be incorrect in this study. The structures of the type C PPAPs (3-6) were revised to corresponding type A structures (3a-6a) via ¹³C NMR spectroscopic analysis and a quantum computational chemistry method. Therefore, only types A and B PPAPs are likely present in plants of the family Clusiaceae.

Stereoselective synthesis of bicyclo[3.n.1]alkenone frameworks by Lewis acid-catalysis

An indium-catalysed α,α′-annulation of cyclic ketones and alkynyl enones, leading to bicyclo[3.n.1]alkenones, is presented.

Furanmonogones A and B: two rearranged acylphloroglucinols with a 4,5-seco-3(2H)-furanone core from the flowers of Hypericum monogynum

Rearranged acylphloroglucinols with an unprecedented 4,5-seco-3(2H)-furanone skeleton, furanmonogones A (1) and B (2), were isolated from the flowers of Hypericum monogynum.

Garmultins A-G, Biogenetically Related Polycyclic Acylphloroglucinols from Garcinia multiflora

Garmultins A and B (1 and 2), two polycyclic polyprenylated acylphloroglucinols characterized by the coupling of two novel cages, 2,11-dioxatricyclo[4.4.1.0^3,9]undecane and tricyclo[4.3.1.0^3,7]decane, along with five biogenetically related analogues (3-7), were isolated from Garcinia multiflora. Their structures and absolute configurations were determined by extensive NMR analysis, X-ray crystallography, and electronic circular dichroism calculations. Three compounds were capable of inhibiting oncogene expression and inducing apoptosis in human erythroleukemia cells.

Enantioselective γ-Alkylation of α,β-Unsaturated Malonates and Ketoesters by a Sequential Ir-Catalyzed Asymmetric Allylic Alkylation/Cope Rearrangement

A catalytic, enantioselective γ-alkylation of α,β-unsaturated malonates and ketoesters is reported. This strategy entails a highly regio- and enantioselective iridium-catalyzed α-alkylation of an extended enolate, and a subsequent translocation of chirality to the γ-position via a Cope rearrangement.

Hyperjapones A-E, Terpenoid Polymethylated Acylphloroglucinols from Hypericum japonicum

Hyperjapones A-E (1-5), novel terpenoid polymethylated acylphloroglucinols (TPAPs) with unusual architectures, were characterized from Hypericum japonicum. Their structures and absolute configurations were determined by comprehensive spectroscopic data and X-ray diffractions. Compound 1 was obtained as a racemic mixture and was separated by a column coated with cellulose tris(4-methylbenzoate) after attempts with various chiral materials. Compounds 1, 2, and 4 exhibited moderate antitumor activities in vitro.