Lipidyl pseudopteranes A-F: isolation, biomimetic synthesis, and PTP1B inhibitory activity of a new class of pseudopteranoids from the Gorgonian Pseudopterogorgia acerosa

Enzyme Inhibitors from Gorgonians and Soft Corals

For decades, gorgonians and soft corals have been considered promising sources of bioactive compounds, attracting the interest of scientists from different fields. As the most abundant bioactive compounds within these organisms, terpenoids, steroids, and alkaloids have received the highest coverage in the scientific literature. However, enzyme inhibitors, a functional class of bioactive compounds with high potential for industry and biomedicine, have received much less notoriety. Thus, we revised scientific literature (1974-2022) on the field of marine natural products searching for enzyme inhibitors isolated from these taxonomic groups. In this review, we present representative enzyme inhibitors from an enzymological perspective, highlighting, when available, data on specific targets, structures, potencies, mechanisms of inhibition, and physiological roles for these molecules. As most of the characterization studies for the new inhibitors remain incomplete, we also included a methodological section presenting a general strategy to face this goal by accomplishing STRENDA (Standards for Reporting Enzymology Data) project guidelines.

Rhodium(iii)-catalyzed synthesis of trisubstituted furans via vinylic C-H bond activation

We report an Rh(iii)-catalyzed one-pot synthesis of trisubstituted furan derivatives through C_vinyl-H activation of α,β-unsaturated ketones with acrylates. The control study revealed that the Heck-type product obtained undergoes Paal-Knorr type cyclization in the presence of an Ag salt. Hence, the Ag salt plays a dual role of a halide scavenger and a Lewis acid catalyst for Paal-Knorr type cyclization. The furan product can be transferred into the respective alcohol and acid derivatives which are useful intermediates in synthesizing biologically active molecules.

Protein tyrosine phosphatase 1B inhibitors from natural sources

Since PTP1B enzyme was discovered in 1988, it has captured the research community's attention. This landmark discovery has stimulated numerous research studies on a variety of human diseases, including cancer, inflammation, and diabetes. Tremendous progress has been made in finding PTP1B inhibitors and exploring PTP1B regulatory mechanisms. This review investigates for the natural PTP1B inhibitors, and focuses on the common characteristics of the discovered structures and structure-activity relationships. To facilitate understanding, all the natural compounds are here divided into five different classes (fatty acids, phenolics, terpenoids, steroids, and alkaloids), according to their skeletons. These PTP1B inhibitors of scaffold structures could serve as a theoretical basis for new concept drug discovery and design.

Meroterpenoids with Protein Tyrosine Phosphatase 1B Inhibitory Activity from a Hyrtios sp. Marine Sponge

Three new meroterpenoids, hyrtiolacton A (1), nakijinol F (2), and nakijinol G (3), along with three known ones, nakijinol B (4), nakijinol E (5), and dactyloquinone A (6), were isolated and characterized from a Hyrtios sp. marine sponge collected from the South China Sea. The new structures were determined based on extensive analysis of HRESIMS and NMR data, and their absolute configurations were assigned by a combination of single-crystal X-ray diffraction and electronic circular dichroism analyses. Hyrtiolacton A (1) represents an unprecedented meroterpenoid featuring an unusual 2-pyrone attached to the sesquiterpene core, which is the first example of a pyrone-containing 4,9-friedodrimane-type sesquiterpene. These compounds were evaluated for their protein tyrosine phosphatase (PTP1B) inhibitory and cytotoxic activities. Nakijinol G (3) showed PTP1B inhibitory activity with an IC₅₀ value of 4.8 μM but no cytotoxicity against four human cancer cell lines.

Diastereoselective Synthesis of Cyclopenta[c]furans by a Catalytic Multicomponent Reaction

A diastereoselective three-component reaction between alkynyl enones, aldehydes and secondary amines is reported. With the aid of a benign indium catalyst, a range of highly substituted cyclopenta[c]furan derivatives can be obtained in a single-step procedure. The formation of the stereodefined heterocyclic motifs takes place via in situ generation of enamines followed by two sequential cyclization steps.

New sesquiterpenoids from the edible mushroom Pleurotus cystidiosus and their inhibitory activity against α-glucosidase and PTP1B

Nine new sesquiterpenoids, clitocybulol derivatives, clitocybulols G-O (1-9) and three known sesquiterpenoids, clitocybulols C-E (10-12), were isolated from the solid culture of the edible fungus Pleurotus cystidiosus. The structures of compounds 1-12 were determined by spectroscopic methods. The absolute configurations of compounds 1-9 were assigned via the circular dichroism (CD) data analysis. Compounds 1, 6 and 10 showed moderate inhibitory activity against protein tyrosine phosphatase-1B (PTP1B) with IC50 values of 49.5, 38.1 and 36.0μM, respectively.

Brominated polyunsaturated lipids with protein tyrosine phosphatase-1B inhibitory activity from Chinese marine sponge Xestospongia testudinaria

A new brominated polyunsaturated lipid, methyl (E,E)-14,14-dibromo-4,6,13-tetradecatrienoate (1), along with three known related analogues (2-4), were isolated from the Et2O-soluble portion of the acetone extract of Chinese marine sponge Xestospongia testudinaria treated with diazomethane. The structure of the new compound was elucidated by detailed spectroscopic analysis and by comparison with literature data. Compound 3 exhibited significant inhibitory activity against protein tyrosine phosphatase 1B (PTP1B), a key target for the treatment of type II diabetes and obesity, with an IC50 value of 5.30 ± 0.61 μM, when compared to the positive control oleanolic acid (IC50 = 2.39 ± 0.26 μM).

A [3 + 2]-annulation approach to tetrasubstituted furans from MBH-carbonates of acetylenic aldehydes via sequential substitution/cycloisomerization

A new organo base-mediated cascade reaction has been developed for the synthesis of uniquely substituted tetrasubstituted furans, 2-furan-3-yl acrylates, starting from MBH-carbonates of acetylenic aldehydes and keto-methylenes.

Ring-opening of hindered cyclic epoxides with potassium carboxylates in the presence of conjugate acids

During attempts to ring-open a highly hindered epoxide, traditional methods were found to be ineffective. An alternative strategy for opening epoxides was implemented that employed a potassium carboxylate in the presence of its conjugate acid in a solvent mixture containing polar and potassium-sequestering components. A systematic analysis of the components of the reaction mixture indicated that the addition of the conjugate acid was the most important feature for providing good conversion. This reaction appears to be general for most classes of carboxylic acids including cinnamic, aromatic, and highly hindered carboxylic acids (30%–79% yield) and only fails with weak carboxylate nucleophiles. Three highly substituted and hindered cyclohexene oxide derivatives were examined for reactivity and the reaction conditions appear to tolerate a variety of functional groups to provide the ring-opened species. This pH-moderate system proved useful for hindered cyclic epoxides when all other techniques failed and should prove general to a wide spectrum of epoxide and carboxylic acid partners in those cases where the use of a strong Lewis or protic acid catalyst, or a strong basic nucleophile, is inappropriate.

Natural products possessing protein tyrosine phosphatase 1B (PTP1B) inhibitory activity found in the last decades

This article provides an overview of approximately 300 secondary metabolites with inhibitory activity against protein tyrosine phosphatase 1B (PTP1B), which were isolated from various natural sources or derived from synthetic process in the last decades. The structure-activity relationship and the selectivity of some compounds against other protein phosphatases were also discussed. Potential pharmaceutical applications of several PTP1B inhibitors were presented.

A halogenated pseudopterane diterpene from the Bahamian octocoral Pseudopterogorgia acerosa

Two new pseudopteranoid diterpenes have been isolated from the gorgonian coral Pseudopterogorgia acerosa and have been characterized by NMR and mass spectrometry. These include 15-chlorodeoxypseudopterolide (1), the first halogenated pseudopterane diterpene, and 11-epi-pseudopteranol (2), an epimer of the previously described 11-pseudopteranol. In addition, six known diterpenes were also isolated from this collection including deoxypseudopterolide (3), pseudopteradiene (4), acerosolide (5), pseudopterolide-methanol adduct (6), 11-pseudopteranol (7), and isogorgiacerodiol (8). The cytotoxicity of these eight compounds towards three cancer cell lines (HeLa, PC-3, and HCT116) was assessed and the chlorinated pseudopteranoid 1 was found to have modest but selective activity against HCT116 (IC50 2.7 µmol/L), whereas its nonchlorinated derivative 3 was inactive. This indicates that the halo functionality can modify the cytotoxic activity of pseudopteranoids and potentially other classes of deterpenes.

Isolation, biomimetic synthesis, and cytotoxic activity of bis(pseudopterane) amines

LC-MS/MS-based screening of the dichloromethane extract of the gorgonian coral Pseudopterogorgia acerosa led to the isolation of a novel bis(pseudopterane) amine (1). The structural assignment of 1 was achieved by 1D and 2D NMR and mass spectrometry analysis. A biomimetic synthesis of 1 and the known symmetrical diterpene 2 from pseudopterolide (3) is described in this report. Bis(pseudopterane) amine showed selective growth inhibition activity against cancer cell lines with IC(50) values of 4.2 microM (HCT116) and 42 microM (HeLa).