First Stereoselective Syntheses of (−)-Siphonodiol and (−)-Tetrahydrosiphonodiol, Bioactive Polyacetylenes from Marine Sponges

Synthesis of Functional Isosorbide-Based Polyesters and Polyamides by Passerini Three-Component Polymerization

Environmental issues are becoming more and more prominent, and bio-based polymers are essential to alleviate environmental degradation by replacing traditional polymers. With this context, a new family of functional isosorbide-based polyesters and polyamides with high glass transition temperature are prepared via Passerini-Three component polymerization (P-3CP). To optimize the P-3CP conditions, the influence of the polymerization solvent, temperature, feed ratio on the molar mass of final polymers are investigated. The higher molar mass (up to 10100 g/mol) and yield (>70 %) are achieved under very mild conditions (30 °C, standard atmosphere). Functional side groups, such as alkenyl, alkynyl and methyl ester, were introduced into polymer structure via P-3CP by using functional isocyanides. The obtained polyesters and polyamides are characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopies, differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). All polymers are thermal stable and amorphous with variable glass transition temperatures (Tg ). The obtained polyester has Tg up to 87.5 °C, while the Tg of polyamides (ISPA-2) is detected to be 97.5 °C depending on the amide bonds in the polymer backbone and the benzene ring side groups. The cytotoxicity is investigated by the CCK-8 assay against mBMSC cells to confirm the biological safety. Overall, this novel strategy provides an efficient approach to produce functional isosorbide-based polyesters and polyamides, which are promising prospect for being applied to biodegradable materials.

Callyspongia spp.: Secondary Metabolites, Pharmacological Activities, and Mechanisms

One of the most widespread biotas in the sea is the sponge. Callyspongia is a sponge genus found in the seas, making it easily available. In this review, the pharmacological activity and mechanism of action of the secondary metabolites of Callyspongia spp. are addressed, which may lead to the development of new drugs and targeted therapeutic approaches. Several scientific databases, such as Google Scholar, PubMed, ResearchGate, Science Direct, Springer Link, and Wiley Online Library, were mined to obtain relevant information. In the 41 articles reviewed, Callyspongia spp. was reported to possess pharmacological activities such as cytotoxicity against cancer cell lines (36%), antifungal (10%), anti-inflammatory (10%), immunomodulatory (10%), antidiabetic and antiobesity (6%), antimicrobial (8%), antioxidant (4%), antineurodegenerative (4%), antihypercholesterolemic (2%), antihypertensive (2%), antiparasitic (2%), antiallergic (2%), antiviral (2%), antiosteoporotic (2%), and antituberculosis (2%) activities. Of these, the antioxidant, antituberculosis, and anti-inflammatory activities of Callyspongia extract were weaker compared with that of the control drugs; however, other activities, particularly cytotoxicity, show promise, and the compounds responsible may be developed into new drugs.

Metabolities from Marine Sponges of the Genus Callyspongia: Occurrence, Biological Activity, and NMR Data

The genus Callyspongia (Callyspongiidae) encompasses a group of demosponges including 261 described species, of which approximately 180 have been accepted after taxonomic reviews. The marine organisms of Callyspongia are distributed in tropical ecosystems, especially in the central and western Pacific, but also in the regions of the Indian, the West Atlantic, and the East Pacific Oceans. The reason for the interest in the genus Callyspongia is related to its potential production of bioactive compounds. In this review, we group the chemical information about the metabolites isolated from the genus Callyspongia, as well as studies of the biological activity of these compounds. Through NMR data, 212 metabolites were identified from genus Callyspongia (15 species and Callyspongia sp.), belonging to classes such as polyacetylenes, terpenoids, steroids, alkaloids, polyketides, simple phenols, phenylpropanoids, nucleosides, cyclic peptides, and cyclic depsipeptides. A total of 109 molecules have been reported with bioactive activity, mainly cytotoxic and antimicrobial (antibacterial and antifungal) action. Thus, we conclude that polyacetylenes, terpenoids and steroids correspond to the largest classes of compounds of the genus, and that future research involving the anticancer action of the species' bioactive metabolites may become relevant.

Sponge chemical defenses are a possible mechanism for increasing sponge abundance on reefs in Zanzibar

Coral reefs are experiencing increasing anthropogenic impacts that result in substantial declines of reef-building corals and a change of community structure towards other benthic invertebrates or macroalgae. Reefs around Zanzibar are exposed to untreated sewage and runoff from the main city Stonetown. At many of these sites, sponge cover has increased over the last years. Sponges are one of the top spatial competitors on reefs worldwide. Their success is, in part, dependent on their strong chemical defenses against predators, microbial attacks and other sessile benthic competitors. This is the first study that investigates the bioactive properties of sponge species in the Western Indian Ocean region. Crude extracts of the ten most dominant sponge species were assessed for their chemical defenses against 35 bacterial strains (nine known as marine pathogens) using disc diffusion assays and general cytotoxic activities were assessed with brine shrimp lethality assays. The three chemically most active sponge species were additionally tested for their allelopathic properties against the scleractinian coral competitor Porites sp.. The antimicrobial assays revealed that all tested sponge extracts had strong antimicrobial properties and that the majority (80%) of the tested sponges were equally defended against pathogenic and environmental bacterial strains. Additionally, seven out of ten sponge species exhibited cytotoxic activities in the brine shrimp assay. Moreover, we could also show that the three most bioactive sponge species were able to decrease the photosynthetic performance of the coral symbionts and thus were likely to impair the coral physiology.

A dramatic enhancing effect of InBr3 towards the oxidative Sonogashira cross-coupling reaction of 2-ethynylanilines

The addition of InBr3 to the oxidative Sonogashira cross-coupling reaction of 2-ethynylaniline with (E)-trimethyl(3,3,3-trifluoroprop-1-enyl)silane led to a dramatic increase in the reactivity to afford the corresponding 1,3-enynes bearing a trifluoromethyl group on their terminal sp(2) carbon. The subsequent cyclization of these 1,3-enynes under palladium catalysis provides access to the corresponding indoles bearing a 3,3,3-trifluoroprop-1-enyl group at their 2-position.

Direct synthesis of Z-alkenyl halides through catalytic cross-metathesis

Olefin metathesis has had a large impact on modern organic chemistry, but important shortcomings remain: for example, the lack of efficient processes that can be used to generate acyclic alkenyl halides. Halo-substituted ruthenium carbene complexes decompose rapidly or deliver low activity and/or minimal stereoselectivity, and our understanding of the corresponding high-oxidation-state systems is limited. Here we show that previously unknown halo-substituted molybdenum alkylidene species are exceptionally reactive and are able to participate in high-yielding olefin metathesis reactions that afford acyclic 1,2-disubstituted Z-alkenyl halides. Transformations are promoted by small amounts of a catalyst that is generated in situ and used with unpurified, commercially available and easy-to-handle liquid 1,2-dihaloethene reagents, and proceed to high conversion at ambient temperature within four hours. We obtain many alkenyl chlorides, bromides and fluorides in up to 91 per cent yield and complete Z selectivity. This method can be used to synthesize biologically active compounds readily and to perform site- and stereoselective fluorination of complex organic molecules.

A systematic study on the Cadiot–Chodkiewicz cross coupling reaction for the selective and efficient synthesis of hetero-diynes

99% selectivity for cross coupling. Excellent yields (upto 94%). Low basic reaction medium, high functional group tolerance. Use of green solvent water.

Enzymatic kinetic resolution of internal propargylic diols. Part I: a new approach for the synthesis of (S)-pent-2-yn-1,4-diol, a natural product from Clitocybe catinus

An efficient two round EKR of bis-substituted propargylic diols has been described and applied for synthesize (S)-pent-2-yn-1,4-diol, a natural product from Clitocybe catinus.

Recent developments and applications of the Cadiot–Chodkiewicz reaction

The classical heterocoupling of a 1-haloalkyne with a terminal alkyne catalyzed by copper salts in the presence of a base for the synthesis of unsymmetrical diynes is termed the Cadiot–Chodkiewicz coupling reaction.

Bioactive norditerpenoids from Flickingeria fimbriata

11 new diterpenoids determined by NMR, X-ray diffraction, calculated ECD and CD exciton chirality methods were isolated from Flickingeria fimbriata.

Graft Copolymers with Polyamide Backbones via Combination of Passerini Multicomponent Polymerization and Controlled Chain-growth Polymerization

We report a facile ‘grafting from’ approach to graft copolymers with polyamide backbones and controlled vinyl polymer or polyester side chains. Two polyamides with in situ-formed pendant bromide or hydroxyl groups were obtained by Passerini-based multicomponent polymerization. They were used respectively to initiate the atom-transfer radical polymerization of vinyl monomers or the ring-opening polymerization of lactones to generate two new types of graft copolymers. One of the important features of the method is that the pendant initiators are generated in situ from non-branching monomers, and they are linked to the polymer backbone by ester bonds. Therefore, the vinyl polymer side chains could be detached from the backbones, and their structures could thus be fully characterized. Moreover, multicomponent polymerization and atom-transfer radical polymerization can even be carried out in a one-pot manner.

A Short Synthesis of (S)-(+)-Siphonodiol

A short synthesis of the enantiomer of the polyacetylenic natural product siphonodiol is described. The synthesis is based on the strategy of taking advantage of the hidden symmetry of the target molecule and minimizing the use of protecting groups, thereby reducing the total number of steps and increasing the overall efficiency.

Marine natural products

This review covers the literature published in 2005 for marine natural products, with 704 citations (493 for the period January to December 2005) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, coelenterates, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (812 for 2005), together with their relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Marine natural products: synthetic aspects

An overview of marine natural products synthesis during 2005 is provided. In a similar vein to earlier installments in this series, the emphasis is on total syntheses of molecules of contemporary interest, new total syntheses, and syntheses that have resulted in structure confirmation or stereochemical assignments.

Synthesis of Naturally Occurring Polyynes

Over the past fifty years, hundreds of polyyne compounds have been isolated from nature. These often unstable molecules are found in sources as common as garden vegetables and as obscure as bacterial cultures. Naturally occurring polyynes feature a wide range of structural diversity and display an equally broad array of biological properties. Early synthetic efforts relied primarily on Cu-catalyzed, oxidative acetylenic homo- and heterocoupling reactions to assemble the polyyne framework. The past 25 years, however, have witnessed a renaissance in the field of polyyne natural product synthesis: transition-metal-catalyzed alkynylation reactions and asymmetric transformations have combined to substantially expand access to natural polyynes. This Review recounts these synthetic achievements and also highlights both the natural source(s) and biological relevance for many of these compounds.