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The importance of ciguatoxins (CTXs) in seafood safety and their emerging occurrence in locations far away from tropical areas highlight the need for simple and low-cost methods for the sensitive and rapid detection of these potent marine toxins to protect seafood consumers. Herein, an electrochemical immunosensor for the detection of CTXs is presented. A sandwich configuration is proposed, using magnetic beads (MBs) as immobilization supports for two capture antibodies, with their combination facilitating the detection of CTX1B, CTX3C, 54-deoxyCTX1B, and 51-hydroxyCTX3C. PoIyHRP-streptavidin is used for the detection of the biotinylated detector antibody. Experimental conditions are first optimized using colorimetry, and these conditions are subsequently used for electrochemical detection on electrode arrays. Limits of detection at the pg/mL level are achieved for CTX1B and 5 1-hydroxyCTX3C. The applicability of the immunosensor to the analysis of fish samples is demonstrated, attaining detection of CTX1B at contents as low as 0.01 mu g/kg and providing results in correlation with those obtained using mouse bioassay (MBA) and cell-based assay (CBA), and confirmed by liquid chromatography coupled to high-resolution mass spectrometry (LC-ESI-HRMS). This user-friendly bioanalytical tool for the rapid detection of CTXs can be used to mitigate ciguatera risk and contribute to the protection of consumer health.

Ciguatoxins are polyether marine toxins that act as sodium channel activators. These toxins cause ciguatera, one of the most widespread nonbacterial forms of food poisoning, which presents several symptoms in humans including long-term neurological alterations. Earlier work has shown that both acute and chronic exposure of primary cortical neurons to synthetic ciguatoxin CTX3C have profound impacts on neuronal function. Thus, the present work aimed to identify relevant neuronal genes and metabolic pathways that could be altered by ciguatoxin exposure. To study the effect of ciguatoxins in primary neurons in culture, we performed a transcriptomic analysis using whole mouse genome microarrays, for primary cortical neurons exposed during 6, 24, or 72 h in culture to CTX3C. Here, we have shown that the effects of the toxin on gene expression differ with the exposure time. The results presented here have identified several relevant genes and pathways related to the effect of ciguatoxins on neurons and may assist in future research or even treatment of ciguatera. Moreover, we demonstrated that the effects of the toxin on gene expression were exclusively consequential of its action as a voltage-gated sodium channel activator, since all the effects of CTX3C were avoided by preincubation of the neurons with the sodium channel blocker tetrodotoxin

The kedarcidin chromophore is a formidible target for total synthesis. Herein, we 19 describe a viable synthesis of this highly unstable natural product. This entailed the early 20 introduction and gram-scale synthesis of 2-deoxysugar conjugates of both L-mycarose and L21 kedarosamine. Key advances include: (1) stereoselective allenylzinc keto-addition to form an 22 epoxyalkyne; (2) -selective glycosylations with 2-deoxy thioglycosides (AgPF6/DTBMP) 23 and Schmidt donors (TiCl4); (3) Mitsunobu aryl etherification to install a hindered 1,2-cis24 configuration; (4) atropselective and convergent Sonogashira-Shiina cyclization sequence; 25 (5) Ohfune-based amidation protocol for naphthoic acid; (6) Ce(III)-mediated nine26 membered enediyne cyclization and ester/mesylate derivatisation; (7) SmI2-based reductive 27 olefination and global HF-deprotection end-game. The longest linear sequence from gram28 scale intermediates is 17-steps, and HRMS data of the synthetic natural product was obtained 29 for the first time

The cyanosporasides A–F are a collection of monochlorinated benzenoid derivatives isolated from the marine actinomycetes Salinispora and Streptomyces sp. All derivatives feature one of two types of cyanocyclopenta[a]indene frameworks, which are regioisomeric in the position of a single chlorine atom. It is proposed that these chloro-substituted benzenoids are formed biosynthetically through the cycloaromatization of a bicyclic nine-membered enediyne precursor. Herein, we report the synthesis of such a bicyclic precursor, its spontaneous transannulation into a p-benzyne, and its differential 1,4 hydrochlorination reactivity under either organochlorine or chloride-salt conditions. Our bioinspired approach culminated in the first regiodivergent total synthesis of the aglycons A/F and B/C, as well as cyanosporasides D and E. In addition, empirical insights into the site selectivity of a natural-like p-benzyne, calculated to be a ground-state triplet diradical, to hydrogen, chlorine, and chloride sources are revealed.

Our understanding of the chemistry and biology of the enediyne class of antitumor antibiotics is still developing and faces further challenges. The cleavage of double-stranded DNA through hydrogen abstraction by enediyne-derived radicals is a generally well-accepted mechanism. However, the mechanisms of several unexpected and complex cytotoxic effects of enediynes,such as RNA and protein damage or the generation of p-quinone species, have yet to be fully elucidated. Despite several carefully crafted experimental and theoretical studies on simplified systems,the behavior of the major chemical perpetrators of such cytotoxicity, namely the biradical intermediates formed by natural enediynes, remains more a matter of conjecture than a point of fact.

In advanced studies directed toward the total synthesis of the kedarcidin chromophore, we have successfully achieved the late-stage installation of the nine-membered diyne ring in the presence of the highly functionalised ansamacrocyclic bridge.

The streamlined assembly of the ansamacrolide framework of the kedarcidin chromophore via an efficient atropselective Sonogashira coupling step is described. To this end, two newly improved practical syntheses of the cyclopentene and dine fragments have been developed, which feature 0.2 mol % catalytic loadings for an RCM step and i-PrMgCl/CH2I2 as a new entry to gem-disubstituted epoxides from ketones, both being applicable to 49-g scales.

Enediyne antitumor antibiotics have attracted immense attention among chemists and biologists alike because of their unique chemical structures, potent antitumor activities, and fascinating biological modes of action. As a novel addition to this family, the nonprotein and extremely strained nine-membered enediyne antibiotic N1999-A2 strongly inhibits the growth of various tumor cell lines and bacteria, and cleaves DNA in a base-specific manner. The attractive features of this molecule lie not only within the chemical structure being analogous to the neocarzinostatin chromophore, itself a potent anticancer agent, but also in that it can invoke remarkably strong biological activities even without a stabilizing apoprotein carrier and a glycoside functionality that can accelerate the rate of DNA cleavage. In this regard, N1999-A2 serves as a leading enediyne-based antitumor agent with minimal functionality that is able to act on DNA selectively. We therefore focused on this unique, unstable, and stereochemically unknown compound and undertook the formidable challenge of devising an efficient strategy that would be flexible enough to ultimately construct a series of related highly strained systems.

Using a versatile synthesis with 13CH3PPh3I and CH313CO2Et as 13C sources, the first examples of nine membered chromophores, which have been differentially labelled with 13C in their carbocyclic enediyne cores, are described.

The ESR spectra for synthetic bicyclo[7.3.0]epoxydodecadienediynes in solution at room temperature are steady. These spectra originate from the Masamune-Bergman cyclization of bicyclo[7.3.0]epoxydodecadienediynes to p-benzyne biradicals and the equilibrium between the two forms. Comparison of the ESR spectra of the unlabeled and 13C-labeled nine-membered enediynes indicated that the spectra are not directly due to the p-benzyne biradicals but rather to more stable secondary radical intermediates.

An efficient and practical synthesis of mycarose and kedarosamine derivatives has been devised from ethyl (S)-lactate v/a a versatile (E)-alkene intermediate. Noteworthy transformations include a highly trans-selective one-pot Julia olefination protocol and intramolecular cyclisation of a 2,3-epoxy carbamate.

The cyanosporasides A–F are a collection of mono chlorinated benzenoid derivatives isolated from the marine actinomycetes Salinispora and Streptomyces sp. All derivatives feature one of two types of cyanocyclopenta[a]indene frameworks, which are regioisomeric in the position of a single chlorine atom. It is proposed that these chloro-substituted benzenoids are formed biosynthetically through the cycloaromatization of a bicyclic nine-membered enediyne precursor. Herein, we report the synthesis of such a bicyclic precursor, its spontaneous transannulation into a p-benzyne, and its differential 1,4 hydrochlorination reactivity under either organochlorine or chloride-salt conditions. Our bioinspired approach culminated in the first regiodivergent total synthesis of the aglycons A/F and B/C, as well as cyanosporasides D and E. In addition, empirical insights into the site selectivity of a natural-like p-benzyne, calculated to be a ground-state triplet diradical, to hydrogen, chlorine, and chloride sources are revealed.