The Identification and Heterologous Expression of the Biosynthetic Gene Cluster Encoding the Antibiotic and Anticancer Agent Marinomycin.

With the rise in antimicrobial resistance, there is an urgent need for new classes of antibiotic with which to treat infectious disease. Marinomycin, a polyene antibiotic from a marine microbe, has been shown capable of killing methicillin-resistant (MRSA) and vancomycin-resistant (VREF), as well as having promising activity against melanoma. An attractive solution to the photoprotection of this antibiotic has been demonstrated.

Structure-Based Design, Synthesis and Biological Evaluation of Bis-Tetrahydropyran Furan Acetogenin Mimics Targeting the Trypanosomatid F1 Component of ATP Synthase.

The protozoan parasites and . are responsible for the severely debilitating neglected Tropical diseases of African sleeping sickness, Chagas disease and leishmaniasis, respectively. As part of our ongoing programme exploring the potential of simplified analogues of the acetogenin chamuvarinin we identified the FoF1-ATP synthase as a target of our earlier triazole analogue series.

Approaches to CNS Drug Delivery with a Focus on Transporter-Mediated Transcytosis.

Drug delivery to the central nervous system (CNS) conferred by brain barriers is a major obstacle in the development of effective neurotherapeutics. In this review, a classification of current approaches of clinical or investigational importance for the delivery of therapeutics to the CNS is presented. This classification includes the use of formulations administered systemically that can elicit transcytosis-mediated transport by interacting with transporters expressed by transvascular endothelial cells.

Design and Synthesis of Broad Spectrum Trypanosomatid Selective Inhibitors.

Neglected tropical diseases caused by parasitic infections are an ongoing and increasing concern that have a devastating effect on the developing world due to their burden on human and animal health. In this work, we detail the preparation of a focused library of substituted-tetrahydropyran derivatives and their evaluation as selective chemical tools for trypanosomatid inhibition and the follow-on development of photoaffinity probes capable of labeling target protein(s) in vitro. Several of these functionalized compounds maintain low micromolar activity against Trypanosoma brucei, Trypanosoma cruzi, Leishmania major, and Leishmania donovani.

Direct and indirect approaches to identify drug modes of action.

Phenotypic assays are becoming increasingly more common among drug discovery practices, expanding drug target diversity as lead compounds identified through such screens are not limited to known targets. While increasing diversity is beneficial to the drug discovery process and the fight against disease, the unknown modes of action of new lead compounds can hamper drug discovery as, in most cases, the process of lead compound optimization is made difficult due to the unknown nature of the target; blindly changing substituents can prove fruitless due to the inexhaustible number of potential combinations, and it is therefore desirable to rapidly identify the targets of lead compounds developed through phenotypic screening. In addition, leads identified through target-based screening often have off-target effects that contribute towards drug toxicity, and by identifying those secondary targets, the drugs can be improved.

Photo-affinity labelling and biochemical analyses identify the target of trypanocidal simplified natural product analogues.

Current drugs to treat African sleeping sickness are inadequate and new therapies are urgently required. As part of a medicinal chemistry programme based upon the simplification of acetogenin-type ether scaffolds, we previously reported the promising trypanocidal activity of compound 1, a bis-tetrahydropyran 1,4-triazole (B-THP-T) inhibitor. This study aims to identify the protein target(s) of this class of compound in Trypanosoma brucei to understand its mode of action and aid further structural optimisation.

Kinetics and Structure of a Cold-Adapted Hetero-Octameric ATP Phosphoribosyltransferase.

Adenosine 5'-triphosphate phosphoribosyltransferase (ATPPRT) catalyzes the first step in histidine biosynthesis, the condensation of ATP and 5-phospho-α-d-ribosyl-1-pyrophosphate to generate N-(5-phospho-β-d-ribosyl)-ATP and inorganic pyrophosphate. The enzyme is allosterically inhibited by histidine. Two forms of ATPPRT, encoded by the hisG gene, exist in nature, depending on the species.

The trypanosome alternative oxidase: a potential drug target?

New drugs against Trypanosoma brucei, the causative agent of Human African Trypanosomiasis, are urgently needed to replace the highly toxic and largely ineffective therapies currently used. The trypanosome alternative oxidase (TAO) is an essential and unique mitochondrial protein in these parasites and is absent from mammalian mitochondria, making it an attractive drug target. The structure and function of the protein are now well characterized, with several inhibitors reported in the literature, which show potential as clinical drug candidates.

Development of Simplified Heterocyclic Acetogenin Analogues as Potent and Selective Trypanosoma brucei Inhibitors.

Neglected tropical diseases caused by parasitic infections are an ongoing and increasing concern. They are a burden to human and animal health, having the most devastating effect on the world's poorest countries. Building upon our previously reported triazole analogues, in this study we describe the synthesis and biological testing of other novel heterocyclic acetogenin-inspired derivatives, namely 3,5-isoxazoles, furoxans, and furazans.

An internal thioester in a pathogen surface protein mediates covalent host binding.

To cause disease and persist in a host, pathogenic and commensal microbes must adhere to tissues. Colonization and infection depend on specific molecular interactions at the host-microbe interface that involve microbial surface proteins, or adhesins. To date, adhesins are only known to bind to host receptors non-covalently.

Non-natural acetogenin analogues as potent Trypanosoma brucei inhibitors.

Neglected tropical diseases remain a serious global health concern. Here, a series of novel bis-tetrahydropyran 1,4-triazole analogues based on the framework of chamuvarinin, a polyketide natural product isolated from the annonaceae plant species are detailed. The analogues synthesized display low micromolar trypanocidal activities towards both bloodstream and insect forms of Trypanosoma brucei, the causative agent of African sleeping sickness, also known as Human African Trypanosomiasis (HAT).

Magnetic retraction of bowel by intraluminal injectable cyanoacrylate-based magnetic glue.

Magnetic retraction offers advantages over physical retraction by graspers because of reduced tissue trauma. The objectives of this study are to investigate a novel method of magnetisation of bowel segments by intraluminal injection of magnetic glue and to demonstrate the feasibility of magnetic retraction of bowel with sufficient force during minimal access surgery. Following an initial materials characterisation study, selected microparticles of stainless steel (SS410- μ Ps) were mixed with chosen cyanoacrylate glue (Loctite 4014).

Mucoadhesive polymer films for tissue retraction in laparoscopic surgery: Ex-vivo study on their mechanical properties.

Safe and effective manipulation of soft tissue during laparoscopic procedures can be achieved by the use of mucoadhesive polymer films. A series of novel adhesive polymer films were formulated in house based on either Carbopol or Chitosan modified systems. The mechanical properties of the polymers and their adherence to bowel were evaluated using ex-vivo pig bowel immersed in 37°C water bath and connected to an Instron tensiometer.

Total synthesis, stereochemical assignment, and biological activity of chamuvarinin and structural analogues.

A highly stereocontrolled synthesis of (+)-chamuvarinin has been completed in 1.5% overall yield over 20 steps. The key fragment coupling reactions were the addition of alkyne 8 to aldehyde 7 (under Felkin-Anh control), followed by the two step activation/cyclization to close the C20-C23 2,5-cis-substituted tetrahydrofuran ring and a Julia-Kocienski olefination at C8-C9 to introduce the terminal butenolide.

Synthesis of the originally proposed structure of palmerolide C.

A stereoselective synthesis of the proposed structure of palmerolide C (1), a cytotoxic marine macrolide isolated from the Antarctic tunicate Synoicum adareanum, utilizes a convergent carbonyl-based coupling strategy to construct the C1-C24 carbon skeleton (see scheme). Compound 1 was shown to be a diastereomer of palmerolide C, and the structural revision of the natural product is proposed.

Synthesis and stereochemical assignment of (+)-chamuvarinin.

A stereocontrolled total synthesis of (+)-chamuvarinin, isolated from the root extract of Uvaria Chamae, utilizes a convergent modular strategy to construct the adjacently linked C15-C28 ether array, followed by a late-stage Julia-Kocienski olefination to append the butenolide motif. This constitutes the first total synthesis of (+)-chamuvarinin, defining the relative and absolute configuration of this unique annonaceous acetogenin.

Development of practical syntheses of the marine anticancer agents discodermolide and dictyostatin.

Initially isolated in trace quantities from deep-sea sponges, the structurally related polyketides discodermolide and dictyostatin share the same microtubule-stabilizing antimitotic mechanism as Taxol. Discodermolide has been the focus of intense research activity in order to develop a practical supply route, and these efforts ultimately allowed its large-scale synthesis and the initiation of clinical trials as a novel anticancer drug. Similarly, the re-isolation and synthesis of dictyostatin continues to stimulate the biological and chemical communities in their quest for the development of new chemotherapeutic agents.

Total synthesis of (-)-reidispongiolide A, an actin-targeting macrolide isolated from the marine sponge Reidispongia coerulea.

A stereocontrolled total synthesis of the microfilament-destabilizing cytotoxic macrolide (-)-reidispongiolide A, isolated from the New Caledonian marine sponge Reidispongia coerulea, is described. This synthesis utilizes a convergent aldol-based strategy to construct the 26-membered macrolactone, followed by the late-stage coupling of a derived aldehyde with an N-vinylformamide-containing ketone subunit to install the full side chain. Two alternative routes were examined for the introduction of the 2E,4E-dienoate region, and a complex Mukaiyama aldol coupling was used to connect the northern and southern hemispheres to install the C13 stereocenter.

Total synthesis and stereochemical reassignment of (+)-dolastatin 19.

[reaction: see text] A revised configurational assignment for the cytotoxic marine macrolide dolastatin 19 is proposed and validated by total synthesis. Key features of the route include an asymmetric vinylogous aldol reaction to install the isolated C13 stereocenter and (E)-trisubstituted alkene, two sequential 1,4-syn boron-mediated aldol reactions, and a Mukaiyama glycosylation to append the l-rhamnose-derived pyranoside.

A second-generation total synthesis of (+)-discodermolide: the development of a practical route using solely substrate-based stereocontrol.

A novel total synthesis of the complex polyketide (+)-discodermolide, a promising anticancer agent of sponge origin, has been completed in 7.8% overall yield over 24 linear steps, with 35 steps altogether. This second-generation approach was designed to rely solely on substrate control for introduction of the required stereochemistry, eliminating the use of all chiral reagents or auxiliaries.

A quantitative evaluation of the effects of inhibitors of tubulin assembly on polymerization induced by discodermolide, epothilone B, and paclitaxel.

Purpose: To determine whether inhibitors of microtubule assembly inhibit polymerization induced by discodermolide and epothilone B, as well as paclitaxel, and to quantitatively measure such effects.

Methods: Inhibition was quantitated by measuring polymer formation either by turbidimetry or by centrifugation, and the amount of inhibitor required to inhibit 50% relative to an appropriate control reaction was determined.

Results: The inhibitory drugs evaluated were four colchicine site agents (combretastatin A-4, podophyllotoxin, nocodazole, and N-acetylcolchinol- O-methyl ether), maytansine, which competitively inhibits the binding of Catharanthus alkaloids to tubulin, halichondrin B and phomopsin A, which noncompetitively inhibit the binding of Catharanthus alkaloids to tubulin, and the depsipeptide dolastatin 15.

Discodermolide interferes with the binding of tau protein to microtubules.

We investigated whether discodermolide, a novel antimitotic agent, affects the binding to microtubules of tau protein repeat motifs. Like taxol, the new drug reduces the proportion of tau that pellets with microtubules. Despite their differing structures, discodermolide, taxol and tau repeats all bind to a site on beta-tubulin that lies within the microtubule lumen and is crucial in controlling microtubule assembly.