Generation Of Novel Analogues Research Articles

Abstract 2452: Deorphanizing TLX: Implications for treatment of glioblastomas

Abstract Nuclear receptors (NRs) are important ligand-dependent transcriptional factors. Presently, no natural or synthetic ligand has been identified for a large group of so- called “orphan” NRs. The orphan NR tailless (TLX, NR2E1), a transcriptional repressor, is a major player in neurogenesis and emerging evidence indicates that it is an excellent target to treat Neural Stem Cell (NSC) derived brain tumors and glioblastomas. Indeed, several groups hypothesized that small molecules de-repressing TLX activity in glioblastoma cells should slow tumor progression and invasiveness by inducing the cyclin-dependent kinase inhibitor p21 and the tumor suppressor pten. Until recently, no chemical probes to modulate TLX activity to test this hypothesis were available, and it was not clear whether TLX was druggable. Our homology models of the TLX ligand binding domain (LBD) suggest that TLX belongs to an emerging class of NRs that lack two LBD helices and fold into an auto-repressed conformation. While our models suggests that TLX could harbor a ligand binding pocket, the consequences of its unusual organization for small molecule development were unknown. We used a medium throughput screening strategy to assess TLX ligand binding capacity. We investigated direct binding of 20,000 compounds to purified human TLX protein and verified interactions with a secondary (orthogonal) assay. We then assessed effects of verified binders on TLX activity. As a result, we reported three compounds that bind to TLX with affinities in the high nanomolar to low micromolar range and enhance TLX transcriptional repressive activity. Based on this study, we could conclude that TLX is druggable. We are now investigating how to de-repress TLX transcriptional activity using derivatives of these small molecules. We are imaging the mode of binding of the three identified ligands and discovering surfaces which bind coregulators of TLX in glioblastomas. This knowledge will allow us to devise strategies to chemically modify novel TLX ligands to disrupt coregulator interactions and to obtain the desirable biological activities. A first generation of novel analogues is currently being tested. In this presentation we will describe ongoing Structure-Activity Relationship studies to identify new specific TLX ligands able to de-repress TLX transcriptional activity. Citation Format: Cindy C. Benod, Rosa Villagomez, Paul Webb. Deorphanizing TLX: Implications for treatment of glioblastomas. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2452. doi:10.1158/1538-7445.AM2015-2452

Development of a concise synthesis of ouabagenin and hydroxylated corticosteroid analogues.

The natural product ouabagenin is a complex cardiotonic steroid with a highly oxygenated skeleton. This full account describes the development of a concise synthesis of ouabagenin, including the evolution of synthetic strategy to access hydroxylation at the C19 position of a steroid skeleton. In addition, approaches to install the requisite butenolide moiety at the C17 position are discussed. Lastly, methodology developed in this synthesis has been applied in the generation of novel analogues of corticosteroid drugs bearing a hydroxyl group at the C19 position.

Asymmetric Total Synthesis of (+)‐Merobatzelladine B

Asymmetric Total Synthesis of (+)‐Merobatzelladine B

The natural product CCR5 antagonist anibamine and its analogs as anti-prostate cancer agents

Prostate cancer is a leading cause of death among males in the United States. As the chemokine receptor CCR5 is over-expressed in more aggressive forms of prostate cancer, and is also a critical receptor in inflammation, chemokine receptor CCR5 antagonists could potentially act as anti-prostate cancer agents. Anibamine, a natural product CCR5 antagonist, provides a unique molecular scaffold for the generation of novel analogs with possible anti-prostate cancer activity. A series of analogs of anibamine were designed, synthesized and tested against several prostate cancer cell lines. The analogs all acted as CCR5 antagonists at micromolar range affinity to the receptor while their anti-proliferative activity varied depending on the cell line type and their chemical structural properties. Further basal cytotoxicity characterization on these compounds indicated some of them may be suitable for in vivo studies.

Heterologous expression systems for polyketide synthases

Polyketide synthases are the main biochemical machinery for the production of a structurally diverse group of natural products, polyketides. Their heterologous expression enables overproduction of target compounds, generation of novel analogs, and provides a basic understanding of their reaction programs. This Highlight outlines the current state of heterologous expression of type I, type II, and type III polyketide synthases of microbial and plant origins.

Heterologous Expression And Genetic Engineering of the Phenalinolactone Biosynthetic Gene Cluster by Using Red/ET Recombineering

The heterologous expression of natural product biosynthetic pathways is of increasing interest in biotechnology and drug discovery. This approach enables the production of complex metabolites in more amenable host organisms and provides the basis for the generation of novel analogues through genetic engineering. Here we describe a straightforward strategy for the heterologous expression of the highly complex phenalinolactone biosynthetic pathway, which was recently cloned from Streptomyces sp. Tü6071. The biosynthetic gene cluster comprises at least 11 transcriptional units that harbor 35 genes, which together catalyze the assembly of structurally unique tricyclic terpene glycosides with antibacterial activity. By using Red/ET recombineering, the phenalinolactone pathway was reconstituted from two cosmids and heterologously expressed in several Streptomyces strains. The established expression system now provides a convenient platform for functional investigations of the biosynthetic genes and the generation of novel analogues, by genetic engineering of the pathway in Escherichia coli. Deletion of a modifying gene from the expression construct resulted in a novel, unglycosylated phenalinolactone derivative; this demonstrates the promise of this methodology.

Expression of biosynthetic gene clusters in heterologous hosts for natural product production and combinatorial biosynthesis

Expression of biosynthetic gene clusters in heterologous hosts for natural product production and combinatorial biosynthesis is playing an increasingly important role in natural product-based drug discovery and development programmes. This review highlights the requirements and challenges associated with this conceptually simple strategy of using surrogate hosts for the production of natural products in good yields and for the generation of novel analogues by combinatorial biosynthesis methods, taking advantage of the recombinant DNA technologies and tools available in the model hosts. Specific topics addressed include: i) the mobilisation of biosynthetic gene clusters using different vector systems; ii) the selection of suitable model heterologous hosts; iii) the requirement of post-translational protein modifications and precursor supply within the model hosts; iv) the influence of promoters and pathway regulators; and v) the choice of suitable fermentation conditions. Lastly, the use of heterologous expression in combinatorial biosynthesis is addressed. Future directions for model heterologous host engineering and the optimisation of natural product biosynthetic gene cluster expression in heterologous hosts are also discussed.

ChemInform Abstract: A New Synthesis of 8‐Methylpsoralen Utilizing a Palladium‐Copper Catalyzed Reaction to Generate the Furan Ring and Thus Allowing for the Generation of Novel Analogues in the 5′‐Position.

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A new synthesis of 8-methylpsoralen utilizing a palladium-copper catalyzed reaction to generate the furan ring and thus allowing for the generation of novel analogs in the 5′-position

A rapid synthesis of 8-methylpsoralen is reported that utilizes a palladium-copper catalyzed reaction to generate the furan ring. Since 8-methylpsoralen is considered one of the most photodynamic methylpsoralens known and given the fact that psoralens in general have been shown to have medicinal value against bacteria and viruses, this synthesis allows for the availability to generate new derivatives by supplying a handle in the 5′-position. 1