京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21784号 / 工博第4601号 / 新制||工||1717(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 中村 正治, 教授 近藤 輝幸, 教授 村田 靖次郎 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

As malaria, caused by Plasmodium spp., continues to afflict millions of people worldwide, there is a dire need for the discovery of novel, inexpensive antimalarial drugs. Although there are effective drugs on the market, the consistent development of drug resistant species has decreased their efficacy, further emphasizing that novel therapeutic measures are urgently needed. Natural products provide the most diverse reservoir for the discovery of unique chemical scaffolds with the potential to effectively combat malarial infections, but, due to their complex structures, they often pose extreme challenges to medicinal chemists during pharmacokinetic optimization. In our laboratory we have performed unbiased, cell-based assays of numerous synthetic compounds from chemical libraries enriched with nature-like elements. This screening has led to the discovery of many original chemical scaffolds with promising antimalarial properties. In an attempt to further characterize these scaffolds, the most promising compounds were assayed in order to determine their cytotoxic effects on mammalian cells. In addition, the development of a drug resistant parasite line of Plasmodium falciparum to the most promising compound was done in order to determine the relative probability for parasite resistance development.

The work disclosed in this dissertation outlines a newly discovered acidic alumina-mediated orthoallylation of unprotected phenols and the application of this method to the synthesis of prenylated phenolic natural products including dorsmanin A and hyperbeanol Q. Chapter 1 consists of a literature review of prenylated phenolic compounds and includes a discussion of their biological significance followed by an extensive review of the various synthetic strategies that have been used to prepare them. It is our intention to publish the content of this chapter as a review article for the synthetic chemistry community. Showcased in Chapter 2 is the optimization of a novel prenylation method via acidic alumina as the promoter. Phenols and allyl alcohols are combined with acidic alumina in 1,2-dichloroethane or acetonitrile to induce a proposed coordination of the substrates to the alumina surface via hydrogen bonding which facilitates the regioselective ortho-prenylation of phenols. The extensive substrate scope of this chemistry is discussed. In Chapter 3, this alumina-mediated prenylation is applied to the syntheses of several acylphloroglucinol natural products and unnatural structural analogues which are evaluated for their antimicrobial and anthelmintic (anti-parasitic) activity. Some of these compounds exhibited antimicrobial activity and some exhibited anthelmintic potential. In Chapter 4, this prenylation strategy is further extended to the syntheses of additional prenylated phenolic natural products: (±)-sanjuanolide and dorsmanin A. Investigations towards the synthesis of HP1 are also reported. Development of the syntheses of these natural product targets provides a useful venue to investigate the scope of our alumina-mediated phenol prenylation chemistry and to identify its scope and limitations. / Thesis / Doctor of Philosophy (PhD)

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<p>The glycopeptide antibiotic vancomycin is used as front line treatment for serious Gram-positive infections and resistance to this drug is widespread. Three genes are essential for resistance, <em>vanHAX</em>, which are controlled by a two-component regulatory system VanR and VanS. Here, glycopeptide resistance is found to be ancient and diverse in the environment. A <em>vanA</em> open reading frame from 30 000 yr old DNA was identified and the enzyme was shown to be as functional as comparable to modern day VanA homologs. In the environment resistance is found to be diverse and widespread. For example, the organism <em>Desulfitobacterium hafniense</em> Y51 VanH was shown as non-essential in conferring inducible resistance. Furthermore in the glycopeptide producer <em>Amycolatopsis balhimycina</em> harboring the classic <em>vanHAX,</em> a functional VanA homolog is described as an orphan gene outside of any recognizable gene cassette .</p> <p>Glycopeptides are natural products made by members of the Actinomycete family and are modified by different types of tailoring enzymes. Of particular interest is the glycopeptide A47934, which is ‘aglyco’, and sulfated. The sulfotransferase StaL will transfer not only a sulfate group to A47934, but a sulfamide and fluorosulfonate group. Focusing on additional tailoring enzymes, the biosynthetic cluster of the sulfated glycopeptide UK68597 was sequenced. This cluster has provided a resource for glycopeptide tailoring enzymes for use to modify the A47934 backbone. Sulfation was the first focus and the substrate promiscuity of StaL was explored to expand the chemical diversity A47934 and vancomycin. This work has led to the discovery that glycopeptide sulfation will antagonize the activation and expression of <em>vanHAX</em>. A new sulfated vancomycin derivative was created with this antagonizing activity in the clinical pathogen <em>Enterococcus faecium</em> of the VanB phenotype. Implications of these results and the further use of tailoring enzymes to modify glycopeptides to antagonize resistance will be discussed.</p> / Doctor of Philosophy (PhD)

The need for new antibiotics has been highlighted recently with the increasing pace of emergence of drug resistant pathogens (MRSA, XDR-TB, etc.). Modification of existing antibiotics with the additions of side chains or other chemical groups and genomics based drug targeting have been the preferred method of drug development at the corporate level in recent years. These approaches have yielded few viable antibiotics and natural products are once again becoming an area of interest for drug discovery. We examined the antimicrobial "Red Soils" of the Hashemite Kingdom of Jordan that have historically been used to prevent infection and cure rashes by the native peoples. Antimicrobial producing bacteria were present in these soils and found to be the reason for their antibiotic activity. After isolation, these bacteria were found to excrete their antimicrobials into the liquid culture media which we could then attempt to isolate for further study. Adsorbent resins were employed to capture the antimicrobial compounds and then elute them in a more concentrated solution. As part of a drug discovery program, we sought a way to quickly characterize other soils for potential antibiotic producing bacteria. The community level physiologic profile was examined to determine if this approach would allow for a rapid categorizing of soils based on their probability of containing antimicrobial producing microorganisms. This method proved to have a high level of variability that could not be overcome even after mixing using a commercial blender. The role of these antimicrobial producing bacteria within their natural microbial community has largely been confined to microbe-plant interactions. The role of antimicrobial-producing microorganisms in driving the diversity of their community has not been a focus of considerable study. The potential of an antimicrobial-producing bacterium to act as a driver of diversity was examined using an artificial microbial community based in a sand microcosm. The changes in the microbial assemblage indicate that antimicrobial-producing bacteria may act in an allelopathic manner rather than in a predatory role. / Ph. D.