Tetramic acid based alkaloids from Aspergillus amoenus Roberg strain UP197-antibiotic properties and new pyranterreones

The fungus Aspergillus amoenus Roberg strain UP197 was shown to produce antibacterial tetramic acid based alkaloids. Two new compounds, pyranterreone I and J (1 and 2), were isolated and characterized, in addition to the known compounds cordylactam, 7-hydroxycordylactam, pyranterreone C, D, F and G. Neither the pyranterreones nor the cordylacctams had previously been tested for antimicrobial activity. Thus, all isolated compounds were tested against a panel of clinically important bacteria and fungi. Pyranterreone C was active against Gram-positive and Gram-negative bacteria, with minimal inhibitory concentrations (MIC) between 1 and 8 mu g/mL, whereas the MICs for all other compounds were >32 mu g/mL. Pyranoterreone C was cytotoxic towards HepG2 cells, and since pyranterreone C reacted rapidly with the nucleophile cysteine, it is likely that the observed antibacterial activity is due to the chemical reactivity rather than enzymatic affinity, making it unsuitable for development as an antibacterial drug

In-peptide amino acid racemization via inter-residue oxazoline intermediates during acidic hydrolysis

Isopedopeptins are antibiotic cyclic lipodepsipeptides containing the subsequence L-Thr-L-2,3-diaminopropanoic acid-D-Phe-L-Val/L-3-hydroxyvaline. Acidic hydrolysis of isopedopeptins in D2O showed the D-Phe residues to racemize extensively in peptides with L-3-hydroxyvaline but not in peptides with L-Val. Similarly, one Leu residue in pedopeptins, which are related peptides containing the subsequence Leu-2,3-diaminopropanoic acid-Leu-L-Val/L-3-hydroxyvaline, was found to racemize in peptides with L-3-hydroxyvaline. Model tetrapeptides, L-Ala-L-Phe-L-Val/3-hydroxyvaline-L-Ala, gave the corresponding results, i.e. racemization of L-Phe only when linked to a L-3-hydroxyvaline. We propose the racemization to proceed via an oxazoline intermediate involving Phe/Leu and the L-3-hydroxyvaline residues. The 3-hydroxyvaline residue may form a stable tertiary carbocation by loss of the sidechain hydroxyl group as water after protonation. Elimination of the Phe/Leu H-2 and ring-closure from the carbonyl oxygen onto the carbocation results in the suggested oxazoline intermediate. The reversed reaction leads to either retained or inversed configuration of Phe/Leu. Such racemization during acidic hydrolysis may occur whenever a 3-hydroxyvaline residue or any amino acid that can form a stable carbocation on the C-3, is present in a peptide. The proposed mechanism for racemization was supported by incorporation of O-18 in the 3-hydroxyvaline sidechain when the acidic hydrolysis was performed in H2O/(H2O)-O-18 (1:1). The 2,3-diaminopropanoic residues of isopedopeptins and pedopeptins were also found to racemize during acidic hydrolysis, as previously described. Based on the results, the configuration of the Leu and 2,3-diaminopropanoic acid residues of the pedopeptins were reassigned to be L-Leu and D-Leu, and 2 x L-2,3-diaminopropanoic acid

Antibacterial Isoquinoline Alkaloids from the Fungus Penicillium Spathulatum Em19

In the search for new microbial antibacterial secondary metabolites, two new compounds (1 and 2) were isolated from culture broths of Penicillium spathulatum Em19. Structure determination by nuclear magnetic resonance and mass spectrometry identified the compounds as 6,7-dihydroxy-5,10-dihydropyrrolo[1,2-b]isoquinoline-3-carboxylic acid (1, spathullin A) and 5,10-dihydropyrrolo[1,2-b]isoquinoline-6,7-diol (2, spathullin B). The two compounds displayed activity against both Gram-negative and -positive bacteria, including Escherichia coli, Acinetobacter baumannii, Enterobacter cloacae, Klebsiella pneumonia, Pseudomonas aeruginosa, and Staphylococcus aureus. Compound 2 was more potent than 1 against all tested pathogens, with minimal inhibitory concentrations down to 1 µg/mL (5 µM) against S. aureus, but 2 was also more cytotoxic than 1 (50% inhibitory concentrations 112 and 11 µM for compounds 1 and 2, respectively, towards Huh7 cells). Based on stable isotope labelling experiments and a literature comparison, the biosynthesis of 1 was suggested to proceed from cysteine, tyrosine and methionine via a non-ribosomal peptides synthase like enzyme complex, whereas compound 2 was formed spontaneously from 1 by decarboxylation. Compound 1 was also easily oxidized to the 1,2-benzoquinone 3. Due to the instability of compound 1 and the toxicity of 2, the compounds are of low interest as possible future antibacterial drugs

Tetramic acid based alkaloids from Aspergillus amoenus Roberg strain UP197-antibiotic properties and new pyranterreones

The fungus Aspergillus amoenus Roberg strain UP197 was shown to produce antibacterial tetramic acid based alkaloids. Two new compounds, pyranterreone I and J (1 and 2), were isolated and characterized, in addition to the known compounds cordylactam, 7-hydroxycordylactam, pyranterreone C, D, F and G. Neither the pyranterreones nor the cordylacctams had previously been tested for antimicrobial activity. Thus, all isolated compounds were tested against a panel of clinically important bacteria and fungi. Pyranterreone C was active against Gram-positive and Gram-negative bacteria, with minimal inhibitory concentrations (MIC) between 1 and 8 mu g/mL, whereas the MICs for all other compounds were >32 mu g/mL. Pyranoterreone C was cytotoxic towards HepG2 cells, and since pyranterreone C reacted rapidly with the nucleophile cysteine, it is likely that the observed antibacterial activity is due to the chemical reactivity rather than enzymatic affinity, making it unsuitable for development as an antibacterial drug

水中可溶性腐植質､金屬離子､有機�J染物間相互作用之研究

污染物在水域中的傳輸過程，受腐值質的影響極大，腐植質藉其酸鹼特性、錯合能 力在液相中和金屬離子進行錯合反應，影響金屬離子的生物毒性及其在水中之移動 特性。對於水中有機污染物則因結構所含電子雲分佈關係，以及極性等因素，與之 進行各項不同作用力之吸附。本研究在探討水中可溶性腐植質(fulvic acid) 與有 機污染物、金屬銅離子三者間作用之互動關係。 研究中，用螢光法探討水中fulvic acid 與Cu的錯合反應，配合配位基模式電腦 運算求形成常數(Kf) 。另以螢光法測定fulvic acid 與有機污染物之Ko/ω值， 及fulvic acid 與有機污染物吸附作用後殘餘之有機污染物量。 研究中，就溶液中的pH值、Cu添加量、有機污染物種類 (Phenol、Aniline、 Benzoic acid) 、Ko/ω值及添加量等因素對於fulvic acid 與Cu、有機污染物 三者間作用之影響作一係列探討。結果顯示，fulvic acid 與Cu之錯合受pH值影 響極大，在pH=7時有最大錯合程度。有機污染物的存在對fulvic acid 與Cu的錯 合影響不大，對fulvic acid 之螢光強度有稍微改變，可知fulvic acid 與有機污 染物間有吸附現象。 fulvic acid與有機污染物間的吸附作用，與物種之Ko/ω 值有關，Ko/ω較相近 者，其吸附力強，Ko/ω 差別較大者，吸附力弱。而Cu的存在有助於 fulvic acid與有機污染物間的吸附作用

Antibacterial Isoquinoline Alkaloids from the Fungus Penicillium Spathulatum Em19

In the search for new microbial antibacterial secondary metabolites, two new compounds (1 and 2) were isolated from culture broths of Penicillium spathulatum Em19. Structure determination by nuclear magnetic resonance and mass spectrometry identified the compounds as 6,7-dihydroxy-5,10-dihydropyrrolo[1,2-b]isoquinoline-3-carboxylic acid (1, spathullin A) and 5,10-dihydropyrrolo[1,2-b]isoquinoline-6,7-diol (2, spathullin B). The two compounds displayed activity against both Gram-negative and -positive bacteria, including Escherichia coli, Acinetobacterbaumannii, Enterobactercloacae, Klebsiellapneumonia, Pseudomonasaeruginosa, and Staphylococcusaureus. Compound 2 was more potent than 1 against all tested pathogens, with minimal inhibitory concentrations down to 1 mu g/mL (5 mu M) against S. aureus, but 2 was also more cytotoxic than 1 (50% inhibitory concentrations 112 and 11 mu M for compounds 1 and 2, respectively, towards Huh7 cells). Based on stable isotope labelling experiments and a literature comparison, the biosynthesis of 1 was suggested to proceed from cysteine, tyrosine and methionine via a non-ribosomal peptides synthase like enzyme complex, whereas compound 2 was formed spontaneously from 1 by decarboxylation. Compound 1 was also easily oxidized to the 1,2-benzoquinone 3. Due to the instability of compound 1 and the toxicity of 2, the compounds are of low interest as possible future antibacterial drugs

雙手性胺基硫醇於不對稱催化反應之應用(Ⅳ)&抗帕金森氏症藥物L-threo-DOPS之全合成

第一部分 壹、摘要 本論文是研究利用手性胺基酸為原料製備雙手性胺基硫醇作為不對稱催化反應的掌性催化劑，催化有機鋅對醛類的不對稱加成，以形成具有光學活性的二級醇；實驗結果顯示在適當的條件時所得到的鏡像超越值(enantiomeric excess)可達99.3%。 本實驗室已發展出一系列以硫原子和氮原子為主之雙牙掌性配位基(bidentate ligand)來做手性源（chiral source）以進行不對稱加成反應。 我們也針對了掌性配基上的取代基變化、掌性配基的用量、醛類的種類、反應溫度等因素進行探討，以求得最佳的反應條件及不對稱催化效果。最後我們也提出可能的反應機構，來對我們的結果作一合理的解釋。 第二部分 本論文是研究以胡椒醛為起始物並利用化合物的非鏡像立體異構物(diastereomer)或鏡像立體異構物(enantiomer)在不同溶劑中之溶解度不同；來製備Anti-Parkinson’s diease的雙手性藥物 L-threo-DOPS，並成功將實驗室技術與工業生產結合。 我們也對實驗各個方面如：溫度、時間、用量等方面去探討；期能以最有效率的方式產出最大的產能。第一部分：雙手性胺基硫醇於不對稱催化反應之應用(Ⅳ) 壹、摘要 1 貳、導論 2 參、結果與討論 12 肆、結論 23 伍、儀器測定及物質處理 24 陸、實驗步驟 25 柒、參考資料 38 第二部分：抗帕金森氏症藥物L-threo-DOPS之全合成 壹、摘要 40 貳、導論 41 參、結果與討論 49 肆、結論 56 伍、儀器測定及物質處理 57 陸、實驗步驟 55 柒、參考資料 65 捌、光譜 6

Antibacterial 3,6-Disubstituted 4‑Hydroxy-5,6-dihydro‑2<i>H</i>‑pyran-2-ones from <i>Serratia plymuthica</i> MF371‑2

Bioassay-guided fractionation of culture extracts of <i>Serratia plymuthica</i> strain MF371-2 resulted in the isolation of two new antibacterial compounds with potent activity against Gram-positive bacteria, including <i>Staphylococcus aureus</i> LMG 15975 (MRSA). A spectroscopic investigation, in combination with synthesis, enabled the characterization of the compounds as 3-butyryl-4-hydroxy-6-heptyl-5,6-dihydro-2<i>H</i>-pyran-2-one (plymuthipyranone A, <b>1</b>) and 3-butyryl-4-hydroxy-6-nonyl-5,6-dihydro-2<i>H</i>-pyran-2-one (plymuthipyranone B, <b>2</b>). The MIC values for <b>1</b> and <b>2</b> against <i>S. aureus</i> LMG 15975 were determined to be 1–2 μg mL^–1 and 0.8 μg mL^–1, respectively. Compound <b>2</b> was found to have potent activity against many strains of <i>S. aureus</i>, including several mupirocin-resistant strains, other species of <i>Staphylococcus</i>, and vancomycin-resistant enterococci. Compound <b>2</b> was slightly cytotoxic for human cells, with CC₅₀ values between 4.7 and 40 μg mL^–1, but the CC₅₀/MIC ratio was ≥10 for many tested combinations of human cells and bacteria, suggesting its possible use as an antibacterial agent. Several analogues were synthesized with different alkyl groups in the 3- and 6-positions (<b>6</b>–<b>13</b>), and their biological properties were evaluated. It was concluded that the activity of the compounds increased with the lengths of the alkyl and acyl substituents