1. |
- Ahlgren, Joakim, et al.
(författare)
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Biogenic phosphorus in oligotropic mountain lake sediments: Differences in composition measured with NMR spectroscopy
- 2006
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Ingår i: Water Research. - Uppsala Univ, Dept Phys & Analyt Chem, S-75124 Uppsala, Sweden. Univ So Denmark, Inst Biol, DK-5230 Odense M, Denmark. Uppsala Univ, Dept Organ & Biol Chem, S-75123 Uppsala, Sweden. Uppsala Univ, Dept Ecol & Evolut, EBC, S-75236 Uppsala, Sweden. : Elsevier BV. - 0043-1354 .- 1879-2448. ; :40, s. 3705-3712
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Tidskriftsartikel (refereegranskat)
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2. |
- Ahlgren, Joakim, et al.
(författare)
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Degradation of organic phosphorus compounds in anoxic Baltic Sea sediments : A P-31 nuclear magnetic resonance study
- 2006
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Ingår i: Limnology and Oceanography. - Uppsala Univ, Dept Ecol & Evolut, Evolutionary Biol Ctr, S-75236 Uppsala, Sweden. Uppsala Univ, Dept Chem, S-75124 Uppsala, Sweden. Univ So Denmark, Inst Biol, DK-5230 Odense, Denmark.. - 0024-3590 .- 1939-5590. ; 51:5, s. 2341-2348
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Tidskriftsartikel (refereegranskat)abstract
- The composition and abundance of phosphorus extracted by NaOH-ethylenediaminetetraacetic acid from anoxic Northwest Baltic Sea sediment was characterized and quantified using solution P-31 nuclear magnetic resonance. Extracts from sediment depths down to 55 cm, representing 85 yr of deposition, contained 18.5 g m(-2) orthophosphate. Orthophosphate monoesters, teichoic acid P, microbial P lipids, DNA P, and pyrophosphate corresponded to 6.7, 0.3, 1.1, 3.0, and 0.03 g P m(-2), respectively. The degradability of these compound groups was estimated by their decline in concentration with sediment depth. Pyrophosphate had the shortest half-life (3 yr), followed by microbial P lipids with a half-life of 5 yr, DNA P (8 yr), and orthophosphate monoesters (16 yr). No decline in concentration with sediment depth was observed for orthophosphate or teichoic acid P.
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3. |
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4. |
- Ahlgren, Joakim, et al.
(författare)
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Release of Organic P Forms from Lake Sediments
- 2011
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 45:2, s. 565-572
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Tidskriftsartikel (refereegranskat)abstract
- The effects of different physical and chemical conditions on the decomposition and release of organic and inorganic P compound groups from the sediment of Lake Erken were investigated in a series of laboratory experiments. Conditions investigated were temperature, oxygen level, and the effects of additions of carbon substrate (glucose) and poison (formalin). The effects on the P compound groups were determined by measurements with 31P NMR before and after the experiments, as well as analysis of P in effluent water throughout the experiment. Phosphate analysis of the effluent water showed that oxygen level was the most influential in terms of release rates, with the sediments under anoxic conditions generally releasing more phosphate than the other treatments. 31P NMR showed that the various treatments did influence the P compound group composition of the sediment. In particular, the addition of glucose led to a decrease in orthophosphate and polyphosphate while the addition of formalin led to a decrease in phosphorus lipids, DNAphosphate and polyphosphate. Oxic conditions resulted in an increase in polyphosphates, and anoxic conditions in a decrease in these. Temperature did not seem to affect the composition significantly.
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5. |
- Ahlgren, Joakim, et al.
(författare)
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Sediment Depth Attenuation of Biogenic Phosphorus Compounds Measured by 31P NMR
- 2005
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Ingår i: Environmental Science and Technology. - Univ Uppsala, Dept Analyt Chem, SE-75124 Uppsala, Sweden. Univ Uppsala, Dept Ecol & Evolut, Uppsala, Sweden. Univ Uppsala, Dept Organ Chem, SE-75124 Uppsala, Sweden. : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 39:3, s. 867-872
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Tidskriftsartikel (refereegranskat)abstract
- Being a major cause of eutrophication and subsequent loss of water quality, the turnover of phosphorus (P) in lake sediments is in need of deeper understanding. A major part of the flux of P to eutrophic lake sediments is organically bound or of biogenic origin. This P is incorporated in a poorly described mixture of autochthonous and allochthonous sediment and forms the primary storage of P available for recycling to the water column, thus regulating lake trophic status. To identify and quantify biogenic sediment P and assess its lability, we analyzed sediment cores from Lake Erken, Sweden, using traditional P fractionation, and in parallel, NaOH extracts were analyzed using 31P NMR. The surface sediments contain orthophosphates (ortho-P) and pyrophosphates (pyro-P), as well as phosphate mono- and diesters. The first group of compounds to disappear with increased sediment depth is pyrophosphate, followed by a steady decline of the different ester compounds. Estimated half-life times of these compound groups are about 10 yr for pyrophosphate and 2 decades for mono- and diesters. Probably, these compounds will be mineralized to ortho-P and is thus potentially available for recycling to the water column, supporting further growth of phytoplankton. In conclusion, 31P NMR is a useful tool to asses the bioavailability of certain P compound groups, and the combination with traditional fractionation techniques makes quantification possible.
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6. |
- Ahlgren, Joakim, et al.
(författare)
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Sediment Phosphorus Extractants for Phosphorus-31 Nuclear Magnetic Resonance Analysis : A Quantitative Evaluation
- 2007
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Ingår i: Journal of Environmental Quality. - Uppsala Univ, Dept Phys & Analyt Chem, S-75124 Uppsala, Sweden. Univ So Denmark, Inst Biol, DK-5230 Odense M, Denmark. Uppsala Univ, Dept Biochem & Organ Chem, S-75124 Uppsala, Sweden. Uppsala Univ, Dept Ecol & Evolut, S-75123 Uppsala, Sweden. : Wiley. - 0047-2425 .- 1537-2537. ; 36:3, s. 892-898
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Tidskriftsartikel (refereegranskat)abstract
- The influence of pre-extractant, extractant, and post-extractant on total extracted amounts of P and organic P compound groups measured with 31P nuclear magnetic resonance (31P-NMR) in lacustrine sediment was examined. The main extractants investigated were sodium hydroxide (NaOH) and sodium hydroxide ethylenediaminetetraacetic acid (NaOH-EDTA) with bicarbonate buffered dithionite (BD) or EDTA as pre-extractants. Post extractions were conducted using either NaOH or NaOH-EDTA, depending on the main extractant. Results showed that the most efficient combination of extractants for total P yield was NaOH with EDTA as pre-extractant, yielding almost 50% more than the second best procedure. The P compound groups varying the most between the different extraction procedures were polyphosphates and pyrophosphates. NaOH with BD as pre-extractant was the most efficient combination for these compound groups.
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7. |
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8. |
- Axen, A, et al.
(författare)
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One-pot synthesis of a 1,3,7,9-tetraazacyclododecane derivative and an investigation of its complexation properties
- 1998
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Ingår i: Journal of Chemical Research, Synopses. - : ROYAL SOC CHEMISTRY. ; :11, s. 712-713
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Tidskriftsartikel (refereegranskat)abstract
- A one-pot synthesis of a 1,3,7,9-tetraazacyclododecane macrocycle in 37% yield from inexpensive starting materials is described, and its complexation properties with metal cations are investigated.
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9. |
- Bergman, Jan, et al.
(författare)
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Synthesis and Reactions of Oxazolones from L‑Tryptophan and α‑Haloacetic Anhydrides
- 1992
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Ingår i: Bulletin des Sociétés chimiques belges. - : Wiley. - 0037-9646. ; 101:7, s. 643-660
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Tidskriftsartikel (refereegranskat)abstract
- Optically active 5(4H)-oxazolones have been synthesized from L-tryptophan and an excess of trifluoro-, trichloro-, and dichloroacetic anhydrides. Some of the 5(4H)-xazolones have been further transformed to the isomeric 5(2H)-oxazolones as well as oxazolones with exocyclic double bonds. Treatment of the various oxazolones under hydrolytic, acidic and Friedel-Crafts acylation conditions gave indole-3-pyruvic acid, alpha,beta-dehydrotryptophans, beta-carbolines as well as the functionalized cyclopentanoindole 32. Treatment of the 4-(3-indolylmethyl)-2-trifluoromethyl-5(2H)-oxazolone (17) with trifluoroacetic acid gave the 3,4-bridged azepinoindole 35.
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10. |
- Bergman, Jan, et al.
(författare)
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Synthesis of cyclopent[b]indolones
- 1990
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Ingår i: Tetrahedron. - 0040-4020 .- 1464-5416. ; 46:17, s. 6067-6084
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Tidskriftsartikel (refereegranskat)abstract
- A number of cyclopent[b]indol-1-ones as well as -3-ones have been synthesized, using a new methodology involving intramolecular ring closure of α,β-unsaturated acylindoles. In some cases 1,2,3,4-tetrahydrocarbazol-4-ones were obtained. This methodology was used in the syntheses of the indole alkaloid yuehchukene and the carbazole alkaloid analogue demethoxycarbazomycin B.
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11. |
- Berner, Simon, et al.
(författare)
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Activity boost of a biomimetic oxidation catalyst by immobilization onto a gold surface
- 2006
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 244:1, s. 86-91
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Tidskriftsartikel (refereegranskat)abstract
- Thiol-functionalized cobalt porphyrins were used as a model system for investigating catalytic activity in homogeneous and heterogeneous oxidation catalysis. Self-assemble monolayers of thiol-functionalized cobalt porphyrins were prepared on a gold surface and served as heterogenous catalysts. These immoblilized molecules prevented the strong inactivation observed for their homogeneous congener. As a result, the turnover number per molecule in heterogeneous catalysis was at least 100 times higher than that of the corresponding homogeneous catalyst. It is atypical for a heterogenized catalyst to outperform its homogeneous congener. The properties of the molecular layers were characterized on the molecular level by means of X-ray photoelectorn spectroscopy (XPS) and scanning tunneling microscopy (STM). The results demonstrate that the performance of these biomimetic catalysts can be dramatically improved if the catalyst arangement can be controlled on the molecular level.
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12. |
- Blom, Magnus, 1984-
(författare)
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Light-Triggered Conformational Switches for Modulation of Molecular Recognition : Applications for Peptidomimetics and Supramolecular Systems
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main focus of this thesis is on photochemical modulation of molecular recognition in various host-guest systems. This involves the design, synthesis and integration of light-triggered conformational switches into peptidomimetic guests and molecular tweezer hosts. The impact of the switches on guest and host structures has been assessed by spectroscopic and computational conformational analysis. Effects of photochemical structure modulation on molecular recognition in protein-ligand and supramolecular host-guest systems are discussed.Phototriggerable peptidomimetic inhibitors of the enzyme M. tuberculosis ribonucleotide reductase (RNR) were obtained by incorporation of a stilbene based amino acid moiety into oligopeptides between 3-9 residues long (Paper I). Interstrand hydrogen bond probability in the E and Z forms of the peptidomimetics was used as a tool for predicting conformational preferences. Considerable differences in inhibitory potency for the E and Z photoisomers were demonstrated in a binding assay.In order to advance the concept of photomodulable inhibitors, synthetic routes towards amino acid derivatives based on the more rigid stiff-stilbene chromophore were developed (Paper II). The effect of E-Z isomerization on the conformational properties of peptidomimetic inhibitors incorporating the stiff-stilbene chromophore was also assessed computationally (Paper III). It was indicated that inhibitors with the more rigid amino acid derivative should display larger conformational divergence between photoisomers than corresponding stilbene derivatives.Bisporphyrin tweezers with enediyne and stiff-stilbene spacers have been synthesized, and the conformational characteristics imposed by the spacers have been studied and compared to a glycoluril linked tweezer. The effects of spacers on tweezer binding of diamine guests and helicity induction by chiral guests have been investigated (Paper IV). Connections between spacer flexibility and host-guest binding strength have been established. The structural properties of the stiff-stilbene spaced tweezer made it particularly susceptible to helicity induction by both monotopic and bitopic chiral guests. Finally, the possibility of photochemical bite-size variation of tweezers with photoswitchable spacers has been assessed. Initial studies have shown that photoisomerization of the tweezers is possible without photochemical decomposition. Conformational analyses indicate that isomerization should impact binding characteristics of the tweezers to a significant extent (Paper V).
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13. |
- Blom, Magnus, et al.
(författare)
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Photomodulable bis-porphyrin molecular tweezers as dynamic host systems for diamine guests
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Bisporphyrin molecular tweezers with an enediyne (1) or a stiff stilbene (2) photoswitchable spacer are proposed as systems for modulation of bitopic binding to diamine guests via E/Z photoisomerization. The photoisomerization has been monitored by UV-Vis and 1H NMR spectroscopy and occurs without side reactions such as Bergman cyclization. Possible applications are rationalized in terms of competitive binding involving monoamine/diamine mixtures, and are supported by conformational analysis of the envisioned host-guest complexes. Binding dynamics for conformationally flexible guests show significantly different performance of aliphatic 1,w-diamine guests with varying N-N distance.
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14. |
- Blom, Magnus, et al.
(författare)
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Photoswitchable peptidomimetics with a stiff-stilbene chromophore for inhibition of Mycobacterium tuberculosis RNR
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Peptidomimetics incorporating two amino acids 1 and 2 with a stiff stilbene chromophore have been screened by a computational study and compared to a previously investigated analog 3 with stilbene chromophore. The effect of E-Z isomerization of the chromophores on the conformational properties of the petidomimetics was assessed via the frequency of hydrogen bonding between the two peptide strands attached to either side of the chromophore. Substantial differences between the three amino acids were thus indicated, in line with the anticipated effect of chromophore rigidity variation.
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15. |
- Blom, Magnus, 1984-, et al.
(författare)
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Synthesis and characterization of photoswitchable stiff-stilbene based amino acid derivatives
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Synthetic routes towards the Boc-protected amino acids 1 and 2 incorporating the stiff stilbene chromophore via the corresponding indanone carboxylic acids have been devised. Crucial steps are a reductive McMurry coupling of the indanone carboxylic acids, yielding stiff stilbene dicarboxylic acid esters. Hydrolysis to the monoester and conversion to the azides, followed by a Curtius rearrangement afforded the Boc-protected amino acid ester 1.
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16. |
- Blom, Magnus, 1984-, et al.
(författare)
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Synthesis and Properties of Bis-Porphyrin Molecular Tweezers : Effects of Spacer Flexibility on Binding and Supramolecular Chirogenesis
- 2016
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Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 21:1
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Ditopic binding of various dinitrogen compounds to three bisporphyrin molecular tweezers with spacers of varying conformational rigidity, incorporating the planar ene-diyne (1), the helical stiff stilbene (2), or the semirigid glycoluril motif fused to the porphyrins (3) are compared. Binding constants Ka = 10^4 to 10^6 M^-1 reveal subtle differences between these tweezers, that are discussed in terms of porphyrin dislocation modes. Exciton coupled circular dichroism (ECCD) of complexes with chiral dinitrogen guests provides experimental evidence for the conformational properties of the tweezers. The results are further supported and rationalized by conformational analysis.
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17. |
- Bäckvall, Jan-Erling, et al.
(författare)
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Evidence for (π-allyl)palladium(II)(quinone) complexes in the palladium-catalyzed 1,4-diacetoxylation of conjugated dienes
- 1988
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Ingår i: Tetrahedron Letters. - 0040-4039 .- 1359-8562. ; 29:18, s. 2243-2246
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Tidskriftsartikel (refereegranskat)abstract
- Evidence for a coordination of p-benzoquinone to palladium in [4-acetoxy-η3-(1,2,3)-cyclohexenyl]-palladium(II) complexes was provided by changes of the 1H NMR chemical shift values of the π-allyl protons and a decrease of the spin-lattice relaxation time constant for the p-benzoquinone protons. The intermediate (π-allyl)palladium(benzoquinone) complexes previously postulated in palladium-catalyzed 1,4-oxidations of 1,3-dienes were detected by NMR spectroscopy.
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18. |
- Bäckvall, Jan-Erling, et al.
(författare)
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Palladium‑Hydroquinone Catalysed Electrochemical 1,4‑Oxidation of Conjugated Dienes
- 1987
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Ingår i: Journal of the Chemical Society. Chemical communications. - 0022-4936. ; 16, s. 1236-1238
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Tidskriftsartikel (refereegranskat)abstract
- The mediator system palladium(II)–hydroquinone was shown to catalyse the anodic oxidation of cyclohexa-1,3-diene in acetic acid to produce selectively either trans- or cis-1,4-diacetoxycyclohex-2-ene (1) depending on the conditions.
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19. |
- Bäckvall, Jan-E., et al.
(författare)
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Stereocontrolled Lactonization Reactions via Palladium-Catalyzed 1,4-Addittion to Conjugated Dienes
- 1993
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 58:20, s. 5445-5451
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Tidskriftsartikel (refereegranskat)abstract
- Stereocontrolledp alladium(I1)-catalyzed1 ,4-chloro-and 1,4-acetoxylactonizations o f conjugated cyclic dienes have been developed to give stereodefined fused lactones. The stereochemistry of the 1,4- acetoxylactonization was controlled by the ligand on the metal catalyst, and in this way either a cisor truns-acetoxylactonization was obtained. This dual stereoselectivity is explained by a stereocontrolled acetate attack (trans or cis, respectively) on the allyl group in the catalytic (π-allyl)- palladium intermediate. To further strengthen the mechanism the intermediate (π-ally1)palladium complex was isolated and fully characterized. A stereospecific synthesis of cis- and truns-2-[6- (benzyloxy)-2,4-heptadien-l-yllacetic a cid (cis- and truns-9) followed by stereoselective Pd(I1)- catalyzed chloro- and acetoxylactonization in acetonelacetic acid resulted in highly functionalized fused lactones with control of the relative stereochemistry at four different carbons.
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20. |
- Bäckvall, Jan-Erling, et al.
(författare)
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Syntheses of (±)-α- and (±)- γ- Lycorane via a Stereocontrolled Organopalladium Route
- 1991
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 56:9, s. 2988-2993
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Tidskriftsartikel (refereegranskat)abstract
- Total syntheses of (+/-)-alpha-and (+/-)-gamma-lycorane are described. The key steps in the syntheses are the stereocontrolled palladium-catalyzed intramolecular 1,4-chloroamidation of 12 to 13 and the subsequent anti-stereoselective copper-catalyzed S(N)2' reaction of allylic chloride 13 with [3,4-(methylenedioxy)phenyl]magnesium bromide to give 14. Hexahydroindole 14 has the required relative stereochemistry between carbons 3a, 7, and 7a for alpha-lycorane (1a) and was transformed to the latter via 15 and 16. The epimeric gamma-lycorane (2) was obtained by performing the Bischler-Napieralski cyclization on 14, which led to a highly stereoselective isomerization to give exclusively 17. Compound 17 was subsequently transformed to 2. The overall yield from ester 8 to (+/-)-alpha- and (+/-)-gamma-lycorane was 40 and 36%, respectively.
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21. |
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22. |
- Chatterjee, Subhrangsu, 1978-
(författare)
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Physicochemical and Structural Aspects of Nucleic Acids
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis consists of seven research publications concerning (i) pKa studies of nucleobases in model nucleotides to understand why RNA duplexes are more stable than DNA duplexes (Paper I), (ii) the role of Me(T)-π interactions in the relative stability of DNA-RNA heteroduplexes (Paper II), (iii) pKa measurements in nucleotides with different 2′-substituents (paper III), (iv) a conformation study of constrained sugars and a pKa study of 1-thyminyl to reveal effect of sugar constraints on the pKa of the nucleobase (paper IV), (v) NMR and MD studies of 1′, 2′-oxetane constrained thymidine incorporated Dickerson Drew dodecamer (paper V), (vi) the sequence dependent pKa perturbation of 9-guaninyl moeity in single stranded (ss) DNA and RNA (paper VI), (vii) the non identical chemical nature of internucleotidic phosphates in (ss) RNA using 31P NMR (paper VI), and an alkaline hydrolysis study of phosphodiesters in ssRNAs (paper VII). The architecture of DNA and RNA molecules is determined by (a) hydrogen bonding (b) base stacking (c) a variety of additional non-covalent interactions. In paper (I) we showed that A-U and G-C base pairings in RNA are more stable than A-T and G-C base pairings in DNA by 4.3 and 1 kJ mol-1 respectively. Me(T)-π interaction plays a dominant role in the relative stability of DNA-RNA duplexes (paper II). In paper III and IV, we have shown that 1′ , 2′- oxetane and azetidine rings have strong inductive effect on pyrimidine bases, and that the H2′-sugar proton can be the marker to understand the pseudoaromaticity of pyrimidine bases, as well as increasing constraints in sugar reducing the basicity of nucleobases. A 1′, 2′-oxetane locked thymidine (T) moiety deforms the local structure of Dickerson-Drew dodecamer, d(CGCGAATTCGCG)2- investigated by High resolution NMR and MD study, as is discussed in the paper V. In papers VI and VII, we showed sequence context dependent pKa (N1) of 9-guaninyl perturbation in (ss) DNAs and RNAs and the non identical chemical nature of inter-nucleotidic phosphate groups in single stranded RNAs.
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23. |
- Emanuelsson, Rikard, et al.
(författare)
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Enthalpic versus Entropic Contribution to the Quinone Formal Potential in a Polypyrrole-Based Conducting Redox Polymer
- 2016
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:38, s. 21178-21183
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Tidskriftsartikel (refereegranskat)abstract
- A conducting redox polymer (CPR) based on pyrrole with a hydroquinone pendant group was synthesized through electropolymerization of the corresponding monomer. The formal potential (E-0') in aqueous solution at different pH as well as in MeCN containing equal amounts of pyridiniumtriflates and the corresponding free pyridine with different pK(a) was investigated. E-0' could be completely recovered in MeCN, and by utilizing pyridine bases with different donor acceptor strengths, a decrease of 61 meV/pK(a) was found that corresponded exactly to the pH dependence of E-0' in aqueous electrolyte. To separate the entropic and enthalpic contributions to E-0', temperature-dependent electrochemistry was performed. Two different modes of operation with changing pH/pK(a) between the two media were revealed. In MeCN, E-0' varies only because of the enthalpic contribution as the entropic contribution is unaffected by change in pKa. In water, there is primarily an entropic contribution to E-0' with changing pH due to solvation of the proton. The presented results are expected to open up for new design possibilities of CRPs based on ion coordinating redox groups for electrical energy storage.
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24. |
- Engdahl, Carin, et al.
(författare)
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Long‑Range Deuterium Isotope Effects on 13C NMR Shifts of Intramolecularly Hydrogen‑Bonded 9‑Hydroxyphenalen‑1‑ones
- 1991
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 29:1, s. 54-62
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Tidskriftsartikel (refereegranskat)abstract
- The 1H and 13C NMR spectra of 9-hydroxyphenalenone (1) and 9-hydroxy-2-methylphenalenone (2) have been completely assigned. Primary and secondary deuterium isotope effects were determined in three solvents (chloroform, acetone and dimethyl sulphoxide), including the effect of temperature on the secondary isotope effects. Both negative and large long-range secondary isotope effects were found for both 1 and 2. The average secondary isotope effects for corresponding carbons follow the same sign and magnitude pattern in both compounds.
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25. |
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26. |
- Erdélyi, Máté, et al.
(författare)
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Chemistry and folding of photomodulable peptides : stilbene and thioaurone-type candidates for conformational switches
- 2008
-
Ingår i: Organic and biomolecular chemistry. - : Royal Society of Chemistry (RSC). - 1477-0520 .- 1477-0539. ; 6:23, s. 4356-4373
-
Tidskriftsartikel (refereegranskat)abstract
- Optimized synthetic strategies for the preparation of photoswitchable molecular scaffolds based on stilbene or on thioaurone chromophores and their conformationally directing properties, as studied by computations and by NMR spectroscopy, are addressed. For the stilbene peptidomimetics 1, 2 and 3, the length of connecting linkers between the chromophore and the peptide strands was varied, resulting in photochromic dipeptidomimetics with various flexibility. Building blocks of higher rigidity, based on para-substituted thioaurone ( 4 and 6) and meta-substituted thioaurone chromophores ( 5 and 7) are shown to have a stronger conformationally directing effect. Design, synthesis, theoretical and experimental conformational analyses are presented.
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27. |
- Erdelyi, Mate, 1975, et al.
(författare)
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Chemistry and Folding of Photomodulable Peptides - Stilbene and Thioaurone-type Conformational Switches
- 2008
-
Ingår i: Organic & Biomolecular Chemistry. - 1477-0520. ; 6:23, s. 5346-4373
-
Tidskriftsartikel (refereegranskat)abstract
- Optimized synthetic strategies for the preparation of photoswitchable molecular scaffolds based on stilbene or on thioaurone chromophores and their conformationally directing properties, as studied by computations and by NMR spectroscopy, are addressed. For the stilbene peptidomimetics 1, 2 and 3, the length of connecting linkers between the chromophore and the peptide strands was varied, resulting in photochromic dipeptidomimetics with various flexibility. Building blocks of higher rigidity, based on para-substituted thioaurone (4 and 6) and meta-substituted thioaurone chromophores (5 and 7) are shown to have a stronger conformationally directing effect. Design, synthesis, theoretical and experimental conformational analyses are presented.
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28. |
- Erdélyi, Máté, et al.
(författare)
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Insight into beta-hairpin stability : a structural and thermodynamic study of diastereomeric beta-hairpin mimetics
- 2002
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Ingår i: New Journal of Chemistry. - 1144-0546 .- 1369-9261. ; 26, s. 834-843:26, s. 834-
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Tidskriftsartikel (refereegranskat)abstract
- Two diastereomers of a model β-hairpin peptide mimetic were synthesized and studied with a combination of experimental (NMR, X-ray, CD, MS, IR) and computational methods (Monte Carlo/molecular mechanics calculations). The secondary structure-stabilizing effects of hydrophobic interactions and hydrogen bonding were investigated. Comparison of the extent of folded hairpin population in non-competitive, polar aprotic, and polar protic solvents illustrates the critical role of intramolecular hydrogen bonding on hairpin stability. Investigation of 1H NMR melting curves of the diastereomeric compounds in a variety of solvents allowed an evaluation of the role of hydrophobic effects on secondary structure stabilization to be made.
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29. |
- Erdelyi, Mate, 1975, et al.
(författare)
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Insight into β -hairpin stability: a structural and thermodynamic study of diastereomeric β-hairpin mimetics
- 2002
-
Ingår i: New Journal of Chemistry. - 1369-9261 .- 1144-0546. ; 26, s. 834-843
-
Tidskriftsartikel (refereegranskat)abstract
- Two diastereomers of a model β-hairpin peptide mimetic were synthesized and studied with a combination of experimental (NMR, X-ray, CD, MS, IR) and computational methods (Monte Carlo/molecular mechanics calculations). The secondary structure-stabilizing effects of hydrophobic interactions and hydrogen bonding were investigated. Comparison of the extent of folded hairpin population in non-competitive, polar aprotic, and polar protic solvents illustrates the critical role of intramolecular hydrogen bonding on hairpin stability. Investigation of 1H NMR melting curves of the diastereomeric compounds in a variety of solvents allowed an evaluation of the role of hydrophobic effects on secondary structure stabilization to be made.
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30. |
- Erdelyi, Mate, 1975, et al.
(författare)
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Rapid Homogeneous-Phase Sonogashira Coupling Reactions Using Controlled Microwave Heating
- 2001
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Ingår i: J. Org. Chem.. - : American Chemical Society (ACS). ; 66:12, s. 4165-4169
-
Tidskriftsartikel (refereegranskat)abstract
- A microwave-enhanced, rapid and efficient homogeneous-phase version of the Sonogashira reaction is presented. It has been applied to the coupling of aryl iodides, bromides, triflates, and aryl chloride, as well as pyridine and thiophene derivatives with trimethylsilylacetylene. Excellent yields (80- 95%) for substrates containing a large variety of substituents in different positions are obtained in 5-25 min.
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31. |
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32. |
- Erdelyi, Mate, 1975, et al.
(författare)
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Rapid microwave-assisted solid phase peptide synthesis
- 2002
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Ingår i: Synthesis. - : Georg Thieme Verlag KG. ; 11, s. 1592-1596:11, s. 1592-1596
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Tidskriftsartikel (refereegranskat)abstract
- A microwave-assisted, rapid solid phase peptide synthesis procedure is presented. It has been applied to the coupling of sterically hindered Fmoc-protected amino acids yielding di- and tripeptides. Optimized conditions for a variety of coupling reagents are reported. Peptides were obtained rapidly (1.5-20 min) and without racemization
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33. |
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34. |
- Erdélyi, Máté, et al.
(författare)
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Rapid Microwave Promoted Sonogashira Coupling Reactions on Solid Phase
- 2003
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 68:16, s. 6431-6434
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Tidskriftsartikel (refereegranskat)abstract
- A microwave-enhanced, rapid, and efficient solidphase version of the Sonogashira reaction is presented. It has been applied to the coupling of aryl iodides and bromides with various acetylene derivatives giving excellent yields in 15 to 25 min. The scopes of homogeneous, solventless, and solid-phase conditions for Sonogashira coupling of aryl halides are compared.
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35. |
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36. |
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37. |
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38. |
- Erdélyi, Máté, 1975-
(författare)
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Towards the Development of Photoswitchable β-Hairpin Mimetics
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Peptide secondary structure mimetics are important tools in medicinal chemistry, as they provide analogues of endogeneous peptides with new physicochemical and pharmacological properties. The β-hairpin motif has been shown to be involved in numerous physiological processes, among others in regulation of eucariotic gene transcription. This thesis addresses the design, synthesis and conformational analysis of photoswitchable β-hairpin mimetics.The developmental work included the establishment of an improved procedure for cross coupling of aryl halides with terminal alkynes. Microwave mediated Sonogashira couplings in closed vessels were optimized under homogeneous and solid-phase conditions furnishing excellent yields for a large variety of substrates within 5 – 25 minutes. In addition, microwave heating was shown not to have any non-conventional effect on the reaction rate.Furthermore, the most important factors affecting β-hairpin stability were evaluated. Studies of tetrapeptide and decapeptide analogues revealed the essential role of the β-turn in initiation of hairpin folding. Moreover, hydrogen bonding was shown to be the main interchain stabilizing force, whereas hydrophobic interactions were found to be relatively weak. Nevertheless, hydrophobic packing appears to provide an important contribution to the thermodynamic stability of β-hairpins.Photoswitchable peptidomimetics were prepared by incorporation of various stilbene moieties into tetra- and decapeptides. Synthesis, photochemical isomerisation and spectroscopic conformational analysis of the compounds were performed.
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39. |
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40. |
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41. |
- Ezzaher, Salah, et al.
(författare)
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Directing protonation in [FeFe] hydrogenase active site models by modifications in their second coordination sphere
- 2010
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 46:31, s. 5775-5777
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Tidskriftsartikel (refereegranskat)abstract
- Subtle changes in the second coordination sphere of [Cl(2)bdtFe(2)-(CO)(4)(Ph2P-CH2-X-CH2-PPh2)] (bdt = benzene-1,2-dithiolate, X = NCH3, NCH2CF3, CH2) that do not influence the electronic character of the Fe-2 center can however direct protonation to three different sites: the N in the bis-phosphane, the Fe-Fe bond or the bdt-S.
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42. |
- Garg, Neeraj, et al.
(författare)
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Preparation of cis-5-methoxy-and-7-methoxy-1-acetoxy-1,2,3,4,4a,10a-hexahydro-9(10H)-phenanthrenone. An epoxide-arene reaction involving a selective 1,2-alkyl shift rearrangement
- 1996
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Ingår i: Tetrahedron. - 0040-4020 .- 1464-5416. ; 52:48, s. 15209-15224
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Tidskriftsartikel (refereegranskat)abstract
- The preparation of cis-1α-acetoxy-7-methoxy-1,2,3,4,4a,10a-hexahydro-9(10H)- phenanthrenone 5 was accomplished starting from 6-methoxy-1-tetralone. Reduction of 7-methoxy-1,2,3, 4,9,10-hexahydro-1-oxo-phenanthrene 8, acetylation and subsequent oxidation delivered 5. Application of an analogus procedure to the preparation of cis-1β-acetoxy-5-methoxy-1,2,3,4,,4a,10a-hexahydro-9(10H)- phenanthrenone 6 was not feasible. A more elaborate route was developed for the synthesis of compound 6, where an epoxide-arene reaction involving a 1,2-alkyl shift rearrangement, constituted a highly selective key transformation. The compounds 5 and 6 were prepared. A route was developed for the synthesis of compound 6, where an epoxide-arene reaction involving a 1,2-alkyl shift rearrangement, constituted a highly selective key transformation.
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43. |
- Georgsson, Jennie, et al.
(författare)
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Angiotensin II Pseudopeptides Containing 1,3,5-Trisubstituted Benzene Scaffolds with High AT2 Receptor Affinity
- 2005
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Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 48:21, s. 6620-6631
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Tidskriftsartikel (refereegranskat)abstract
- Two 1,3,5-trisubstituted aromatic scaffolds intended to serve as γ-turn mimetics have been synthesized and incorporated in five pseudopeptide analogues of angiotensin II (Asp-Arg-Val-Tyr-Ile-His-Pro-Phe), replacing Val-Tyr-Ile, Val-Tyr, or Tyr-Ile. All the tested compounds exhibited nanomolar affinity for the AT2 receptor with the best compound (3) having a Ki of 1.85 nM. Four pseudopeptides were AT2 selective, while one (5) also exhibited good affinity for the AT1 receptor (Ki = 30.3 nM). This pseudopeptide exerted full agonistic activity in an AT2 receptor induced neurite outgrowth assay but displayed no agonistic effect in an AT1 receptor functional assay. Molecular modeling, using the program DISCOtech, showed that the high-affinity ligands could interact similarly with the AT2 receptor as other ligands with high affinity for this receptor. A tentative agonist model is proposed for AT2 receptor activation by angiotensin II analogues. We conclude that the 1,3,5-trisubstituted benzene rings can be conveniently prepared and are suitable as γ-turn mimics.
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44. |
- Gogoll, Adolf, et al.
(författare)
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Alkylation and Convalent Adduct Formation of 2-Oxopurine
- 1993
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Ingår i: Heterocycles. - 0385-5414 .- 1881-0942. ; 36:2, s. 231-235
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Tidskriftsartikel (refereegranskat)abstract
- 2-Oxopurine reacted with benzyl bromide and ethanol to give the covalent adduct 1,3,7-tribenzyl-6-ethoxy-2-oxopurine, as well as dibenzylated products. Carbon-carbon bond formation was observed in the reaction between 2-oxopurine, dry silica gel, and benzyl bromide, giving rise to 6-hydroxy-1,3,8-tribenzyl-2-oxopurine.
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45. |
- Gogoll, Adolf, et al.
(författare)
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Chemical shift assignment of geminal protons in 3,7-diazabicyclo [3.3.1]nonanes : An unexpected deviation from the axial/equatorial chemical shift order
- 1997
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Ingår i: Magnetic Resonance in Chemistry. - : John Wiley & Sons. - 0749-1581 .- 1097-458X. ; 35:1, s. 13-20
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Tidskriftsartikel (refereegranskat)abstract
- The chemical shift order of axial and equatorial methylene protons in 1,5-disubstituted 3,7-diazabicyclo[3.3.1]nonan-9-ones may be altered by substituents in the 1,5-positions, but the corresponding alcohols behave differently. Unambiguous signal assignments for a series of the title compounds are provided, based on 3JCH coupling constants and on {1H} 13C heteronuclear Overhauser effects. Substituent anisotropy effects as a source of the chemical shift changes are discussed.
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46. |
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47. |
- Gogoll, Adolf, 1957-, et al.
(författare)
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Complete 1H and 13C NMR spectral assignment of venturicidin A by 2D NMR spectroscopy
- 1989
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 27:9, s. 863-871
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Tidskriftsartikel (refereegranskat)abstract
- After correlation of the majority of signals by COSY and one-bond heteronuclear correlation, the complete assignment of the 1H and 13C NMR spectra of the macrolide antibiotic venturicidin A required the application of long-range CH coupling information. This was accessible by the COLOC-S and selective INEPT experiments, and the sensitivity of these experiments is discussed. Steric information was obtained from a NOESY spectrum, and the solution structure compared with that in the crystal.
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48. |
- Gogoll, Adolf, et al.
(författare)
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Configurational Assignment of Acyclic (π-Allyl)Palladium Complexes : Analytical Application of Chelating Nitrogen Ligands
- 1995
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Ingår i: Organometallics. - : American Chemical Society (ACS). - 0276-7333 .- 1520-6041. ; 14:3, s. 1354-1364
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Tidskriftsartikel (refereegranskat)abstract
- A method for assignment of the relative stereochemistry in acyclic pi-allyl)palladium complexes by H-1 NMR H-H coupling constants has been developed. It is based on the introduction of nitrogen chelating ligands of the bipyridyl type into the complexes. The analytical suitability of several other types of nitrogen chelating ligands has also been investigated. A model for rationalization of the observed relation between stereochemistry and spectral parameters is proposed. Introduction of the chelating ligand also affects the syn,anti equilibrium of the complexes. Isomer ratios depend upon the relative stereochemistry of the side chain as well as on the chelating ligand.
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49. |
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50. |
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