The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform
Hendrik Luesch - One of the best experts on this subject based on the ideXlab platform.
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Tiglicamides A–C, cyclodepsipeptides from the marine cyanobacterium Lyngbya confervoides
2015Co-Authors: Susan Matthew, Valerie J Paul, Hendrik LueschAbstract:The Floridian marine cyanobacterium Lyngbya confervoides afforded three new cyclodepsipeptides, termed Tiglicamides A–C (1–3), along with their previously reported analogues largamides A–C (4– 6), all of which possess an unusual Tiglic Acid moiety. Their structures were deduced by one- and two-dimensional NMR combined with mass spectrometry and the absolute configurations established by chiral HPLC and Marfey’s analysis of the degradation products. Compounds 1–3 moderately inhibited porcine pancreatic elastase in vitro with IC50 values from 2.14 to 7.28 µM. Compounds 1–6 differ from each other by one amino Acid residue within the cyclic core structure, suggesting an unusually relaxed substrate specificity of the nonribosomal peptide synthetase that is the putative biosynthetic enzyme responsible for the corresponding amino Acid incorporation. Keywords Marine cyanobacteria; Lyngbya confervoides; cyclodepsipeptides; nonribosomal peptide synthesis; elastase inhibitors 1
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Tiglicamides a c cyclodepsipeptides from the marine cyanobacterium lyngbya confervoides
Phytochemistry, 2009Co-Authors: Susan Matthew, Valerie J Paul, Hendrik LueschAbstract:Abstract The Floridian marine cyanobacterium Lyngbya confervoides afforded cyclodepsipeptides, termed Tiglicamides A–C ( 1 – 3 ), along with their previously reported analogues largamides A–C ( 4 – 6 ), all of which possess an unusual Tiglic Acid moiety. Their structures were deduced by one- and two-dimensional NMR combined with mass spectrometry and the absolute configurations established by chiral HPLC and Marfey’s analysis of the degradation products. Compounds 1 – 3 moderately inhibited porcine pancreatic elastase in vitro with IC 50 values from 2.14 to 7.28 μM. Compounds 1 – 6 differ from each other by one amino Acid residue within the cyclic core structure, suggesting an unusually relaxed substrate specificity of the nonribosomal peptide synthetase that is the putative biosynthetic enzyme responsible for the corresponding amino Acid incorporation.
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largamides a c Tiglic Acid containing cyclodepsipeptides with elastase inhibitory activity from the marine cyanobacterium lyngbya confervoides
Planta Medica, 2009Co-Authors: Susan Matthew, Valerie J Paul, Hendrik LueschAbstract:Three unusual Tiglic Acid-containing cyclodepsipeptides, possessing the revised regioisomeric structures for largamides A - C (1-3), have been isolated from the marine cyanobacterium Lyngbya confervoides collected from southeastern Florida. The two-dimensional structures were determined by NMR spectroscopy and the absolute configurations by chiral HPLC analysis of degradation products. Compounds 1-3 are moderate inhibitors of mammalian elastase activity in vitro with IC 50 values ranging from 0.53 to 1.41 μM. Supporting information available online at http://www.thieme-connect.de/ejournals/toc/ plantamedica
Leroy Cronin - One of the best experts on this subject based on the ideXlab platform.
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embedding alkenes within an icosahedral inorganic fullerene nh4 42 mo132o372 l 30 h2o 72 for trapping volatile organics
Chemical Science, 2020Co-Authors: Robert Pow, Weimin Xuan, Deliang Long, Nicola L Bell, Leroy CroninAbstract:Eight alkene-functionalized molybdenum-based spherical Keplerate-type (inorganic fullerene) structures have been obtained via both direct and multistep synthetic approaches. Driven by the opportunity to design unique host–guest interactions within hydrophobic, π-electron rich confined environments, we have synthesised {(NH4)42[Mo132O372(L)30(H2O)72]}, where L = (1) acrylic Acid, (2) crotonic Acid, (3) methacrylic Acid, (4) Tiglic Acid, (5) 3-butenoic Acid, (6) 4-pentenoic Acid, (7) 5-hexenoic Acid, and (8) sorbic Acid. The compounds, which are obtained in good yield (10–40%), contain 30 carboxylate-coordinated alkene ligands which create a central cavity with hydrophobic character. Extensive Nuclear Magnetic Resonance (NMR) spectroscopy studies contribute significantly to the complete characterisation of the structures obtained, including both 1D and 2D measurements. In addition, single-crystal X-ray crystallography and subsequently-generated electron density maps are employed to highlight the distribution in ligand tail positions. These alkene-containing structures are shown to effectively encapsulate small alkyl thiols (1-propanethiol (A), 2-propanethiol (B), 1-butanethiol (C), 2-butanethiol (D) and 2-methyl-1-propanethiol (E)) as guests within the central cavity in aqueous solution. The hydrophobically driven clustering of up to 6 equivalents of volatile thiol guests within the central cavity of the Keplerate-type structure results in effective thermal protection, preventing evaporation at elevated temperatures (ΔT ≈ 25 K).
Susan Matthew - One of the best experts on this subject based on the ideXlab platform.
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Tiglicamides A–C, cyclodepsipeptides from the marine cyanobacterium Lyngbya confervoides
2015Co-Authors: Susan Matthew, Valerie J Paul, Hendrik LueschAbstract:The Floridian marine cyanobacterium Lyngbya confervoides afforded three new cyclodepsipeptides, termed Tiglicamides A–C (1–3), along with their previously reported analogues largamides A–C (4– 6), all of which possess an unusual Tiglic Acid moiety. Their structures were deduced by one- and two-dimensional NMR combined with mass spectrometry and the absolute configurations established by chiral HPLC and Marfey’s analysis of the degradation products. Compounds 1–3 moderately inhibited porcine pancreatic elastase in vitro with IC50 values from 2.14 to 7.28 µM. Compounds 1–6 differ from each other by one amino Acid residue within the cyclic core structure, suggesting an unusually relaxed substrate specificity of the nonribosomal peptide synthetase that is the putative biosynthetic enzyme responsible for the corresponding amino Acid incorporation. Keywords Marine cyanobacteria; Lyngbya confervoides; cyclodepsipeptides; nonribosomal peptide synthesis; elastase inhibitors 1
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Tiglicamides a c cyclodepsipeptides from the marine cyanobacterium lyngbya confervoides
Phytochemistry, 2009Co-Authors: Susan Matthew, Valerie J Paul, Hendrik LueschAbstract:Abstract The Floridian marine cyanobacterium Lyngbya confervoides afforded cyclodepsipeptides, termed Tiglicamides A–C ( 1 – 3 ), along with their previously reported analogues largamides A–C ( 4 – 6 ), all of which possess an unusual Tiglic Acid moiety. Their structures were deduced by one- and two-dimensional NMR combined with mass spectrometry and the absolute configurations established by chiral HPLC and Marfey’s analysis of the degradation products. Compounds 1 – 3 moderately inhibited porcine pancreatic elastase in vitro with IC 50 values from 2.14 to 7.28 μM. Compounds 1 – 6 differ from each other by one amino Acid residue within the cyclic core structure, suggesting an unusually relaxed substrate specificity of the nonribosomal peptide synthetase that is the putative biosynthetic enzyme responsible for the corresponding amino Acid incorporation.
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largamides a c Tiglic Acid containing cyclodepsipeptides with elastase inhibitory activity from the marine cyanobacterium lyngbya confervoides
Planta Medica, 2009Co-Authors: Susan Matthew, Valerie J Paul, Hendrik LueschAbstract:Three unusual Tiglic Acid-containing cyclodepsipeptides, possessing the revised regioisomeric structures for largamides A - C (1-3), have been isolated from the marine cyanobacterium Lyngbya confervoides collected from southeastern Florida. The two-dimensional structures were determined by NMR spectroscopy and the absolute configurations by chiral HPLC analysis of degradation products. Compounds 1-3 are moderate inhibitors of mammalian elastase activity in vitro with IC 50 values ranging from 0.53 to 1.41 μM. Supporting information available online at http://www.thieme-connect.de/ejournals/toc/ plantamedica
Alfons Baiker - One of the best experts on this subject based on the ideXlab platform.
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ftir study of chiral modifier reactant interactions the cinchonidine alkenoic Acid system
Journal of The Chemical Society-perkin Transactions 1, 2002Co-Authors: Davide Ferri, Thomas Burgi, Alfons BaikerAbstract:Cyclic cinchonidine ∶ Acid complexes (1 ∶ 1 and 1 ∶ 2) of the chiral modifier cinchonidine (CD) and an alkenoic Acid, Tiglic Acid, in dichloromethane solvent have been observed by FTIR spectroscopy. Both the OH and the quinuclidine N atom of CD are involved in the hydrogen bond with the Acid molecule(s). Such dual-site modifier–reactant interactions play an important role in the enantioselective hydrogenation of alkenoic Acids over CD-modified Pd catalysts. The stability of these 1 ∶ 1 and 1 ∶ 2 complexes has been probed by addition of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), a stronger base than CD. DBU builds ion pairs with the Acid (with 1 ∶ 1 and 1 ∶ 2 stoichiometry) and a hydrogen bond with the OH of CD. However, despite the large difference in basicity between CD and DBU, 1 ∶ 2 CD ∶ Acid complexes can still be detected when more than 0.5 equivalent DBU was added with respect to the Acid, at which ratio the enantiomeric excess (ee) drops dramatically. Hence, the molecular structure of CD favours formation of cyclic complexes via a dual-site interaction, which is not possible for DBU ∶ Acid complexes, and stabilises 1 ∶ 2 CD ∶ Acid species, which are proposed to be responsible for enantiodifferentiation.
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enantioselective hydrogenation of α β unsaturated carboxylic Acids over cinchonidine modified palladium nature of modifier reactant interaction
Journal of Catalysis, 1999Co-Authors: K Borszeky, Thomas Burgi, T Mallat, Z Zhaohui, Alfons BaikerAbstract:The mechanism of enantiodifferentiation in the hydrogenation of alkenoic Acids over cinchona-modified Pd has been investigated using the Tiglic Acid → 2-methyl-butanoic Acid transformation as test reaction. Application of simple derivatives of cinchonidine, modified at the (C-9)–OH and/or the quinuclidine nitrogen, proved that both functional groups are involved in the enantiodiscriminating step. Addition of a strong base (1,8-diazabicyclo[5.4.0]undec-7-ene, DBU) to Tiglic Acid prior to hydrogenation revealed that one cinchonidine molecule interacts with a dimer of Tiglic Acid on the metal surface. Ab initio calculations corroborate the existence of an energetically favored Acid dimer–cinchonidine intermediate stabilized by hydrogen bonding, involving both the OH and the quinuclidine nitrogen of cinchonidine.
Waldemar Adam - One of the best experts on this subject based on the ideXlab platform.
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diastereoselective reactions of the Tiglic Acid functionality mediated by oxazolidine chiral auxiliaries a mechanistic comparison of dmd andm cpba epoxidations versus singlet oxygen and ptad ene reactions
European Journal of Organic Chemistry, 2005Co-Authors: Aurelia Pastor, Waldemar Adam, Thomas Wirth, Gabor TothAbstract:2,2-Dimethyloxazolidines have been utilized as chiral auxiliaries for the diastereoselective functionalization of the optically active Tiglic Acid derivatives (S)-1 by means of epoxidation with DMD or m-CPBA and ene reactions with 1O2 or PTAD. In the DMD and m-CPBA epoxidations, high diastereoselectivities but opposite senses of diastereomer selection were observed. In contrast, the stereochemistry of the 1O2 and PTAD ene reactions depended on the size of the attacking enophile: whereas essentially perfect diastereoselectivity was obtained with PTAD, much lower stereoselection was observed with 1O2. The stereochemical results for the DMD and m-CPBA epoxidations and the PTAD ene reaction are explained in terms of the energy differences for the corresponding diastereomeric transition states, dictated by steric and electronic effects. The PTAD ene reaction for these Tiglic Acids (S)-1 provides, after removal of the chiral auxiliaries, an attractive synthetic route for optically active β-amino Acid derivatives.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
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efficient pi facial control in the ene reaction of nitrosoarene triazolinedione and singlet oxygen with Tiglic amides of the bornane derived sultam as chiral auxiliary an economical synthesis of enantiomerically pure nitrogen and oxygen functionalized acrylic Acid derivatives
Journal of the American Chemical Society, 2002Co-Authors: Waldemar Adam, Oliver Krebs, Hansgeorg Degen, Chantu R SahamollerAbstract:The ene reaction of 4-nitronitrosobenzene (ArNO), N-phenyl-1,2,4-triazoline-3,5-dione (PTAD), and singlet oxygen (1O2) with the optically active Tiglic-Acid derivatives of Oppolzer's bornane-derived sultam affords the respective ene products regioselectively in excellent diastereoselectivity (de up to 99%) and in good yield (55-90%). The enophiles ArNO and PTAD give with the methyl-substituted substrate exclusively the like-configured ene adduct, while 1O2 leads to an 83:17 diastereomeric mixture. With the sterically more demanding isopropyl-substituted derivative even the smallest enophile 1O2 forms exclusively the like diastereomer. The high diastereoselectivity is rationalized in terms of the proper conformational alignment of the substrate and a preferred enophilic attack from the C(beta)-re face of the double bond. This concept offers an efficient synthetic route to enantiomerically pure nitrogen- and oxygen-functionalized acrylic Acid derivatives.
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Efficient π-facial control in the ene reaction of nitrosoarene, triazolinedione, and singlet oxygen with Tiglic amides of the bornane-derived sultam as chiral auxiliary: An economical synthesis of enantiomerically pure nitrogen- and oxygen-functionalized acrylic Acid derivatives
Journal of the American Chemical Society, 2002Co-Authors: Waldemar Adam, Hans‐georg Degen, Oliver Krebs, Chantu R. Saha-möllerAbstract:The ene reaction of 4-nitronitrosobenzene (ArNO), N-phenyl-1,2,4-triazoline-3,5-dione (PTAD), and singlet oxygen (1O2) with the optically active Tiglic-Acid derivatives of Oppolzer's bornane-derived sultam affords the respective ene products regioselectively in excellent diastereoselectivity (de up to 99%) and in good yield (55−90%). The enophiles ArNO and PTAD give with the methyl-substituted substrate exclusively the like-configured ene adduct, while 1O2 leads to an 83:17 diastereomeric mixture. With the sterically more demanding isopropyl-substituted derivative even the smallest enophile 1O2 forms exclusively the like diastereomer. The high diastereoselectivity is rationalized in terms of the proper conformational alignment of the substrate and a preferred enophilic attack from the C(β)-re face of the double bond. This concept offers an efficient synthetic route to enantiomerically pure nitrogen- and oxygen-functionalized acrylic Acid derivatives.