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Search for "CD-spectroscopy" in Full Text gives 57 result(s) in Beilstein Journal of Organic Chemistry.
Investigation of the network of preferred interactions in an artificial coiled-coil association using the peptide array technique
- Raheleh Rezaei Araghi,
- Carsten C. Mahrenholz,
- Rudolf Volkmer and
- Beate Koksch
Beilstein J. Org. Chem. 2012, 8, 640–649, doi:10.3762/bjoc.8.71
- on a C-8 column (Phenomenex® Luna C8, 10 μM, 250 mm × 21.2 mm). The identities of peptides were confirmed using an ESI–TOF instrument. Circular-dichroism (CD) spectroscopy [18]: Peptide samples were analyzed in 10 mM phosphate buffer (pH 7.4). Far-ultraviolet circular-dichroism spectra and GndHCl
Graphical Abstract
Figure 1: (a) Helical wheel representation of the tetrameric Acid-pp/B3β2γ helix bundle, (b) sequences of Aci...
Figure 2: (a) Sequence for random mutation resulting in 1764 spots. The randomized positions are denoted by Xa...
Figure 3: Glycine scanning of Acid-pp sequences. The substituted glycines are highlighted in red. Each sequen...
Figure 4: Heat-map diagrams depicting the quantitatively measured SIs for Acid-pp sequences containing mutati...
Figure 5: (a) The complete sequences of the selected α-mutants. (b) CD and (c) thermal denaturation spectra o...
Figure 6: Size-exclusion chromatograms of equimolar mixtures of B3β2γ with (a) Acid-pp, (b) VaVdEeEg, (c) LaLd...
Conserved and species-specific oxylipin pathways in the wound-activated chemical defense of the noninvasive red alga Gracilaria chilensis and the invasive Gracilaria vermiculophylla
- Martin Rempt,
- Florian Weinberger,
- Katharina Grosser and
- Georg Pohnert
Beilstein J. Org. Chem. 2012, 8, 283–289, doi:10.3762/bjoc.8.30
- comparison of the obtained NMR and MS spectra by co-injection with authentic standards [3]. Stereochemistry of PGE2 was verified with CD spectroscopy in comparison with an authentic standard. Spectroscopic data of 5. 5-((1E,3E,5E,7Z,10Z)-hexadeca-1,3,5,7,10-pentaenyl)dihydrofuran-2(3H)-one (5) was obtained
Graphical Abstract
Figure 1: UPLC–ESIMS-based metabolic profiles of Gracilaria vermiculophylla (A) and Gracilaria chilensis (B) ...
Scheme 1: 5-((1E,3,5E,7Z,10Z)-hexadeca-1,3,5,7,10-pentaenyl)dihydrofuran-2(3H)-one (5) with 1H–1H COSY (bold ...
Scheme 2: Suggested pathway for the biosynthesis of 5.
Figure 2: Relative risk (mean ± 95% confidence interval) of Echinolittorina peruviana attachment on surfaces ...
Gelation or molecular recognition; is the bis-(α,β-dihydroxy ester)s motif an omnigelator?
- Peter C. Griffiths,
- David W. Knight,
- Ian R. Morgan,
- Amy Ford,
- James Brown,
- Ben Davies,
- Richard K. Heenan,
- Stephen M. King,
- Robert M. Dalgliesh,
- John Tomkinson,
- Stuart Prescott,
- Ralf Schweins and
- Alison Paul
Beilstein J. Org. Chem. 2010, 6, 1079–1088, doi:10.3762/bjoc.6.123
- , m = 4, indicating a rather rigid structure, with a Gaussian cross-section of 25–40 Å depending on gelator concentration and structure. The rodlike segments were typically hundreds of Å in length, suggesting a stacked geometry that was later confirmed with CD spectroscopy. With an increase in
Graphical Abstract
Figure 1: Schröder–van Laar analysis for the melting of toluene (open symbols) and ethanol/water (filled symb...
Figure 2: SANS from 50 mg ml−1 G6 in a range of solvents, 25 °C; d-acetone (circles), d-chloroform (triangles...
Figure 3: SANS from G6 25 °C in d-toluene as a function of G6 concentration; 5 mg ml−1 (circles), 10 mg ml−1 ...
Figure 4: SANS from a series of homologous gelators, G5 (circles), G6 (squares) and G8 (triangles) in d-tolue...
Figure 5: SANS from 50 mg ml−1 G6 in d-toluene, 25 °C; hydrogenous gelator (empty symbols) and partially deut...
Figure 6: SANS from 35 mg ml−1 G6 in 75% d-ethanol/25% D2O, 37 °C; hydrogenous gelator (empty symbols) and pa...
Figure 7: SESANS data for 50 mg ml−1 G6 in deuterated toluene, 25 °C.
Figure 8: Inelastic neutron spectroscopy from toluene gels (upper Figure): red deuterated toluene/hydrogenous...
Figure 9: Inelastic neutron spectroscopy from cyclohexane gels (upper Figure): red deuterated cyclohexane/hyd...
Scheme 1: Synthesis of hydrogenous gelators.
Scheme 2: Structure of partially deuterated gelators.
Oxalyl retro-peptide gelators. Synthesis, gelation properties and stereochemical effects
- Janja Makarević,
- Milan Jokić,
- Leo Frkanec,
- Vesna Čaplar,
- Nataša Šijaković Vujičić and
- Mladen Žinić
Beilstein J. Org. Chem. 2010, 6, 945–959, doi:10.3762/bjoc.6.106
- interactions of enantiomers that lead to diasteromeric assemblies with a certain level of organization. FTIR, 1H NMR and CD investigations To identify supramolecular interactions that stabilize gel assemblies, the selected gels were studied by 1H NMR, FTIR and CD spectroscopy. Valuable information on the self
Graphical Abstract
Scheme 1: Oxalyl retro-dipetide gelators; each b to a, (a) LiOH/MeOH, H2O; (b) H+; each b to c: (c) NH3/MeOH.
Figure 1: Chiral bis(amino acid)-(I) and bis(amino alcohol)-(II)-oxalamide gelators.
Figure 2: TEM images (PWK staining) of: (S,S)-1a H2O/DMSO gel.
Figure 3: TEM images (PWK staining) of: (S,R)-1a H2O/DMSO gel.
Figure 4: TEM images (PWK staining) of: (S,R)-1b toluene gel showing the presence of short tape like aggregat...
Figure 5: The concentration dependence of NH and C*H chemical shifts in (S,R)-1b toluene-d8 gel samples (conc...
Figure 6: The concentration dependence of NH and C*H chemical shifts in (S,S)-1b and its racemate (S,S)-1b/(R...
Figure 7: Temperature dependence of: a) oxalamide NH protons (▲), Leu-NH protons (Δ) and b) oxalamide-α-Leu-C...
Figure 8: Temperature dependent CD spectra of: a) (S,R)-1b decalin gel (c = 3.4·10−2 M); b) (S,S)-1b decalin ...
Figure 9: X-ray powder diffractograms of (a) (S,R)-1b and (b) (S,S)-1b xerogels prepared from their toluene g...
Figure 10: (a) Fully minimized the lowest energy conformations of (S,S)-1b (top) and (S,R)-1b generated by sys...
Figure 11: Schematic presentation of the proposed (S,S)-1b and (S,R)-1b basic packing model based on XRPD, 1H ...
Figure 12: X-ray powder diffraction (XRPD) diagram of (S,R)-1a water/DMSO xerogel.
Molecular recognition of organic ammonium ions in solution using synthetic receptors
- Andreas Späth and
- Burkhard König
Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32
Graphical Abstract
Figure 1: Biologically important amines and quaternary ammonium salts: histamine (1), dopamine (2) and acetyl...
Figure 2: Crown ether 18-crown-6.
Figure 3: Conformations of 18-crown-6 (4) in solvents of different polarity.
Figure 4: Binding topologies of the ammonium ion depending on the crown ring size.
Figure 5: A “pseudorotaxane” structure consisting of 24-crown-8 and a secondary ammonium ion (5); R = Ph.
Figure 6: Typical examples of azacrown ethers, cryptands and related aza macrocycles.
Figure 7: Binding of ammonium to azacrown ethers and cryptands [111-113].
Figure 8: A 19-crown-6-ether with decalino blocking groups (11) and a thiazole-dibenzo-18-crown-6-ether (12).
Figure 9: 1,3-Bis(6-oxopyridazin-1-yl)propane derivatives 13 and 14 by Campayo et al.
Figure 10: Fluorescent azacrown-PET-sensors based on coumarin.
Figure 11: Two different pyridino-cryptands (17 and 18) compared to a pyridino-crown (19); chiral ammonium ion...
Figure 12: Pyridino-18-crown-6 ligand (21), a similar acridino-18-crown-6 ligand (22) and a structurally relat...
Figure 13: Ciral pyridine-azacrown ether receptors 24.
Figure 14: Chiral 15-crown-5 receptors 26 and an analogue 18-crown-6 ligand 27 derived from amino alcohols.
Figure 15: C2-symmetric chiral 18-crown-6 amino alcohol derivatives 28 and related macrocycles.
Figure 16: Macrocycles with diamide-diester groups (30).
Figure 17: C2-symmetric chiral aza-18-crown-6 ethers (31) with phenethylamine residues.
Figure 18: Chiral C-pivot p-methoxy-phenoxy-lariat ethers.
Figure 19: Chiral lariat crown ether 34.
Figure 20: Sucrose-based chiral crown ether receptors 36.
Figure 21: Permethylated fructooligosaccharide 37 showing induced-fit chiral recognition.
Figure 22: Biphenanthryl-18-crown-6 derivative 38.
Figure 23: Chiral lariat crown ethers derived from binol by Fuji et al.
Figure 24: Chiral phenolic crown ether 41 with “aryl chiral barriers” and guest amines.
Figure 25: Chiral bis-crown receptor 43 with a meso-ternaphthalene backbone.
Figure 26: Chromogenic pH-dependent bis-crown chemosensor 44 for diamines.
Figure 27: Triamine guests for binding to receptor 44.
Figure 28: Chiral bis-crown phenolphthalein chemosensors 46.
Figure 29: Crown ether amino acid 47.
Figure 30: Luminescent receptor 48 for bis-alkylammonium guests.
Figure 31: Luminescent CEAA (49a), a bis-CEAA receptor for amino acids (49b) and the structure of lysine bindi...
Figure 32: Luminescent CEAA tripeptide for binding small peptides.
Figure 33: Bis crown ether 51a self assembles co-operatively with C60-ammonium ion 51b.
Figure 34: Triptycene-based macrotricyclic dibenzo-[24]-crown-8 ether host 52 and guests.
Figure 35: Copper imido diacetic acid azacrown receptor 53a and the suggested His-Lys binding motif; a copper ...
Figure 36: Urea (54) and thiourea (55) benzo crown receptor for transport and extraction of amino acids.
Figure 37: Crown pyryliums ion receptors 56 for amino acids.
Figure 38: Ditopic sulfonamide bridged crown ether receptor 57.
Figure 39: Luminescent peptide receptor 58.
Figure 40: Luminescent receptor 59 for the detection of D-glucosamine hydrochloride in water/ethanol and lumin...
Figure 41: Guanidinium azacrown receptor 61 for simple amino acids and ditopic receptor 62 with crown ether an...
Figure 42: Chiral bicyclic guanidinium azacrown receptor 63 and similar receptor 64 for the enantioselective t...
Figure 43: Receptors for zwitterionic species based on luminescent CEAAs.
Figure 44: 1,10-Azacrown ethers with sugar podand arms and the anticancer agent busulfan.
Figure 45: Benzo-18-crown-6 modified β-cyclodextrin 69 and β-cyclodextrin functionalized with diaza-18-crown-6...
Figure 46: Receptors for colorimetric detection of primary and secondary ammonium ions.
Figure 47: Porphyrine-crown-receptors 72.
Figure 48: Porphyrin-crown ether conjugate 73 and fullerene-ammonium ion guest 74.
Figure 49: Calix[4]arene (75a), homooxocalix[4]arene (75b) and resorcin[4]arene (75c) compared (R = H, alkyl c...
Figure 50: Calix[4]arene and ammonium ion guest (R = H, alkyl, OAcyl etc.), possible binding sites; A: co-ordi...
Figure 51: Typical guests for studies with calixarenes and related molecules.
Figure 52: Lower rim modified p-tert-butylcalix[5]arenes 82.
Figure 53: The first example of a water soluble calixarene.
Figure 54: Sulfonated water soluble calix[n]arenes that bind ammonium ions.
Figure 55: Displacement assay for acetylcholine (3) with a sulfonato-calix[6]arene (84b).
Figure 56: Amino acid inclusion in p-sulfonatocalix[4]arene (84a).
Figure 57: Calixarene receptor family 86 with upper and lower rim functionalization.
Figure 58: Calix[6]arenes 87 with one carboxylic acid functionality.
Figure 59: Sulfonated calix[n]arenes with mono-substitution at the lower rim systematically studied on their r...
Figure 60: Cyclotetrachromotropylene host (91) and its binding to lysine (81c).
Figure 61: Calixarenes 92 and 93 with phosphonic acids groups.
Figure 62: Calix[4]arene tetraphosphonic acid (94a) and a double bridged analogue (94b).
Figure 63: Calix[4]arene tetraphosphonic acid ester (92c) for surface recognition experiments.
Figure 64: Calixarene receptors 95 with α-aminophosphonate groups.
Figure 65: A bridged homocalix[3]arene 95 and a distally bridged homocalix[4]crown 96.
Figure 66: Homocalix[3]arene ammonium ion receptor 97a and the Reichardt’s dye (97b) for colorimetric assays.
Figure 67: Chromogenic diazo-bridged calix[4]arene 98.
Figure 68: Calixarene receptor 99 by Huang et al.
Figure 69: Calixarenes 100 reported by Parisi et al.
Figure 70: Guest molecules for inclusion in calixarenes 100: DAP × 2 HCl (101a), APA (101b) and Lys-OMe × 2 HC...
Figure 71: Different N-linked peptido-calixarenes open and with glycol chain bridges.
Figure 72: (S)-1,1′-Bi-2-naphthol calixarene derivative 104 published by Kubo et al.
Figure 73: A chiral ammonium-ion receptor 105 based on the calix[4]arene skeleton.
Figure 74: R-/S-phenylalaninol functionalized calix[6]arenes 106a and 106b.
Figure 75: Capped homocalix[3]arene ammonium ion receptor 107.
Figure 76: Two C3 symmetric capped calix[6]arenes 108 and 109.
Figure 77: Phosphorous-containing rigidified calix[6]arene 110.
Figure 78: Calix[6]azacryptand 111.
Figure 79: Further substituted calix[6]azacryptands 112.
Figure 80: Resorcin[4]arene (75c) and the cavitands (113).
Figure 81: Tetrasulfonatomethylcalix[4]resorcinarene (114).
Figure 82: Resorcin[4]arenes (115a/b) and pyrogallo[4]arenes (115c, 116).
Figure 83: Displacement assay for acetylcholine (3) with tetracyanoresorcin[4]arene (117).
Figure 84: Tetramethoxy resorcinarene mono-crown-5 (118).
Figure 85: Components of a resorcinarene based displacement assay for ammonium ions.
Figure 86: Chiral basket resorcin[4]arenas 121.
Figure 87: Resorcinarenes with deeper cavitand structure (122).
Figure 88: Resorcinarene with partially open deeper cavitand structure (123).
Figure 89: Water-stabilized deep cavitands with partially structure (124, 125).
Figure 90: Charged cavitands 126 for tetralkylammonium ions.
Figure 91: Ditopic calix[4]arene receptor 127 capped with glycol chains.
Figure 92: A calix[5]arene dimer for diammonium salt recognition.
Figure 93: Calixarene parts 92c and 129 for the formation molecular capsules.
Figure 94: Encapsulation of a quaternary ammonium cation by two resorcin[4]arene molecules (NMe4+@[75c]2 × Cl−...
Figure 95: Encapsulation of a quaternary ammonium cation by six resorcin[4]arene molecules (NMe3D+@[130]6 × Cl−...
Figure 96: Structure and schematic of cucurbit[6]uril (CB[6], 131a).
Figure 97: Cyclohexanocucurbit[6]uril (CB′[6], 132) and the guest molecule spermine (133).
Figure 98: α,α,δ,δ-Tetramethylcucurbit[6]uril (134).
Figure 99: Structure of the cucurbituril-phthalhydrazide analogue 135.
Figure 100: Organic cavities for the displacement assay for amine differentiation.
Figure 101: Displacement assay methodology for diammonium- and related guests involving cucurbiturils and some ...
Figure 102: Nor-seco-Cucurbituril (±)-bis-ns-CB[6] (140) and guest molecules.
Figure 103: The cucurbit[6]uril based complexes 141 for chiral discrimination.
Figure 104: Cucurbit[7]uril (131c) and its ferrocene guests (142) opposed.
Figure 105: Cucurbit[7]uril (131c) guest inclusion and representative guests.
Figure 106: Cucurbit[7]uril (131c) binding to succinylcholine (145) and different bis-ammonium and bis-phosphon...
Figure 107: Paraquat-cucurbit[8]uril complex 149.
Figure 108: Gluconuril-based ammonium receptors 150.
Figure 109: Examples of clefts (151a), tweezers (151b, 151c, 151d) and clips (151e).
Figure 110: Kemp’s triacid (152a), on example of Rebek’s receptors (152b) and guests.
Figure 111: Amino acid receptor (154) by Rebek et al.
Figure 112: Hexagonal lattice designed hosts by Bell et al.
Figure 113: Bell’s amidinium receptor (156) and the amidinium ion (157).
Figure 114: Aromatic phosphonic acids.
Figure 115: Xylene phosphonates 159 and 160a/b for recognition of amines and amino alcohols.
Figure 116: Bisphosphonate recognition motif 161 for a colorimetric assay with alizarin complexone (163) for ca...
Figure 117: Bisphosphonate/phosphate clip 164 and bisphosphonate cleft 165.
Figure 118: N-Methylpyrazine 166a, N-methylnicotinamide iodide (166b) and NAD+ (166c).
Figure 119: Bisphosphate cavitands.
Figure 120: Bisphosphonate 167 of Schrader and Finocchiaro.
Figure 121: Tweezer 168 for noradrenaline (80b).
Figure 122: Different tripods and heparin (170).
Figure 123: Squaramide based receptors 172.
Figure 124: Cage like NH4+ receptor 173 of Kim et al.
Figure 125: Ammonium receptors 174 of Chin et al.
Figure 126: 2-Oxazolin-based ammonium receptors 175a–d and 176 by Ahn et al.
Figure 127: Racemic guest molecules 177.
Figure 128: Tripods based on a imidazole containing macrocycle (178) and the guest molecules employed in the st...
Figure 129: Ammonium ion receptor 180.
Figure 130: Tetraoxa[3.3.3.3]paracyclophanes 181 and a cyclophanic tetraester (182).
Figure 131: Peptidic bridged paraquat-cyclophane.
Figure 132: Shape-selective noradrenaline host.
Figure 133: Receptor 185 for binding of noradrenaline on surface layers from Schrader et al.
Figure 134: Tetraphosphonate receptor for binding of noradrenaline.
Figure 135: Tetraphosphonate 187 of Schrader and Finocchiaro.
Figure 136: Zinc-Porphyrin ammonium-ion receptors 188 and 189 of Mizutani et al.
Figure 137: Zinc porphyrin receptor 190.
Figure 138: Zinc porphyrin receptors 191 capable of amino acid binding.
Figure 139: Zinc-porphyrins with amino acid side chains for stereoinduction.
Figure 140: Bis-zinc-bis-porphyrin based on Tröger’s base 193.
Figure 141: BINAP-zinc-prophyrin derivative 194 and it’s guests.
Figure 142: Bisaryl-linked-zinc-porphyrin receptors.
Figure 143: Bis-zinc-porphyrin 199 for diamine recognition and guests.
Figure 144: Bis-zinc-porphyrin crown ether 201.
Figure 145: Bis-zinc-porphyrin 202 for stereodiscrimination (L = large substituent; S = small substituent).
Figure 146: Bis-zinc-porphyrin[3]rotaxane and its copper complex and guests.
Figure 147: Dien-bipyridyl ligand 206 for co-ordination of two metal atoms.
Figure 148: The ligand and corresponding tetradentate co-complex 207 serving as enantioselective receptor for a...
Figure 149: Bis(oxazoline)–copper(II) complex 208 for the recognition of amino acids in aqueous solution.
Figure 150: Zinc-salen-complexes 209 for the recognition tertiary amines.
Figure 151: Bis(oxazoline)–copper(II) 211 for the recognition of amino acids in aqueous solution.
Figure 152: Zn(II)-complex of a C2 terpyridine crown ether.
Figure 153: Displacement assay and receptor for aspartate over glutamate.
Figure 154: Chiral complex 214 for a colorimetric displacement assay for amino acids.
Figure 155: Metal complex receptor 215 with tripeptide side arms.
Figure 156: A sandwich complex 216 and its displaceable dye 217.
Figure 157: Lanthanide complexes 218–220 for amino acid recognition.
Figure 158: Nonactin (221), valinomycin (222) and vancomycin (223).
Figure 159: Monesin (224a) and a chiral analogue for enantiodiscrimination of ammonium guests (224b).
Figure 160: Chiral podands (226) compared to pentaglyme-dimethylether (225) and 18-crown-6 (4).
Figure 161: Lasalocid A (228).
Figure 162: Lasalocid derivatives (230) of Sessler et al.
Figure 163: The Coporphyrin I tetraanion (231).
Figure 164: Linear and cyclic peptides for ammonium ion recognition.
Figure 165: Cyclic and bicyclic depsipeptides for ammonium ion recognition.
Figure 166: α-Cyclodextrin (136a) and novocaine (236).
Figure 167: Helical diol receptor 237 by Reetz and Sostmann.
Figure 168: Ammonium binding spherand by Cram et al. (238a) and the cyclic[6]metaphenylacetylene 238b in compar...
Figure 169: Receptor for peptide backbone and ammonium binding (239).
Figure 170: Anion sensor principle with 3-hydroxy-2-naphthanilide of Jiang et al.
Figure 171: 7-bromo-3-hydroxy-N-(2-hydroxyphenyl)naphthalene 2-carboxamide (241) and its amine binding.
Figure 172: Naturally occurring catechins with affinity to quaternary ammonium ions.
Figure 173: Spiropyran (244) and merocyanine form (244a) of the amino acid receptors of Fuji et al.
Figure 174: Coumarin aldehyde (245) and its iminium species with amino acid bound (245a) by Glass et al.
Figure 175: Coumarin aldehyde appended with boronic acid.
Figure 176: Quinolone aldehyde dimers by Glass et al.
Figure 177: Chromogenic ammonium ion receptors with trifluoroacetophenone recognition motifs.
Figure 178: Chromogenic ammonium ion receptor with trifluoroacetophenone recognition motif bound on different m...
(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties
- José L. Jiménez Blanco,
- Fernando Ortega-Caballero,
- Carmen Ortiz Mellet and
- José M. García Fernández
Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20
- by 10-membered ring hydrogen bond arrangement (Figure 8). Similar conformational studies combined with CD spectroscopy have been carried out for homo-oligomers of silyl-protected δ-2,4-trans-oxetane-SAAs with different configurations. The results showed that 6-deoxy-L-altronate, D-fuconate and 6
Graphical Abstract
Figure 1: Schematic representation of sugar aminoacids (SAAs) and (pseudo)amide oligosaccharide mimetics.
Figure 2: Natural SAAs structures and natural nucleosidic antibiotics.
Scheme 1: Synthetic route to the target amide-linked sialooligomers. (a) Fmoc-Cl, NaHCO3, H2O, dioxane, 0 °C....
Figure 3: The general structure of glycoamino acids and their corresponding oligomers.
Figure 4: Conformational analysis of the β(1→2)-amide-linked glucooligomer 9.
Figure 5: Short oligomeric chains of C-glycosyl D-arabino THF amino acid oligomers.
Figure 6: (A) Stereoview of the minimized structure of compound 16 (produced by a 500 ps simulation) that mos...
Figure 7: Structures of linear oxetane-β- and δ-SAA homo-oligomers 19–20.
Figure 8: 10-Membered ring H-bonds in compound 21 consistent with NMR and modelling investigations.
Figure 9: General structure of carbopeptoid-oligonucleotide conjugates.
Figure 10: Protected derivatives of 2,6-diamino-2,6-dideoxy-β-D-glucopyranosyl carboxylic acid 22 and 23.
Figure 11: Cyclic homo-oligomers containing glucopyranoid-SAAs.
Scheme 2: Strategy for solid-phase synthesis of cyclic trimers and tetramers containing pyranoid δ-SAAs.
Figure 12: Cyclic tetramers of L-rhamno- and D-gulo-configured oxetane-SAAs.
Figure 13: Aminoglycosidic antibiotics of the glycocinnamoylspermidine family.
Scheme 3: Synthesis of (thio)trehazoline, via triflate, from β-hydroxy(thio)urea.
Figure 14: Approaches to access pseudoamide-type oligosaccharide mimics.
Figure 15: Calystegine B2 analogues 38 and 39 with urea-linked disaccharide structure.
Figure 16: Rotameric equilibrium shift of 40 by formation of a bidentate hydrogen bond.
Figure 17: Nucleotide analogues with thiourea and S-methylisothiouronium linkers.
Scheme 4: Retrosynthetic approach to synthesize thiourea-linked glycooligomers.
Figure 18: Rotameric equilibria for β-(1→6)-thiourea-linked glucodimer 41.
Figure 19: Schematic representation of (a) cyclodextrin (CDs) and (b) cyclotrehalan (CTs) family members.
Scheme 5: Synthesis of guanidine-linked pseudodisaccharides via carbodiimide.
Figure 20: β(1→6)-Guanidine-linked pseudodi- and pseudotrisaccharides 47 and 48.
Scheme 6: Synthesis of N-benzylguanidine-linked CT2 50.
Figure 21: Structure of RNG and DNG.
Figure 22: Preparation of Fmoc-guanidinium derivatives.
Figure 23: Structures of the homo-oligomeric RNG derivatives 51–55.
Figure 24: Phosphoramidite building block 56.
Figure 25: Structures of DNGs 57–65.
Figure 26: Structure of the phosphoramidite building block 66.
An enantiomerically pure siderophore type ligand for the diastereoselective 1 : 1 complexation of lanthanide(III) ions
- Markus Albrecht,
- Olga Osetska,
- Thomas Abel,
- Gebhard Haberhauer and
- Eva Ziegler
Beilstein J. Org. Chem. 2009, 5, No. 78, doi:10.3762/bjoc.5.78
- investigated by spectrophotometric methods. Only in the case of La3+ and Eu3+ were well defined 1 : 1 complexes formed. On the basis of CD spectroscopy and DFT calculations the configuration at the metal centre of the La3+ complex was determined to show Λ helicity. The coordination compounds [(1a)Ln] presented
- should be prototypes for further lanthanide(III) complexes with an enterobactine analogue binding situation. Keywords: CD spectroscopy; enterobactin; lanthanide; macrocycles; molecular modeling; Introduction The availability of metal ions for biological systems is essential for growth and function
- ) ions, while smaller cations lead to an unspecific complex formation (probably oligomerization or polymerization). On the basis of ab initio calculations and CD spectroscopy we could show that the formed complex (1a)La exhibits exclusively Λ helicity. We were able to isolate the corresponding lanthanum
Graphical Abstract
Figure 1: Structural formula of the siderophore enterobactine.
Scheme 1: Preparation of the compound 1a-H3 by utilization of a multiple Claisen-rearrangement.
Figure 2: 1H NMR spectra (300 MHz, CDCl3) of the ether compound 4 (top) and the ligand 1a-H3 (bottom).
Figure 3: Positive ESI MS of [(1a)La] in chloroform showing the peaks of {K[(1a)La]}+ (m/z = 1600.8) as well ...
Figure 4: CD and UV absorption titration curves for complexation of ligand 1a-H3 with lanthanum(III)nitrate h...
Figure 5: Titration curve observed for ligand 1a-H3 upon addition of lanthanum(III) nitrate hexahydrate.
Figure 6: Molecular structures of the Λ2 (left) and Δ2 (right) isomers of complex 1b·La calculated by using B...
Figure 7: UV and CD spectra of the complex (Λ)-1·La. Blue and violet curve: experimentally determined spectra...
