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Search for "NMR titration" in Full Text gives 58 result(s) in Beilstein Journal of Organic Chemistry.
A new fluorescent chemosensor for fluoride anion based on a pyrrole–isoxazole derivative
- Zhipei Yang,
- Kai Zhang,
- Fangbin Gong,
- Shayu Li,
- Jun Chen,
- Jin Shi Ma,
- Lyubov N. Sobenina,
- Albina I. Mikhaleva,
- Guoqiang Yang and
- Boris A. Trofimov
Beilstein J. Org. Chem. 2011, 7, 46–52, doi:10.3762/bjoc.7.8
- emission spectra upon the addition of F−, resulting in highly selectivity for fluoride detection over other anions, such as Cl−, Br−, I−, HSO4−, H2PO4− and AcO− in CH3CN. 1H NMR titration, time-dependent density functional theory (TDDFT) calculations and other experiments confirm that the sensing process
- recognize fluoride anion (F−) with high selectivity and sensitivity over other anions (Cl−, Br−, I−, HSO4−, H2PO4− and AcO−). Both 1H NMR titration experiments and time-dependent density functional theory (TDDFT) calculations demonstrated that the mechanism is deprotonation of the pyrrole-NH. Results and
- −. 1H NMR titration 1H NMR titration was also carried out to confirm the deprotonation of receptor 1 by F−. Figure 9 shows the series of 1H NMR spectra of 1 upon the addition of increasing amounts of TBAF in DMSO-d6. As discussed above, HF2− anion was formed when the receptor was deprotonated by F− via
Graphical Abstract
Figure 1: (a) Receptor 1. (b) ORTEP drawing of receptor 1. Thermal ellipsoids are drawn at the 30% probabilit...
Figure 2: The absorption spectra of receptor 1 (5 μM) in the absence or presence of a 50 equiv of F−, Cl−, Br−...
Figure 3: The fluorescence spectra of receptor 1 (5 μM) in the absence or presence of a 50 equiv of F−, Cl−, ...
Figure 4: Comparison of fluorescence emission of 1 (5 μM) in CH3CN after the addition of 50 equiv of tetrabut...
Figure 5: UV–vis absorption changes of 1 (5 μM) upon the addition of TBAF in CH3CN.
Figure 6: Fluorescence emission changes of 1 (5 μM) upon the addition of TBAF in CH3CN (excited at 340 nm).
Figure 7: The fit of the experimental data of fluorescence emission of 1 (5 μM) upon the addition of F− at 40...
Figure 8: Fluorescence emission changes of 1 (5 μM) upon the addition of F− and OH− (5 equiv) in CH3CN (excit...
Figure 9: Partial 1H NMR (400 MHz) spectra of receptor 1 in the presence of 0, 0.2, 0.6, 1.0, 1.4, 1.6, 2.0, ...
Figure 10: Anionic form a and b of receptor 1.
Preparation, structures and preliminary host–guest studies of fluorinated syn-bis-quinoxaline molecular tweezers
- Markus Etzkorn,
- Jacob C. Timmerman,
- Matthew D. Brooker,
- Xin Yu and
- Michael Gerken
Beilstein J. Org. Chem. 2010, 6, No. 39, doi:10.3762/bjoc.6.39
- –c, depicting the inversion of the electrostatic potential in the pincer subunits upon increasing the degree of fluorination. NMR titration experiments with electron-rich arenes (1,4-dimethoxybenzene, 1,3,5-trimethoxybenzene, N,N-dimethylaniline, N,N,N′,N′-tetramethyl-p-phenylenediamine) were carried
Graphical Abstract
Scheme 1: Fluorinated molecular tweezers.
Scheme 2: Synthesis of non-fluorinated and fluorinated syn-bis-quinoxalines.
Figure 1: (a) Thermal ellipsoid image of the tweezer molecular 16c in the structure 16c · CH3CO2C2H5; thermal...
Figure 2: Electrostatic potential surfaces of 16a–c (Spartan 06 [41]: B3LYP/6-31G*//B3LYP/6-31G*; legend in kcal/...
Figure 3: 1H NMR spectra (CD2Cl2, 500 MHz) of 16c (host [black]) upon titration with N,N,N′,N′-tetramethyl-p-...
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
- ion binding processes are direct absorption and emission measurements utilizing chromophores in the receptor or analyte molecule, displacement assays with suitable dyes, NMR titration experiments, isothermal titration calorimetry and transport through an organic phase monitored by HPLC, NMR [37][38
- and (S)-1-methyl-1,2-propanediol for the enantiomeric recognition of amino acid ester derivatives [161]. The four similar macrocycles have been shown to be complexing agents for primary organic ammonium salts by 1H NMR titration. The best example, the depicted host 29, exhibited enantioselective
- showed a considerable binding affinity and enantiomeric discrimination of aromatic amine salts [162]. The binding properties were evaluated by 1H NMR titration in acetonitrile. For the (R,R)- and (S,S)-configurated host with a phenyl residue, the highest differences in the Kass values were observed: (R
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
- phosphate were obtained from NMR titration experiments for both series of glucooligomers. The binding affinity of the thiourea and guanidine oligomers was stronger than in the case of the urea analogues. Stimulated by the interesting supramolecular properties and applications of cyclodextrins (CDs), a range
- and evaluated as phosphate binders in water (Figure 20) [76]. Association constants (Kas) for binding with dimethyl and phenyl phosphate were obtained from NMR titration experiments for both compounds. The results indicated that the binding strength depends strongly on the acidity of the NH protons
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.
Synthesis of indolo[3,2-b]carbazole-based new colorimetric receptor for anions: A unique color change for fluoride ions
- Ajit Kumar Mahapatra,
- Giridhari Hazra and
- Prithidipa Sahoo
Beilstein J. Org. Chem. 2010, 6, No. 12, doi:10.3762/bjoc.6.12
- ), and not hydrogen bonding to it, is responsible for the drastic color change [47], as a result of a change in the optical properties of chromogenic indolocarbazole skeleton. This is in agreement with the NMR titration data. Such deprotonation was related to the acidity of the H-bond donor site and the
Graphical Abstract
Figure 1: The structure of the indolocarbazole-based chemosensor 1.
Scheme 1: Synthesis of receptor 1.
Figure 2: The AM1 optimized structure of receptor 1 (heat of formation = −8.29 kcal/mol).
Figure 3: Color changes of receptor 1 (A) (c = 1.1 × 10−4 M) in CH3CN/H2O (4:1 v/v) on addition of tetrabutyl...
Figure 4: UV spectral change of receptor 1 (c = 1.1 × 10−4 M) upon gradual addition of [Bu4N]+F− (left side) ...
Scheme 2: Schematic representation (the circles represent the indolocarbazole moiety) of the two-step process...
Figure 5: The Job plot of 1 with fluoride ion from UV method in CH3CN/H2O (4:1 v/v).
Figure 6: Fluorescence change of receptor 1 (c = 4.475 × 10−5 M) upon gradual addition of [Bu4N]+F− (left sid...
Figure 7: Binding constant calculation curves for receptor 1 vs F−, Cl−, Br−, I−, AcO−, HSO4−, and H2PO4− (le...
Figure 8: 1H NMR spectra of receptor 1 (bottom), 1 with [Bu4N]+F− 1:2 [receptor 1:(Bu4N)+F−] (middle) and exc...
Size selective recognition of small esters by a negative allosteric hemicarcerand
- Holger Staats and
- Arne Lützen
Beilstein J. Org. Chem. 2010, 6, No. 10, doi:10.3762/bjoc.6.10
- esters 5–7, however, did not result in any significant shifts indicating size-selective discrimination of the different esters. In order to evaluate this phenomenon further we performed an NMR titration to determine the association constant for the binding of the arguably best guest ethyl acetate
- as the internal standard. Analysis of the binding isotherms obtained from the NMR titration experiments was done by non-linear regression methods. Qualitative binding studies of 2 and the model substrates 3–7. 1H NMR spectra (500.1 MHz, 298 K in mesitylene-d12, c0(2) = 5 mmol/L) of a) 2, b) 2 and 15
- equiv of 3, c) 2 and 15 equiv of 4, d) 2 and 15 equiv of 5, e) 2 and 15 equiv of 6, f) 2 and 15 equiv of 7. Marked in red rectangles are the regions of the signals of the acetal and some of the bipyridine hydrogen atoms of 2. 1H NMR titration (500.1 MHz, 298 K, c0(2) = 5.3 mmol/L) of 2 with increasing
Graphical Abstract
Scheme 1: Bis(resorcinarene) esters of 4,4′- and 4,6′-(2,2′-bipyridyl)dicarboxylic acid, 1 and 2, respectivel...
Scheme 2: Simple esters used as model substrates in this study.
Figure 1: Qualitative binding studies of 2 and the model substrates 3–7. 1H NMR spectra (500.1 MHz, 298 K in ...
Figure 2: 1H NMR titration (500.1 MHz, 298 K, c0(2) = 5.3 mmol/L) of 2 with increasing amounts of ethyl aceta...
Scheme 3: Binding model of the negative cooperative allosteric behaviour of 2.
Recognition properties of receptors consisting of imidazole and indole recognition units towards carbohydrates
- Monika Mazik and
- André Hartmann
Beilstein J. Org. Chem. 2010, 6, No. 9, doi:10.3762/bjoc.6.9
- carbohydrates were investigated by 1H NMR spectroscopic titrations in CDCl3 and DMSO-d6/CDCl3 mixtures. The stoichiometry of the receptor–sugar complexes was determined by mole ratio plots [51][52] and by the curve-fitting analysis of the titration data [53]. The 1H NMR titration experiments [54] with octyl β
Graphical Abstract
Figure 1: Examples of hydrogen bonds in the complex of a) galactose-binding protein with D-glucose [3], b) Amara...
Figure 2: Structures of receptors 1–5.
Figure 3: Structures of sugars investigated in this study.
Scheme 1: Reaction conditions: a) AlCl3, CH3CH2Br, 0 °C to r. t., 12 h (85%) [47]; b) 33% HBr in CH3COOH, ZnBr2, ...
Figure 4: Structures of the recently described phenanthroline/aminopyridine-based receptors showing α- vs. β-...
Figure 5: Partial 1H NMR spectra (400 MHz; CDCl3) of receptor 4 (a), 5 (b), 1 (c), and 3 (d) before (bottom) ...
Figure 6: Partial 1H NMR spectra (400 MHz, CDCl3) of 5 after addition of (from bottom to top) 0.00–1.63 equiv...
Figure 7: Energy-minimized structure of the 1:1 a) and 2:1 complex b) formed between receptor 4 and β-galacto...
Figure 8: Examples of hydrogen bonding motifs indicated by molecular modeling studies in the 1:1 complex betw...
Synthesis and binding studies of two new macrocyclic receptors for the stereoselective recognition of dipeptides
- Ana Maria Castilla,
- M. Morgan Conn and
- Pablo Ballester
Beilstein J. Org. Chem. 2010, 6, No. 5, doi:10.3762/bjoc.6.5
- themselves can be regarded as strands 1 and 3 of a three-stranded β-sheet, with cross-linking between the chains through the 4-position of adjacent phenylalanine residues. We also report on the conformational equilibria of these receptors in solution as well as on their tendency to dimerize. 1H NMR titration
- study of the molecular recognition properties of the receptors toward the different guests. All binding constants were determined using 1H NMR titration experiments. As an example, Figure 10a shows a series of spectra acquired during the titration of receptor 2 with n-C6H13-D-Ala-D-Ala-NH2. We monitored
- temperature show that the variation in chemical shift fits a simple theoretical dimerization model, although higher order aggregation cannot be ruled out. Using 1H NMR titration experiments we have determined the association constant values of the 1:1 complexes formed between receptors 1, 2, 15, and 17 and a
Graphical Abstract
Figure 1: Schematic representation of the design of a host–guest complex based on antiparallel β-sheet geomet...
Figure 2: Molecular structures of the two designed receptors 1 and 2 having different relative orientations o...
Figure 3: CAChe minimized structures for the “endo” complexes formed between receptors 1 (a) and 2 (b) and th...
Scheme 1: Synthesis of tetraprotected bis(alanyl)benzophenones 3 from L-phenylalanine 7.
Scheme 2: Deprotection reactions of bis(alanyl)benzophenone units 3.
Scheme 3: Synthesis of the linear tetrapeptides 15 and 17 as mixtures of diastereoisomers.
Figure 4: a) Molecular structures of the two major diastereoisomers of the cyclic receptors obtained from the...
Figure 5: Reverse-phase HPLC chromatograms of the purified fraction obtained from macrocyclization reactions ...
Figure 6: Variable-temperature 1H NMR experiments of 1 in chloroform-d solution. The proton signals that appe...
Figure 7: Small fraction of the columnar arrangement observed in solid-state packing of receptor 1. Two adjac...
Figure 8: Molecular structures of the guests used in the binding experiments.
Figure 9: Selected region of the variable-concentration 1H NMR spectra acquired using chloroform-d solutions ...
Figure 10: a) Selected region of a series 1H NMR spectra acquired during titration of receptor 2 with n-C6H13-...
Figure 11: CAChe minimized structures for two possible binding geometries, a) exo and b) endo complexes formed...
