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Search for "self-association" in Full Text gives 32 result(s) in Beilstein Journal of Organic Chemistry.
Synthesis of chiral sulfoximine-based thioureas and their application in asymmetric organocatalysis
- Marcus Frings,
- Isabelle Thomé and
- Carsten Bolm
Beilstein J. Org. Chem. 2012, 8, 1443–1451, doi:10.3762/bjoc.8.164
- improved by dilution [48][74][75][76]. This effect was attributed to the formation of less active aggregates by thioureas self-association at high concentrations resulting in lower enantioselectivities [77]. Interestingly, a dilution effect was also observed in our study. Thus, changing the molar substrate
Graphical Abstract
Figure 1: General structure of sulfoximines 1 and one of the enantiomers of S-methyl-S-phenylsulfoximine ((S)-...
Figure 2: Structures of chiral mono- and bifunctional (bis-)thioureas that have been used as organocatalysts.
Scheme 1: Synthesis of compound (S)-3.
Scheme 2: Organocatalytic desymmetrization of the cyclic anhydride 4 with (S)-3.
Scheme 3: Attempted synthesis of sulfonimidoyl-substituted thiourea (R)-9.
Scheme 4: Synthesis of the sulfonimidoyl-containing thioureas (S)-12 and (S)-13.
Scheme 5: Syntheses of ethylene-linked sulfonimidoyl-containing thioureas (SS,SC)-18 and (RS,SC)-19.
Partial thioamide scan on the lipopeptaibiotic trichogin GA IV. Effects on folding and bioactivity
- Marta De Zotti,
- Barbara Biondi,
- Cristina Peggion,
- Matteo De Poli,
- Haleh Fathi,
- Simona Oancea,
- Claudio Toniolo and
- Fernando Formaggio
Beilstein J. Org. Chem. 2012, 8, 1161–1171, doi:10.3762/bjoc.8.129
- analogues maintain the mixed 310-/α-helical structure and the self-association propensity of the native lipopeptide. They also preserve, at least to a great extent, its well-established capability to interact with model phospholipid membranes and to exhibit activity against Gram-positive bacterial strains
Graphical Abstract
Figure 1: List of primary structures and abbreviations for the peptides studied in this work. The [Leu11-OMe]...
Scheme 1: Synthesis of ψ[CS-NH]2. 1: Coupling in the presence of EDC/HOBt. 2: Deprotection by using TFA/DCM. ...
Scheme 2: Synthesis of ψ[CS-NH]5. 1: Coupling in the presence of EDC/HOBt. 2: Deprotection by using TFA/DCM. ...
Scheme 3: Synthesis of ψ[CS-NH]9. 1: Deprotection by catalytic hydrogenation with Pd/C. 2: Coupling with n-Oc...
Figure 2: RP-HPLC profiles obtained for [Leu11-OMe] trichogin GA IV (tric-OMe) and its ψ[CS-NH]2, ψ[CS-NH]5, ...
Figure 3: Far-UV (panel I) and near-UV (panel II) CD spectra of [Leu11-OMe] trichogin GA IV (tric-OMe) and it...
Figure 4: FT-IR absorption spectra (3550–3200 cm−1 region) in CDCl3 solution of [Leu11-OMe] trichogin GA IV (...
Figure 5: Region of the amide NH protons in the H/H-ROESY spectrum of ψ[CS-NH]9 (400 MHz, 1 mM in CD3CN solut...
Figure 6: Fingerprint region of the H/H-ROESY spectrum of ψ[CS-NH]9 (400 MHz, 1 mM in CD3CN solution, 298 K)....
Figure 7: Fingerprint region of the H/H-ROESY spectrum of ψ[CS-NH]9 (400 MHz, 1 mM in CD3CN solution, 298 K)....
Figure 8: Ribbon representation of the lowest energy (138.7 kcal/mol) 3D structure obtained for ψ[CS-NH]9. Al...
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
- universality of the radius would seem to be a feature of the gelator structure rather than the solvent, i.e., self-association driven by a molecular recognition process, as opposed to a classical aggregation such as that observed in surfactants. There is a negligible variation in the scattering behavior with
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.
Chain stopper engineering for hydrogen bonded supramolecular polymers
- Thomas Pinault,
- Bruno Andrioletti and
- Laurent Bouteiller
Beilstein J. Org. Chem. 2010, 6, 869–875, doi:10.3762/bjoc.6.102
- ., their interaction with EHUT, their self-association was probed. Self-association of bis-thiourea Chain stoppers S2 and S3 cannot self-associate because they contain only hydrogen bond acceptors, however this is not the case for S4, and it is of interest to determine the conditions under which S4 can be
Graphical Abstract
Figure 1: Structures of monomer EHUT and chain stoppers.
Figure 2: Substituted urea conformation. If R is alkyl, the most stable conformation is b); if R = H, the mos...
Figure 3: FTIR spectra, at 20 °C, for CDCl3 solutions of S4 (a) or EHUT (b), at several concentrations.
Figure 4: SANS intensity versus scattering vector for 12 mM solutions of EHUT or S4 in d8-toluene, at 22 °C. ...
Figure 5: Relative viscosity for solutions of EHUT (20 mM) in 1,3,5-trimethylbenzene at 25 °C, with increasin...
Figure 6: Relative viscosity for solutions of EHUT (1.1 mM) in toluene at 25 °C, with increasing molar fracti...
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
- novel spirocyclic precursor 9b with the crucial syn-orientation of its two alkene moieties. The crystal structure of 16c displays two features typical of a molecular tweezer: inclusion of a solvent molecule in the molecular cleft and self-association of the self-complementary scaffolds. Furthermore
- , host–guest NMR studies of compound 16c in solution show chemical exchange between the unbound and bound electron-rich guest, N,N,N′,N′-tetramethyl-p-phenylenediamine. Keywords: crystal structure; fluorine; molecular tweezers; quinoxalines; self-association; Introduction A broad variety of
- framework 16c differ only slightly from the parameters of the non-fluorinated compound 4a, although the latter does not include any solvent in the cleft and, furthermore, lacks the interpenetrating self-association displayed in 16c [19]. Conversely, 4a shows π-π–interaction of two adjacent molecules by
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
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...
Self-association of an indole based guanidinium-carboxylate-zwitterion: formation of stable dimers in solution and the solid state
- Carolin Rether,
- Wilhelm Sicking,
- Roland Boese and
- Carsten Schmuck
Beilstein J. Org. Chem. 2010, 6, No. 3, doi:10.3762/bjoc.6.3
Graphical Abstract
Figure 1: Self-assembly of zwitterion 1 to give dimer 1·1 and self-assembly of zwitterion 2 to give dimer 2·2...
Scheme 1: Synthesis of zwitterion 2.
Scheme 2: Synthesis of compound 2·H+.
Figure 2: 1H NMR spectra of zwitterion 2 (bottom) and its protonated form 2·H+ (top).
Figure 3: Part of the 1H NMR spectrum of 2 in [D6]DMSO showing the complexation-induced shifts of the indole ...
Figure 4: Representative binding isotherm of the aromatic proton d (left) and the indole NH proton (right).
Figure 5: Binding isotherm of the guanidinium NH2 protons.
Figure 6: Crystal structure of dimer 2·2 with hydrogen bond distances (Å) and dihedral angles.
Figure 7: Side view of dimer 2·2 in the solid state.
Figure 8: Part of the crystal lattice of zwitterion 2.
Scheme 3: An attractive H-bond in 1 (left) is replaced by a repulsive steric interaction in 2 (right).
Figure 9: Energy-minimized structure for dimer 2·2 with hydrogen bond distances (Å) and dihedral angles.
