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Search for "ee determination" in Full Text gives 6 result(s) in Beilstein Journal of Organic Chemistry.
Stereodynamic tetrahydrobiisoindole “NU-BIPHEP(O)”s: functionalization, rotational barriers and non-covalent interactions
- Golo Storch,
- Sebastian Pallmann,
- Frank Rominger and
- Oliver Trapp
Beilstein J. Org. Chem. 2016, 12, 1453–1458, doi:10.3762/bjoc.12.141
- ) barriers. Functionalization of stereodynamic BIPHEP ligands at the biaryl core offers multiple possibilities. The introduction of achiral, non-covalent interaction sites allows for ee determination of chiral analytes via NMR spectroscopy [21] as well as deracemization of the BIPHEPs with HPLC stationary
- a key step in deracemization of stereodynamic compounds but they also allow ee determination in solution by NMR spectroscopy. However, the formation of diastereomeric adducts between chiral compounds and BIPHEP(O) [25] or BINAP(O) [26] has so far rarely been investigated. In a subsequent part of our
Graphical Abstract
Figure 1: Synthetic overview of “NU-BIPHEP(O)s”. A) Rhodium catalyzed double [2 + 2 + 2] cycloaddition. B) Ac...
Figure 2: Investigation of 3,5-dichlorobenzoyl modified tetrahydrobiisoindole “NU-BIPHEP(O)” 3. A) Three sign...
Figure 3: Investigation of “NU-BIPHEP(O)” 1b. A) Solid-state structure determined by X-ray crystallography. H...
Figure 4: Enantioselective DHPLC investigation of tetrahydrobiisoindole “NU-BIPHEP(O)” 3. A) Elution profiles...
Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate
- James A. B. Laurenson,
- John A. Parkinson,
- Jonathan M. Percy,
- Giuseppe Rinaudo and
- Ricard Roig
Beilstein J. Org. Chem. 2013, 9, 2660–2668, doi:10.3762/bjoc.9.301
- d-chloroform/diisopropyl tartrate showed distinct baseline separated signals for different enantiomers. Keywords: asymmetric; dihydroxylation; ee determination; fluorination; fluorosugars; organo-fluorine; Introduction Selective fluorination can be used to make subtle but decisive modifications of
- methods. Catalytic asymmetric dihydroxylation can be carried out in moderate to good yields and in excellent ee using the AQN ligands. Chiral HPLC was used for ee determination of the dibenzoate derivatives, but a chiral 19F{1H} NMR method was developed to determine the enantiomeric purities of the non
Graphical Abstract
Scheme 1: Key steps from the synthesis of 6-fluoro-D-olivose (6) from D-glucose (1).
Scheme 2: De novo asymmetric syntheses of 6-deoxy-6-fluorohexoses [13].
Scheme 3: Fluorobutenoate building block 14, and related species 16 and 19 from the literature [14-16].
Scheme 4: Fluorobutenoate building blocks 25 and 26 prepared from crotonic acid.
Figure 1: Side product 27 isolated from attempted fluorination.
Figure 2: The ligand panel used in the asymmetric dihydroxylation studies. The bold oxygen shows the point of...
Scheme 5: Typical AD procedure; see Table 1 for outcomes.
Scheme 6: Conversion of enantiomerically-enriched diols to dibenzoates for HPLC analysis.
Figure 3: Diisopropyl L-tartrate (30) used as a chiral modifier for NMR determination of ee.
Figure 4: Partial 19F{1H} NMR spectra (376 MHz, L-(+)-DIPT/CDCl3, 300 K) spectra of (a) racemate 28c, (b) dio...
Figure 5: Partial 19F{1H} NMR (400 MHz, L-(+)-DIPT/CDCl3, 300 K) spectra of 28b and 28a using optimised condi...
Scheme 7: Applying cyclic sulfate methodology to gain access to anti-diastereoisomers (transformations were d...
Scheme 8: Protecting and chain extending the educts of asymmetric dihydroxylation.
Enantioselective reduction of ketoimines promoted by easily available (S)-proline derivatives
- Martina Bonsignore,
- Maurizio Benaglia,
- Laura Raimondi,
- Manuel Orlandi and
- Giuseppe Celentano
Beilstein J. Org. Chem. 2013, 9, 633–640, doi:10.3762/bjoc.9.71
- . Chemical shifts were determined relative to tetramethylsilane (for hydrogen atoms) and residual solvent peaks (for carbon atoms). Optical rotations were obtained on a Perkin-Elmer 241 polarimeter at 589 nm. HPLC for ee determination was performed on Agilent 1100 instrument under the conditions reported
Graphical Abstract
Figure 1: Catalysts of types A–D.
Figure 2: Catalysts of types E–H.
Figure 3: Proposed approach in this work.
Scheme 1: Stereoselective reduction of ketones.
Figure 4: Catalysts synthesized and studied in this work.
Figure 5: Calculated transition states for catalyst 6.
Towards racemizable chiral organogelators
- Jian Bin Lin,
- Debarshi Dasgupta,
- Seda Cantekin and
- Albertus P. H. J. Schenning
Beilstein J. Org. Chem. 2010, 6, 960–965, doi:10.3762/bjoc.6.107
- , C39H62N2O3): 607.51 [M + H]+. IR ν (cm−1): 3403; 2918; 2849; 1652; 1514; 1263; 1120; 719. M.p. 80.5 °C. (R)-enantiomer: [α]25D 4.8 (c 0.01, CHCl3), (S)-enantiomer: [α]25D −4.4 (c 0.01, CHCl3). ee Determination by HPLC [18]: The octane solution (2 mL) of the imine (1 mM) and DBU (1 equiv) was mixed with 1 mL
- of 0.25 M HCl solution and the aqueous solution extracted two times with 1 mL of CHCl3. The remaining aqueous solution of phenylglycine amide HCl salt was used as such for the ee determination by the following HPLC method. Column; crownether Cr (+) 150 x 4.6 mm ID, eluent; aqueous HClO4 pH = 1.2
Graphical Abstract
Scheme 1: Synthesis of R-3 and S-3.
Figure 1: Concentration-dependent 1H NMR spectra of R-3 in chloroform (CDCl3). The red colours indicate the h...
Figure 2: a) R-3 gel in octane (5 mM); b) octane solution containing a mixture of R-3 (2.5 mM) and S-3 (2.5 m...
Figure 3: a) Concentration-dependent 1H NMR spectra of R-3 in cyclohexane-d12 and b) the shift of N–H signal ...
Figure 4: The evolution of ln(ee × 100) for the racemization of R-3 (1 mM) in the presence of 1 equivalent of...
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...
Chiral trimethylsilylated C2- symmetrical diamines as phosphorous derivatizing agents for the determination of the enantiomeric excess of chiral alcohols by 1H NMR
- Anne-Sophie Chauvin and
- Alexandre Alexakis
Beilstein J. Org. Chem. 2006, 2, No. 6, doi:10.1186/1860-5397-2-6
- peak can be easily performed. This ee determination can be made either with the P(III) or with the P(V) derivatives, after reaction with sulphur, although superposition of peaks occurs more often in the latter case. With some N,N'-dimethyl-1,2-bis-(3-trimethylsilanyl-phenyl)-ethane-1,2-diamine 3
Graphical Abstract
Scheme 1: C2-diamines used in this study.
Scheme 2: Synthesis of diamines 1 and 2.
Scheme 3: Synthesis of diamine 3.
Figure 1: 1H NMR spectrum in the -0.4↔0.6 ppm region of 2-(2-isopropyl-5-methyl-cyclohexyloxy)-1,3-bis-trimet...
