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Search for "catechol" in Full Text gives 63 result(s) in Beilstein Journal of Organic Chemistry.
Complete σ* intramolecular aromatic hydroxylation mechanism through O2 activation by a Schiff base macrocyclic dicopper(I) complex
- Albert Poater and
- Miquel Solà
Beilstein J. Org. Chem. 2013, 9, 585–593, doi:10.3762/bjoc.9.63
- in mind the key role of dioxygen in biology, in particular toward Cu and Fe metal centers, being involved in the catalytic cycle of proteins, including dinuclear copper-active sites, such as hemocyanin, tyrosinase and catechol oxidases [1][2][3][4][5][6][7], either transporting or activating O2, its
Graphical Abstract
Figure 1: Stationary points located along the reaction path of the aromatic hydroxylation mechanism (some H a...
Figure 2: Computed structures of the potential equilibrium between the peroxo and bis-μ-oxo intermediates (so...
Figure 3: Computed structures for a potential alternative pathway f→g of the σ* mechanism (some H atoms omitt...
Figure 4: Computed structures for a potential alternative pathway e→g of the σ* mechanism (some H atoms omitt...
Figure 5: Computed structures for a potential alternative pathway j→i of the σ* mechanism (Gibbs energies in ...
Figure 6: Computed structures for a potential alternative pathway b→g of the σ* mechanism (some H atoms omitt...
Figure 7: Computed structures for a potential alternative pathway c→g of the σ* mechanism (some H atoms omitt...
Efficient electroorganic synthesis of 2,3,6,7,10,11-hexahydroxytriphenylene derivatives
- Carolin Regenbrecht and
- Siegfried R. Waldvogel
Beilstein J. Org. Chem. 2012, 8, 1721–1724, doi:10.3762/bjoc.8.196
- Carolin Regenbrecht Siegfried R. Waldvogel Institute for Organic Chemistry, Mainz University, Duesbergweg 10–14, 55128 Mainz, Germany 10.3762/bjoc.8.196 Abstract 2,3,6,7,10,11-Hexahydroxytriphenylene of good quality and purity can be obtained via anodic treatment of catechol ketals and subsequent
- . The shift of potentials is supported by cyclic voltammetry studies. Keywords: catechol; electrochemical oxidation; hexahydroxytriphenylene; ketals; propylene carbonate; Introduction The unique spectroscopic and geometric features of triphenylenes give rise to a variety of applications for this very
- [8][9]. Typically, the oxidative trimerization of catechol derivatives can be induced by metal salts in high oxidation states, for example by molybdenum pentachloride [4][10]. Electrochemical methods can be applied to realize the oxidative trimerization since the formation of metal waste is avoided
Graphical Abstract
Scheme 1: Experimental conditions for the anodic oxidation of catechol ketals.
Figure 1: Cyclic voltammograms of catechol ketal 1a in ACN and PC and triphenylene ketal 2a in ACN, for magni...
Scheme 2: Acid-catalyzed cleavage of ketal moieties.
Synthesis of 5-oxyquinoline derivatives for reversal of multidrug resistance
- Torsten Dittrich,
- Nils Hanekop,
- Nacera Infed,
- Lutz Schmitt and
- Manfred Braun
Beilstein J. Org. Chem. 2012, 8, 1700–1704, doi:10.3762/bjoc.8.193
- ). Similar activity is provided by catechol-derived acetal 13a, whereas, at this transporter, the acetals derived from 1,2-diphenylethanediol, are still active as transport inhibitors, but their activity is slightly lower than that of zosuquidar (31% relative transport activity). The full details of the
- the solvent in a rotary evaporator, the residue was purified by flash chromatography. For the preparation of catechol-derived acetals 11c and 12c, toluene was used instead of chloroform, and trifluoromethanesulfonic acid instead of p-toluenesulfonic acid. General procedure for the N-arylation of N-Boc
Graphical Abstract
Scheme 1: Lead structure of zosuquidar (1a) and new inhibitors 2–13 (series a); precursors 2–13 (series b); p...
Scheme 2: Synthetic route to compounds 2a–13a. Reagents and conditions: (a) K3PO4, CH2Cl2, reflux, 3 h; then ...
Scheme 3: Preparation of N-Boc-protected 4-aminopiperidines 3c and 4c. Reagents and conditions: (a) NaOt-Bu, ...
Highly enantioselective access to cannabinoid-type tricyles by organocatalytic Diels–Alder reactions
- Stefan Bräse,
- Nicole Volz,
- Franziska Gläser and
- Martin Nieger
Beilstein J. Org. Chem. 2012, 8, 1385–1392, doi:10.3762/bjoc.8.160
- former experiments of our group [29][30][31] it became apparent that without a catalyst no conversion towards the desired product occurred. Only the homodimer of the diene 10 could be isolated. Metal-based Lewis acids (e.g., catechol boronates) proved to be inefficient or too reactive. Due to the fact
Graphical Abstract
Figure 1: An assortment of natural products synthesized by Diels–Alder reactions.
Figure 2: Intermediates towards the total synthesis of (−)-Δ9-tetrahydrocannabinol (4).
Scheme 1: Synthesis of thiourea catalysts 9a–l.
Scheme 2: Organocatalytic Diels–Alder reaction with thiourea-catalysis.
Figure 3: Formation of the iminium-ion.
Scheme 3: Synthesis of electron poor imidazolidinone catalysts.
Figure 4: Crystal structure of the side product from the reaction of 13.
Figure 5: Confirmation of the relative configuration with NOESY experiments and X-ray crystal structures of t...
Scheme 4: Co-catalyst screening.
Scheme 5: Screening of imidazolidinone catalysts 15.
Catalysis: transition-state molecular recognition?
- Ian H. Williams
Beilstein J. Org. Chem. 2010, 6, 1026–1034, doi:10.3762/bjoc.6.117
- concept. It is shown that reactant binding is intrinsically inhibitory, and that attempts to design catalysts that focus simply upon attractive interactions in a binding site may fail. Free-energy changes along the reaction coordinate for SN2 methyl transfer catalysed by the enzyme catechol-O-methyl
- an archetypal reaction in organic chemistry and an important process in biochemistry. Catechol-O-methyl transferase (COMT) catalyses methyl transfer from S-adenosylmethionine (SAM) to a catechol (Scheme 1), and this reaction manifests an unusually large inverse secondary kinetic isotope effect as
- 4-nitrophenylxylobioside and BCX wild-type (black) and Tyr69Phe mutant (red). Hydrogen-bond distances HY…Oring (red) and HY…Onuc (blue) to boat conformer of RC, TS and glycosyl-enzyme COV intermediate, as shown by QM/MM MD simulation in active site of BCX. SN2 methyl transfer from SAM to catechol
Graphical Abstract
Figure 1: Free energy profiles for reactions of substrate S uncatalysed and catalysed by enzyme E, showing ho...
Scheme 1: SN2 methyl transfer from SAM to catechol catalysed by COMT.
Figure 2: Energetic analysis of the compression hypothesis for enzyme-catalysed methyl transfer.
Figure 3: Catalyst design for methyl transfer: (a) the reaction to be catalysed; (b) dipoles favourably align...
Scheme 2: SN2 methyl transfer (a) uncatalysed and (b) within a cryptand cavity.
Figure 4: Free energy analysis of COMT catalysis.
Scheme 3: Formation of glycosyl-enzyme covalent intermediate COV.
Figure 5: Conformational change of the xylose ring from chair (via envelope) with long OYHY…Oring hydrogen bo...
Figure 6: AM1/OPLS potentials of mean force for formation of glycosyl-enzyme covalent intermediate between 4-...
Figure 7: Hydrogen-bond distances HY…Oring (red) and HY…Onuc (blue) to boat conformer of RC, TS and glycosyl-...
9,10-Dioxa-1,2-diaza-anthracene derivatives from tetrafluoropyridazine
- Graham Pattison,
- Graham Sandford,
- Dmitrii S. Yufit,
- Judith A. K. Howard,
- John A. Christopher and
- David D. Miller
Beilstein J. Org. Chem. 2010, 6, No. 45, doi:10.3762/bjoc.6.45
- 3LE, U.K. GlaxoSmithKline R&D, Medicines Research Centre, Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2NY, United Kingdom 10.3762/bjoc.6.45 Abstract Reaction of tetrafluoropyridazine with catechol gives a tricyclic 9,10-dioxa-1,2-diaza-anthracene system by a sequential nucleophilic aromatic
- fluorinated heterocycles for the preparation of novel heterocyclic structures and focussed upon the synthesis of ring fused systems that could be derived from the reaction of tetrafluoropyridazine (3) with catechol (4). In principle, two possible systems 5 and 6 may be formed depending upon the
- ]dioxino[2,3-c]pyridazine also referred to as benzodioxinopyridazine) systems are very rare heterocyclic structures and only a handful of analogues based upon this molecular skeleton have been synthesised, mainly by the reaction of chlorinated pyridazines with catechol [14][15][16]. In this paper, we
Graphical Abstract
Scheme 1: Synthesis of novel tricyclic heterocycles from pentafluoropyridine.
Scheme 2: Synthetic route to dioxa-diaza-anthracene derivatives.
Scheme 3: Reactions of tetrafluoropyridazine 3 with sodium phenoxide.
Scheme 4: Synthesis of dioxa-1,2-diaza-anthracene scaffold 5.
Scheme 5: Mechanism of formation of 5.
Scheme 6: Reactions of dioxa-1,2-diaza-anthracene scaffold 5 with nucleophiles.
Figure 1: Molecular structure of 4-allylamino-3-fluoro-9,10-dioxa-1,2-diaza-anthracene (9b).
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...
Templated versus non-templated synthesis of benzo-21-crown-7 and the influence of substituents on its complexing properties
- Wei Jiang and
- Christoph A. Schalley
Beilstein J. Org. Chem. 2010, 6, No. 14, doi:10.3762/bjoc.6.14
- for C7 [29]. Meanwhile, the low yield and long procedure discourage the application of intramolecular macrocylization to the synthesis of C7’s derivatives. Therefore, an alternative procedure with improved efficiency was sought. The synthetic procedure with catechol and hexa(ethylene glycol
- template during the synthesis of C7 from catechol and 3 results in a much more easily achievable separation of uncomplexed C7. We speculate that the lower solubility of this salt in organic solvent helps to separate the crown ether from the salt during the extraction. The effect of substituents on binding
- -withdrawing aldehyde group which decreases the electron-donating and hydrogen-bond accepting ability of the oxygen atoms on the catechol [32]. Consequently, electron-withdrawing substitution on C7 should be avoided when aiming at strong binding between the two building blocks. Literature reports that a change
Graphical Abstract
Scheme 1: Two synthetic procedures for the preparation of benzo-21-crown-7 (C7) and its formyl analogue 4: To...
Scheme 2: Molecular structures of guests 5-H•PF6, 6-H•PF6, and 7-H•PF6, and their complexes with 2-(n), C7 an...
Figure 1: 1H NMR spectra (500 MHz, 298 K, CDCl3:CD3CN = 2:1, 10.0 mM) of 5-H•PF6 (a), mixture of 5-H•PF6 and ...
Figure 2: ESI-FTICR mass spectrum of a mixture of 5-H•PF6 and 2-(n) in dichloromethane.
Figure 3: 1H NMR spectra (500 MHz, 298 K, CDCl3, 10.0 mM) of (a) C7, (b) C7 in the presence of 1 eq. KPF6, (c...
Figure 4: 1H NMR spectra (500 MHz, 298 K, CDCl3:CD3CN = 2:1, 10.0 mM) of (a) 6-HoPF6, (b) mixture of 6-HoPF6 ...
Figure 5: 1H NMR spectra (500 MHz, 298 K, CDCl3:CD3CN = 2:1, 10.0 mM) of (a) 6-H•PF6, equimolar mixtures of (b...
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
- fluoride have been reported as chromogenic chemosensors, but a indolocarbazole ligand for the anion remains to be developed. Recently, Bhardwaj et al. reported a tripodal receptor [39] bearing catechol groups [40] for the chromogenic sensing of fluoride ions. Numerous bis(indolyl)methanes and their
- CH3CN in the presence of I2 for 45 min afforded the desired receptor 1 in 82% yield. To look into the orientation of hydrogen bond donors around the carbazole motif, we optimized the structure by the AM1 method [45] (Figure 2). It is evident from Figure 2 that the two catechol units do not lie in the
- than other anions, since the catechol moiety is particularly effective in binding smaller anions. The deprotonation occurred at a slightly higher concentration of acetate than fluoride due to higher electronegativity, smaller size, and higher basicity of F− ions, which make them bind strongly with
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...
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
- cases the one observed for enterobactin [23][24]. Enterobactin resembles the ideal raw model for the design of highly efficient metal ion receptors. It combines two different structural aspects which are important for effective binding of the metals: (i) Chelating moieties: Catechol is an efficient
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...
An efficient partial synthesis of 4′-O-methylquercetin via regioselective protection and alkylation of quercetin
- Nian-Guang Li,
- Zhi-Hao Shi,
- Yu-Ping Tang,
- Jian-Ping Yang and
- Jin-Ao Duan
Beilstein J. Org. Chem. 2009, 5, No. 60, doi:10.3762/bjoc.5.60
- selective protection of the catechol group with dichlorodiphenylmethane in diphenyl ether as solvent and on the selective protection of the hydroxyl groups at positions 3 and 7 with chloromethyl ether. Keywords: alkylation; high yield; 4′-O-methylquercetin; partial synthesis; regioselective protection
- partial synthesis from quercetin (1) and relies on successive and selective protection of the different quercetin phenolic functions. Initially, we decided to adopt an alternative strategy which relies upon a selective protection of the catechol ring to make the later selective methylation easier. Hydroxy
- (4 equiv) and K2CO3 (4.2 equiv) in acetone led to the formation of 5, whose phenolic functions with the exception of the hydroxyl group at position 5 were protected. From compound 5, we first focused on the catechol ring deprotection by cleaving the diphenylmethylene ketal. Two different methods were
Graphical Abstract
Figure 1: Structures of quercetin and methylated metabolites.
Scheme 1: Synthesis of 4′-O-methylquercetin (2, tamarixetin). a) Ph2CCl2, Ph2O, 175 °C, 30 min, 86%; b) MOMCl...
Figure 2: ROESY correlations of compound 2.
Mitomycins syntheses: a recent update
- Jean-Christophe Andrez
Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33
- installed the three carbon chain on the newly formed para-methoxyphenol which was subsequently oxidized to the quinone then reduced to yield the corresponding para-catechol. This latter compound was protected with benzyl groups. Although this sequence of protecting group interconversion required many steps
Graphical Abstract
Scheme 1: Aziridine containing natural products.
Scheme 2: Mitomycin structures and nomenclature.
Scheme 3: Base catalysed epimerization of mitomycin B.
Scheme 4: Biosynthesis of mitomycin C (MMC) 7.
Scheme 5: Mode of action of mitomycin C.
Scheme 6: The N–C3–C9a disconnection.
Scheme 7: Danishefsky’s Retrosynthesis of mitomycin K.
Scheme 8: Hetero Diels–Alder reaction en route to mitomycins.
Scheme 9: Nitroso Diels–Alder cycloaddition.
Scheme 10: Frank azide cycloadddition.
Scheme 11: Final steps of mitomycin K synthesis. aPDC, DCM; bPhSCH2N3, PhH, 80 °C; cL-selectride, THF, −78 °C; ...
Scheme 12: Naruta–Maruyama retrosynthesis.
Scheme 13: Synthesis of a leucoaziridinomitosane by nitrene cycloaddition. aAlCl3-Et2O; bNaH, ClCH2OMe; cn-BuL...
Scheme 14: Thermal decomposition of azidoquinone 51.
Scheme 15: Diastereoselectivity during the cycloaddition.
Scheme 16: Oxidation with iodo-azide.
Scheme 17: Williams’ approach towards mitomycins.aDEIPSCl, Imidazole, DCM; bPd/C, HCO2NH4, MeOH; cAllocCl, NaH...
Scheme 18: Synthesis of pyrrolidones by homoconjugate addition.
Scheme 19: Homoconjugate addition on the fully functionalized substrate.
Scheme 20: Introduction of the olefin.
Scheme 21: Retrosynthesis of N–C9a, N–C3 bond formation.
Scheme 22: Synthesis of the pyrrolo[1,2]indole 82 using N-PSP activation.aAc2O, Py; bAc2O, Hg(OAc)2, AcOH, 90%...
Scheme 23: Synthesis of an aziridinomitosane. am-CPBA, DCM then iPr2NH, CCl4 reflux; bK2CO3, MeOH; cBnBr, KH; d...
Scheme 24: Oxidation products of a leucoaziridinomitosane obtained from a Polonovski oxidation.
Scheme 25: Polonovski oxidation of an aziridinomitosane. am-CPBA; bPd/C, H2; cDimethoxypropane, PPTS.
Scheme 26: The C1–C9a disconnection.
Scheme 27: Ziegler synthesis of desmethoxymitomycin A.aIm2C=O, THF; bNH3; cTMSOTf, 2,6-di-tert-butylpyridine, ...
Scheme 28: Transformation of sodium erythorbate.aTBDMSCl; bNaN3; cPPh3; d(Boc)2O, DMAP; eTBAF; fTf2O, Pyr.
Scheme 29: Formation of C9,C10-unsaturation in the mitomycins. am-CPBA, DCM; bO3, MeOH; cMe2S; dKHMDS, (EtO)3P...
Scheme 30: Fragmentation mechanism.
Scheme 31: Michael addition-cyclisation.
Scheme 32: SmI2 8-endo-dig cyclisation.
Scheme 33: Synthesis of pyrrolo[1,2-a]indole by 5-exo-dig radical cyclization.
Scheme 34: The C9–C9a disconnection.
Scheme 35: Intramolecular nitrile oxide cycloaddition.
Scheme 36: Regioselectivity of the INOC.
Scheme 37: Fukuyama’s INOC strategy.
Scheme 38: Synthesis of a mitosane core by rearrangement of a 1-(1-pyrrolidinyl)-1,3-butadiene.
Scheme 39: Sulikowski synthesis of an aziridinomitosene. aPd(Tol3P)2Cl2, Bu3SnF, 140; bH2, Pd/C; cTFAA, Et3N; d...
Scheme 40: Enantioselective carbene insertion.
Scheme 41: Parson’s radical cyclization.
Scheme 42: Cha’s mitomycin B core synthesis.
Scheme 43: The N-aromatic disconnection.
Scheme 44: Kishi retrosynthesis.
Scheme 45: Kishi synthesis of a starting material. aallyl bromide, K2CO3, acetone, reflux; bN,N-Dimethylanilin...
Scheme 46: Kishi synthesis of MMC 7. aLDA, THF, −78 °C then PhSeBr, THF, −78 °C; bH2O2, THF-EtOAc; cDIBAL, DCM...
Scheme 47: Acid catalyzed degradation of MMC 7.
Scheme 48: In vivo formation of apomitomycin B.
Scheme 49: Advanced intermediate for apomitomycin B synthesis.
Scheme 50: Remers synthesis of a functionalized mitosene. aTMSCl, Et3N, ZnCl2 then NBS; bAcOK; cNH2OH; dPd/C, H...
Scheme 51: Coleman synthesis of desmethoxymitomycin A. aSnCl2, PhSH, Et3N, CH3CN; bClCO2Bn, Et3N; cPPh3, DIAD,...
Scheme 52: Transition state and pyrrolidine synthesis.
Scheme 53: Air oxidation of mitosanes and aziridinomitosanes.
Scheme 54: The C9-aromatic disconnection.
Scheme 55: Synthesis of the aziridine precursor. aLHMDS, THF; bNaOH; c(s)-α-Me-BnNH2, DCC, HOBT; dDIBAL; eK2CO3...
Scheme 56: Synthesis of 206 via enamine conjugate addition.
Scheme 57: Rapoport synthesis of an aziridinomitosene.
Scheme 58: One pot synthesis of a mitomycin analog.
Scheme 59: Synthesis of compound 218 via intramolecular Heck coupling. aEtMgCl, THF, then 220; bMsCl, Et3N; cN...
Scheme 60: Elaboration of indole 223. aEt3N, Ac2O; bAcOH; cSOCl2, Et3N; dNaN3, DMF; eH2SO4, THF; fK2CO3, MeOH; ...
Scheme 61: C9-C9a functionalization from indole.
Scheme 62: Synthesis of mitomycin K. a2 equiv. MoO5.HMPA, MeOH; bPPh3, Et3N, THF-H2O; cMeOTf, Py, DCM; dMe3SiCH...
Scheme 63: Configurational stability of mitomycin K derivatives.
Scheme 64: Epimerization of carbon C9a in compound 227b.
Scheme 65: Corey–Chaykovsky synthesis of indol 235.
Scheme 66: Cory intramolecular aza-Darzens reaction for the formation of aziridinomitosene 239.
Scheme 67: Jimenez synthesis of aziridinomitosene 242.
Scheme 68: Von Braun opening of indoline 244.
Scheme 69: C9a oxidation of an aziridinomitosane with DDQ/OsO4.
Scheme 70: Synthesis of epi-mitomycin K. aNaH, Me2SO4; bH2, Pd/C; cMitscher reagent [165]; d[(trimethylsilyl)methyl...
Scheme 71: Mitomycins rearrangement.
Scheme 72: Fukuyama’s retrosynthesis.
Scheme 73: [2+3] Cycloaddition en route to isomitomycin A. aToluene, 110 °C; bDIBAL, THF, −78 °C; cAc2O, Py.; d...
Scheme 74: Final steps of Fukuyama’s synthesis.
Scheme 75: “Crisscross annulation”.
Scheme 76: Synthesis of 274; the 8-membered ring 274 was made using a crisscross annulation. a20% Pd(OH)2/C, H2...
Scheme 77: Conformational analysis of compound 273 and 275.
Scheme 78: Synthesis of a mitomycin analog. aNa2S2O4, H2O, DCM; bBnBr (10 equiv), K2CO3, 18-crown-6 (cat.), TH...
Scheme 79: Vedejs retrosynthesis.
Scheme 80: Formation of the azomethine ylide.
Scheme 81: Vedejs second synthesis of an aziridinomitosene. aDIBAL; bTPAP, NMO; c287; dTBSCl, imidazole.
Scheme 82: Trityl deprotection and new aziridine protecting group 300.
Scheme 83: Ene reaction towards benzazocinones.
Scheme 84: Benzazocenols via homo-Brook rearrangement.
Scheme 85: Pt-catalyzed [3+2] cycloaddition.
Scheme 86: Carbonylative lactamization entry to benzazocenols. aZn(OTf)2, (+)-N-methylephedrine, Et3N, TMS-ace...
Scheme 87: 8 membered ring formation by RCM. aBOC2O, NaHCO3; bTBSCl, Imidazole, DMF; callyl bromide, NaH, DMF; ...
Scheme 88: Aziridinomitosene synthesis. aTMSN3; bTFA; cPOCl3, DMF; dNaClO2, NaH2PO4, 2-methyl-2-butene; eMeI, ...
Scheme 89: Metathesis from an indole.
Scheme 90: Synthesis of early biosynthetic intermediates of mitomycins.
The Elbs and Boyland- Sims peroxydisulfate oxidations
- E. J. Behrman
Beilstein J. Org. Chem. 2006, 2, No. 22, doi:10.1186/1860-5397-2-22
- the peroxyphosphates has been little developed[31][32] although there is a prelimary report of the use of peroxymonophosphate to carry out the synthesis of catechol monophosphates analgous to the reaction reported in [4] with peroxymonosulfate. [33] Biographical material on Elbs (1858–1933) and
Graphical Abstract
Scheme 1: The Elbs and Boyland-Sims Oxidations.
Scheme 2: The Intermediate in the Boyland-Sims Oxidation
Scheme 3: The Intermediate in the Elbs Oxidation.
Scheme 4: Reaction of Caro's Acid Anion with 2,5-dinitrofluorobenzene.
Scheme 5: Ortho- and para-intermediates for the Elbs Oxidation.
Scheme 6: Reaction of an Elbs Intermediate with the Hydroxide Ion.
Scheme 7: A Catalytic Cycle for Peroxydisulfate Consumption.
Scheme 8: A Non-catalytic cycle for Peroxydisulfate Consumption.
