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Search for "amide group" in Full Text gives 93 result(s) in Beilstein Journal of Organic Chemistry.
Metal-mediated aminocatalysis provides mild conditions: Enantioselective Michael addition mediated by primary amino catalysts and alkali-metal ions
- Matthias Leven,
- Jörg M. Neudörfl and
- Bernd Goldfuss
Beilstein J. Org. Chem. 2013, 9, 155–165, doi:10.3762/bjoc.9.18
- -sulfobenzoic moiety according to TS-14a–d (Figure 3 and Figure 4). This conformation allows the formation of an intramolecular bond between the lithium ion and the nitrogen of the amide group. A similar structural property is found in the X-ray crystallographic structure of compound 5 (Figure 1). The same
Graphical Abstract
Scheme 1: Activation of amine-bonded Michael acceptors by protonation versus Lewis acid interaction.
Scheme 2: Synthesis of 4-hydroxycoumarin derivatives by Michael addition [19-27].
Scheme 3: Precatalysts 5–8 and synthesis from chiral 1,2-diamines and 2-sulfobenzoic anhydrides.
Figure 1: X-ray crystallographic structure of 5. The conformation of the 2-sulfobenzoic moiety is fixed by hy...
Figure 2: Michael acceptors employed as substrates in the nucleophilic addition of 4-hydroxycoumarin (1).
Scheme 4: Computationally analyzed pathways A (C-protonation), and B (N-protonation), arising from the additi...
Scheme 5: Computed energy profile for reaction path A (C-protonation) and B (N-protonation) corresponding to ...
Figure 3: Enantio-determining transition states arising from the addition of 4-hydroxycoumarin to cyclohexeno...
Figure 4: The competing enantio-determining transition structures TS-14a and TS-14g. The reason for the desta...
Fifty years of oxacalix[3]arenes: A review
- Kevin Cottet,
- Paula M. Marcos and
- Peter J. Cragg
Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22
- product (Figure 23) [69]. The structure revealed that a [HgCl2]2 fragment bridged between two macrocycles through coordination to one amide group of each. The cations were thus exo to the macrocyclic cavity and represented the first example in which a cation was not bound within the annulus. Marcos
- also shows that ketone 24 is a weak extracting agent, with a slight preference for Ag+. This is in agreement with the higher basicity of the carbonyl oxygen in the amide group compared with the ketone group. 4.2.4 Lanthanides: Marcos investigated the lanthanide extraction by both 17a [70] and 24 [39
Graphical Abstract
Figure 1: Calixarenes and expanded calixarenes: p-tert-Butylcalix[4]arene (1), p-tert-butyldihomooxacalix[4]a...
Figure 2: Conventional nomenclature for oxacalix[n]arenes.
Scheme 1: Synthesis of oxacalix[3]arenes: (i) Formaldehyde (37% aq), NaOH (aq), 1,4-dioxane; glacial acetic a...
Figure 3: p-tert-Butyloctahomotetraoxacalix[4]arene (4a) [16].
Figure 4: X-ray crystal structure of 3a showing phenolic hydrogen bonding (IUCr ID AS0508) [17].
Scheme 2: Stepwise synthesis of asymmetric oxacalix[3]arenes: (i) MOMCl, Adogen®464; (ii) 2,2-dimethoxypropan...
Figure 5: X-ray crystal structure of heptahomotetraoxacalix[3]arene 5 (CCDC ID 166088) [21].
Scheme 3: Oxacalix[3]arene synthesis by reductive coupling: (i) Me3SiOTf, Et3SiH, CH2Cl2; R1, R2 = I, Br, ben...
Scheme 4: Oxacalix[3]naphthalene: (i) HClO4 (aq), wet CHCl3 (R = tert-butyl, 6a, H, 6b) [20].
Figure 6: Conformers of 3a.
Scheme 5: Origin of the 25:75 cone:partial-cone statistical distribution of O-substituted oxacalix[3]arenes (p...
Scheme 6: Synthesis of alkyl ethers 7–10: (i) Alkyl halide, NaH, DMF [24].
Scheme 7: Synthesis of a pyridyl derivative 11a: (i) Picolyl chloride hydrochloride, NaH, DMF [26,27].
Figure 7: X-ray crystal structure of partial-cone 11a (CCDC ID 150580) [26].
Scheme 8: Lower-rim ethyl ester synthesis: (i) Ethyl bromoacetate, NaH, t-BuOK or alkali metal carbonate, THF...
Scheme 9: Forming chiral receptor 13: (i) Ethyl bromoacetate, NaH, THF; (ii) NaOH, H2O/1,4-dioxane; (iii) S-P...
Figure 8: X-ray crystal structure of 16 (IUCr ID PA1110) [32].
Scheme 10: Lower rim N,N-diethylamide 17a: (i) N,N-Diethylchloroacetamide, NaH, t-BuOK or alkali metal carbona...
Scheme 11: Capping the lower rim: (i) N,N-Diethylchloroacetamide, NaH, THF; (ii) NaOH, H2O/1,4-dioxane; (iii) ...
Figure 9: X-ray crystal structure of 18 (CCDC ID 142599) [33].
Scheme 12: Extending the lower rim: (i) Glycine methyl ester, HOBt, dicyclohexycarbodiimide (DCC), CH2Cl2; (ii...
Scheme 13: Synthesis of N-hydroxypyrazinone derivative 23: (i) 1-[3-(Dimethylamino)propyl]-3-ethylcarbodiimide...
Scheme 14: Synthesis of 24: (i) 1-Adamantyl bromomethyl ketone, NaH, THF [39].
Scheme 15: Synthesis of 25 and 26: (i) (Diphenylphosphino)methyl tosylate, NaH, toluene; (ii) phenylsilane, to...
Figure 10: X-ray crystal structure of 27 in the partial-cone conformer (CCDC ID SUP 90399) [41].
Scheme 16: Synthesis of strapped oxacalix[3]arene derivatives 28 and 29: (i) N,N’-Bis(chloroacetyl)-1,2-ethyle...
Figure 11: A chiral oxacalix[3]arene [45].
Figure 12: X-ray crystal structure of asymmetric oxacalix[3]arene 30 incorporating t-Bu, iPr and Et groups (CC...
Scheme 17: Reactions of an oxacalix[3]arene incorporating an upper-rim Br atom with (i) Pd(OAc)2, PPh3, HCO2H,...
Scheme 18: Synthesis of acid 39: (i) NaOH, EtOH/H2O, HCl (aq) [47].
Figure 13: Two forms of dimeric oxacalix[3]arene 40 [47].
Scheme 19: Capping the upper rim: (i) t-BuLi, THF, −78 °C; (ii) NaBH4, THF/EtOH; (iii) 1,3,5-tris(bromomethyl)...
Figure 14: Oxacalix[3]arene capsules 46 and 47 formed through coordination chemistry [52,53].
Figure 15: X-ray crystal structure of the 3b-vanadyl complex (CCDC ID 240185) [57].
Scheme 20: Effect of Ti(IV)/SiO2 on 3a: (i) Ti(OiPr)4, toluene; (ii) triphenylsilanol, toluene; (iii) partiall...
Figure 16: X-ray crystal structures of oxacalix[3]arene complexes with rhenium: 3b∙Re(CO)3 (CCDC ID 620981, le...
Figure 17: X-ray crystal structure of the La2·3a2 complex (CSD ID TIXXUT) [60].
Figure 18: X-ray crystal structures of [3a∙UO2]− with a cavity-bound cation (CCDC ID 135575, left) and without...
Figure 19: X-ray crystal structure of a supramolecule comprising two [3g·UO2]− complexes that encapsulate a di...
Figure 20: X-ray crystal structure of oxacalix[3]arene 49 capable of chiral selectivity (CSD ID HIGMUF) [65].
Figure 21: The structure of derivative 50 incorporating a Reichardt dye [66].
Figure 22: Phosphorylated oxacalix[3]arene complexes with transition metals: (Left to right) 26∙Au, 26∙Mo(CO)3...
Figure 23: X-ray crystal structure of [17a·HgCl2]2 (CCDC ID 168653) [69].
Figure 24: X-ray crystal structures of 3f with C60 (CCDC ID 182801, left) [76] and a 1,4-bis(9-fluorenyl) C60 deri...
Figure 25: X-Ray crystal structure of 3i and 6a encapsulating C60 (CCDC ID 102473 and 166077) [23,79].
Figure 26: A C60 complexing cationic oxacalix[3]arene 51 [81].
Figure 27: An oxacalix[3]arene-C60 self-associating system 53 [87].
Scheme 21: Synthesis of fluorescent pyrene derivative 55: (i) Propargyl bromide, acetone; (ii) CuI, 1-azidomet...
Scheme 22: Synthesis of responsive rhodamine derivative 57: (i) DCC, CH2Cl2 [91].
Scheme 23: Synthesis of nitrobenzyl derivative 58: (i) 1-Bromo-4-nitrobenzyl acetate, K2CO3, refluxing acetone...
Figure 28: X-ray crystal structure of [Na2∙17a](PF6)2 (CCDC ID 116656) [97].
Synthetic approaches to multifunctional indenes
- Neus Mesquida,
- Sara López-Pérez,
- Immaculada Dinarès and
- Ermitas Alcalde
Beilstein J. Org. Chem. 2011, 7, 1739–1744, doi:10.3762/bjoc.7.204
- %. Compound 7 was then conveniently transformed to the corresponding acetamide 8. The reduction of the amide group with AlH3·NMe2Et was the critical step for the preparation of the key inden-5-amine 9 due to the particularly troublesome isolation process [18]. Thus, a different synthetic option was examined
Graphical Abstract
Scheme 1: Retrosynthetic pathways to 3,5-disubstituted indenes bearing two functional groups: Indenylsulfonam...
Scheme 2: Reagents and conditions: (i) (a) EtOAc, LHMDS, THF, −78 °C, (b) H2SO4, H2O, 60 °C [18]; (ii) (a) SOCl2,...
Scheme 3: Reagents and conditions: (i) (a) EtOAc, LHMDS, THF, −78 °C, (b) H2SO4, H2O, 60 °C [18]; (ii) (a) SOCl2,...
Scheme 4: Reagents and conditions: (i) KNO3, H2SO4, −5 °C; (ii) (a) EtOAc, LHMDS, THF, −78 °C, (b) H2SO4, H2O...
Figure 1: Key NMR responses for compounds 17, 19 and 23: 1D NOESY experiments.
Access to pyrrolo-pyridines by gold-catalyzed hydroarylation of pyrroles tethered to terminal alkynes
- Elena Borsini,
- Gianluigi Broggini,
- Andrea Fasana,
- Chiara Baldassarri,
- Angelo M. Manzo and
- Alcide D. Perboni
Beilstein J. Org. Chem. 2011, 7, 1468–1474, doi:10.3762/bjoc.7.170
- intramolecular hydroarylation gave 6-exo-dig or 6-endo-dig processes, depending on the substitution of the alkyne. In both cases, products arising from a direct reaction as well as products involving a 1,2-shift of the amide group were obtained, their ratio being influenced by the polarity of the solvent. The
Graphical Abstract
Scheme 1: Pd-catalyzed cyclization of N-allyl-pyrrole-2-carboxamides.
Figure 1: Significant relationships among hydrogen and carbon atoms arising from 2D-NMR studies to determine ...
Scheme 2: Proposed mechanism for the formation of the six-membered products.
NMR studies of anion-induced conformational changes in diindolylureas and diindolylthioureas
- Damjan Makuc,
- Jennifer R. Hiscock,
- Mark E. Light,
- Philip A. Gale and
- Janez Plavec
Beilstein J. Org. Chem. 2011, 7, 1205–1214, doi:10.3762/bjoc.7.140
- involved in hydrogen-bonding interactions with the bound anionic guest, whilst the amide group interacted only weakly with the bound anion. These observations led to the design of diindolylureas and diindolylthioureas [36][37][38]. These compounds have remarkably high affinities for oxo-anions such as
Graphical Abstract
Figure 1: Anion receptors 1–4 together with their atomic numbering scheme.
Figure 2: 1H NMR spectra of 1 in the absence of anions (a) and upon addition of one equivalent of the followi...
Figure 3: Three representative conformational families of rotamers of 1. Notations refer to the orientations ...
Figure 4: NOE enhancements of 1 in the absence of anions (a) and upon addition of one equivalent of acetate a...
Figure 5: Surface plot of the relative potential energy of 1 as a function of the two constitutive [C6–C7–N7α...
Figure 6: Freely optimized structure at the B3LYP/6-311+G(d,p) level of theory and side view showing deviatio...
Figure 7: 1H NMR chemical shift changes, Δδ = δ (in the presence of anions) – δ (in the absence of anions), i...
Figure 8: Freely optimized structures at the B3LYP/6-311+G(d,p) level of theory and side view showing deviati...
Figure 9: Conformational preferences and proposed binding mode for the 3·AcO− 1:1 complex.
Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates
- Wang-Yong Yang,
- Samantha A. Marrone,
- Nalisha Minors,
- Diego A. R. Zorio and
- Igor V. Alabugin
Beilstein J. Org. Chem. 2011, 7, 813–823, doi:10.3762/bjoc.7.93
- higher probability of intercepting the reactive excited state via reaction with a π-system. The photochemical reactivity for the o-substituted acetylene 5 was drastically changed (Scheme 5). In this case, photoexcitation leads to the formation of an oxygen–carbon bond between the amide group and the
- . A similar trend has been previously observed for the lifetimes of m-substituted enediynes [63]. The absorption spectra of all four acetylenes are shown in Figure 6. The core Ph-TFP-acetylene (Ph-TFP) chromophore without the amide group has no significant absorption at >320 nm. The lowest absorptions
Graphical Abstract
Figure 1: Structure of C-lysine conjugates.
Figure 2: Alternative pathways of enediyne photoreactivity: photo-Bergman cyclization (left), C1–C5 cyclizati...
Figure 3: Summary of possible mechanistic alternatives for the observed DNA cleavage by monoacetylene conjuga...
Scheme 1: Proposed mechanism of photocycloaddition of acetylene with 1,4-CHD.
Figure 4: p-, m-, and o-amidyl acetylenes and respective lysine conjugates.
Scheme 2: Synthesis of amido-substituted monoacetylenes and lysine conjugates. Reagents and conditions: a. Pd...
Scheme 3: Photochemical reactions of TFP-substituted aryl alkynes with selected π-systems. In short, the reac...
Scheme 4: Photocycloaddition of amido acetylenes with 1,4-CHD.
Scheme 5: Possible mechanism for photochemical hydration of diaryl acetylene moiety catalyzed by the ortho-am...
Figure 5: Stern–Volmer plots of three regioisomers, 3 (blue diamond), 4 (red square), and 5 (green triangle),...
Figure 6: Absorption spectra of three isomers, 3, 4, 5, and Ph-TFP in acetonitrile (10 μM).
Figure 7: Quantified DNA cleavage data for 1 (a), 6 (b) and 7 (c). Blue: Form I (supercoiled) DNA; red: Form ...
Figure 8: Effect of hydroxyl radical/singlet oxygen scavengers (20 mM) on the efficiency of DNA cleavage at p...
Figure 9: Cell proliferation assay using A375 cells (human melanoma) and compound 1 (green square), 6 (red up...
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
- moieties which avoids the problem of multi-anion sensitivity. The common anion recognition moieties, i.e., a pyrrole NH and an amide group, present in the structure behave as proton donors. Isoxazoles and their derivatives are important intermediates in preparation of many natural products and related
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.
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
- ; d) the surface morphology of the dried gel obtained from R-3 in octane (15 mM) observed by FESEM. a) Concentration-dependent 1H NMR spectra of R-3 in cyclohexane-d12 and b) the shift of N–H signal of amide group versus concentration. The evolution of ln(ee × 100) for the racemization of R-3 (1 mM
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...
Pyridinium based amphiphilic hydrogelators as potential antibacterial agents
- Sayanti Brahmachari,
- Sisir Debnath,
- Sounak Dutta and
- Prasanta Kumar Das
Beilstein J. Org. Chem. 2010, 6, 859–868, doi:10.3762/bjoc.6.101
- existence of a non-hydrogen bonded amide group. Hydrogen bond formation is accompanied by a decrease in the bond order and hence the observed shift in the carbonyl stretching frequency to a lower value underlines the participation of intermolecular H-bonding in the gel state [37]. In addition, the N–H
Graphical Abstract
Figure 1: Structure of amphiphiles 1–5.
Scheme 1: Synthetic procedure of the amphiphiles.
Figure 2: Variation of the Tgel with concentration of amphiphiles 1 and 2.
Figure 3: (a, b) FESEM images of the dried gels of 1 and 2, respectively at their MGC. (c, d) Two- and three-...
Figure 4: Luminescence spectra of 2 in water (λex = 330 nm) at various concentrations and room temperature.
Figure 5: FTIR spectra of (a) 1 and (b) 2 in CHCl3 solution (dashed line) and in D2O at the gel state (solid ...
Figure 6: 2D-NOESY spectra of 2 (2%, w/v) in DMSO-d6 with 70% water.
Figure 7: XRD diagram of the dried gel of 2.
Figure 8: Schematic representation of the possible arrangement of molecules during hydrogelation of 2.
Figure 9: MTT assay based percent NIH3T3 cell viability as a function of concentration of amphiphile 2.
Novel tetracyclic structures from the synthesis of thiolactone-isatin hybrids
- Renate Hazel Hans,
- Hong Su and
- Kelly Chibale
Beilstein J. Org. Chem. 2010, 6, No. 78, doi:10.3762/bjoc.6.78
- , involves an in situ deprotonation at C-5 of the thiolactone ring system by the relatively basic potassium salt of 5. This is followed by the regioselective, intramolecular addition of the nucleophile to the ketonic carbonyl facilitated by (i) the strong electrophilicity of the α-keto amide group of the
Graphical Abstract
Figure 1: Natural product and natural product-like hybrids.
Figure 2: Structures of thiolactomycin (1), isatin (2), the desired hybrid 3 and tetracycle 4.
Scheme 1: Reagents and conditions: (a) KOH, MeOH, 25 °C, 95–100% (b) 6, DMF, 60 °C, 9–36%.
Scheme 2: Proposed mechanism for the formation of tetracycles 4.
Figure 3: (a) Molecular structure of the tetracycle 4a. (b) Structure of the dimer of 4a showing the atomic n...
Figure 4: Molecular structure of (a) 4b and (b) 4c, with ellipsoidal model of probability level = 35%.
RAFT polymers for protein recognition
- Alan F. Tominey,
- Julia Liese,
- Sun Wei,
- Klaus Kowski,
- Thomas Schrader and
- Arno Kraft
Beilstein J. Org. Chem. 2010, 6, No. 66, doi:10.3762/bjoc.6.66
- polymers which are water-soluble at room temperature and even allow thermoprecipitation with a bound protein guest. NIPAM-based polymers are also reminiscent of peptides since both contain an amide group in the repeat unit. RAFT makes use of a chain transfer agent (CTA) for which we selected the water
Graphical Abstract
Figure 1: Structures of monomers 1–7 and chain transfer agent 8 used in the RAFT polymerizations.
Figure 2: a) Second derivative UV–vis spectra [17-19] observed during a full titration of a stock solution of RAFT c...
Figure 3: Isothermal calorimetric binding curves for selected polymer/protein host–guest pairs. a) Typical bi...
Figure 4: Graphical illustration of the potential binding mode on hemoglobin tetramer (represented as electro...
Molecular recognition of organic ammonium ions in solution using synthetic receptors
- Andreas Späth and
- Burkhard König
Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32
Graphical Abstract
Figure 1: Biologically important amines and quaternary ammonium salts: histamine (1), dopamine (2) and acetyl...
Figure 2: Crown ether 18-crown-6.
Figure 3: Conformations of 18-crown-6 (4) in solvents of different polarity.
Figure 4: Binding topologies of the ammonium ion depending on the crown ring size.
Figure 5: A “pseudorotaxane” structure consisting of 24-crown-8 and a secondary ammonium ion (5); R = Ph.
Figure 6: Typical examples of azacrown ethers, cryptands and related aza macrocycles.
Figure 7: Binding of ammonium to azacrown ethers and cryptands [111-113].
Figure 8: A 19-crown-6-ether with decalino blocking groups (11) and a thiazole-dibenzo-18-crown-6-ether (12).
Figure 9: 1,3-Bis(6-oxopyridazin-1-yl)propane derivatives 13 and 14 by Campayo et al.
Figure 10: Fluorescent azacrown-PET-sensors based on coumarin.
Figure 11: Two different pyridino-cryptands (17 and 18) compared to a pyridino-crown (19); chiral ammonium ion...
Figure 12: Pyridino-18-crown-6 ligand (21), a similar acridino-18-crown-6 ligand (22) and a structurally relat...
Figure 13: Ciral pyridine-azacrown ether receptors 24.
Figure 14: Chiral 15-crown-5 receptors 26 and an analogue 18-crown-6 ligand 27 derived from amino alcohols.
Figure 15: C2-symmetric chiral 18-crown-6 amino alcohol derivatives 28 and related macrocycles.
Figure 16: Macrocycles with diamide-diester groups (30).
Figure 17: C2-symmetric chiral aza-18-crown-6 ethers (31) with phenethylamine residues.
Figure 18: Chiral C-pivot p-methoxy-phenoxy-lariat ethers.
Figure 19: Chiral lariat crown ether 34.
Figure 20: Sucrose-based chiral crown ether receptors 36.
Figure 21: Permethylated fructooligosaccharide 37 showing induced-fit chiral recognition.
Figure 22: Biphenanthryl-18-crown-6 derivative 38.
Figure 23: Chiral lariat crown ethers derived from binol by Fuji et al.
Figure 24: Chiral phenolic crown ether 41 with “aryl chiral barriers” and guest amines.
Figure 25: Chiral bis-crown receptor 43 with a meso-ternaphthalene backbone.
Figure 26: Chromogenic pH-dependent bis-crown chemosensor 44 for diamines.
Figure 27: Triamine guests for binding to receptor 44.
Figure 28: Chiral bis-crown phenolphthalein chemosensors 46.
Figure 29: Crown ether amino acid 47.
Figure 30: Luminescent receptor 48 for bis-alkylammonium guests.
Figure 31: Luminescent CEAA (49a), a bis-CEAA receptor for amino acids (49b) and the structure of lysine bindi...
Figure 32: Luminescent CEAA tripeptide for binding small peptides.
Figure 33: Bis crown ether 51a self assembles co-operatively with C60-ammonium ion 51b.
Figure 34: Triptycene-based macrotricyclic dibenzo-[24]-crown-8 ether host 52 and guests.
Figure 35: Copper imido diacetic acid azacrown receptor 53a and the suggested His-Lys binding motif; a copper ...
Figure 36: Urea (54) and thiourea (55) benzo crown receptor for transport and extraction of amino acids.
Figure 37: Crown pyryliums ion receptors 56 for amino acids.
Figure 38: Ditopic sulfonamide bridged crown ether receptor 57.
Figure 39: Luminescent peptide receptor 58.
Figure 40: Luminescent receptor 59 for the detection of D-glucosamine hydrochloride in water/ethanol and lumin...
Figure 41: Guanidinium azacrown receptor 61 for simple amino acids and ditopic receptor 62 with crown ether an...
Figure 42: Chiral bicyclic guanidinium azacrown receptor 63 and similar receptor 64 for the enantioselective t...
Figure 43: Receptors for zwitterionic species based on luminescent CEAAs.
Figure 44: 1,10-Azacrown ethers with sugar podand arms and the anticancer agent busulfan.
Figure 45: Benzo-18-crown-6 modified β-cyclodextrin 69 and β-cyclodextrin functionalized with diaza-18-crown-6...
Figure 46: Receptors for colorimetric detection of primary and secondary ammonium ions.
Figure 47: Porphyrine-crown-receptors 72.
Figure 48: Porphyrin-crown ether conjugate 73 and fullerene-ammonium ion guest 74.
Figure 49: Calix[4]arene (75a), homooxocalix[4]arene (75b) and resorcin[4]arene (75c) compared (R = H, alkyl c...
Figure 50: Calix[4]arene and ammonium ion guest (R = H, alkyl, OAcyl etc.), possible binding sites; A: co-ordi...
Figure 51: Typical guests for studies with calixarenes and related molecules.
Figure 52: Lower rim modified p-tert-butylcalix[5]arenes 82.
Figure 53: The first example of a water soluble calixarene.
Figure 54: Sulfonated water soluble calix[n]arenes that bind ammonium ions.
Figure 55: Displacement assay for acetylcholine (3) with a sulfonato-calix[6]arene (84b).
Figure 56: Amino acid inclusion in p-sulfonatocalix[4]arene (84a).
Figure 57: Calixarene receptor family 86 with upper and lower rim functionalization.
Figure 58: Calix[6]arenes 87 with one carboxylic acid functionality.
Figure 59: Sulfonated calix[n]arenes with mono-substitution at the lower rim systematically studied on their r...
Figure 60: Cyclotetrachromotropylene host (91) and its binding to lysine (81c).
Figure 61: Calixarenes 92 and 93 with phosphonic acids groups.
Figure 62: Calix[4]arene tetraphosphonic acid (94a) and a double bridged analogue (94b).
Figure 63: Calix[4]arene tetraphosphonic acid ester (92c) for surface recognition experiments.
Figure 64: Calixarene receptors 95 with α-aminophosphonate groups.
Figure 65: A bridged homocalix[3]arene 95 and a distally bridged homocalix[4]crown 96.
Figure 66: Homocalix[3]arene ammonium ion receptor 97a and the Reichardt’s dye (97b) for colorimetric assays.
Figure 67: Chromogenic diazo-bridged calix[4]arene 98.
Figure 68: Calixarene receptor 99 by Huang et al.
Figure 69: Calixarenes 100 reported by Parisi et al.
Figure 70: Guest molecules for inclusion in calixarenes 100: DAP × 2 HCl (101a), APA (101b) and Lys-OMe × 2 HC...
Figure 71: Different N-linked peptido-calixarenes open and with glycol chain bridges.
Figure 72: (S)-1,1′-Bi-2-naphthol calixarene derivative 104 published by Kubo et al.
Figure 73: A chiral ammonium-ion receptor 105 based on the calix[4]arene skeleton.
Figure 74: R-/S-phenylalaninol functionalized calix[6]arenes 106a and 106b.
Figure 75: Capped homocalix[3]arene ammonium ion receptor 107.
Figure 76: Two C3 symmetric capped calix[6]arenes 108 and 109.
Figure 77: Phosphorous-containing rigidified calix[6]arene 110.
Figure 78: Calix[6]azacryptand 111.
Figure 79: Further substituted calix[6]azacryptands 112.
Figure 80: Resorcin[4]arene (75c) and the cavitands (113).
Figure 81: Tetrasulfonatomethylcalix[4]resorcinarene (114).
Figure 82: Resorcin[4]arenes (115a/b) and pyrogallo[4]arenes (115c, 116).
Figure 83: Displacement assay for acetylcholine (3) with tetracyanoresorcin[4]arene (117).
Figure 84: Tetramethoxy resorcinarene mono-crown-5 (118).
Figure 85: Components of a resorcinarene based displacement assay for ammonium ions.
Figure 86: Chiral basket resorcin[4]arenas 121.
Figure 87: Resorcinarenes with deeper cavitand structure (122).
Figure 88: Resorcinarene with partially open deeper cavitand structure (123).
Figure 89: Water-stabilized deep cavitands with partially structure (124, 125).
Figure 90: Charged cavitands 126 for tetralkylammonium ions.
Figure 91: Ditopic calix[4]arene receptor 127 capped with glycol chains.
Figure 92: A calix[5]arene dimer for diammonium salt recognition.
Figure 93: Calixarene parts 92c and 129 for the formation molecular capsules.
Figure 94: Encapsulation of a quaternary ammonium cation by two resorcin[4]arene molecules (NMe4+@[75c]2 × Cl−...
Figure 95: Encapsulation of a quaternary ammonium cation by six resorcin[4]arene molecules (NMe3D+@[130]6 × Cl−...
Figure 96: Structure and schematic of cucurbit[6]uril (CB[6], 131a).
Figure 97: Cyclohexanocucurbit[6]uril (CB′[6], 132) and the guest molecule spermine (133).
Figure 98: α,α,δ,δ-Tetramethylcucurbit[6]uril (134).
Figure 99: Structure of the cucurbituril-phthalhydrazide analogue 135.
Figure 100: Organic cavities for the displacement assay for amine differentiation.
Figure 101: Displacement assay methodology for diammonium- and related guests involving cucurbiturils and some ...
Figure 102: Nor-seco-Cucurbituril (±)-bis-ns-CB[6] (140) and guest molecules.
Figure 103: The cucurbit[6]uril based complexes 141 for chiral discrimination.
Figure 104: Cucurbit[7]uril (131c) and its ferrocene guests (142) opposed.
Figure 105: Cucurbit[7]uril (131c) guest inclusion and representative guests.
Figure 106: Cucurbit[7]uril (131c) binding to succinylcholine (145) and different bis-ammonium and bis-phosphon...
Figure 107: Paraquat-cucurbit[8]uril complex 149.
Figure 108: Gluconuril-based ammonium receptors 150.
Figure 109: Examples of clefts (151a), tweezers (151b, 151c, 151d) and clips (151e).
Figure 110: Kemp’s triacid (152a), on example of Rebek’s receptors (152b) and guests.
Figure 111: Amino acid receptor (154) by Rebek et al.
Figure 112: Hexagonal lattice designed hosts by Bell et al.
Figure 113: Bell’s amidinium receptor (156) and the amidinium ion (157).
Figure 114: Aromatic phosphonic acids.
Figure 115: Xylene phosphonates 159 and 160a/b for recognition of amines and amino alcohols.
Figure 116: Bisphosphonate recognition motif 161 for a colorimetric assay with alizarin complexone (163) for ca...
Figure 117: Bisphosphonate/phosphate clip 164 and bisphosphonate cleft 165.
Figure 118: N-Methylpyrazine 166a, N-methylnicotinamide iodide (166b) and NAD+ (166c).
Figure 119: Bisphosphate cavitands.
Figure 120: Bisphosphonate 167 of Schrader and Finocchiaro.
Figure 121: Tweezer 168 for noradrenaline (80b).
Figure 122: Different tripods and heparin (170).
Figure 123: Squaramide based receptors 172.
Figure 124: Cage like NH4+ receptor 173 of Kim et al.
Figure 125: Ammonium receptors 174 of Chin et al.
Figure 126: 2-Oxazolin-based ammonium receptors 175a–d and 176 by Ahn et al.
Figure 127: Racemic guest molecules 177.
Figure 128: Tripods based on a imidazole containing macrocycle (178) and the guest molecules employed in the st...
Figure 129: Ammonium ion receptor 180.
Figure 130: Tetraoxa[3.3.3.3]paracyclophanes 181 and a cyclophanic tetraester (182).
Figure 131: Peptidic bridged paraquat-cyclophane.
Figure 132: Shape-selective noradrenaline host.
Figure 133: Receptor 185 for binding of noradrenaline on surface layers from Schrader et al.
Figure 134: Tetraphosphonate receptor for binding of noradrenaline.
Figure 135: Tetraphosphonate 187 of Schrader and Finocchiaro.
Figure 136: Zinc-Porphyrin ammonium-ion receptors 188 and 189 of Mizutani et al.
Figure 137: Zinc porphyrin receptor 190.
Figure 138: Zinc porphyrin receptors 191 capable of amino acid binding.
Figure 139: Zinc-porphyrins with amino acid side chains for stereoinduction.
Figure 140: Bis-zinc-bis-porphyrin based on Tröger’s base 193.
Figure 141: BINAP-zinc-prophyrin derivative 194 and it’s guests.
Figure 142: Bisaryl-linked-zinc-porphyrin receptors.
Figure 143: Bis-zinc-porphyrin 199 for diamine recognition and guests.
Figure 144: Bis-zinc-porphyrin crown ether 201.
Figure 145: Bis-zinc-porphyrin 202 for stereodiscrimination (L = large substituent; S = small substituent).
Figure 146: Bis-zinc-porphyrin[3]rotaxane and its copper complex and guests.
Figure 147: Dien-bipyridyl ligand 206 for co-ordination of two metal atoms.
Figure 148: The ligand and corresponding tetradentate co-complex 207 serving as enantioselective receptor for a...
Figure 149: Bis(oxazoline)–copper(II) complex 208 for the recognition of amino acids in aqueous solution.
Figure 150: Zinc-salen-complexes 209 for the recognition tertiary amines.
Figure 151: Bis(oxazoline)–copper(II) 211 for the recognition of amino acids in aqueous solution.
Figure 152: Zn(II)-complex of a C2 terpyridine crown ether.
Figure 153: Displacement assay and receptor for aspartate over glutamate.
Figure 154: Chiral complex 214 for a colorimetric displacement assay for amino acids.
Figure 155: Metal complex receptor 215 with tripeptide side arms.
Figure 156: A sandwich complex 216 and its displaceable dye 217.
Figure 157: Lanthanide complexes 218–220 for amino acid recognition.
Figure 158: Nonactin (221), valinomycin (222) and vancomycin (223).
Figure 159: Monesin (224a) and a chiral analogue for enantiodiscrimination of ammonium guests (224b).
Figure 160: Chiral podands (226) compared to pentaglyme-dimethylether (225) and 18-crown-6 (4).
Figure 161: Lasalocid A (228).
Figure 162: Lasalocid derivatives (230) of Sessler et al.
Figure 163: The Coporphyrin I tetraanion (231).
Figure 164: Linear and cyclic peptides for ammonium ion recognition.
Figure 165: Cyclic and bicyclic depsipeptides for ammonium ion recognition.
Figure 166: α-Cyclodextrin (136a) and novocaine (236).
Figure 167: Helical diol receptor 237 by Reetz and Sostmann.
Figure 168: Ammonium binding spherand by Cram et al. (238a) and the cyclic[6]metaphenylacetylene 238b in compar...
Figure 169: Receptor for peptide backbone and ammonium binding (239).
Figure 170: Anion sensor principle with 3-hydroxy-2-naphthanilide of Jiang et al.
Figure 171: 7-bromo-3-hydroxy-N-(2-hydroxyphenyl)naphthalene 2-carboxamide (241) and its amine binding.
Figure 172: Naturally occurring catechins with affinity to quaternary ammonium ions.
Figure 173: Spiropyran (244) and merocyanine form (244a) of the amino acid receptors of Fuji et al.
Figure 174: Coumarin aldehyde (245) and its iminium species with amino acid bound (245a) by Glass et al.
Figure 175: Coumarin aldehyde appended with boronic acid.
Figure 176: Quinolone aldehyde dimers by Glass et al.
Figure 177: Chromogenic ammonium ion receptors with trifluoroacetophenone recognition motifs.
Figure 178: Chromogenic ammonium ion receptor with trifluoroacetophenone recognition motif bound on different m...
(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties
- José L. Jiménez Blanco,
- Fernando Ortega-Caballero,
- Carmen Ortiz Mellet and
- José M. García Fernández
Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20
- : carbopeptoids The replacement of the glycosidic oxygen atom by an amide group leads to amide-linked sugars (Figure 1), which are synthesised by the sequential coupling of SAAs to form a class of compounds commonly referred to as carbopeptoids. The use of the amide functional group to connect sugar building
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 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
- receptors, we studied their dimerization behavior in chloroform solution. Using the same methodology described above for the receptors, we calculated the dimerization constants of all guest molecules. The values obtained are summarized in Table 2. With an additional amide group with respect to diamides, the
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...
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
- occupied by the carbonyl oxygen which forms an H-bond to the guanidinium moiety and thus actually helps to keep the molecule planar. This amide group in 1 is replaced by the aromatic benzene ring in 2, thereby replacing an attractive H-bond with a repulsive steric interaction. This twisted, non-planar
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.
An expedient and new synthesis of pyrrolo[1,2-b]pyridazine derivatives
- Rajeshwar Reddy Sagyam,
- Ravinder Buchikonda,
- Jaya Prakash Pitta,
- Himabindu Vurimidi,
- Pratap Reddy Padi and
- Mahesh Reddy Ghanta
Beilstein J. Org. Chem. 2009, 5, No. 66, doi:10.3762/bjoc.5.66
- ethyl alcohol to provide alkenyl imine 9, which was characterized on the basis of its mass, 1H and 13C NMR, DEPT, and IR spectral data. Compound 9 was heated in toluene in the presence of p-TSA for 10–12 h and the resulting compound was found to be identical to product 6a. Hydrolysis of the amide group
Graphical Abstract
Figure 1: Unsubstituted pyrrolo[1,2-b]pyridazine.
Scheme 1: Reagents and conditions: i) p-TSA (0.5 equiv), toluene/cyclohexane (4:15), reflux, 15–18 h; ii) p-T...
Figure 2: Depiction with proprietary numbering of compound 6a.
Scheme 2: Plausible mechanistic pathway.
Scheme 3: Reagents and conditions: i) p-TSA (1.5 equiv), toluene/cyclohexane (1:1), reflux, 10.0 h.
Scheme 4: Reagents and conditions: i) p-TSA (2.0 equiv), toluene (30.0 volumes).
The tert- amino effect in heterocyclic chemistry: Synthesis of new fused pyrazolinoquinolizine and 1,4-oxazinopyrazoline derivatives
- Dipak Prajapati and
- Kalyan Jyoti Borah
Beilstein J. Org. Chem. 2007, 3, No. 43, doi:10.1186/1860-5397-3-43
- = 8.6 Hz). The mass spectrum revealed a strong molecular ion peak at 335 (M+). It is to be noted that in the end product 6a one nitrile group is reduced to the corresponding amide group. But it is not yet clear why only one nitrile group is reduced and the other remains intact under the reaction
Graphical Abstract
Scheme 1: Reagents and conditions: (a) DMF, POCl3; (b) piperidine, ethanol, triethylamine; (c) malonodinitril...
Scheme 2: Mechanism for the formation of pyrazolinoquinolizines 6.
Colchitaxel, a coupled compound made from microtubule inhibitors colchicine and paclitaxel
- Karunananda Bombuwala,
- Thomas Kinstle,
- Vladimir Popik,
- Sonal O. Uppal,
- James B. Olesen,
- Jose Viña and
- Carol A. Heckman
Beilstein J. Org. Chem. 2006, 2, No. 13, doi:10.1186/1860-5397-2-13
- paclitaxel binding to tubulin. This group needed to be protected during derivatization. Since acid hydrolysis of the acetamide group in (2) also results in a loss of the methyl group on the adjacent tropolone ring [36], the method of Lebeau and coworkers was used to transform the amide group into the
Graphical Abstract
Scheme 1: Reagents and conditions for synthesis of N-glutaryl-deacetylcolchicine. The reagents used at each s...
Scheme 2: Reagents and conditions for protection of paclitaxel and coupling to N-glutaryl-deacetylcolchicine ...
Figure 1: Microtubule arrangement as visualized by immunofluorescence localization of β-tubulin. Cells were t...
Figure 2: Projections of a VRO showing + ends localized by antibody against EB1 in a control cell. Cell was t...
Figure 3: Projections of a VRO showing + ends localized by antibody against EB1 in colchitaxel-treated cell. ...
Figure 4: Microtubule arrangement as visualized by immunofluorescence localization of β-tubulin. Cells were t...
