Showing papers on "Amide published in 2001"
TL;DR: Mechanistic studies showed that the reaction involves rate-limiting oxidative addition of aryl halide, and use of new, optically active heterocyclic carbene ligands gave substantial enantioselectivity in formation of an alpha,alpha-disubstituted oxindole.
Abstract: Catalysts comprised Pd(OAc)2 and either PCy3 or sterically hindered N-heterocyclic carbene ligands provide fast rates for a palladium-catalyzed synthesis of oxindoles by amide α-arylation. This catalyst system allowed for room-temperature reactions in some cases and reactions of aryl chlorides at 70 °C. Most important, reactions occurred in high yields under mild conditions to form the quaternary carbon in α,α-disubstituted oxindoles. The combined inter- and intramolecular reaction afforded an efficient synthetic method for formation of α-aryloxindole derivatives. Surprisingly, catalysts containing tert-butylphosphine ligands, which have been most reactive for ketone arylations, were less active than those containing PCy3. Use of new, optically active heterocyclic carbene ligands gave substantial enantioselectivity in formation of an α,α-disubstituted oxindole. In contrast, a variety of optically active phosphine ligands that were tested gave poor enantioselectivity. Mechanistic studies showed that the re...
483 citations
TL;DR: Amide proton temperature coefficients offer an attractive and simple way to confirm existence of hydrogen bonds in NMR determined structures and do not change with pH unless they correspond to conformational changes.
Abstract: Correlations between amide proton temperature coefficients (deltasigmaHN/deltaT) and hydrogen bonds were investigated for a data set of 793 amides derived from 14 proteins. For amide protons showing temperature gradients more positive than -4.6 ppb/K there is a hydrogen bond predictivity value exceeding 85%. It increases to over 93% for amides within the range between -4 and -1 ppb/K. Detailed analysis shows an inverse proportionality between amide proton temperature coefficients and hydrogen bond lengths. Furthermore, for hydrogen bonds of similar bond lengths, values of temperature gradients in alpha-helices are on average I ppb/K more negative than in beta-sheets. In consequence. a number of amide protons in alpha-helices involved in hydrogen bonds shorter than 2 A show deltasigmaHN/deltaT < -4.6 ppb/K. Due to longer hydrogen bonds, 90% of amides in 3(10) helices and 98% in beta-turns have temperature coefficients more positive than -4.6ppb/K. Ring current effect also significantly influences temperature coefficients of amide protons. In seven out of eight cases non-hydrogen bonded amides strongly deshielded by neighboring aromatic rings show temperature coefficients more positive than -2 ppb/K. In general, amide proton temperature gradients do not change with pH unless they correspond to conformational changes. Three examples of pH dependent equilibrium showing hydrogen bond formation at higher pH were found. In conclusion, amide proton temperature coefficients offer an attractive and simple way to confirm existence of hydrogen bonds in NMR determined structures.
360 citations
TL;DR: In this paper, a condensing agent, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM), was used for the selective formation of carboxamides in an alcohol or water.
303 citations
TL;DR: It is shown that many of the side chain amide groups of Asn and Gln residues in the C-terminal domain of the protein are affected by a chemical exchange process which may be important in facilitating the rapid binding of hydrophobic ligands to the cavity.
Abstract: A new NMR experiment is presented for the measurement of μs−ms time scale dynamics of Asn and Gln side chains in proteins. Exchange contributions to the 15N line widths of side chain residues are determined via a relaxation dispersion experiment in which the effective nitrogen transverse relaxation rate is measured as a function of the number of refocusing pulses in constant-time, variable spacing CPMG intervals. The evolution of magnetization from scalar couplings and dipole−dipole cross-correlations, which has limited studies of exchange in multi-spin systems in the past, does not affect the extraction of accurate exchange parameters from relaxation profiles of NH2 groups obtained in the present experiment. The utility of the method is demonstrated with an application to a Leu → Ala cavity mutant of T4 lysozyme, L99A. It is shown that many of the side chain amide groups of Asn and Gln residues in the C-terminal domain of the protein are affected by a chemical exchange process which may be important in f...
283 citations
TL;DR: It is revealed that the amide I, II, and III bands differ in their sensitivities to changes in protein conformation: For example, strong bands in the region 1620-1630 and 1685-1695 cm(-1) were seen in the amid I region of aggregated protein spectra, while absorbance of such magnitudes was not observed in theAmide II and III region.
232 citations
TL;DR: The combined results of AFM, XPS, and solid-state NMR provided a robust explanation for the mechanism of flux enhancement of the aromatic polyamide T FC membranes with the addition of DMSO, which would contribute to not only a fundamental understanding of the process but also an advanced designing of the so-called "tailor-fit" TFC membranes.
Abstract: The present paper explores the role of dimethyl sulfoxide (DMSO) used as an additive to modify the morphological as well as the molecular nature of aromatic polyamide during the formation of thin-film-composite (TFC) membranes. In addition, it elucidates the mechanism of enhancing the reverse osmosis (RO) permeation of the resulting membranes in proportion to the addition of DMSO. Morphological studies by atomic force microscopy (AFM) observed that as the concentration of DMSO increased, the surface roughness and the surface area of the aromatic polyamide TFC membranes became higher and larger, compared to FT-30 membrane for which DMSO was not added during interfacial reaction. Such morphological changes were brought about from fluctuating interface through reducing the immiscibility between aqueous/organic phases by DMSO and provided more opportunities to have contact with water molecules on the surface, participating in the enhancement of the water permeability. Chemical composition studies by X-ray photoelectron spectroscopy (XPS) revealed that there was a considerable increase of the cross-linked amide linkages relative to the linear pendant carboxylic acid groups in the TFC membranes of more DMSO addition. The increase of such amide linkages as hydrogen bonding sites facilitated the diffusion of water molecules through the thin films and played a favorable role in elevating water flux without considerable loss of salt rejection. Relaxation and motion analyses by 1H solid-state nuclear magnetic resonance (NMR) spectroscopy also confirmed the XPS revelation on the basis of measurements of the spin-lattice relaxation time in the rotating frame, T1rho, and determination of the correlation time, tau(c), for the aromatic polyamides forming thin films. The trend of longer tau(c)'s with the increase of DMSO concentration reflected the thin-film aromatic polyamides of less locally mobile chains, accompanied by the higher degree of cross-linking and, hence, the greater number of amide groups. The combined results of AFM, XPS, and solid-state NMR provided a robust explanation for the mechanism of flux enhancement of the aromatic polyamide TFC membranes with the addition of DMSO, which would contribute to not only a fundamental understanding of the process but also an advanced designing of the so-called "tailor-fit" TFC membranes.
212 citations
TL;DR: A simple, palladium-catalyzed method to convert aryl halides to the parent anilines using lithium bis(trimethylsilyl)amide (LiN(SiMe3)2) is reported, which is faster than competing generation of benzyne intermediates and provides the aniline products regiospecifically.
183 citations
TL;DR: In this article, a 6-31G(d) basis set was used for a small amide, N-methyl acetamide (NMA), as an efficient way for calculating amide I and amide II frequencies that are directly comparable to those commonly measured in solution.
Abstract: Density functional theory DFT(BPW91) level calculations with modified 6-31G(d) basis sets are tested for a small amide, N-methyl acetamide (NMA), as an efficient way for calculating amide I and amide II frequencies that are directly comparable to those commonly measured in solution. The calculational results are compared to experimentally measured FTIR spectra in gas and solution phases. The 6-31G(d) basis set at the DFT level yields vibrational frequencies that have the best agreement with the gas-phase experiment, as compared to amide I and II frequencies calculated with the same basis at the HF, CASSCF, MP2, QCISD, and CCD levels. The DFT(BPW91)/6-31G(d) level calculation for the NMA·3H2O hydrogen-bonded complex with an Onsager or CPCM reaction field yields amide I, II, and III frequencies comparable to the experiment in aqueous solution. The amide I and, to a smaller degree, amide II frequencies are found to be sensitive to the exponent of the d function in the basis set. Use of more diffuse (smaller ...
180 citations
TL;DR: Three-coordinate zinc complexes are potential catalysts for the ring-opening of cyclic monomers such as lactide and oxiranes by use of a bulky Schiff base ligand and are prepared and characterized by X-ray crystallography.
Abstract: Three-coordinate zinc complexes are potential catalysts for the ring-opening of cyclic monomers such as lactide and oxiranes. By use of a bulky Schiff base ligand, monomeric zinc amide and phenoxide are prepared and characterized by X-ray crystallography.
179 citations
TL;DR: The low first ionisation potential (58 eV) of indium coupled with its stability towards air and water, suggest that this metallic element should be a useful reducing agent for organic substrates as mentioned in this paper.
Abstract: The low first ionisation potential (58 eV) of indium coupled with its stability towards air and water, suggest that this metallic element should be a useful reducing agent for organic substrates The use of indium metal for the reduction of CN bonds in imines, the heterocyclic ring in benzo-fused nitrogen heterocycles, of oximes, nitro compounds and conjugated alkenes and the removal of 4-nitrobenzyl protecting groups is described Thus the heterocyclic ring in quinolines, isoquinolines and quinoxalines is selectively reduced using indium metal in aqueous ethanolic ammonium chloride Treatment of a range of aromatic nitro compounds under similar conditions results in selective reduction of the nitro groups; ester, nitrile, amide and halide substituents are unaffected Likewise indium in aqueous ethanolic ammonium chloride is an effective method for the deprotection of 4-nitrobenzyl ethers and esters Indium is also an effective reducing agent under non-aqueous conditions and α-oximino carbonyl compounds can be selectively reduced to the corresponding N-protected amine with indium powder, acetic acid in THF in the presence of acetic anhydride or di-tert-butyl dicarbonate Conjugated alkenes are also reduced by indium in THF–acetic acid
160 citations
TL;DR: Both aliphatic and aromatic aldehydes react with secondary amines to yield carboxylic acid amides in good to excellent yields.
Patent•
27 Sep 2001
TL;DR: In this paper, the authors present an active carbamic acid compounds which inhibit HDAC activity and which have the formula (1) wherein: A is an aryl group; Q 1 is an acid leader group having a backbone of at least 2 carbon atoms; J is an amide linkage selected from: -NR1C(=O)- and -C( =O)NR1-; R1 is an amido substituent; and, Q 2 is acid leader groups; and pharmaceutically acceptable salts, solvates, amides,
Abstract: This invention pertains to certain active carbamic acid compounds which inhibit HDAC activity and which have the formula (1) wherein: A is an aryl group; Q1 is an aryl leader group having a backbone of at least 2 carbon atoms; J is an amide linkage selected from: -NR1C(=O)- and -C(=O)NR1-; R1 is an amido substituent; and, Q2 is an acid leader group; and pharmaceutically acceptable salts, solvates, amides, esters, ethers, chemically protected forms, and prodrugs thereof. The present invention also pertains to pharmaceutical compositions comprising such compounds, and the use of such compounds and compositions, both in vitro and in vivo, to inhibit HDAC, and, e.g., to inhibit proliferative conditions, such as cancer and psoriasis.
TL;DR: In this article, the synthesis of N,N-bis(pyrimid-2-yl)amine and N-acetyl-N, N-bis (pyrimide-2yl)amide from compound 2 and its X-ray structure has been determined.
TL;DR: 3,5-Bis(perfluorodecyl)phenylboronic acid has been synthesized based on the direct coupling of perfluorodeecyl iodide with 1,3-diiodobenzene as mentioned in this paper.
Abstract: 3,5-Bis(perfluorodecyl)phenylboronic acid has been synthesized based on the direct coupling of perfluorodecyl iodide with 1,3-diiodobenzene. This new boronic acid is shown to be a "green" catalyst for the direct amide condensation reaction by virtue of the strong electron-withdrawing effect and the immobility in the fluorous recyclable phase of the perfluorodecyl group.
TL;DR: In the early 1980s, Blackburn and McKenna suggested that α-fluorination might lead to phosphonates that better mimic natural phosphates as mentioned in this paper, and the α,α-difluorinated phosphonate inhibitors have received more attention in the past decade or so.
TL;DR: Thiomandelic acid is a broad spectrum inhibitor of metallo-beta-lactamases, with a submicromolar K(i) value for all nine enzymes tested, except the Aeromonas hydrophila enzyme; such a wide spectrum of activity is unprecedented.
TL;DR: In this article, phase transitions of poly(n-n-propylmethacrylamide) (PnPMA) and poly(N-isopropylmethylamide (PiPMA)) in H2O and D2O were investigated by using Fourier transform infrared (FTIR) spectroscopy.
Abstract: Phase transitions of poly(N-n-propylmethacrylamide) (PnPMA) and poly(N-isopropylmethacrylamide) (PiPMA) in H2O and D2O have been investigated by using Fourier transform infrared (FTIR) spectroscopy. IR spectra of these polymer solutions have been collected as a function of temperature in both heating and cooling processes. The positions of IR bands due to the alkyl and amide groups of these polymers critically shift at their phase transition temperatures (Tp). The amide II, C−H stretching and C−H bending bands undergo red shift, whereas the amide I band undergoes a blue shift upon the coil-to-globule transitions. The amide I bands of PnPMA and PiPMA measured below their Tp consist of three (1642, 1611, and 1586 cm-1) and two (1635 and 1606 cm-1) Gaussian components, respectively. The areas of the 1642 cm-1 component of PnPMA and the 1635 cm-1 component of PiPMA, which can be attributed to the carbonyl group that forms a hydrogen bond with an amide N−D group (CO···D−N), increase with temperature while the ...
TL;DR: It was concluded that the hydrophobicity is a negative parameter for the toxicity and biodegradability of the surfactants.
Abstract: In this paper, a systematic investigation into the structure−property relationship of long-chain N-alkyl amide 1, O-alkyl ester arginine 2, and N-acyl arginine methyl ester analogues 3 is reported. The surface properties were studied by adsorption isotherm curves. Biological properties such as antimicrobial activity, hemolysis, ocular irritation, aquatic toxicity, and biodegradability are discussed and correlated with some specific parameters of the surfactants. These surfactants constitute a novel class of bio-based materials of low toxicity, excellent surface properties, and a wide antimicrobial activity. They selectively disrupt bacteria membranes at submicellar concentrations, but not erythrocytes or skin cell membranes. The presence of two positive cationic charges enhances the antimicrobial activity. The incorporation of ester functionality accelerates biodegradation. From the data obtained, it was concluded that the hydrophobicity is a negative parameter for the toxicity and biodegradability of the...
TL;DR: Results indicate that samarium(0) plays an important role in the reduction process and that 1,1'-dioctyl-4,4'-bipyridinium dibromide acts as an electron-transfer catalyst and is essential in the activation of samarium (0) metal.
Abstract: A mild and efficient electron-transfer method was developed for the chemoselective reduction of aromatic nitro groups using samarium(0) metal in the presence of a catalytic amount of 1,1'-dioctyl-4,4'-bipyridinium dibromide. This method was found to give the product aromatic amine in 79-99% yield with selectivity over a number of other functional and protecting groups such as alkene, azide, benzyl ether, nitrile, amide, halide, p-toluenesulfonamide, t-Boc, tert-butyldiphenylsilyl ether, and aliphatic nitro groups. Our results also indicate that samarium(0) plays an important role in the reduction process and that 1,1'-dioctyl-4,4'-bipyridinium dibromide acts as an electron-transfer catalyst and is essential in the activation of samarium(0) metal. The major active reducing agent responsible for the reduction is believed to be the radical cation species formed from 1,1'-dioctyl-4,4'-bipyridinium dibromide.
TL;DR: Yttrium dialkyl complexes form cationic alkyl species that are active ethene polymerisation catalysts and when activated with PhNMe2H][B(C6F5)4] as discussed by the authors.
TL;DR: The first water-soluble asymmetric hydrogen-transfer ruthenium(II) catalyst system consisting of [Ru(p-cymene)Cl2]2, (S)-proline amide, and sodium formate, which gives high conversion rates with high ee values up to 95.3% and is reusable, has been developed.
Patent•
15 Mar 2001
TL;DR: In this paper, a water soluble or water dispersible polymer composition is disclosed and the repeat units characterized by the formula I: wherein E is the repeat unit remaining after polymerization of an ethylenically unsaturated compound; preferably, a carboxylic acid, sulfonic acid, phosphonic acid or amide form thereof or mixtures thereof.
Abstract: A water soluble or water dispersible polymer composition is disclosed. The polymer has the repeat units characterized by the formula I: Wherein E is the repeat unit remaining after polymerization of an ethylenically unsaturated compound; preferably, a carboxylic acid, sulfonic acid, phosphonic acid, or amide form thereof or mixtures thereof. R1 is H or lower (C1-C4) alkyl. G is —CH2— or —CHCH3—; R2 is CH2—CH2—On or CH2—CHCH3—On where n ranges from about 1 to 100, preferably about 1 to 20. X is an anionic radical selected from the group consisting of SO3, PO3, or COO; Z is H or hydrogens or any water soluble cationic moiety which counterbalances the valence of the anionic radical X, including but not limited to Na, K, Ca, or NH4. F, when present, is a repeat unit having the structure of formula II: wherein X and Z are the same as in Formula I. R4 is H or lower (C1-C4) alkyl. R5 is hydroxy substituted alkyl or alkylene having from about 1 to 6 carbon atoms.
TL;DR: The pendant protonated amine, in conjunction with the carbonyl face of the Fe(III) coordination shell, is proposed to play an important role in the recognition and membrane transport processes.
Abstract: Ferrioxamine B was successfully co-crystallized with ethanolpentaaquomagnesium(II) and perchlorate ions as counter ions, C27H62Cl3FeMgN6O26, and the crystal structure has been determined by single-crystal X-ray diffraction. The crystals are monoclinic, space group P21/n, four molecules per unit cell with dimensions a=21.1945(7) A, b=10.0034(3) A, c=106.560(1) A, and β=106.560(1)°. The crystal structure contains a racemic mixture of Λ-N-cis,cis and Δ-N-cis,cis coordination isomers. The structural parameters and the conformational features of ferrioxamine B compare very well with those of ferrioxamines D1 and E, with an exception of the orientation of the pendant protonated amine, which is pointing away from the connecting amide chains and towards the carbonyl face of the inner coordination shell distorted octahedron. This pendant protonated amine, in conjunction with the carbonyl face of the Fe(III) coordination shell, is proposed to play an important role in the recognition and membrane transport processes.
TL;DR: In this article, the synthesis, properties and reactions of 3,5,7-trimethyl-1-azatricyclo[3.3.13,7]decan-2-one, 7 (the "most twisted amide") were reported.
Abstract: Details are reported of the synthesis, properties and reactions of 3,5,7-trimethyl-1-azatricyclo[3.3.1.13,7]decan-2-one, 7 (the “most twisted amide”). Its spectroscopic properties show clearly that 7 is a ketone rather than an amide, albeit a ketone with a tertiary amino group directly attached to the carbonyl carbon. The amino group is basic (pKa ∼ 5.2) and nucleophilic, while the CO group reacts normally as a ketone, giving the corresponding twisted enamine with the methylene Wittig reagent and acetals under standard conditions. As expected, 7 is rapidly hydrolysed to the bicyclic amino acid 15, but, remarkably, hydrolysis is readily reversible under mild acidic conditions, and in methanol the amino acid is converted to the twisted amide in 80% yield. This cyclisation of the amino acid is an extraordinarily efficient intramolecular reaction: the effective molarity of the amine nucleophile is estimated at 1012 M: the carboxylate anion thus acting as an efficient acylating agent for both secondary and tertiary amine groups. The hydrate of the conjugate acid, typically a high-energy intermediate in amide hydrolysis, is stable in dilute aqueous acid and as the crystalline hydrochloride.
TL;DR: In this paper, the effect of different isomerization states (trans-trans, cis-trans and cis-cis) on the energetics of GGG at the most important protonation sites including the terminal amino group and amide oxygen and nitrogen atoms was investigated.
Abstract: Detailed analysis of the possible fragmentation channels of protonated GGG suggests that a pre-dissociation cis-trans isomerization of the N-terminal amide bond has to take place when y1 ions are formed on the ‘diketopiperazine’ pathway. Quantum chemical calculations were performed in order to determine the effect of different isomerization states (trans-trans, cis-trans, trans-cis, and cis-cis) on the energetics of protonation of GGG at the most important protonation sites including the terminal amino group and amide oxygen and nitrogen atoms. These calculations indicate that cis-trans isomerization is energetically feasible for protonated GGG and the relative energy of the most stable such species that contain a cis amide bond is at a few kcal/mol calculated with respect to the trans-trans global minimum. Analysis of the possible pathways for the cis-trans isomerization suggests that this process involves species protonated at the nitrogen of the N-terminal amide bond. Detailed discussion of the fate of such species indicates that cis-trans isomerization of the N-terminal amide bond of protonated GGG is kinetically controlled while a low-energy pathway connecting the most stable trans-trans and cis-trans species no doubt exists. Copyright © 2001 John Wiley & Sons, Ltd.
TL;DR: The coordination of four n-butylnicotinamide ligands to a platinum(II) centre provides a facile method of organizing amide H-bond donors for anion binding; the PF6− complex is an effective receptor for a variety of oxo-anions.
TL;DR: In this article, a two-step method involving a final thermal polyesterification was used to synthesize sequential poly(ester amide) s derived from glycine, whose molecular weights were in general higher than those obtained with the previously reported synthesis on the basis of interfacial polyamidation.
Abstract: Sequential poly(ester amide)s s derived from glycine were synthesized by a two-step method, involving a final thermal polyesterification. Molecular weights were in general higher than those obtained with the previously reported synthesis on the basis of interfacial polyamidation. Polymers with stiff units like oxaloyl or terephthaloyl residues were thermally characterized and their degradability studied by using different types of enzymes. Polymers containing short diols are degradable in papain solutions, the degradation rate being higher for oxalic derivatives.
TL;DR: Multinuclear high-pressure NMR spectroscopy revealed that this selectivity switch is mainly due to reversible formation of the carbamic acid in the solvent CO2, which reduces the tendency for intramolecular ring closure at the Rh-acyl intermediate.
Abstract: Supercritical carbon dioxide (scCO2) acts simultaneously as solvent and temporary protecting group during homogeneously rhodium-catalyzed hydroaminomethylation of ethyl methallylic amine. Cyclic amines are formed as the major products in scCO,, whereas the cyclic amide is formed preferentially in conventional solvents. Multinuclear high-pressure NMR spectroscopy revealed that this selectivity switch is mainly due to reversible formation of the carbamic acid in the solvent CO2, which reduces the tendency for intramolecular ring closure at the Rh-acyl intermediate. These results substantiate the general concept of using scCO2 as a protective medium for amines in homogeneous catalysis and demonstrate for the first time its application for selectivity control.
TL;DR: In this paper, the authors used FTIR spectroscopies to investigate the local environment of europium perchlorate, Eu3+ ions in luminescent sol−gel derived materials.
Abstract: Infrared and photoluminescence spectroscopies have been used to investigate the local environment of the Eu3+ ions in luminescent sol−gel derived materialsdi-ureasilsbased on a hybrid framework represented by U(600). This host is composed of a siliceous backbone grafted, through urea cross-links, to both ends of polymer segments incorporating 8.5 oxyethylene repeat units. The active centers have been introduced as europium perchlorate, Eu(ClO4)3. Samples with compositions n = 232, 62, 23, 12, and 6 (where n denotes the ratio of (OCH2CH2) moieties per lanthanide ion) have been examined. The combination of the information retrieved from the analysis of characteristic bands of the FTIR spectrathe perchlorate and the Amide I/Amide II featureswith that obtained from the photoluminescence data demonstrates that at compositions n = 232 and 62 the anions are free, whereas the Eu3+ ions are complexed by the heteroatoms of the polyether chains. At higher salt concentration, the cations are bonded, not only to the C...
TL;DR: The combined data from the IR and 1H NMR spectra indicate that the sulfonic acid, sulfonate anion, and Ca(II) complex have a substantially weak intramolecular NH...O hydrogen bond between the SO3 oxygen and amide NH.
Abstract: The novel intramolecularly NH···O hydrogen-bonded Ca(II)−aryl sulfonate complex, [Ca2(SO3-2-t-BuCONHC6H4)2(H2O)4]n(2-t-BuCONHC6H4SO3)2n (1), sulfonate anion, (HNEt3)(SO3-2-t-BuCONHC6H4) (2a), (PPh4)(SO3-2-t-BuCONHC6H4) (2b), (n-Bu4N)(SO3-2-t-BuCONHC6H4) (2c), and sulfonic acid, 2-t-BuCONHC6H4SO3H (3), were synthesized. The structures of 1, 2a, and 2b depict the presence of the formation of NH···O hydrogen bonds between the amide NH and S−O oxygen for a series of compounds as determined by IR and 1H NMR analyses both in the solid state and in the solution state. Thus, the NH···O hydrogen bonds with neutral amide groups are available for investigation of the electronic state of the O- anion. The combined data from the IR and 1H NMR spectra indicate that the sulfonic acid, sulfonate anion, and Ca(II) complex have a substantially weak intramolecular NH···O hydrogen bond between the SO3 oxygen and amide NH. In the detailed comparison with the intense NH···O hydrogen bonds for the carboxylate, weak NH···O hydro...