Size Of Substituent Research Articles

Convenient Access to Ferrocene Fused aza-Heterocycles via the Intramolecular Ritter Reaction: Synthesis of Novel Racemic Planar-Chiral 3,4-Dihydroferroceno[c]pyridines and 1H-Ferroceno[c]pyrroles

An efficient and easy approach to the synthesis of novel racemic planar-chiral 3,4-dihydroferroceno[c]pyridines and 1H-ferroceno[c]pyrroles via the intramolecular Ritter reaction of 2-ferrocenyl-3,3-dimethylbutan-2-ol with nitriles and thiocyanates in the presence of MeSO3H was developed. Aromatic and aliphatic nitriles, phenylacetonitriles, and β-oxonitriles produced exclusively 3,4-dihydroferroceno[c]pyridines. The condensation of 2-ferrocenyl-3,3-dimethylbutan-2-ol with various thiocyanates, including alkyl thiocyanates, benzyl thiocyanate, and ethyl 2-thiocyanatoacetate, yielded not only 3,4-dihydroferroceno[c]pyridines but also 1H-ferroceno[c]pyrroles. The selectivity of these reactions depended on the temperature and the order of addition. The size of substituents at the α-position to the sulfur atom of thiocyanates also had a significant effect on the distribution of products.

5-Halogenation of Uridine Suppresses Protonation-Induced Tautomerization and Enhances Glycosidic Bond Stability of Protonated Uridine: Investigations via IRMPD Action Spectroscopy, ER-CID Experiments, and Theoretical Calculations.

Uridine (Urd), a canonical nucleoside of RNA, is the most commonly modified nucleoside among those that occur naturally. Uridine has also been an important target for the development of modified nucleoside analogues for pharmaceutical applications. In this work, the effects of 5-halogenation of uracil on the structures and glycosidic bond stabilities of protonated uridine nucleoside analogues are examined using tandem mass spectrometry and computational methods. Infrared multiple photon dissociation (IRMPD) action spectroscopy experiments and theoretical calculations are performed to probe the structural influences of these modifications. Energy-resolved collision-induced dissociation experiments along with survival yield analyses are performed to probe glycosidic bond stability. The measured IRMPD spectra are compared to linear IR spectra predicted for the stable low-energy conformations of these species computed at the B3LYP/6-311+G(d,p) level of theory to determine the conformations experimentally populated. Spectral signatures in the IR fingerprint and hydrogen-stretching regions allow the 2,4-dihydroxy protonated tautomers (T) and O4- and O2-protonated conformers to be readily differentiated. Comparisons between the measured and predicted spectra indicate that parallel to findings for uridine, both T and O4-protonated conformers of the 5-halouridine nucleoside analogues are populated, whereas O2-protonated conformers are not. Variations in yields of the spectral signatures characteristic of the T and O4-protonated conformers indicate that the extent of protonation-induced tautomerization is suppressed as the size of the halogen substituent increases. Trends in the energy-dependence of the survival yield curves find that 5-halogenation strengthens the glycosidic bond and that the enhancement in stability increases with the size of the halogen substituent.

London Dispersion Stabilizes Chloro-Substituted cis-Double Bonds

AbstractWe present a combined experimental and computational study on the thermodynamic stability of cis- and trans-alkenes substituted with dispersion energy donor (DED) groups. To investigate the role of noncovalent interactions on equilibrium of cis- and trans-alkenes we utilized hydrochlorination reactions. While the general assumption is that increasing steric bulk favors the trans-alkene, we observe an equilibrium shift towards the more crowded cis-alkene with increasing substituent size. With the aim to quantify noncovalent interactions, we performed a double mutant cycle to experimentally gauge the attractive potential of bulky substituents. Additionally, we utilized local energy decomposition analysis at the DLPNO-CCSD(T)/def2-TZVP level of theory. We found LD interactions and Pauli exchange repulsion to be the most dominant components to influence cis- and trans-alkene equilibria.

Selectivity of dehydrogenative silicone–oxygen bond formation in diphenylsilane by base and base‐activated catalysts

AbstractVarious base catalysts and base‐activated catalysts were evaluated for their steric inhibitions and selectivity in silicon–oxygen bond formation between hydroxyl groups and each of the two active hydrogen sites of diphenylsilane. Three hydroxides, six amines, and an organic‐soluble N‐heterocyclic carbene‐copper alkoxide complex (CuIPr‐NHC) were reviewed using in situ FTIR monitoring of reaction progress for the stepwise consumption of both Si–H bonds in diphenylsilane in the presence of water and various alcohols. Hydroxide catalysts with sodium, potassium, and tetramethylammonium (TMA) cations showed strong dependence of cation identity on reaction rate and observable rate order but did not lead to accumulation of a once‐oxidized silane. Amine catalysts exhibited varying levels of selectivity to the once oxidized silane, leading to accumulation of diphenylsilanol and hydride terminated oligomers with relative reaction rates seemingly dependent on the size of amine's alkyl substituents. CuIPr‐NHC showed very limited reactivity to the second dehydrogenation step in comparison to the first, leading to high accumulation of once‐oxidized silane. Leveraging this, the production of diphenyl(monoalkoxy)silanes has been demonstrated with representative primary, secondary, and tertiary alcohols.

Structure‐activity Relation of Halogenated 2,5‐Dimethoxyamphetamines Compared to their α‑Desmethyl (2C) Analogues

Objective and hypothesis4‐Substituted derivatives of 2,5‐dimethoxyamphetamine (referred to as DOX derivatives) exhibit psychedelic and euphoria‐inducing effects, mainly mediated by 5‐HT2A receptor activation; for this reason, they are used recreationally but also bear therapeutic potential. Studies in humans and animals revealed that 4‐substitution with halogens results in high clinical potency, which increased with increasing size of the halogen. We therefore hypothesized that increasing size of the halogen substituent results in increased affinity at the 5‐HT2A receptor. Hence, we investigated the interaction profiles of 4‐halogenated DOX derivatives with monoaminergic receptors and transporters, and the trace amine‐associated receptor (TAAR) 1 and compared the obtained values to already known data of their α‐desmethyl (2C) analogues. This will lead to a better understanding of the structure‐activity relationship and potential side effects of these compounds, which could lead to novel and more efficacious drug candidates for drug‐assisted psychotherapy.MethodsWe assessed the binding affinity of 2,5‐dimethoxyamphetamine and its halogenated derivatives (DOF, DOC, DOB, and DOI) at several human serotonin (5‐HT) receptor subtypes, adrenergic and dopaminergic receptors, the trace amine‐associated receptor (TAAR) 1, and monoamine transporters. We determined the binding affinity by displacement of radioactively labeled ligands by the DOX derivatives by liquid scintillation counting in cell membrane preparations from cells transfected with the respective human receptor or transporter. Moreover, we investigated the activation potency of the DOX derivatives at the 5‐HT2A and 5‐HT2B receptor by calcium mobilization and at the TAAR1 by cAMP accumulation in cells transfected with the respective human receptor.ResultsThe 5‐HT2A receptor selectivity was substantially increased with increasing size of the halogen, with DOI displaying almost three orders of magnitude higher selectivity towards the 2A receptor subtype than DOF. All tested DOX derivatives were partial to full 5‐HT2A receptor agonists. The observed 5‐HT2 receptor interaction potency of the DOX derivatives is comparable to previously reported values of their 2C analogues, but with increased 5‐HT2A vs. 5‐HT1Aselectivity. None of the tested derivatives showed relevant affinity in the nanomolar range for TAAR1, α1A, α2A, D2, or monoamine transporters.ConclusionThe increased 5‐HT2A vs. 5‐HT1A selectivity of halogenated DOX derivatives compared to their 2C analogues may explain their increased clinical potency. However, increased 5‐HT2A vs. 5‐HT1A selectivity may also increase the risk of seizures. Hence, while DOX derivatives display advantages as 5‐HT2A‐selective compounds for pharmacological research, for clinical applications they may be inferior to 2C derivatives due to their potentially increased risks for seizures.

Modular synthesis of diphosphoramidite ligands derived from 1,8,10,9-triazaboradecalin and their complexes with Ni, Pd, and Pt

Here we report a convenient synthesis of new diphosphoramidite ligands derived from 1,8,10,9-triazaboradecalin (TBD) and describe their complexes with group 10 metals. Treating the chlorinated and structurally characterized ligand precursor ClTBDPhos (L1) with four equivalents of HOR (R = C3H7 or C3HF6) in the presence of NEt3 yielded the diphosphoramidite ligands iPrOTBDPhos (L2) and F-iPrOTBDPhos (L3) in good yields. L2 and L3 were used to prepare a variety of Ni, Pd, and Pt complexes with chloride and 1,2-benzenedithiolate ligands so their structures and spectroscopic properties could be compared to similar complexes with methoxy-substituted MeOTBDPhos such as (MeOTBDPhos)PdCl2, which is reported here for the first time. Single-crystal XRD studies on the (ROTBDPhos)PtCl2 complexes revealed that increasing the size of alkoxy substituents from MeO to iPrO to F-iPrO decreases the P-M-P bite angle from 97.47(3)° in (MeOTBDPhos)PtCl2 to 93.98(4)° in (F-iPrOTBDPhos)PtCl2. Similar changes were observed in the dithiolate complexes (iPrOTBDPhos)Pt(S2C6H4) and (F-iPrOTBDPhos)Pt(S2C6H4), and the structural studies revealed longer Pt-P bond distances compared to the dichloride complexes that correlated to ca. 1000 Hz decrease in their 195Pt-31P coupling constants. No significant changes were observed in the ligand bond distances in complexes containing the methoxy and isoproxy-substituted ligands, but complexes with fluorinated F-iPrOTBDPhos revealed subtle, but significant differences in their P-N, P-O, and B-N distances that reflect substituent-induced electronic changes in the ligand. Overall, this work establishes a more convenient synthetic entry into the chemistry of alkoxy-substituted TBDPhos ligands for ongoing studies with these and related transition metal complexes.

Quantitative 1H-NMR analysis reveals steric and electronic effects on the substrate specificity of benzoate dioxygenase in Ralstonia eutropha B9.

The cis-dihydroxylation of arenes by Rieske dearomatizing dioxygenases (RDDs) represents a powerful tool for the production of chiral precursors in organic synthesis. Here, the substrate specificity of the RDD benzoate dioxygenase (BZDO) in Ralstonia eutropha B9 whole cells was explored using quantitative 1H nuclear magnetic resonance spectroscopy (q1H-NMR). The specific activity, specific carbon uptake, and regioselectivity of the dihydroxylation reaction were evaluated in resting cell cultures for a panel of 17 monosubstituted benzoates. Two new substrates of this dioxygenase system were identified (2-methyl- and 3-methoxybenzoic acid) and the corresponding cis-diol metabolites were characterized. Higher activities were observed for benzoates with smaller substituents, predominantly at the 3-position. Elevated activities were also observed in substrates bearing greater partial charge at the C-2 position of the benzoate ring. The regioselectivity of the reaction was directly measured using q1H-NMR and found to have positive correlation with increasing substituent size. These results widen the pool of cis-diol metabolites available for synthetic applications and offer a window into the substrate traits that govern specificity for BZDO.

Synthesis and Evaluation of a Library of Alternating Amphipathic Copolymers to Solubilize and Study Membrane Proteins.

Amphipathic copolymers such as poly(styrene-maleic acid) (SMA) are promising tools for the facile extraction of membrane proteins (MPs) into native nanodiscs. Here, we designed and synthesized a library of well-defined alternating copolymers of SMA analogues in order to elucidate polymer properties that are important for MP solubilization and stability. MP extraction efficiency was determined using KcsA from E. coli membranes, and general solubilization efficiency was investigated via turbidimetry experiments on membranes of E. coli, yeast mitochondria, and synthetic lipids. Remarkably, halogenation of SMA copolymers dramatically improved solubilization efficiency in all systems, while substituents on the copolymer backbone improved resistance to Ca2+. Relevant polymer properties were found to include hydrophobic balance, size and positioning of substituents, rigidity, and electronic effects. The library thus contributes to the rational design of copolymers for the study of MPs.

The Role of Lateral Substituent Size in Azobenzene Chromophores on Photo- and Chiro-Optical Properties of Photoactive Polymethacrylates

The Role of Lateral Substituent Size in Azobenzene Chromophores on Photo- and Chiro-Optical Properties of Photoactive Polymethacrylates

Chiral pillar[n]arenes: Conformation inversion, material preparation and applications

Chiral pillar[n]arenes have shown great research value and application prospect in construction of chiral materials and chiral applications, due to their inherent planar chiral configurations, chiral recognition ability, easy modification and highly symmetric hydrophobic cavity. This review systematically summarized the conformation inversion factors of planar chiral pillar[5]arenes (pR/pS), such as solvents, temperature, substituent size, alkyl chains, chiral and achiral guest molecules. We firstly introduced the applications of chiral pillar[n]arenes for constructing chiral materials and pointed out that planar conformation inversion showed a great potential role in constructing chiral materials. Then, we mainly concluded the chiral applications of chiral and planar chiral pillar[n]arenes like chiral enantiomer analysis by circular dichroism, electrochemistry or chiral fluorescence sensing. From this review, we found that the inherent planar chiral conformation of chiral pillar[n]arenes have played a very important role in chiral field in the future.

Synthesis and Structure-Activity Relationships of New 2-Phenoxybenzamides with Antiplasmodial Activity.

The 2-phenoxybenzamide 1 from the Medicines for Malaria Venture Malaria Box Project has shown promising multi-stage activity against different strains of P. falciparum. It was successfully synthesized via a retrosynthetic approach. Subsequently, twenty-one new derivatives were prepared and tested for their in vitro activity against blood stages of the NF54 strain of P. falciparum. Several insights into structure-activity relationships were revealed. The antiplasmodial activity and cytotoxicity of compounds strongly depended on the substitution pattern of the anilino partial structure as well as on the size of substituents. The diaryl ether partial structure had further impacts on the activity. Additionally, several physicochemical and pharmacokinetic parameters were calculated (log P, log D7.4 and ligand efficiency) or determined experimentally (passive permeability and CYP3A4 inhibition). The tert-butyl-4-{4-[2-(4-fluorophenoxy)-3-(trifluoromethyl)benzamido]phenyl}piperazine-1-carboxylate possesses high antiplasmodial activity against P. falciparum NF54 (PfNF54 IC50 = 0.2690 µM) and very low cytotoxicity (L-6 cells IC50 = 124.0 µM) resulting in an excellent selectivity index of 460. Compared to the lead structure 1 the antiplasmodial activity was improved as well as the physicochemical and some pharmacokinetic parameters.

Energy barriers to rotation in axially chiral quinazoline-4-ones

Axially chiral 2-thioxo-3-(o-aryl)-quinazolin-4-ones and 2-(benzylthio)-3-(o-aryl)-quinazolin-4-ones were synthesized and their energy barriers to rotation about the N3-Caryl bond were determined by thermal racemization of the separated enantiomers. The rotational barriers were found to range from 112.7 to 140.8 kJ/mol, depending on size of the ortho substituent and to increase linearly with the size of the van der Waals radii of the ortho-halogen substituents. Although the isolation of the enantiomers of the N–C axially chiral compounds bearing an ortho-fluoro substituent are rare because of small size of fluorine atom, we found that the rotational barriers of quinazolin-4-ones bearing an ortho-fluoro group are high enough allowing the isolation of enantiomers.

Fluorescent Liquid Tetrazines.

Tetrazines with branched alkoxy substituents are liquids at ambient temperature that despite the high chromophore density retain the bright orange fluorescence that is characteristic of this exceptional fluorophore. Here, we study the photophysical properties of a series of alkoxy-tetrazines in solution and as neat liquids. We also correlate the size of the alkoxy substituents with the viscosity of the liquids. We show using time-resolved spectroscopy that intersystem crossing is an important decay pathway competing with fluorescence, and that its rate is higher for 3,6-dialkoxy derivatives than for 3-chloro-6-alkoxytetrazines, explaining the higher fluorescence quantum yields for the latter. Quantum chemical calculations suggest that the difference in rate is due to the activation energy required to distort the tetrazine core such that the and the higher-lying states cross, at which point the spin-orbit coupling exceeding 10 cm allows for efficient intersystem crossing to occur. Femtosecond time-resolved anisotropy studies in solution allow us to measure a positive relationship between the alkoxy chain lengths and their rotational correlation times, and studies in the neat liquids show a fast decay of the anisotropy consistent with fast exciton migration in the neat liquid films.

Canopy Catalysts for Alkyne Metathesis: Investigations into a Bimolecular Decomposition Pathway and the Stability of the Podand Cap.

Molybdenum alkylidyne complexes with a trisilanolate podand ligand framework (“canopy catalysts”) are the arguably most selective catalysts for alkyne metathesis known to date. Among them, complex 1 a endowed with a fence of lateral methyl substituents on the silicon linkers is the most reactive, although fairly high loadings are required in certain applications. It is now shown that this catalyst decomposes readily via a bimolecular pathway that engages the Mo≡CR entities in a stoichiometric triple‐bond metathesis event to furnish RC≡CR and the corresponding dinuclear complex, 8, with a Mo≡Mo core. In addition to the regular analytical techniques, 95Mo NMR was used to confirm this unusual outcome. This rapid degradation mechanism is largely avoided by increasing the size of the peripheral substituents on silicon, without unduly compromising the activity of the resulting complexes. When chemically challenged, however, canopy catalysts can open the apparently somewhat strained tripodal ligand cages; this reorganization leads to the formation of cyclo‐tetrameric arrays composed of four metal alkylidyne units linked together via one silanol arm of the ligand backbone. The analogous tungsten alkylidyne complex 6, endowed with a tripodal tris‐alkoxide (rather than siloxide) ligand framework, is even more susceptible to such a controlled and reversible cyclo‐oligomerization. The structures of the resulting giant macrocyclic ensembles were established by single‐crystal X‐ray diffraction.

Induced Nematic Phase of New Synthesized Laterally Fluorinated Azo/Ester Derivatives.

A new series of laterally fluorinated mesomorphic compounds, namely 2-fluoro-4-((4-(alkyloxy)phenyl)diazenyl)phenyl 4-substitutedbenzoate (Inx) were prepared and evaluated for their mesophase behavior. The synthesized series constitutes five members that possess different terminally attached polar groups (X). Their molecular structures were confirmed by elemental analyses and both FT-IR and NMR spectroscopy. Examination of the prepared derivatives was conducted via experimental and theoretical tools. Mesomorphic investigations were carried by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). DSC and POM measurements indicated that except for the un-substituted analogue, all other derivatives were purely nematogenic, possessing their nematic (N) mesophase enantiotropically. This is to say that insertions of terminal polar substituents on their mesogenic structures induced the N phase. In addition, the location of lateral and terminal polar moieties played a considerable role in achieving good thermal N stability. Computational calculations were investigated to determine the deduced optimized molecular structures. Theoretical data indicated that both size and polarity of the terminal substituent (X) have essential impact on the thermal parameters and optical properties of possible geometries.

Nickel-Catalyzed Oxidative Transamidation of Tertiary Aromatic Amines with N-Acylsaccharins

AbstractThe use of tertiary amines as surrogates for secondary amines has prominent advantages in terms of stabilization and ease of handling. A Ni-catalyzed transamidation of N-acylsaccharins with tertiary aromatic amines is reported. By using tert-butyl hydroperoxide as the terminal oxidant, this reaction permits selective cleavage of the C(sp3)–N bonds of unsymmetrical tertiary aromatic amines depending on the sizes of the alkyl substituents.

Thermoswitching of Helical Inversion of Dynamic Polyphenylacetylenes through cis-trans Isomerization of Amide Pendants

The cis-trans isomerization of amides plays a vital role in all kinds of structural changes and biological activities, involving protein folding, protein misfolding, and even protein molecular recognition. However, the helical inversion of synthetic macromolecules arising from the cis-trans isomerization of tertiary amides, as a good mimic of natural protein, has been rarely researched. Herein, we synthesized meta-disubstituted polyphenylacetylenes (PPAs) with different N-substituted tertiary amides as one of the pendants, poly{(−)-3-methoxycarbonyl-5-[N-methyl-N-(S)-(1-phenylethyl)carbamoyl]phenylacetylene}(sP-NMe) and poly{(−)-3-methoxycarbonyl-5-[N-propyl -N-(S)-(1-phenylethyl)carbamoyl]phenylacetylene} (sP-NPr). The cis-trans isomerization of amides was investigated by a combinational analysis of 1H/13C nuclear magnetic resonance (NMR), heteronuclear multiple quantum coherence (HMQC), variable-temperature NMR, Raman spectroscopy, ultraviolet–visible (UV–vis) spectroscopy, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and computer calculations. The substituted amide of sP-NMe favors the trans isomer at low temperatures, and the polyene main chain takes the right-handed helical conformation. When increasing the temperature, the ratio of the cis isomer in sP-NMe increases, which causes helical inversion. The screw sense of the polymer backbone of sP-NMe can be thermoreversibly switched upon tuning the cis-trans isomerization equilibrium of the tertiary amide pendant. In comparison, sP-NPr has the left-handed conformation with the majority of the cis isomer owing to the bulky propyl group, and cis-trans isomerization cannot induce helical inversion upon thermal treatment. The results reveal that helical inversion caused by the cis-trans isomerization of amide groups is highly dependent on the size of N-alkyl substituents.

Tuning the Reactivity and Bonding Properties of the Pt(II) Complexes by the Substitution(s) on the Trans‐Coordinated Non‐Aromatic Amine Ligand

AbstractKinetics of the hydration reaction and the bonding properties of the trans‐[Pt(NH3)2(NH2X)Cl]+ complexes (X=H, CH3, F, Cl, Br, NH2, NO2, OH, dimethylamine (DMA), cyclopropyl (CyP), cyclohexyl (CyH)) were studied theoretically by DFT methodology in the gas phase and the water solution. The electron‐donating and electron‐withdrawing X substituents lower and increase, respectively, the activation free energy (ΔG≠) and Pt‐trans ligand binding energies (BEs) to a similar extent as meta and para substituents of the pyridine ligand studied previously (ACS Omega, 2020, 5, 11768). For the saturated hydrocarbon X substituents (X=H, CH3, CyP, CyH), the ΔG≠ values and Pt‐trans ligand BEs decrease with the logarithm of the X substituent size being best quantified by the number of electrons. The additivity of the substituent effects was studied on the NF3 ligand and worked well for ligand charges and Pt−trans ligand BEs. The influence of chelation was evaluated by the comparison of the CyH system and the complexes with the cyclohexanediamine (DACH) ligand. Finally, the effect of isomerization was studied on the complexes with the 1,2‐bis(aminomethyl)cyclobutane (BAMCB) ligand. Thus, this study also evaluates the influence of the non‐leaving ligands present in cisplatin, oxaliplatin, lobaplatin, JM118, and JM11 drugs on the reactivity of the Pt(II) complexes in the same ligand environment.

Ni-catalyzed enantioselective [2 + 2 + 2] cycloaddition of malononitriles with alkynes

Summary Efficient strategies to assemble enantioenriched pyridine derivatives are highly important, given their significance in both synthetic and medicinal chemistry. Here, we report an enantioselective nickel-catalyzed intermolecular [2 + 2 + 2] cycloaddition of alkyne-tethered malononitriles with alkynes for the synthesis of densely substituted pyridines. The α-all-carbon quaternary center adjacent to pyridine is introduced by desymmetrizing the two cyano groups of disubstituted malononitriles. Notably, terminal alkynes are also tolerated with good regioselectivity to afford tetrasubstituted pyridines. Zinc halide is essential to enable the occurrence of the transformation by promoting the hetero-cyclometallation step. The reaction uses bio-renewable 2-MeTHF as the solvent and features mild reaction conditions, good functional group compatibilities, and enantioselectivities. This study offers a straightforward approach to the valuable enantioenriched heteroarenes from feedstock chemicals by forming three bonds and one quaternary stereocenter simultaneously in a single reaction step.

Thermochemical study of anthranilate derivatives: Effect of the size of the alkyl substituent

The gas-phase enthalpies of formation of two fragrance compounds, methyl anthranilate and butyl anthranilate, at T = 298.15 K, were determined from the combination of the corresponding enthalpies of vaporisation and energies of combustion, obtained from Calvet microcalorimetry and combustion calorimetry measurements, respectively. Additionally, theoretical calculations were performed, using the G3(MP2)//B3LYP composite method, to estimate the gas-phase enthalpies of formation of the two fragrance compounds. The good agreement between the experimental and computational gas-phase enthalpies of formation of the methyl anthranilate and butyl anthranilate, provided the confidence for extending the theoretical study to propyl anthranilate. Furthermore, the results were interpreted in terms of enthalpic increments, aiming to evaluate and understand the energetic effect inherent to the alkyl group (methyl, ethyl, propyl or butyl) present in the ester functional group of the anthranilate derivatives.