Synthesis, Molecular Modeling of Novel Substituted Pyridazinones and their Vasorelaxant Activities.

BACKGROUND: Hypertension, one of the most common cardiovascular diseases that can cause coronary disease, stroke, myocardial infarction, and sudden death, it is the major contributor to cardiac failure as well as renal insufficiency. OBJECTIVES: As there are many cardio-active pyridazinone-base derivatives in clinical use, therefore, we aimed to synthesize a new series of pyridazin-3-ones and evaluate their vasorelaxant activity. METHODS: A new series of synthesized compounds were carried out first by the synthesis of 6- flouroarylpyridazinones by cyclization of 3-(4-flourobenzoyl) propionic acid with hydrazine hydrate or arylhydrazines to provide the corresponding pyridazinone derivatives 2a-d. Mannich reaction was performed using morpholine or piperidine formaldehyde to obtain compounds 3a,b. On the other hand, reaction of 2a with various chloroacetamide intermediates, in dimethylformamide and potassium carbonate as a catalyst, afforded the target compounds 5a-c. The aromatic acid hydrazide intermediates 6a-g were prepared in 50-90% yield, by reacting to the prepared esters with hydrazine hydrate under reflux in ethanol. The two compounds 8a,b were prepared via condensation of 7a,b with ethyl chloroacetate in dry acetone. Finally, the target 2,4,6-trisubstituted pyridazinones 9a-c derivatives were obtained by the reaction of 7a with the appropriate aromatic aldehyde or substituted acetophenones. The new compounds were then evaluated for their vasorelaxant properties using isolated thoracic rat aortic rings. In addition, a homology model was built and molecular modeling simulation of these compounds into the active sites of the newly created α1a-adrenoceptor model was performed in order to predict and rationalize their affinities toward this receptor. RESULTS: Among these compounds; 5a was the most potent, it exhibited approximately two-times the activity of prazosin (IC50 = 0.250, 0.487 mmol, respectively) also, fourteen compounds were more potent than prazosin.

Synthesis and Pharmacological Evaluation of Novel Silodosin-Based Arylsulfonamide Derivatives as α1A/α1D-Adrenergic Receptor Antagonist with Potential Uroselective Profile.

Benign prostatic hyperplasia (BPH) is the most common male clinical problem impacting the quality of life of older men. Clinical studies have indicated that the inhibition of α1A-/α1D adrenoceptors might offer effective therapy in lower urinary tract symptoms. Herein, a limited series of arylsulfonamide derivatives of (aryloxy)ethyl alicyclic amines was designed, synthesized, and biologically evaluated as potent α1-adrenoceptor antagonists with uroselective profile. Among them, compound 9 (3-chloro-2-fluoro-N-([1-(2-(2-(2,2,2-trifluoroethoxy)phenoxy]ethyl)piperidin-4-yl)methyl)benzenesulfonamide) behaved as an α1A-/α1D-adrenoceptor antagonist (Ki(α1) = 50 nM, EC50(α1A) = 0.8 nM, EC50(α1D) = 1.1 nM), displayed selectivity over α2-adrenoceptors (Ki(α2) = 858 nM), and a 5-fold functional preference over the α1B subtype. Compound 9 showed adequate metabolic stability in rat-liver microsome assay similar to the reference drug tamsulosin (Clint = 67 and 41 µL/min/mg, respectively). Compound 9 did not decrease systolic and diastolic blood pressure in normotensive anesthetized rats in the dose of 2 mg/kg, i.v. These data support development of uroselective agents in the group of arylsulfonamides of alicyclic amines with potential efficacy in the treatment of lower urinary tract symptoms associated to benign prostatic hyperplasia.

Chiral analogues of (+)-cyclazosin as potent α1B-adrenoceptor selective antagonist.

(+)-Cyclazosin [(+)-1] is one of most selective antagonists of the α1B-adrenoceptor subtype (selectivity ratios, α1B/α1A = 13, α1B/α1D = 38-39). To improve the selectivity, we synthesized and pharmacologically studied the blocking activity against α1-adrenoceptors of several homochiral analogues of (+)-cyclazosin featuring different substituents on the carbonyl or amine groups, namely (-)-2, (+)-3, (-)-4-(-)-8, (+)-9. Moreover, we studied the activity of some their opposite enantiomers, namely (-)-1, (-)-3, (+)-6, and (-)-9, to evaluate the influence of stereochemistry on selectivity. The benzyloxycarbonyl and methyl (4aS,8aR) analogues (+)-3 and (-)-6 improved in a significant way the α1B selectivity of the progenitor compound: 4 and 14 time vs. the α1D subtype and 35 and 77 times vs. the α1A subtype, respectively. The study confirmed the importance of the hydrophobic cis-octahydroquinoxaline moiety of these molecules for the establishment of interactions with the α1-adrenoceptors as well that of their (4aS,8aR) stereochemistry to grant selectivity for the α1B subtype. Hypotheses on the mode of interaction of these compounds were advanced on the basis of molecular modeling studies performed on compound (+)-3.

Novel naftopidil derivatives containing methyl phenylacetate and their blocking effects on α1D/1A-adrenoreceptor subtypes.

α1-Adrenoceptor (α1-AR) antagonists are considered to be the most effective monotherapy agents for lower urinary tract symptoms associated with benign prostatic hyperplasia (LUTS/BPH). In this study, we synthesized compounds 2-17, which are novel piperazine derivatives that contain methyl phenylacetate. We then evaluated the vasodilatory activities of these compounds. Among them, we found that compounds 2, 7, 12, which contain 2-OCH3, 2-CH3 or 2, 5-CH3, respectively, exhibited potent α1-blocking activity similar to protype drug naftopidil (1). The antagonistic effects of 2, 7, and 12 on the (-)-noradrenaline-induced contractile response of isolated rat prostatic vas deferens (α1A), spleen (α1B) and thoracic aorta (α1D) were further characterized to assess the sub receptor selectivity. Compared with naftopidil (1) and terazosin, compound 12 showed the most desirable α1D/1A subtype selectivity, especially improved α1A subtype selectivity, and the ratios pA2 (α1D)/pA2 (α1B) and pA2 (α1A)/pA2 (α1B) were 17.0- and 19.5-fold, respectively, indicating less cardiovascular side effects when used to treat LUTS/BPH. Finally, we investigated the chiral pharmacology of 12. We found, however, that the activity of enantiomers (R)-12 and (S)-12 are not significantly different from that of rac-12.

Identification of 3,4-dihydro-2H-thiochromene 1,1-dioxide derivatives with a phenoxyethylamine group as highly potent and selective α1D adrenoceptor antagonists.

A series of phenoxyethylamine derivatives was designed and synthesized to discover potent and selective human α1D adrenoceptor (α1D adrenergic receptor; α1D-AR) antagonists. Compound 7 was taken from our internal compound collection as an attractive starting point and exhibited moderate binding affinity for α1D-AR and high selectivity against α1A- and α1B-ARs. We focused on modifying the 2-methylsulfonylbenzyl group of 7 to discover novel compounds structurally distinct from other reported α1-AR antagonists containing the phenoxyethylamine motif. Study of structure activity relationship guided by a targeted ligand-lipophilicity efficiency score led to the discovery of a novel scaffold of 3,4-dihydro-2H-thiochromene 1,1-dioxide for selective α1D-AR antagonists. Further optimization studies resulted in the identification of (4S)-N4-[2-(2,5-difluorophenoxy)ethyl]-N6-methyl-3,4-dihydro-2H-thiochromene-4,6-diamine 1,1-dioxide, (S)-41, as a novel, highly potent and selective α1D-AR antagonist. Herein, we provide details of the structure activity relationship of the phenoxyethylamine analog for the potency and selectivity.

Quinazoline based α1-adrenoreceptor antagonists with potent antiproliferative activity in human prostate cancer cell lines.

New α1-adrenoreceptor (α1-AR) antagonists related to prazosin and doxazosin were synthesized by replacing piperazine ring with (S)- or (R)-3-aminopiperidine. Binding studies indicated that the S configuration at the 3-C position of the piperidine ring is crucial for an optimal interaction of the compounds at all three α1-AR subtypes. Quinazolines 9 and 10, bearing a quinone ring on the lateral chain, exhibited also potent antiproliferative activity in LNCaP androgen-sensitive prostate cancer cell lines, higher than that of doxazosin. Compound 10 increased apoptosis, in terms of DNA fragmentation, without triggering cell necrosis. The prooxidant activity found in compound 10 may underlie its ability to inhibit cell proliferation in synergy with the effect mediated by α1-AR antagonism. Due to its better biological profile compared to doxazosin for LNCaP cell line, compound 10 might be a valuable lead compound for the design of new prostate antitumor agents.

Design, Synthesis, and Biological Evaluation of Novel Tetrahydroprotoberberine Derivatives (THPBs) as Selective α1A-Adrenoceptor Antagonists.

A novel series of tetrahydroprotoberberine derivatives (THPBs) were designed, synthesized, and evaluated as selective α1A-adrenergic receptors (AR) antagonists for the treatment of benign prostatic hyperplasia. On the basis of the pharmacophore model of the marketed drug silodosin, THPBs were modified by introducing an indole segment into their core scaffolds. In calcium assays, 7 out of 32 compounds displayed excellent antagonistic activities against α1A-ARs, with IC50 less than 250 nM. Among them, compound (S)-27 had the most potent biological activity; its IC50 toward α1A-AR was 12.8 ± 2.2 nM, which is 781 and 20 times more selective than that toward α1B- and α1D-AR, respectively. In the functional assay using isolated rat tissues, compound (S)-27 inhibited norepinephrine-induced urethra smooth muscle contraction potently (IC50 = 0.5 ± 0.3 nM), without inhibiting the aortic contraction (IC50 > 1000 nM), displaying a better tissue selectivity than the marketed drug silodosin. Additional results of preliminary safety studies (acute toxicity and hERG inhibition) and pharmacokinetics studies indicated the potential druggability for compound (S)-27 which is a promising lead for the development of selective α1A-AR antagonists for the treatment of BPH.

Synthesis and structure-activity relationships of novel arylpiperazines as potent antagonists of α1-adrenoceptor.

Arylpiperazines 2-11 were synthesized, and their biological profiles at α1-adrenergic receptors (α1-ARs) assessed by binding assays in CHO cells expressing human cloned subtypes and by functional experiments in isolated rat vas deferens (α1A), spleen (α1B), and aorta (α1D). Modifications at the 1,3-benzodioxole and phenyl phamacophoric units resulted in the identification of a number of potent compounds (moderately selective with respect to the α1b-AR), in binding experiments. Notably, compound 7 (LDT451) showed a subnanomolar pKi of 9.41 towards α1a-AR. An encouragingly lower α1B-potency was a general trend for all the series of compounds, which showed α1A/D over α1B selectivity in functional assays. If adequately optimized, such peculiar selectivity could have relevance for a potential LUTS/BPH therapeutic application.

Design, Synthesis, and Biological Evaluation of Indoline and Indole Derivatives as Potent and Selective α1A-Adrenoceptor Antagonists.

A series of indoline and indole derivatives were designed, synthesized, and evaluated as selective α1A-adrenergic receptor (α1A-AR) antagonists for the treatment of benign prostatic hyperplasia (BPH). In this study, two highly selective and potent α1A-AR antagonists, compounds (R)-14r (IC50 = 2.7 nM, α1B/α1A = 640.1, α1D/α1A = 408.2) and (R)-23l (IC50 = 1.9 nM, α1B/α1A = 1506, α1D/α1A = 249.6), which exhibited similar activities and better selectivities in cell-based calcium assays as compared with the marketed drug silodosin (IC50 = 1.9 nM, α1B/α1A = 285.9, α1D/α1A = 14.4), were identified. In the functional assays with isolated rat tissues, compounds (R)-14r and (R)-23l also showed high potency and uroselectivity. Most importantly, (R)-14r and (R)-23l can significantly decrease the micturition frequency and increase the mean voided volume of the BPH rats in a dose-dependent manner, making them worthy of further investigation for the development of anti-BPH agents.

Antiarrhythmic and α-Adrenoceptor Antagonistic Properties of Novel Arylpiperazine Derivatives of Pyrrolidin-2-one.

In an effort to develop α-adrenoceptor antagonists with antiarrhythmic activity, we designed a series of pyrrolidin-2-one derivatives. The α1- and α2-adrenorecepor affinities of the new pyrrolidin-2-one derivatives were determined using a radioligand binding assay. The most active compound was then tested in vitro for intrinsic activity toward α(1A)- and α(1B)-adrenoceptors and in vitro for antiarrhythmic activity in epinephrine-induced arrhythmia in rats. The highest affinity for the α1-adrenoceptor (pK(i) = 7.01) was displayed by 1-{4-[4-(2-methoxy-5-chlorophenyl)-piperazin-1-yl]-methyl}-pyrrolidin-2-one (9). 1-[4-(2-Fluorophenyl)-piperazin-1-yl]-methyl-pyrrolidin-2-one (7) showed the highest affinity toward the α2-adrenoceptor (pK(i) = 6.52). Intrinsic activity studies of compound 9 showed that this compound is an antagonist of both α(1A)- (EC50 = 0.5 nM) and α(1B)- (EC50 = 51.0 nM) adrenoceptors. Compound 9 displayed antiarrhythmic activity in rats (ED50 = 5.0 mg/kg (3.13-7.99)). New derivatives of pyrrolidin-2-one with α1 -adrenoceptor affinity were identified. We propose that the antiarrhythmic activity of compound 9 is related to its antagonism of α(1A)- and α(1B)-adrenoceptors.

Synthesis and evaluation of aporphine analogs containing C1 allyl isosteres at the h5-HT(2A) receptor.

A series of C1 aporphine analogs related to compound 5 and that contain substituted allylic, alkynyl, nitrile, ester and benzyl groups was synthesized and evaluated for affinity at h5HT2A and α1A receptors in functional activity assays that measure calcium release. The presence of branched allylic substituent groups diminished affinity for the h5HT2A receptor. Likewise, the alkynyl, nitrile and ester derivatives evaluated displayed lower 5-HT2A receptor affinity as compared to 5. Hydrophobic, steric and electronic effects impact the affinity of p-substituted benzyl derivatives 8i-8k but in different ways. High hydrophobicity and size favor 5-HT2A affinity whereas, high electronegativity disfavors 5-HT2A affinity. p-Bromobenzyl analog 8k was identified as a 5-HT2A receptor selective ligand, with the highest 5-HT2A receptor affinity of any aporphine known to date. Most of the other analogs were selective for the 5-HT2A versus the α1A receptor. ChemScore binding energies from docking studies correlated qualitatively with the observed trends in affinity for 8i-8k, although the binding energies were not well differentiated quantitatively.

Prazosin-Conjugated Matrices Based on Biodegradable Polymers and α-Amino Acids--Synthesis, Characterization, and in Vitro Release Study.

Novel and promising macromolecular conjugates of the α1-adrenergic blocker prazosin were directly synthesized by covalent incorporation of the drug to matrices composed of biodegradable polymers and α-amino acids for the development of a polymeric implantable drug delivery carrier. The cyto- and genotoxicity of the synthesized matrices were evaluated using a bacterial luminescence test, protozoan assay, and Salmonella typhimurium TA1535. A new urethane bond was formed between the hydroxyl end-groups of the synthesized polymer matrices and an amine group of prazosin, using 1,1'-carbonyldiimidazole (CDI) as a coupling agent. The structure of the polymeric conjugates was characterized by various spectroscopy techniques. A study of hydrogen nuclear magnetic resonance ((1)H-NMR) and differential scanning calorimetry (DSC) thermodiagrams indicated that the presence of prazosin pendant groups in the macromolecule structures increased the polymer's rigidity alongside increasing glass transition temperature. It has been found that the kinetic release of prazosin from the obtained macromolecular conjugates, tested in vitro under different conditions, is strongly dependent on the physicochemical properties of polymeric matrices. Furthermore, the presence of a urethane bond in the macromolecular conjugates allowed for obtaining a relatively controlled release profile of the drug. The obtained results confirm that the pharmacokinetics of prazosin might be improved through the synthesis of polymeric conjugates containing biomedical polymers and α-amino acids in the macromolecule.

Novel naftopidil-related derivatives and their biological effects as alpha1-adrenoceptors antagonists and antiproliferative agents.

Eleven novel naftopidil-related compounds that contain amide and indole groups were designed and synthesized. The biological effects of these compounds on three α1-adrenoceptor subtypes and cancerous human prostate cell lines (PC-3, DU-145, and LNCaP) were determined. Compounds 2, 3, 5, 11, and 12 exhibited an α1-adrenoceptor antagonistic activity, whereas compounds 9, 10, and 12 displayed moderate antiproliferative activities. Compound 3 exhibited a significant α(1D/1A) blocking activity in isolated rat tissues (97.7- and 64.6-fold selective for α(1D) and α(1A) compared with α(1B)) but not a relevant cytotoxic activity. Compound 12 demonstrated a potent and selective α(1D/1A) antagonistic activity (47.9- and 19.1-fold for α(1D) and α(1A) compared with α1B) and a potent antiproliferative activity in PC-3 cells (IC50 = 15.70 µM). Further testing confirmed that compound 12 inhibited the growth of PC-3 cells by inducing apoptosis and G0/G1 cell cycle arrest, which was mediated by α1-adrenoceptor. Therefore, compound 12 is a potential multipotent agent that can act as an effective α1-adrenoceptor subtype antagonist for treating benign prostatic hyperplasia and a preventive medication against human prostate cancer.

α-Adrenoceptor antagonistic and hypotensive properties of novel arylpiperazine derivatives of pyrrolidin-2-one.

This study focused on a series of pyrrolidin-2-one derivatives connected via two or four methylene units to arylpiperazine fragment. The compounds obtained for α1- and α2-adrenoceptors were assessed. The compound with highest affinity for the α1-adrenoceptors was 1-{4-[4-(2-chloro-phenyl)-piperazin-1-yl]-butyl}-pyrrolidin-2-one (10 h) with pKi=7.30. Compound with pKi (α1) ⩾6.44 were evaluated in functional bioassays for intrinsic activity at α1A- and α1B-adrenoceptors. All compounds tested were antagonists of the α1B-adrenoceptors. Additionally, compounds 10e and 10h were α1A-adrenoceptors antagonist. The dual α1A-/α1B-adrenoceptors antagonists, compounds 10e and 10h were also tested in vivo for their hypotensive activity in rats. These compounds, when dosed of 1.0 mg/kg iv in normotensive, anesthetized rats, significantly decreased systolic and diastolic pressure and their hypotensive effects lasted for longer than one hour.

Design, synthesis and alpha1-adrenoreceptor blocking activity of new arylpiperazines containing acetophenone substituents.

Alpha1-AR antagonists are currently first-line therapy for lower urinary tract symptoms associated with benign prostatic hyperplasia (LUTS/BPH). In this study, we report the synthesis of a new series of arylpiperazine derivatives containing acetophenone (3-17) which possess alpha1-adrenoreceptor blocking activity. The in vitro alpha1-adrenoreceptor blocking activity of each derivative was first screened using rabbit thoracic aortic rings by measuring the relaxation response (%) activated by (-)-noradrenaline (3 microM). Compounds 6 and 7 with 2,5-dimethoxy and 2-ethoxy substituent were found to have significant vasodilatory effect. Since the presence of a chiral carbon in the structure, 6 and 7 together with their enantiomers 14-17 were further evaluated by testing diastolic effect on rabbit thoracic aorta, prostate and bladder smooth muscle. The S-enantiomer was found to have more potent diastolic activity than the R-enantiomer and racemate, 17 being the most effective alpha1-adrenoreceptor antagonist. In order to assess tissue selectivity, the antagonistic effect of 17 on the (-)-noradrenaline induced contractile response of isolated rat vas deferens (alpha(1A)), spleen (alpha(1B)) and aorta (alpha(1D)) was characterized finally. Compared with naftopidil (1) and terazosin, compound 17 exhibited higher selectivity (18-fold) for the alpha(1D)-adrenoceptor subtype as compared to the alpha(1B)-adrenoceptor subtype, indicating less cardiovascular side effects for the treatment of LUTS/BPH. These data suggest that the acetophenone is a new effective adrenergic receptor ligand as well as incentivizes further research regarding pharmacological properties of chiral molecules.

Molecular design and synthesis of 1,4-disubstituted piperazines as α(1)-adrenergic receptor blockers.

A new series of 4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylic acid amide and 3,5,6,8-tetrahydropyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-one derivatives were designed, synthesized, their binding and functional properties as α1-adrenoreceptors blockers were evaluated. A new validated α1-adrenoreceptor blocker pharmacophore model (hypothesis) was generated using Discovery Studio 2.5. The compare-fit study for the designed molecules with the generated hypothesis was fulfilled and several compounds showed significant high fit values. Compounds IVa-c, VIIa-d, VIIIa-c, Xa-c, XIa-d have shown blocking activity ranging from 46.73% up to 94.74% compared to 99.17% for prazosin.

Combining on-chip synthesis of a focused combinatorial library with computational target prediction reveals imidazopyridine GPCR ligands.

Using the example of the Ugi three-component reaction we report a fast and efficient microfluidic-assisted entry into the imidazopyridine scaffold, where building block prioritization was coupled to a new computational method for predicting ligand-target associations. We identified an innovative GPCR-modulating combinatorial chemotype featuring ligand-efficient adenosine A1/2B and adrenergic α1A/B receptor antagonists. Our results suggest the tight integration of microfluidics-assisted synthesis with computer-based target prediction as a viable approach to rapidly generate bioactivity-focused combinatorial compound libraries with high success rates.

Studies on novel pyridine and 2-pyridone derivatives of N-arylpiperazine as α-adrenoceptor ligands.

This paper describes the synthesis of a series of new N-arylpiperazine derivatives of pyridine and 2-pyridone. The in vitro pharmacological study indicated that all of the compounds possess affinity towards α1-adrenoceptors, with exception of 6d, and are selective over α2 receptor. The most potent compound 5f displayed 62-fold α2/α1 selectivity with Ki value of 27.3 nM for α1 receptor. Selectivity of other ligands ranged from 6 to more than 146-fold. Hydrochlorides of selected compounds with the best α1-adrenoceptor affinity (7b, 7e, 7f, 8b) were tested in vivo (hypotensive activity test in rats) and the results proved their α-adrenoreceptor antagonistic activity. Furthermore, the lipophilicity of the investigated compounds has been assessed experimentally and in silico.

Design, synthesis and biological evaluation of novel 7-mercaptocoumarin derivatives as α(1)-adrenoceptor antagonists.

Study on the pharmacophore model of α(1)-adrenoceptor (α(1)-AR) antagonists led to design a series of novel 7-mercaptocoumarin derivatives as α(1)-AR antagonists. All designed compounds have been synthesized and biologically evaluated. The results showed that most of them exhibited strong antagonistic activity. Especially compound 6 showed excellent activity, which was better than that of the reference compound prazosin. Structure-activity relationship studies revealed that small hydrophobic group at the terminal heterocyclic ring and ortho substituents on the phenyl ring of phenylpiperazine moiety were the essential structural factors for α(1)-AR antagonistic activity. The pharmacophore modeling studies further clarified their structural contributions to antagonistic activity and also demonstrated that 7-mercaptocoumarin moiety could be a useful scaffold for design of α(1)-AR antagonists.

Synthesis and SAR-study for novel arylpiperazine derivatives of 5-arylidenehydantoin with α1-adrenoceptor antagonistic properties.

The study is focused on a series of 5-arylidenehydantoin derivatives with a phenylpiperazine-hydroxypropyl fragment at N3 of the hydantoin ring. The compounds were assessed on their affinity for α(1)-adrenoceptors and evaluated in functional bioassays for their antagonistic properties. Crystal structures of (Z)-5-(4-chlorobenzylidene)-3-(3-(4-(2-ethoxyphenyl)piperazin-1-yl)-2-hydroxypropyl)imidazolidine-2,4-dione (7) and hydrochloride of (Z)-5-(4-chlorobenzylidene)-3-(2-hydroxy-3-(4-(2-methoxyphenyl)piperazin-1-yl)propyl)imidazolidine-2,4-dione (10a) were solved using the X-ray diffraction method. Classical molecular mechanics (MMFFs force field, MCMM, MacroModel) were used to predict 3D structure of compounds 5a-18a using a crystal structure of 7. SAR analysis was performed on the basis of Barbaro's pharmacophore model and structural properties of previously investigated α(1)-adrenoceptor antagonists possessing a hydantoin fragment. Most of the compounds exhibited significant affinities for α(1)-ARs in nanomolar range (40-290 nM). The highest activities (K(i)<75 nM) were observed for compounds possessing a 2-alkoxyphenylpiperazine fragment and two methoxy substituents at the benzylidene moiety. The results indicated that chemical properties, number and positions of substituents at the 5-arylidene fragment influenced the power of α(1)-affinities as follows: 3,4-di CH(3)O>2,4-di CH(3)O>4-Cl>2,3-di CH(3)O>H>4-N(CH(3))(2).