Synthesis and structure-activity relationships of novel 2',2'-difluoro analogues of docetaxel

To investigate the role of the 2'-hydroxy group at the C-13 side chain of docetaxel in the antitumor activity, we prepared several 2',2'-difluoro derivatives of docetaxel and evaluated their cytotoxicity against mouse leukemia and human tumor cell lines and their microtubule disassembly-inhibitory activity. These analogues were prepared by esterification of protected 10-deacetylbaccatin III (21) with appropriate alpha, alpha-difluorinated carboxylic acids (Charts 1 and 2). Among these 2',2'-difluorodocetaxel derivatives, 2',2'-difluorodocetaxel (23b) was approximately 3-10 times as active as 2'-fluorodocetaxel (29a) in terms of cytotoxicity. In addition, the 3'-(2-furyl) (23h) and 3'-(2-pyrrolyl) (23p) analogues showed activity comparable or superior to that of docetaxel (2).     

Agents for the treatment of overactive detrusor. IV. Synthesis and structure-activity relationships of cyclic analogues of terodiline

A series of pyrrolidine derivatives were synthesized and examined for inhibitory activity on detrusor contraction in vivo. Among those compounds, 5,5-dimethyl-2-(2,2-diphenylethyl)-3-isopropylidenepyrrolidine+ ++ hydrochloride (41.HCl), 2-(2,2-di(4-fluorophenyl)ethylene)-5,5-dimethyl-3-isopropylidenepyrro lidine hydrochloride (42.HCl), (+)-5,5-dimethyl-2-(N,N-diphenylaminomethyl)-3-isopropylidenepy rrolidine hydrochloride (+)-(43a.HCl), (-)-5,5-dimethyl-2-(N,N-diphenylaminomethyl)-3-isopropylidenepy rrolidine hydrochloride (-)-(43a.HCl), and 2-(N,N-di(4-fluorophenyl)aminomethyl)-5,5-dimethyl-3-isopropylidenepy rrolidine methanesulfonate (43b.MsOH) showed stronger inhibitory activity on detrusor contraction than terodiline.     

7-Azetidinylquinolones as antibacterial agents. Synthesis and structure-activity relationships

A series of novel antibacterial quinolones and naphthyridones has been prepared which contain 7-azetidinyl substituents in place of the usual piperazine or aminopyrrolidine groups. These azetidinyl derivatives were evaluated for in vitro activity by determining minimum inhibitory concentrations against a variety of bacteria. In vivo efficacy in the mouse infection model and blood levels in the mouse were determined for several compounds. The influence on the structure-activity relationships of varying substituents in the azetidine ring and at position 8 (CH, CF, CCl, N) and N-1 (ethyl, fluoroethyl, cyclopropyl, tert-butyl, 4-fluorophenyl, and 2,4-difluorophenyl) was also studied. Compounds with outstandingly broad-spectrum activity, particularly against Gram-positive organisms, improved in vivo efficacy, and high blood levels were identified in this work. 7-Azetidinyl-8-chloroquinolones were considered as warranting further development.     

Synthesis and structure-activity relationships of 2-pyrazinylcarboxamidobenzoates and beta-ionylideneacetamidobenzoates with retinoidal activity

The structure-activity relationships of two series of novel retinoids (2-pyrazinylcarboxamidobenzoates and beta-ionylideneacetamidobenzoates) have been investigated by evaluating their ability to induce differentiation in both human promyelocytic leukemia (HL60) cells and mouse embryonal carcinoma (P19) cells. The most active compound (ED50 = 8.3 x 10(-9) M) of the 2-pyrazinylcarboxamidobenzoates is 4-[2-(5,6,7,8-tetrahydro-5,5,8, 8-tetramethylquinoxalyl)carboxamido]benzoic acid (9u), while the most active analogue of the beta-ionylideneacetamidobenzoates is 4-[3-methyl-5-(2',6',6'-trimethyl-1'-cyclohexen-1'-yl)-(2E, 4E)-pentadienamido]benzoic acid (10a, ED50 = 3.2 x 10(-8) M). Our studies identify an absolute requirement for the carboxylic acid moiety on the aromatic ring to be para relative to the amide linkage for activity. Benzoate substitutions in the ortho position relative to the terminal carboxylate (9d,k,r) are well-tolerated; however, a methoxy substituent meta relative to the terminal carboxylate gives rise to only weakly active analogues (9x). Conformational studies (NMR, X-ray crystallography) of the 2-pyrazinylcarboxamidobenzoates indicate that the preferred conformation exhibits a trans-amide bond and an internal hydrogen bond between the quinoxaline N1 and HN amide which locks the torsional angle between C2 and CO in the s-trans conformation. N-Methylation (9y) results in loss of activity. Studies indicate that there is now a cis-amide bond present which redirects the carboxylate toward the pharmacophoric gem-dimethyl groups. The distance between the gem-dimethyl group and the terminal carboxylate appears to be too short to activate the retinoid receptor. N-Methylation in the beta-ionylideneacetamidobenzoate series (10c) also results in the formation of a cis-amide bond and loss of activity.     

Synthesis and structure-activity data of some new epibatidine analogues

The high-pressure Diels-Alder reaction of N-carbomethyoxypyrroles and phenyl vinyl sulfone affords versatile intermediates for the palladium-catalyzed preparation of new epibatidine analogues. Structure-activity relationships of new epibatidine analogues are presented. High affinities of Ki = 0.81 and 2.6 nM for the [3H]-cytisine rat brain nicotinic acetylcholine binding sites were found for the 5-pyrimidinyl and the 5-(2-amino)-pyrimidinyl epibatidine analogues, respectively.     

Synthesis and structure-activity relationships of dequalinium analogues as K+ channel blockers. Investigations on the role of the charged heterocycle

Small conductance Ca(2+)-activated K+ (SKCa) channels occur in many cells but have been relatively little studied. Dequalinium, a bis-quinolinium compound, has recently been shown to be the most potent nonpeptidic blocker of this K+ channel subtype. This paper examines the importance of the quinolinium rings for blocking activity. Analogues of dequalinium were synthesised in which one quinolinium group was removed (1 and 2) or replaced by a triethylammonium group (3). They have been assayed in vitro for their ability to block the after-hyperpolarization (mediated by the opening of SKCa channels) that follows the action potential in rat sympathetic neurones. The compound having one quinolinium and one triethylammonium group (3) showed reduced activity, and it is suggested that the stronger binding to the channel of the quinolinium relative to the triethylammonium group may be related to differences in their electrostatic potential energy maps. Two monoquaternary compounds (1 and 2) were tested, but they exhibited a different pharmacological profile that did not allow definite conclusions to be drawn concerning their potency as blockers of the SKCa channel. Replacement of both quinolinium groups by pyridinium, acridinium, isoquinolinium, or benzimidazolium reduced but did not abolish activity. These results show that compounds having a number of different heterocyclic cations are capable of blocking the SKCa channel. However, among the heterocycles studied, quinoline is optimal. Furthermore, charge delocalization seems to be important: the higher the degree of delocalization the more potent the compound.     

Synthesis and structure-activity relationships of 3,7-dimethyl-1-propargylxanthine derivatives, A2A-selective adenosine receptor antagonists

A series of 8-substituted derivatives of 3,7-dimethyl-1-propargylxanthine (DMPX) was synthesized and investigated as A2A adenosine receptor antagonists. Different synthetic strategies for the preparation of DMPX derivatives and analogues were explored. A recently developed synthetic procedure starting from 3-propargyl-5,6-diaminouracil proved to be the method of choice for the preparation of this type of xanthine derivatives. The novel compounds were investigated in radioligand binding studies at the high-affinity adenosine receptor subtypes A1 and A2A and compared with standard A2A adenosine receptor antagonists. Structure-activity relationships were analyzed in detail. 8-Styryl-substituted DMPX derivatives were identified that exhibit high affinity and selectivity for A2A adenosine receptors, including 8-(m-chlorostyryl)-DMPX (CS-DMPX, Ki A2A = 13 nM, 100-fold selective), 8-(m-bromostyryl)-DMPX (BS-DMPX, Ki A2A = 8 nM, 146-fold selective), and 8-(3,4-dimethoxystyryl)-DMPX (Ki A2A = 15 nM, 167-fold selective). These and other novel compounds are superior to the standard A2A adenosine receptor antagonists KF17837 (4) and CSC (5) with respect to A2A affinity and/or selectivity.     

Synthesis and structure-activity relationships of 3-hydrazono-1H-2-indolinones with antituberculosis activity

OBJECTIVES: To evaluate endometrial responses to three different forms of amenorrhea-inducing HRT in postmenopausal women. MATERIAL AND METHODS: Fifty-one postmenopausal women completing a one-year HRT trial with percutaneous estradiol gel containing 1.5 mg estradiol daily combined with a levonorgestrel-releasing intrauterine device (LNG-IUD) (n=18), or natural progesterone 100 mg daily orally (n= 19) or vaginally (n=15) during 1-25 calendar days of each month. Endometrial thickness and uterine size were measured by transvaginal ultrasound, and endometrial cytology/histology was assessed from specimens taken by needle aspiration before the study and at 12 months. RESULTS: Before medication, the median endometrial thickness was 2.0 mm in the LNG-IUD group, 2.4 mm in the oral P group and 2.5 mm in the vaginal P group. At 12 months of therapy the respective values, 3.0, 2.7 and 2.4 mm, did not differ significantly from the initial values. LNG-IUD induced epithelial atrophy in all women, which was accompanied by stromal decidualization in 12 women. On the contrary, only four women in the oral P group and five women in the vaginal P group had an inactive or atrophic endometrium. The remaining cases were dominated by proliferative features. No hyperplasia was seen in any of the groups. CONCLUSION: LNG-IUD appeared to be an effective method of counteracting the stimulatory effect of estrogen on the endometrium, whereas natural progesterone given orally or vaginally was not sufficiently effective in this function at the doses used. The vaginal and oral administrations of progesterone did not differ from each other in this respect.     

Synthesis and structure-activity relationships of dual histamine H2 and gastrin receptor antagonists with decreased hydrophobicity

In order to study structure-activity relationships of the previously reported dual histamine H2 and gastrin receptor antagonists and also to improve their low oral absorbability, we tried two chemical modifications. One tried to decrease the high hydrophobicity of the parent hybrid compounds to an appropriate level by incorporating a hydrophilic group into the molecule and the other by replacing the more hydrophobic groups with less hydrophobic ones. The former compounds (type I) involved hybrid compounds with a hydroxyl group at a position of a spacer, a piperidine moiety of H2A, or a phenyl ring at the C5 of the benzodiazepine skeleton as well as those with a free carboxyl group in the piperidine moiety of H2A. The latter (type II) involved hybrid compounds with the C5-phenyl group replaced with either a methyl group or hydrogen atom. Among them, only a type I compound, ([2-[3-(3-piperidin-1-ylmethylphenoxy)propylcarbamoyl] ethylcarbamoyl]methyl)carbamic acid 3-[3-[5-(3-hydroxyphenyl)-1-methyl-2-oxo-2,3-dihydro-1H-1,4-benzodiaz epin-3-yl]ureido]benzyl ester (18), showed potent dual histamine H2 and gastrin receptor antagonistic activity, whereas others resulted in a significant decrease of histamine H2 receptor antagonistic activity. The in vivo gastric acid antisecretory activity of 18 evaluated by Schild's rat method, however, did not suggest any notable improvement in oral absorbability.     

Design, synthesis, derivatization, and structure-activity relationships of simplified, tricyclic, 1,2,4-trioxane alcohol analogues of the antimalarial artemisinin

Novel C4-(hydroxyalkyl)trioxanes 5d and 5e were designed and synthesized based on an understanding of the molecular mechanism of action of similar 1,2,4-trioxanes structurally related to the antimalarial natural product artemisinin (1). In vitro efficacies of these two new pairs of C4-diastereomers against chloroquine-sensitive Plasmodium falciparum support conclusions about the importance to antimalarial activity of formation of a C4 radical by a 1,5-hydrogen atom abstraction. Derivatives 6, 7, and 21 of C4 beta-substituted trioxane alcohols 4a, 5d, and 5e were prepared, each in a single-step, high-yielding transformation. Four of these new analogues, 6a-c and 7, are potent in vitro antimalarials, having 140 to 50% of the efficacy of the natural trioxane artemisinin (1).     

Synthesis, structure, and structure-activity relationships of divalent thrombin inhibitors containing an alpha-keto-amide transition-state mimetic

A new class of divalent thrombin inhibitors is described that contains an alpha-keto-amide transition-state mimetic linking an active site binding group and a group that binds to the fibrinogen-binding exosite. The X-ray crystallographic structure of the most potent member of this new class, CVS995, shows many features in common with other divalent thrombin inhibitors and clearly defines the transition-state-like binding of the alpha-keto-amide group. The structure of the active site part of the inhibitor shows a network of water molecules connecting both the side-chain and backbone atoms of thrombin and the inhibitor. Direct peptide analogues of the new transition-state-containing divalent thrombin inhibitors were compared using in vitro assays of thrombin inhibition. There was no direct correlation between the binding constants of the peptides and their alpha-keto-amide counterparts. The most potent alpha-keto-amide inhibitor, CVS995, with a Ki = 1 pM, did not correspond to the most potent divalent peptide and contained a single amino acid deletion in the exosite binding region with respect to the equivalent region of the natural thrombin inhibitor hirudin. The interaction energies of the active site, transition state, and exosite binding regions of these new divalent thrombin inhibitors are not additive.     

Synthesis and structure-activity relationships of 7-(2-aminoalkyl)morpholinoquinolones as anti-Helicobacter pylori agents

A series of the titled compounds was synthesized and tested for anti-Helicobacter pylori activities. We discovered Y-34867 having the most potent activity against Helicobacter pylori among the quinolones tested along with high photostability. Furthermore, Y-34867 showed an excellent therapeutic effect in the experimental Helicobacter pylori infected Mongolian gerbil model.     

Inotropic agents. Synthesis and structure-activity relationships of new milrinone related cAMP PDE III inhibitors

The synthesis of 6-substituted 5-acyl-1,2-dihydro-2-oxo-3-pyridinecarbonitriles 1b,c, 1,2,5,6,7,8-hexahydro-2,5-dioxo-3-quinolinecarbonitriles 1d-g and esters of 5-cyano-1,6-dihydro-2-methyl-6-oxo-3-pyridinecarboxylic acid 2b-e is described. In the case of 1e and 1f, a careful elucidation of the reaction mechanism is discussed. As milrinone analogues, the above compounds were tested on contractile activity and frequency rate of spontaneously beating atria from reserpine-treated guinea pigs. The methyl and the benzyl esters 2b and 2e showed an appreciable positive inotropic activity when compared to milrinone. A fitting study with the DISCO (Distance Comparison) model has been carried out on 2e. This modeling approach allowed for the improvement of the pharmacophoric requirements for a better interaction with the cAMP-specific PDE (PDE III), thought to be the final biological target of these cardiotonic agents.     

Synthesis and structure-activity relationships of cephalosporins, 2-isocephems, and 2-oxaisocephems with C-3' or C-7 catechol or related aromatics

A series of cephalosporins, 2-isocephems, and 2-oxaisocephems with C-3' catechol-containing (pyridinium-4-thio)methyl groups and 2-isocephems with C-7 catechol related aromatics have been prepared and evaluated for antimicrobial activity. It turns out that these compounds have highly potent activity against Gram-negative bacteria, especially resistant pathogens such as Pseudomonas aeruginosa. The most active compound of the series was (6S,7S)-7-[2-(2-aminothiazol-4-yl)-2-[(Z)-[(1,5-dihydroxy-4-pyr idon-2-yl) methoxy]imino]acetamido]-3-[[[(4-methyl-5-carboxymethyl)thiazol-2- yl] thio]methyl]-8-oxo-1-aza-4-thiabicyclo [4.2.0] oct-2-ene-2-carboxylic acid which exhibited potent in vitro activity against clinically isolated P, aeruginosa and Acinetobacter baumanii which is also resistant to many anti-infectives, and good in vivo efficacy against clinically isolated P aeruginosa.     

Synthesis and structure-activity relationships of 2-pyridones: II. 8-(Fluoro-substituted pyrrolidinyl)-2-pyridones as antibacterial agents

The 8-position side chain of 2-pyridones is believed to be involved in the binding with bacterial DNA gyrase to form the ternary complex, making them very important for the activity of 2-pyridones. A series of 2-pyridones having fluoro-substituted amines at the 8-position has been synthesized and their antibacterial activities and parmacokinetic properties are reported.     

Synthesis and structure-activity relationships of dual histamine H2 and gastrin receptor antagonists with modified benzodiazepine skeletons

Three different types of dual histamine H2 and gastrin receptor antagonists, e.g. those bearing a benzazepine, benzoxazepine, or benzothiazepine skeleton instead of the benzodiazepine one as a gastrin receptor antagonistic moiety were synthesized to reduce high hydrophobicity of parent compounds and evaluated for the dual activities. These skeletal modifications significantly potentiated the binding affinity of dual antagonists with histamine H2 receptor but markedly diminished their binding affinity with the gastrin receptor and the gastrin versus CCK-A receptor selectivity. We evaluated in vivo gastric acid antisecretory activities for some representative compounds by the rat pylorus ligation method for 10 mg kg(-1) dose by oral route. However, they exerted only low inhibitory activities for oral dose with % inhibition values ranging between 32 and 53%.     

Synthesis and quantitative structure-activity relationships of N-(1-benzylpiperidin-4-yl)phenylacetamides and related analogues as potent and selective sigma1 receptor ligands

The significance of proteomic research is coupled with the recent exponential growth of these investigations. Currently, the most popular techniques used for these studies include the coupling of 1- and 2-dimensional electrophoresis with mass spectrometric analysis of the extracted and digested proteins. However, detection limits of gel staining methods have led to a search for complimentary techniques that afford the detection of lower concentrations of biologically relevant proteins. In the present studies, we have evaluated the applicability of on-line capillary electrophoresis - mass spectrometry (CE-MS) for this application. Specifically, we used membrane preconcentration-CE-MS (mPC-CE-MS) to analyze 13 samples of human aqueous humor (AH) from patients with various ocular pathologies (cataract, cataract plus glaucoma, and cataract plus pseudoexfoliation syndrome). This approach enabled rapid analysis of a relatively large volume (1 microL of each specimen, and a protein map for each was created. Measured average molecular weights (Mr) were used to tentatively identify proteins after search of the SWISS-PROT database using TagIdent from ExPaSy. Among those proteins tentatively identified are beta-2 microglobulin (Mr 11731.2), apolipoprotein A1 (Mr 28078.6) and serum albumin (Mr 66400). Proteins with Mr of 4349 (unidentified), 11731.2 (beta-2 microglobulin), 13400-14100 (immunoglobulin fragments), 28078.2 (apolipoprotein A1) and approximately 68000 (serum albumin) were observed in the majority of specimens. Generally no significant differences were noted in the protein composition of aqueous humor samples from different pathologies. However, the absence of an Mr 13345 protein and its oxidized form (Mr 13361) in samples from patients with pseudoexfoliation syndrome was noted. Occasionally the alpha-and beta-chains of hemoglobin, a contaminant in aqueous humor introduced during sampling, were also detected. We conclude from these studies that mPC-CE-MS is an attractive complimentary technique for proteome research, as this approach enables direct mapping and characterization of low concentrations of proteins that are present in complex physiologically derived fluids.     

Pentagastrin analogs containing alpha-aminooxy acids, III. Biological studies and structure-activity relationships

The stimulation of gastric acid flow by thirty-six new pentagastrin analogs administered intravenously, intrajejunally and intrarectally was determined in rats. Some of the analogs are several times more active than the pentagastrin (Peptavlon, I.C.I.) used as control. Unlike the control, some analogs are absorbed in active form from the jejunum. The N-terminal substitution with alpha-aminooxy acids seems to increase the gastric secretory response, probably by improving the enzymatic resistance of the molecule to various enzymes. None of the analogs tested significantly inhibit the gastric acid output in rats induced by pentagastrin. Structure-activity relationships are discussed.     

Sensory irritation, pulmonary irritation and structure-activity relationships of alcohols

Sensory irritation due to inhalation of n-pentanol, n-heptanol, sec-butanol and tert-pentanol was determined from the reflexively induced decrease in respiratory rate in CF-1 mice. The concentration-effect relations followed Michaelis-Menten equations, complying with receptor mediated processes. The relations were transformed into nearly rectilinear relationships in log concentration-effect plots, and the extrapolated threshold concentrations (RD-0) from the lines were 120, 28, 640 and 1210 ppm, respectively, obtained from the first 2 min of the exposure period. These values were comparable to those found in Swiss-Webster mice and to those obtained by electrophysiological experiments in Sprague-Dawley rats. The hydrophobic properties of the receptor biophase were found to approach that of the internal part of the bilayer membrane. Estimates on threshold limit values (TLV) were obtained and were found in reasonable agreement with the established values. The nose has a scrubbing effect, which reduces the concentration in the lungs in normal mice. n-Pentanol, sec-butanol and tert-pentanol decreased tidal volume in normal mice, explained either by an activation of receptors in the upper airways or by a sensitization of the stretch receptors. Two types of pulmonary responses were seen in tracheal-cannulated mice, which could be explained by an effect on stretch receptors and another type of lung receptors.     

Synthesis and glutathione S-transferase structure-affinity relationships of nonpeptide and peptidase-stable glutathione analogues

A series of nonpeptidic glutathione analogues where the peptide bonds were replaced by simple carbon-carbon bonds or isosteric E double bonds were prepared. The optimal length for the two alkyl chains on either side of the mercaptomethyl group was evaluated using structure-affinity relationships. Affinities of the analogues 14a-f, 23, and 25 were evaluated for a recombinant GST enzyme using a new affinity chromatography method previously developed in our laboratory. Analysis of these analogues gives an additional understanding for GST affinity requirements: (a) the carbon skeleton must conserve that of glutathione since analogue 14a showed the best affinity (IC50 = 5.2 microM); (b) the GST G site is not able to accommodate a chain length elongation of one methylene group (no affinity for analogues 14c,f); (c) a one-methylene group chain length reduction is tolerated, much more for the "Glu side" (14d, IC50 = 10.1 microM) than for the "Gly side" (14b, IC50 = 1800 microM); (d) the mercaptomethyl group must remain at position 5 as shown from the null affinity of the 6-mercaptomethyl analogue 14e; (e) the additional peptide isosteric E double bond (25) or hydroxyl derivative (23) in 14e did not help to retrieve affinity. This work reveals useful information for the design of new selective nonpeptidic and peptidase-stable glutathione analogues.