Volume 73, Issue 9

Structure­activity relationships are rarely straightforward, and often are more complicated than they appear. For this reason, the use of site-directed mutagenesis as a complementary tool to analyze structure­activity relationships has been invaluable. Here, we illustrate how site-directed mutagenesis has led to greater insight into the molecular basis for molecular recognition of norbinaltorphimine and to the design of novel kappa antagonists. Given the paucity of high-resolution crystal structures for membrane-bound receptors, the use of a coordinated "two-dimensional" paradigm that involves molecular modification of both the ligand and the receptor, affords a useful approach to the study of molecular recognition. This paradigm has led to the design of highly potent and selective kappa opioid receptor antagonists that are derivatives of the delta opioid receptor antagonist, naltrindole.

Although the existence of plasma- and tissue-bound semicarbazide-sensitive amine oxidases (SSAOs) has been recognized earlier, the physiological relevance of the enzyme still remains uncertain. Recent data suggest that elevated serum SSAO activity might cause endothelial injury. Formation of cytotoxic metabolites (e.g., formaldehyde) and increased oxidative stress might lead to initiation or progression of atherosclerosis. Significant positive correlation was found between serum SSAO activity and severity of atherosclerosis, and diabetic macrovascular complications. Effective and selective inhibitors of human SSAO might exert cytoprotective effect on endothelial cells. Compounds, having similar structure to mexiletine, were synthesized and studied relating to SSAO activity. The reference substrate was MDL-72974A. Unfortunately, our new compounds did not reach the potency of the reference substance using human serum samples. In conclusion, we suppose that vascular and soluble SSAO enzymes might have different inhibitor sensitivity. Further studies are required to determine whether the soluble or vascular isoform of SSAO will be the main therapeutic target in the future.

A facile convergent total synthesis of the selective, potent, and orally active V2 non-peptide antagonist, SR-121463, was developed by modification of the discovery route. One of the late intermediates, the sulfonyl chloride 1, was synthesized from 3-hydroxybenzoic acid (19) by regioselective sulfonation, O-methylation and amidation in four steps. Another late intermediate, indolin-2-one 2, was prepared from p-phenetidine (8) through the indolin-2-one 16, where the cyclohexanone moiety of 27 was introduced into the active 3-methylene group of 16 by sequential transformation using methyl acrylate and KOtBu. After formation of the cyclic ketal moiety of 13, its ring-opening was achieved by using NaBH4 in the presence of CCl3COOH. The morpholino group in 2 was introduced in accordance with the discovery approach, starting from the 2-hydroxyethoxy derivative 14 through the tosyloxy derivative 15 with morpholine in a one-pot reaction. In this way, the indolin-2-one 2 was synthesized from 8 in six steps. Finally, acylation of the indolin-2-one 2 was achieved with the sulfonyl chloride 1 in the presence of KOtBu in dimethyl sulfoxide (DMSO) at room temperature. This synthetic route proved to be applicable for the large-scale synthesis of SR-121463.

The aim of this article is to briefly present progress in the development of the potent adenosine receptor (AR) antagonists with high selectivity for either A1, A2A, or A2B ARs. The structural requirements for each AR subtype were discussed as well as their potential therapeutic use. In the search for new AR antagonists, series of imidazo-, pyrimido-, and diazepino-purindione derivatives as well as oxazolo-, oxazino-, and oxazepino-purindiones were designed, synthesized, and preliminarily evaluated in pharmacological studies. Oxygen-containing tricyclic derivatives were shown to be moderately potent AR antagonists exhibiting selectivity either for A1 or A2A ARs. Tricyclic purindiones with nitrogen in the third ring were generally more A2A AR selective. The compounds tested in vivo according to the Antiepileptic Drug Development Program of the National Institutes of Health (USA) were generally active as anticonvulsants in chemically induced seizures.

The substitution of acridine molecule in positions 1 and/or 4 with diaminoalkylo residue may result in obtaining derivatives displaying antitumor activity. The diaminoalkylo residue can be attached to acridine either directly or indirectly as a carboxamido moiety. In the former case, the presence of appropriate substituent in position para to diaminoalkylo residue is crucial for antitumor activity. Also, heterocyclic aromatic rings condensed with the acridine core can be considered as such substituents. Additional substituents introduced into the acridine core, especially those that may be transformed into quinoid systems, significantly increase antitumor activity of modified analogs. It is, however, of utmost importance that the presence of diaminoalkylo residue is the indispensable prerequisite for biological activity of acridines. Among several groups of synthesized diaminoalkyloacridines, the most potent antineoplastic properties toward a wide spectrum of transplantable tumors are exhibited by acridine-4-carboxamides, imidazo-, triazolo-, and pyrazoloacridinones. Two derivatives belonging to the above groups, acridine-4-carboxamide DACA and imidazoacridinone C-1311, are currently in clinical trials. Other derivatives exhibiting potent antitumor activity, that could be considered as close analogs of diaminolkyloacridines, are pyrazoloacridines, one of which is currently under clinical evaluation.

The process of preclinical drug discovery consists of two steps: finding of initial hits (binding ligands to a medicinal relevant target, usually a protein) and lead optimization. Nuclear magnetic resonance spectroscopy is a powerful tool that can provide valuable information to every step of drug development. NMR is commonly used for characterizing the structure and molecular dynamics of target or ligand molecules. During the structure-based lead optimization, NMR provides insight into the structural and dynamical properties of the target-ligand complex. Recently, the use of NMR in the lead finding process by screening technologies has been shown. For the latter use, new techniques have also been developed. Those techniques, in combination with high throughput, have lead to an efficient screening of libraries composed of small molecules. In this article, the role of NMR during the discovery of a drug candidate is described.

In this report we will describe the preparation and the biological activity of a novel class of heterocyclic arotinoids endowed with potent cytotoxic and apoptotic acitivity. Structure­activity relationship studies revealed that the different stereochemistry at the C9 double bond of retinoids seems associated with a different biological activity: potent apoptotic activity for the cis-isomers, whereas differentiating activity for the trans structures. An interesting modified Wittig procedure that allows easily to arotinoids will also be described. The substitution of the alkenyl portion with a more flexible oxymethyl or aminomethyl moiety gave compounds with poor activity, whereas isoxazole-bridged arotinoids allowed compounds active also on multidrug-resistant (MDR) leukemia cell lines.

Elevated lipid level is supposed to be one of the main risk factors of atherosclerosis and subsequent cardiovascular disease (and is connected to mortality). Therefore, lipid lowering is one of the major targets in cardiovascular disease treatment and prevention. Also, blood platelets play a pivotal role in the development of atherosclerosis and fatal thrombus formation in the course of coronary heart disease. Therefore, there is a great necessity to acquire drugs inhibiting platelet aggregation and clot generation. The present paper reviews new chemical structures in development for the treatment and prevention of hyperlipidemia, atherosclerosis, and subsequent cardiovascular disease. The authors' recent results are also reported regarding synthesis of a new group of a-asarone analogs. These compounds were identified as an original class of agents exhibiting hypolipidemic and antiplatelet (mice, rats) activities. Although the mechanism of the compounds' pharmacological activity has not been identified, quantum-mechanical calculations allowed structural requirements to be described that correspond to the activity (a hypothetical pseudoreceptor structure). Since it is known that asarone and its derivatives may exhibit genotoxicity, calculations were carried out to identify derivatives of possibly low genotoxic activity.

The variety of biological agents directed toward the tubulin system exceeds those acting on DNA, making it an important target for cancer chemotherapy. However, the complicated chemical structures and restricted access to the natural resources, in combination with the development of drug resistance, limit the first generation of natural products. Considerable efforts in the search and synthesis of new synthetic compounds, such as small molecular tubulin inhibitors, gave access to novel potential/promising drugs. Among these substances, two series of novel, easily accessible indole classes were identified as tubulin-destabilizing agents. Owing to the synthetic nature, potent in vitro and in vivo antitumoral activity, and efficacy against multidrug-resistant (MDR) tumors, D-24851 and D-64131 have significant potential in cancer treatment.

The linear-solvent strength (LSS) model of gradient elution in high-performance liquid chromatography (HPLC) has been demonstrated to provide parameters of lipophilicity and acidity of analytes. pKa and log kw values are determined in three gradient runs. The first two experiments use an aqueous buffered eluent with a wide-range organic modifier gradient at pH of buffer, providing suppression of ionization of the analyte. That experiment allows an estimate of contents of the organic modifier in the mobile phase (%B), producing requested retention coefficient, k, for the nonionized form of the analyte. The next experiment is carried out with the latter %B and a pH-gradient of the aqueous component of the eluent that is sufficient to overlap possible pKa value of the analyte. The initial pH of the buffer used to make the mobile phase is selected to insure that the analyte is in nonionized form. The resulting retention time allows an estimate of pKa in a solvent of the given %B. The log kw parameter obtained correlated well with the corresponding value obtained by the standard procedure of extrapolation of retention data determined in a series of isocratic measurements. The correlation between log kw and the reference parameter of lipophilicity, log P, was very good for a series of test analytes. The values of pKa were found to correlate with the literature pKa data determined in water for a set of aniline derivatives studied.

The first synthesis of both enantiomers of the antifungal drug bifonazole (1a) and related imidazole compounds 1i and 5b,c is described, starting from enantiomerically pure or enriched amines 6a­d. Construction of the imidazole ring on amines 6a­d was performed in a straightforward manner affording the final compounds in good overall yield and with very high enantiomeric purity, as determined by enantioselective HPLC. Biological evaluation in vitro of the single enantiomers of 1a,i and 5b,c against different strains of Candida albicans did not show any enantioselectivity. Finally, the pseudoreceptor modeling technique was applied to generate a model able to explain and predict the inhibitory activity of azole compounds against C. albicans P45014DM.

In the age of high-throughput screening and combinatorial chemistry, the focus of drug discovery is to replace the sequential approach with the most effective parallel approach. By the completion of the human gene-map, understanding and healing a disease require the integration of genomics, proteomics, and, very recently, metabolomics with early utilization of diverse small-molecule libraries to create a more powerful "total" drug discovery approach. In this post-genomic era, there is an enhanced demand for information-enriched combinatorial libraries which are high-quality, chemically and physiologically stable, diverse, and supported by measured and predicted data. Furthermore, specific marker libraries could be used for early functional profiling of the genome, proteome, and metabolome. In this new operating model, called "combinatorial chemical genomics", an optimal combination of the marker and high-quality libraries provides a novel synergy for the drug discovery process at a very early stage.

New racemic and chiral methyl 2-{[4-(4-chlorophenyl)-4-hydroxypiperi-din-1-yl]methyl}-1-phenylcyclopropanecarboxylate derivatives were synthesized in order to obtain sigma ligands with increased affinity and selectivity compared to (+)-MPCB and haloperidol. The cis-(±)-7 racemic mixture showed a better binding affinity and selectivity than the (±)-8 trans isomers. Between the two cis enantiomers, (+)-7, with configuration (1R,2S), showed a very high affinity and the best selectivity for s1. All compounds synthesized (7­9) showed a reduced or negligible affinity for opioid and dopaminergic D1 and D2 receptors. Nociceptive in vivo test confirms that (+)-7 (namely MR200), such as non-selective antagonist haloperidol, increased the analgesic effect induced by the k opioid selective ligand U50,488H and reversed the inhibiting effect of (+)-pentazocine on analgesia.

The commission has already published two documents on the source-based names of linear copolymers and nonlinear polymers; however, in some cases this nomenclature leads to ambiguous names. The present document proposes a generic source-based nomenclature that solves these problems and yields clearer source-based names. A generic source-based name comprises two parts: polymer class (generic) name followed by a colon 2) the actual or hypothetical monomer name(s), always parenthesized in the case of a copolymer The formula, the structure-based name, the source-based name, and the generic source-based name of the polymer are given for each example in the document. In some cases, only generic source-based give unambiguous names, for example, when a polymer has more than one name or when it is obtained through a series of intermediate structures. The rules concern mostly polymers with one or more types of functional group or heterocyclic system in the main chain, but to some extent they are also applicable to polymers with side-groups, carbon-chain polymers such as vinyl or diene polymers, spiro and cyclic polymers, and networks. Prepared by a Working Group consisting of R. E. Bareiss (Germany), R. B. Fox (USA), K. Hatada (Japan), K. Horie (UK), A. D. Jenkins (UK), J. Kahovec (Czech Republic), P. Kubisa (Poland), E. Maréchal (France), I. Meisel (Germany), W. V. Metanomski (USA), I. Mita (Japan), R. F. T. Stepto (UK), and E. S. Wilks (USA)

Since density functional theory (DFT) achieved a remarkable break-through in computational chemistry, the important general question "How reliable are quantum chemical calculations for spectroscopic properties?" should be answered anew. In this project, the most successful density functionals, namely the Becke B3LYP functionals, and the correlation-consistent polarized valence quadruple zeta basis sets (cc-pvqz) are applied to small molecules. In particular, the complete set of experimentally known diatomic molecules formed by the atoms H to Ar (these are 214 species) is uniformly calculated, and calculated spectroscopic properties are compared with experimental ones. Computationally demanding molecules, such as open-shell systems, anions, or noble gas compounds, are included in this study. Investigated spectroscopic properties are spectroscopic ground state, equilibrium internuclear distance, harmonic vibrational wavenumber, anharmonicity, vibrational absolute absorption intensity, electric dipole moment, ionization potential, and dissociation energy. The same computational method has also been applied to the ground-state geometries of 56 polyatomic molecules up to the size of benzene. Special sections are dedicated to nuclear magnetic resonance (NMR) chemical shifts and isotropic hyperfine coupling constants. Each set of systems for a chosen property is statistically analyzed, and the above important question "How reliable...?" is mathematically answered by the mean absolute deviation between calculated and experimental data, as well as by the worst agreement. In addition to presentation of numerous quantum chemically calculated spectroscopic properties, a corresponding updated list of references for experimentally determined properties is presented.