ABSTRACT
We report the X-ray analysis at 2.0 A resolution for crystals of the aspartic proteinase endothiapepsin (EC 3.4.23.6) complexed with a potent difluorostatone-containing tripeptide renin inhibitor (CP-81,282). The scissile bond surrogate, an electrophilic ketone, is hydrated in the complex. The pro-(R) (statine-like) hydroxyl of the tetrahedral carbonyl hydrate is hydrogen-bonded to both active-site aspartates 32 and 215 in the position occupied by a water in the native enzyme. The second hydroxyl oxygen of the hydrate is hydrogen-bonded only to the outer oxygen of Asp 32. These experimental data provide a basis for a model of the tetrahedral intermediate in aspartic proteinase-mediated cleavage of the amide bond. This indicates a mechanism in which Asp 32 is the proton donor and Asp 215 carboxylate polarizes a bound water for nucleophilic attack. The mechanism involves a carboxylate (Asp 32) that is stabilized by extensive hydrogen bonding, rather than an oxyanion derivative of the peptide as in serine proteinase catalysis.
Subject(s)
Aspartic Acid Endopeptidases/chemistry , Amino Acid Sequence , Aspartic Acid , Aspartic Acid Endopeptidases/metabolism , Binding Sites , Hydrogen Bonding , Models, Molecular , Oligopeptides/metabolism , Protein Conformation , Renin/antagonists & inhibitors , X-Ray Diffraction/methodsABSTRACT
Experimental and computational approaches to estimate solubility and permeability in discovery and development settings are described. In the discovery setting 'the rule of 5' predicts that poor absorption or permeation is more likely when there are more than 5 H-bond donors, 10 H-bond acceptors, the molecular weight (MWT) is greater than 500 and the calculated Log P (CLogP) is greater than 5 (or MlogP > 4.15). Computational methodology for the rule-based Moriguchi Log P (MLogP) calculation is described. Turbidimetric solubility measurement is described and applied to known drugs. High throughput screening (HTS) leads tend to have higher MWT and Log P and lower turbidimetric solubility than leads in the pre-HTS era. In the development setting, solubility calculations focus on exact value prediction and are difficult because of polymorphism. Recent work on linear free energy relationships and Log P approaches are critically reviewed. Useful predictions are possible in closely related analog series when coupled with experimental thermodynamic solubility measurements.
Subject(s)
Computers , Permeability , Pharmaceutical Preparations/chemistry , Pharmacology/instrumentation , Solubility , Adsorption , Chemical Phenomena , Chemistry, Physical , ThermodynamicsABSTRACT
A model has been constructed using computer graphics for human renin based on the sequence derived from that of the gene and the 3-dimensional structure defined at high resolution for other homologous aspartic proteinases. Human renin can adopt a 3-dimensional structure close to that of other aspartic proteinases, in which amino acids corresponding to intron-exon junctions in the gene are at surface regions in the 3-dimensional structure. As expected, the essential catalytic residues are retained and the nearby residue 304 is alanine as in the mouse sequence, supporting the idea that Asp 304 of other aspartic proteinases may contribute to the low pH of their optimal activity. There are interesting differences at subsite S3' which may contribute to the specificity of human renin. Certain residues at the surface of the enzyme adjacent to the active site cleft are unique to renins and may play a role in recognition and binding of angiotensinogen.
Subject(s)
Genes , Renin , Amino Acid Sequence , Animals , Base Sequence , Humans , Mice , Models, Molecular , Pepsin A , Protein Conformation , Renin/genetics , Renin/metabolism , Software , Submandibular Gland/enzymology , X-Ray DiffractionABSTRACT
The aldose reductase inhibitor 2,3-dihydro-6-fluorospiro[4H-1-benzopyran-4,4'-imidazolidine]-2',5 '-dione was resolved into its enantiomers. Sorbinil, the S isomer, was found to be a better inhibitor of the enzyme in vitro and in vivo than the corresponding R isomer. X-ray data on sorbinil, which were used to determine its absolute configuration, are presented. NMR studies of sorbinil in solution indicate the existence of two conformers with a low energy barrier for interconversion.
Subject(s)
Aldehyde Reductase/antagonists & inhibitors , Imidazoles/pharmacology , Imidazolidines , Sugar Alcohol Dehydrogenases/antagonists & inhibitors , Chemical Phenomena , Chemistry, Physical , Crystallization , Imidazoles/chemical synthesis , Isomerism , Magnetic Resonance Spectroscopy , Molecular Conformation , Thermodynamics , X-Ray DiffractionABSTRACT
A Free-Wilson analysis of the antibacterial activity found in a variety of quinoxaline 1,4-dioxides prepared and tested in these laboratories unexpectedly predicted that potent activity should be found in the case where the heterocyclic ring system was substituted with an acetyl group in the 2 position and a hydroxymethyl group in the 3 position (2). The synthesis and antibacterial activity of this compound, which was actually isolated in the hemiketal form (3), and of several of its derivatives are reported. 1-Hydroxy-1-methyl-1,3-dihydrofuro[3,4-b]quinoxaline 4,9-dioxide (3) possesses exceptional activity in vivo against Escherichia coli, Salmonella choleraesuis, and Pasteurella multocida.
Subject(s)
Anti-Bacterial Agents/chemical synthesis , Quinoxalines/chemical synthesis , Animals , Bacteria/drug effects , Bacterial Infections/drug therapy , Female , Male , Mice , Microbial Sensitivity Tests , Quinoxalines/pharmacology , Structure-Activity RelationshipABSTRACT
A series of trans-8-fluoro-5-(4-fluorophenyl)-2,3,4,4a,5, 9b-hexahydro-1H-pyrido[4,3-b]indoles with various N-2 substituents has been prepared and tested for neuroleptic activity [( 3H]spiroperidol binding and amphetamine antagonism). Several members of this series showed exceptional in vivo potency, especially the hydantoin derivatives 27-30. Resolution into the enantiomers showed that neuroleptic activity is associated with the 4aS,9bS absolute configuration. These rigid neuroleptics have been correlated with other rigid neuroleptics [(+)-dexclamol, Ro 22-1319] and can serve to further define the topography of the dopamine receptor.
Subject(s)
Carbolines/pharmacology , Receptors, Dopamine/metabolism , Stereotyped Behavior/drug effects , Animals , Chemical Phenomena , Chemistry , Dextroamphetamine/antagonists & inhibitors , Male , Mice , Molecular Conformation , Rats , Rats, Inbred Strains , Receptors, Dopamine/drug effects , Spiperone/metabolism , Stereoisomerism , Structure-Activity RelationshipABSTRACT
A systematic approach to the replacement of acidic groups with potential bioisosteres is described. The strategy involves simple nucleophilic displacement of a common alkyl halide precursor with a variety of mercaptoazoles and related molecules. The mercaptoazoles and their oxidized derivatives (sulfinyl- and sulfonylazoles) represent a series of possible surrogates for acidic groups which span a pKa range from about 4.5-11.5. This simple strategy was extended to include 2-hydroxy- or 2-aminothiophenyl groups which function as relatively nonacidic isosteres for a phosphonic acid. By replacing the phosphonic acid of 2-amino-7-phosphonoheptanoate (AP-7) with these groups, we have synthesized novel N-methyl-d-aspartate (NMDA) antagonists.
Subject(s)
2-Amino-5-phosphonovalerate/analogs & derivatives , Amino Acids/chemical synthesis , Aspartic Acid/analogs & derivatives , Amino Acids/pharmacology , Animals , Aspartic Acid/antagonists & inhibitors , Models, Molecular , N-Methylaspartate , Rats , Receptors, N-Methyl-D-Aspartate , Receptors, Neurotransmitter/drug effects , Structure-Activity RelationshipABSTRACT
Imidoline, 1-[2-(N,N-dimethylamino)ethyl]-3-m-chlorophenyl-2-imidazolidinone, has been found to be as potent as chlorpromazine in increasing striatal DOPA accumulation and prolactin secretion in vivo. In contrast, imidoline exhibited only weak inhibitory activity towards dopamine-sensitive adenylate cyclase and 3H-spiroperidol binding to striatal membranes in vitro. These neuroleptic effects in vivo are probably caused by blockade of dopamine receptors since imidoline did not deplete the striatum of dopamine. Imidoline is of interest because its structure is distinct from those of other neuroleptics. A proposed active conformation involves intramolecular hydrogen bonding between the protonated dimethylamino group and the oxygen of the imidazolidinone ring. The spatial relationship between the amine nitrogen and phenyl ring in this conformation allows proper fit of imidoline with key dimensions described for the dopamine receptor.
Subject(s)
Antipsychotic Agents/pharmacology , Imidazoles/pharmacology , Receptors, Dopamine/drug effects , 3,4-Dihydroxyphenylacetic Acid/metabolism , Adenylyl Cyclase Inhibitors , Animals , Binding Sites , Chlorpromazine/pharmacology , Male , Molecular Conformation , Rats , Spiperone/metabolism , Structure-Activity RelationshipABSTRACT
The SAR of a series of 2-(7-chromanyl)benzoic acids has been investigated with the aim of identifying potent and selective LTB4 receptor antagonists that maintain potency in complex biological fluids. We found optimal activity in derivatives with electron-withdrawing groups in the benzoic acid ring and with an unsubstituted C-3 benzyl group on the chromanol nucleus. While compounds containing a 3-(4-phenyl)benzyl chromanol substituent were potent LTB4 receptor antagonists, the increased lipophilicity imparted by the additional phenyl substituent led to decreased potency in the presence of plasma proteins. From among the potent compounds identified, CP-195543, the 5'-trifluoromethyl 3-benzyl chromanol, was selected for development.