Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “AMIDINES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources
PubMed2005

Peptide de novo sequencing facilitated by a dual-labeling strategy.

A novel peptide derivatization strategy based on guanidination and amidination is presented. Mass-coded labels help distinguish N- and C-terminal fragment ions produced by collision-induced dissociation and are of general utility since peptide N-termini are coded. The amidine labels also promote specific fragmentation pathways that elucidate N-terminal residues and provide valuable internal calibrants. This strategy is demonstrated with the tryptic peptides of several model proteins, including two that are phosphorylated. Additionally, interpreted peptide sequences are matched against a database of over 80,000 proteins to assess the selectivity of this sequencing approach.

Amino Acid Sequence↗
PubMed2000

Detailed structural analysis of glycosidase/inhibitor interactions: complexes of Cex from Cellulomonas fimi with xylobiose-derived aza-sugars.

Detailed insights into the mode of binding of a series of tight-binding aza-sugar glycosidase inhibitors of two fundamentally different classes are described through X-ray crystallographic studies of complexes with the retaining family 10 xylanase Cex from Cellulomonas fimi. Complexes with xylobiose-derived aza-sugar inhibitors of the substituted "amidine" class (xylobio-imidazole, K(i) = 150 nM; xylobio-lactam oxime, K(i) = 370 nM) reveal lateral interaction of the "glycosidic" nitrogen with the acid/base catalyst (Glu127) and hydrogen bonding of the sugar 2-hydroxyl with the catalytic nucleophile (Glu233), as expected. Tight binding of xylobio-isofagomine (K(i) = 130 nM) appears to be a consequence of strong interactions of the ring nitrogen with the catalytic nucleophile while, surprisingly, no direct protein contacts are made with the ring nitrogen of the xylobio-deoxynojirimycin analogue (K(i) = 5800 nM). Instead the nitrogen interacts with two ordered water molecules, thereby accounting for its relatively weaker binding, though it still binds some 1200-fold more tightly than does xylobiose, presumably as a consequence of electrostatic interactions at the active site. Dramatically weaker binding of these same inhibitors to the family 11 xylanase Bcx from Bacillus circulans (K(i) from 0.5 to 1.5 mM) is rationalized for the substituted amidines on the basis that this enzyme utilizes a syn protonation trajectory and likely hydrolyzes via a (2,5)B boat transition state. Weaker binding of the deoxynojirimycin and isofagomine analogues likely reflects the energetic penalty for distortion of these analogues to a (2,5)B conformation, possibly coupled with destabilizing interactions with Tyr69, a conserved, catalytically essential active site residue.

1-Deoxynojirimycin↗
PubMed1975

Specific transformations at the N-terminal region of phospholipase A2.

Treatment of porcine pancreatic prophospholipase A2 with methyl acetimidate converted all lysine residues into epsilon-acetimidolysine residues. Enzymatically active epsilon-amidinated phospholipase A2 (AMPA) was obtained from the epsilon-amidinated zymogen by limited tryptic proteolysis cleaving the Arg7-Ala8 bond. AMPA was used to prepare des-Ala8-, des-(Ala8,Leu9)- and des-(ALa8),Leu9,Trp10)-AMP by successive Edman degradations, and des-(A la 8-Arg13)-AMPA by selective splitting of the Arg13-Ser14 bond by trypsin. Structural analogues of AMPA with different N-terminal amino acid residues, viz., D-Ala, beta-Ala, and Gly, have been prepared by reacting des-Ala8-AMPA with the corresponding N-t-Boc-N-hydroxysuccinimide esters of these amino acids. Similarly, the only Trp10 residue has been substituted for Phe by coupling of des-(Ala8-,Leu9,Trp10)-AMPA with N-t-Boc-L-Ala-L-Leu-L-Phe-N-hydroxysuccinimide ester. The feasibility of these substitutions has been proven unambiguously by the retroconversion of des-Ala8-AMPA and of [Ala7]AMPA into AMPA having identical enzymatic activity as the starting AMPA. The single Trp10 residue in native phospholipase A2 and its zymogen was specifically sulfenylated using 0-nitrophenyl-sulfenyl chloride. The homogenous proteins were kinetically analyzed using short-chain lecithins in the monomeric and micellar region. All modified AMPA analogues, except those in which two or more of the N-terminal amino acid residues are removed, show enzymatic activities toward monermic substrate comparable to that of AMPA, indicating that the active site region is still intact. Only [Gly8]-, [beta-Ala8]-, and [Ala8,Leu9,Phe10]AMPA exhibit a dramatic increase in enzymatic activity similar to that of AMPA upon passing the critical micellar concentration (cmc) of the substrate. From these results it can be concluded that the N-terminal region of the enzyme requires a very precise architecture in order to interact with lipid-water interfaces and consequently to display its full enzymatic activity.

Acetamides↗
PubMed2005

Theoretical and synthetic investigations of carbodiimide insertions into Al-CH3 and Al-N(CH3)2 bonds.

Carbodiimides are known to insert into aluminum-carbon bonds to form four-membered bidentate amidinate chelate rings. Insertions into Al-R and Al-NR'2 (R, R' = alkyl) have been reported in the literature. We have devised a mechanism for these insertions and modeled it using density functional theory (DFT) calculations. The calculated barrier heights for competitive insertions show the insertion into Al-N(CH3)2 goes through a lower barrier than the reaction with Al-CH3 for diisopropyl carbodiimide due to the necessity of forming a pentavalent carbon intermediate in the Al-CH3 case. However, insertion into Al-CH3 has the lower barrier for the reaction with di-tert-butyl carbodiimide because of steric effects, which is consistent with the published experimental results. We have synthesized aluminum amidinates containing two and three acetamidinate rings via insertion of 2 and 3 equiv of diisopropylcarbodiimide into trimethylaluminum (TMA). The crystal structure for [CH3C(N(i)Pr)2]2 AlCH3 is reported. We have found that, although the first insertion is rapid at room temperature, the second and third insertions require refluxing above 70 degrees C. We have calculated the barrier heights for the first and second insertion and have found that this is due to a higher barrier for the migration of the methyl group in the second insertion. This higher barrier is the result of the lack of an exergic precoordination of the carbodiimide to the metal center, which facilitates the first insertion.

Journal Article↗
PubMed1998

Iminoacylation. 1. Addition of Ketoximes or Aldoximes to Platinum(IV)-Bound Organonitriles.

The metal-mediated iminoacylation reaction of ketoximes or aldoximes upon treatment with the organonitrile platinum(IV) complexes trans-[PtCl(4)(RCN)(2)] proceeds under relatively mild conditions in acetonitrile (R = Me) or in chloroform (R = CH(2)Ph, Ph) to give trans-[PtCl(4)(NH=C(R)ON=CR(1)R(2))(2)] (R(1) = R(2) = Me; R(1)R(2) = C(4)H(8), R(1)R(2) = C(5)H(10), R(1)R(2) = (H)Ph, R(1)R(2) = (H)C(6)H(4)(OH)-o; 1-14) in 90-95% yield. All these compounds were characterized by elemental analyses (C, H, N, Cl, Pt), FAB mass spectrometry, and IR and (1)H, (13)C{(1)H}, and (195)Pt NMR spectroscopies. X-ray structure determinations of [PtCl(4)(NH=C(Me)ON=CMe(2))(2)] (1) and [PtCl(4){NH=C(Me)ON=C(C(5)H(10))}(2)] (3) disclosed their overall trans-configuration and the amidine one-end rather than N,N-bidentate coordination mode of the N-donor ligands. The iminoacyl species are in E-conformation which is held by a rather weak N-H.N hydrogen bond between the amidine =NH atom and the oxime nitrogen with the following observed distances and angles for 1 and [3]: N(1).N(2), and N(1)-H, N(1)H.N(2) are 2.605 [2.592], 0.74 [0.71], and 2.20 [2.25] Å; N(1)-H.N(2) is 115 degrees [111 degrees ]. No evidence of the Z-conformation in solution was obtained by NMR spectroscopy. Compounds trans-[PtCl(4)(NH=C(R)ON=CR(1)R(2))(2)] are unexpectedly stable toward hydrolysis both in the solid state and in solutions.

Journal Article↗
PubMed1999

Synthesis and Characterization of Functionalized N,N'-Diphenylformamidinate Silver(I) Dimers: Solid-State Structures and Solution Properties.

Functionalized N,N'-diphenylformamidines and their deprotonated silver(I) complexes have been synthesized: silver(I) N,N'-di(4-alkyl)phenylformamidinate (alkyl = methyl, ethyl, n-butyl, and n-hexadecyl) 1-4; silver(I) N,N'-di(4-trifluoromethyl)phenylformamidinate 5, silver(I) N,N'-di(3-methoxy)phenylformamidinate 6, silver(I) N,N'-di(3-methylmercapto)phenylformamidinate 7, silver(I) N,N'-di(2-methoxy)phenylformamidinate 8, silver(I) N,N'-di(2-methylmercapto)phenylformamidinate 9. The effects of increasing the coordination number of the silver(I) centers by donor substituents on the phenyl groups have been investigated by solution and solid-state studies. Variable-temperature proton NMR (223-303 K) for 1-4 shows coupling between the proton attached to the amidinate carbon and the (107/109)Ag centers at room temperature which is unaffected by cooling (2). For the four-coordinate complexes, 8 and 9, such coupling is only observed on cooling. Molecular weight measurements recorded in solution by vapor pressure osmometry at 310 K show some aggregation to higher molecular weight species than simple dimers for 1-4 and 6, but 8 and 9 exist as discrete dimeric species. Measurement of thermal stability shows the expected increase in stability with increasing coordination number. Compounds 8 and 9 were structurally characterized by X-ray methods. Both show four-coordinate silver dimers bridged by two amidinate ligands with additional longer interactions with the ether oxygens or thioether sulfurs.

Journal Article↗
PubMed1999

Quadruply Bonded Dichromium Complexes with Variously Fluorinated Formamidinate Ligands.

Complexes of chromium with various amidinate anions of N,N'-di(biphenyl)formamidine (DbiPhF), N,N'-di(pentafluorophenyl)formamidine (DPh(F)()5F), N,N'-di(p-fluorophenyl)formamidine (DPh(p)(-)(F)F), N,N'-di(o-fluorophenyl)formamidine (DPh(o)(-)(F)F), N,N'-di(3,5-fluorophenyl)formamidine (DPh(3,5)(-)(F)F), and N,N'-di(m-fluorophenyl)formamidine (DPh(m)(-)(F)F) have been synthesized and structurally characterized to study the response of the M-M multiple bond to the donor capacity of the ligand by varying the substituents of the aromatic rings. All six of these dinuclear fluorinated amidinate derivatives of the chromium(II) compounds have the paddlewheel configuration. The synthetic route involves the reaction of CrCl(2) with the corresponding lithium salt of the ligands, LiDArF (where Ar = o-C(6)H(4)F, m-C(6)H(4)F, p-C(6)H(4)F, p-C(6)H(4)C(6)H(5), C(6)F(5), or 3,5-C(6)H(3)F(2)). Compounds [Cr(2)(DPh(p)(-)(F)F)(4)] (1), [Cr(2)(DPh(m)(-)(F)F)(4)] (2), [Cr(2)(DPh(3,5)(-)(F)F)(4)].C(6)H(14) (3.C(6)H(14)), and [Cr(2)(DbiPhF)(4)].0.7CH(2)Cl(2) (4.0.7CH(2)Cl(2)) show no variation in the Cr-Cr quadruple bond length, even though the ligands have very different basicities. In the solid state, [Cr(2)(DPh(F)()5F)(4)] (5) shows close axial contacts between the o-F atoms and the chromium metal centers. The (19)F NMR show an unresolved and broad signal for all o-F atoms that cannot be resolved even at very low temperature. To assess the efficiency of the contacts, [Cr(2)(DPh(o)(-)(F)F)(4)] (6) was prepared.( )()The crystal structure shows the same kind of Cr.F interactions as in 5, and an elongation of the Cr-Cr quadruple bond, compared with the values for the complexes 1, 2, 3, and 4. These new complexes reveal that the electronic contribution of the ligand basicity to the M-M bond is smaller and less important than the axial interactions of the chromium centers. Crystal data: for 1, orthorhombic, space group Fddd with a = 25.25(7) Å, b = 26.752(12) Å, c = 28.57(4) Å, alpha = beta = gamma = 90 degrees, and Z = 16; for 2, triclinic, space group P&onemacr; with a = 9.606(12) Å, b = 9.727(10) Å, c = 13.249(11) Å, alpha = 69.24(1) degrees, beta = 73.84(2) degrees, gamma = 84.24(2) degrees, and Z = 1; for 3.C(6)H(14), triclinic, P&onemacr; with a = 10.8274(10) Å, b = 13.739(2) Å, c = 18.152(4) Å, alpha = 83.25(1) degrees, beta = 75.61(2) degrees, gamma = 70.246(10) degrees, and Z = 2; for 4.0.7CH(2)Cl(2), triclinic P1 with a = 9.689(2) Å, b = 13.7088(3) Å, c = 16.844(3) Å, alpha = 69.90(3) degrees, beta = 87.10(3) degrees, gamma = 70.13(3) degrees, and Z = 1; for 5, monoclinic, C2/c with a = 19.114(3) Å, b = 18.957(3) Å, c = 29.923(6) Å, beta = 97.27(1) degrees, and Z = 4; for 6, triclinic, P&onemacr; with a =10.225(2) Å, b = 11.312(2) Å, c = 11.797(3) Å, alpha = 117.08(1) degrees, beta = 96.432(2) degrees, gamma = 107.52(2) degrees, and Z = 1.

Journal Article↗
PubMed2004

Thiophene-based diamidine forms a "super" at binding minor groove agent.

The DNA minor groove is the interaction site for many enzymes and transcription control proteins and as a result, development of compounds that target the minor groove is an active research area. In an effort to develop biologically active minor groove agents, we are preparing and exploring the DNA interactions of a systematic set of diamidine derivatives with a powerful array of methods including DNase I footprinting, biosensor-SPR methods, and X-ray crystallography. Surprisingly, conversion of the parent phenyl-furan-phenyl diamidine to a phenyl-thiophene-benzimidazole derivative yields a compound with over 10-fold-increased affinity for the minor groove at AT sequences. Single conversion of the furan to a thiophene or a phenyl to benzimidazole does not cause a similar increase in affinity. X-ray results indicate a small bond angle difference between the C-S-C angle of thiophene and the C-O-C angle of furan that, when amplified out to the terminal amidines of the benzimidazole compounds, yields a very significant difference in the positions of the amidines and their DNA interaction strength.

Adenine↗
PubMed2000

Potent and selective indolomorphinan antagonists of the kappa-opioid receptor.

The indole moiety in the delta-opioid antagonist, naltrindole (2, NTI), was employed as a scaffold to hold an "address" for interaction with the kappa-opioid receptor. The attachment of the address to the 5'-position of the indole moiety was based on superposition of NTI upon the kappa antagonist, norbinaltorphimine (1, norBNI). A variety of cationic groups were employed as a kappa address in an effort to investigate its interaction with the anionic address subsite, Glu297, on the kappa receptor. Some of the groups that were employed for this purpose were amines, amidines, guanidines, and quaternary ammonium. Members of the series were found to have a varying degree of kappa antagonist potency and kappa selectivity when tested in smooth muscle preparations. The 5'-guanidine derivative 12a (GNTI) was the most potent member of the series and had the highest kappa selectivity ratio. GNTI was 2 times more potent and 6-10-fold more selective than norBNI (1). In general, the order of potency in the series was: guanidines > amidines approximately quaternary ammonium > amines. The kappa antagonist potency appeared to be a function of a combination of the pK(a) and distance constraint of the cationic substituent of the ligand. Receptor binding studies were qualitatively in agreement with the pharmacological data. Molecular modeling studies on 12a suggested that the protonated N-17 and guanidinium groups of GNTI are associated with Asp138 (TM3) and Glu297 (TM6), respectively, while the phenolic hydroxyl may be involved in donor-acceptor interactions with the imidazole ring of His291. It was concluded that the basis for the high kappa selectivity of GNTI is related both to association with the nonconserved Glu297 residue and to unfavorable interactions with an equivalent position in mu- and delta-opioid receptors.

Cell Line↗
PubMed1994

Design, synthesis, and neurochemical evaluation of 2-amino-5-(alkoxycarbonyl)-3,4,5,6-tetrahydropyridines and 2-amino-5-(alkoxycarbonyl)-1,4,5,6-tetrahydropyrimidines as M1 muscarinic receptor agonists.

Four regioisomers of 2-amino-(methoxycarbonyl)-3,4,5,6-tetrahydropyridine (2a-5a) were synthesized as the racemates to evaluate the utility of exocyclic amidines in the development of novel agonists for M1 muscarinic receptors. Of the four regioisomers, only racemic 2-amino-5-(methoxycarbonyl)-3,4,5,6-tetrahydropyridine (4a; CDD-0075-A) displayed high affinity (IC50 = 10 +/- 3.0 microM) and activity at muscarinic receptors coupled to PI metabolism in the rat cortex (260 +/- 4.5% stimulation above basal levels at 100 microM). A series of 2-amino-5-(alkoxycarbonyl)-3,4,5,6-tetrahydropyridines then was synthesized for further evaluation as M1 agonists. Only the propargyl derivative (4d) retained substantial agonist activity (120 +/- 14% at 100 microM) in this series. On the basis of the activity of the 5-(alkoxycarbonyl)-1,4,5,6- tetrahydropyrimidines (1a and 1d) and the 2-amino-5-(alkoxycarbonyl)-3,4,5,6-tetrahydropyridines, the corresponding cyclic guanidine derivatives were synthesized and tested. 2-Amino-5-(methoxycarbonyl)-1,4,5,6-tetrahydropyrimidine (7a) displayed a modest affinity for muscarinic receptors in the CNS (22 +/- 5.3 microM) and an ability to stimulate PI turnover in rat cerebral cortex (81 +/- 16% at 100 microM). The propargyl derivative (7d) also had modest binding affinity (31 +/- 15 microM) and high activity (150 +/- 8.5% at 100 microM), as expected based on the activity of propargyl esters of 1,4,5,6-tetrahydropyrimidine and 2-amino-3,4,5,6-tetrahydropyridine. Computational chemical studies revealed five distinct minimum-energy conformations for 1a, (R)-4a, and 7a, and three for 1d, (R)-4d, and 7d, each with a unique orientation of the ester moiety. Each of the five conformations for 1a could be superimposed upon a unique conformer of (R)-4a and 7a, suggesting that the compounds interact with muscarinic receptors in a similar fashion. Taken together, the data indicate the general utility of amidine systems as suitable replacements for the ammonium group of acetylcholine in developing ligands with activity at M1 muscarinic receptors in the central nervous system. Such compounds might be useful in the treatment of patients with Alzheimer's disease.

Alzheimer Disease↗
PubMed1992

Synthesis and antiviral evaluation of N-carboxamidine-substituted analogues of 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamidine hydrochloride.

Ten, hitherto unreported, analogues of 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamidine hydrochloride (2a, ribamidine) and methyl carboximidate 5 have been synthesized. These include the N-cyano (2b), N-alkyl (2c-e), N-amino acid (2f-h), N,N'-disubstituted (6, 7a,b), and the N-methylated carboxamide (1f) analogues of ribavirin. In addition, a new facile synthesis of carboxamidine 2a was also developed. All compounds were evaluated for biological activity against the following RNA viruses: Punta Toro (PT) and sandfly fever (SF) viruses (bunyaviruses); Japanese encephalitis (JE), yellow fever (YF), and dengue-4 viruses (flaviviruses); parainfluenza type 3 (PIV3), respiratory syncytial virus (RSV), and measles viruses (paramyxoviruses); influenza A and influenza B viruses (orthomyxoviruses); Venezuelan equine encephalomyelitis virus (VEE, alphavirus); human immunodeficiency virus type-1 (HIV-1, lentivirus); the DNA-containing vaccinia (VV) virus (poxvirus); and adeno type 5 (Ad5) viruses. All of the compounds except for 2b and 7a,b exhibited activity against the bunyaviruses such as that observed with 2a; however, higher IC50 values were generally observed. Glycine analogue 2f showed activity in PT-virus-infected mice in terms of increased survivors and decreased markers of viral pathogenicity. Carboxamidine 2a, carboximidate 5, and dimethyl amidine 6 exhibited activity against dengue type-4 virus. Monomethyl amidine 2c demonstrated activity against RSV, PIV3, and, to a lesser extent, influenza A and B. Activity of 2c generally required higher IC50 values than unsubstituted 2a. The latter exhibited hitherto unreported activity against RSV; therapeutic indices for 2a against RSV and PIV3 were greater than 64 and greater than 21. No substantial in vitro activity was observed for any of the compounds tested against Ad5, measles, JE, YF, VEE, or HIV-1. In addition, evidence is presented which argues in favor of a distinct antiviral mechanism of action for carboxamidines, e.g. 6, in contrast to a role as a carboxamide precursor.

Animals↗
PubMed1990

S-[2-[(2'-carbamoylethyl)amino]ethyl] phosphorothioate and related compounds as potential antiradiation agents.

A reinvestigation of the radiation protection activity of S-[2-[(2'-carbamylethyl)amino]ethyl] lithium hydrogen phosphorothioate (4a) revealed that this compound possessed good (70% protection at a dose of 600 mg/kg) activity. The thione and imino bioisosteres of 4, S-[2-(2'-thiocarbamylethylamino)ethyl] lithium hydrogen phosphorothioate (13a) and S-[2-(2'-amidinoethylamino)ethyl] phosphorothioic acid (18b) showed 100% protection at doses of 300 and 150 mg/kg, respectively. The N-methyl (4b) and tert-butyl (4c) analogues of amide 4a, the N-methyl (13b) analogue of the thioamide 13a, the N-methyl (18a) analogue of amidine (18b), and the cyclic amidine S-[2-[[2'-(4,5-dihydroimidozoyl)ethyl]amino]ethyl] lithium hydrogen phosphorothioate (21) all showed 80% protection at the highest dose tested.

Amifostine↗
PubMed1977

Synthesis and antiprotozoal activity of 2,5-bis(4-guanylphenyl)furans.

Eighteen substituted 2,5-bis(4-guanylphenyl)furans and related analogues, including "masked" amidines in which the guanyl function is incorporated into a heterocyclic ring, have been synthesized and their antimalarial and antitrypanosomal activity has been evaluated. None of the compounds exhibited high orders of antimalarial activity; however, 11 were very active against Trypanosoma rhodesiense in mice. Six compounds, including 2,5-bis(4-guanylphenyl)furan (4) and its 3-chloro (32), 3,4-dichloro (31), 3-methyl (25), 3,4-dimethyl (20), and 3-chloro-4-methyl (38) derivatives, produced cures in mice at submilligram dosage levels; the 3,4-dimethyl (20) analogue exhibited a prolonged curative effect providing protection for 30 days after a single dose against a challenge by T. rhodesiense. These six compounds are somewhat more active in this screen than stilbamidine, hydroxystilbamidine, and pentamidine. The "masked" amidines generally exhibited lower antitrypanosomal activity than their true guanyl counterparts. Compound 4 was synthesized from 1,4-di-p-bromophenyl-1,4-butanedione by cyclodehydrative furanization to 2,5-bis(4-bromophenyl)furan (2) which was allowed to react with Cu2(CN)2 to produce the corresponding bis-nitrile 3. The latter compound was ultimately converted by way of an imidate ester into 4. Similarly, the 3- and/or 4-substituted derivatives of 2 were employed to prepare the other members of the series.

Animals↗
PubMed2002

Distribution of furamidine analogues in tumor cells: influence of the number of positive charges.

Fluorescence microscopy has been used to study the cellular distribution properties of a series of DNA binding cationic compounds related to the potent antiparasitic drug furamidine (DB75). The compounds tested bear a diphenylfuran or a phenylfuranbenzimidazole unfused aromatic core substituted with one or two amidine or imidazoline groups. The synthesis of five new compounds is reported. The B16 melanoma cell line was used to compare the capacities of mono-, bis-, and tetracations to enter the cell and nuclei. The high-resolution fluorescence pictures show that in the furamidine series, the compounds with two or four positive charges selectively accumulate in the cell nuclei whereas, in most cases, those bearing only one positive charge show reduced cell uptake capacities. One of the monocationic compounds, DB607, distributes in the cytoplasm, possibly in mitochondria, with no distinct nuclear accumulation. In sharp contrast, furamidine and benzimidazole analogues, including the drug DB293 that forms DNA minor groove dimers, efficiently accumulate in the cell nuclei and the intranuclear distribution of these DNA minor groove binders is significantly different from that seen with the DNA intercalating drug propidium iodide. The results suggest that the presence of two amidine terminal groups plays a role in facilitating nuclear accumulation into cells, probably as a result of nucleic acid binding. The determination of DNA melting temperature increases on addition of these compounds supports the importance of DNA binding in nuclear uptake.

Animals↗
PubMed2004

Structural selectivity of aromatic diamidines.

Competition dialysis was used to study the interactions of 13 substituted aromatic diamidine compounds with 13 nucleic acid structures and sequences. The results show a striking selectivity of these compounds for the triplex structure poly dA:(poly dT)2, a novel aspect of their interaction with nucleic acids not previously described. The triplex selectivity of selected compounds was confirmed by thermal denaturation studies. Triplex selectivity was found to be modulated by the location of amidine substituents on the core phenyl-furan-phenyl ring scaffold. Molecular models were constructed to rationalize the triplex selectivity of DB359, the most selective compound in the series. Its triplex selectivity was found to arise from optimal ring stacking on base triplets, along with proper positioning of its amidine substituents to occupy the minor and the major-minor grooves of the triplex. New insights into the molecular recognition of nucleic acid structures emerged from these studies, adding to the list of available design principles for selectively targeting DNA and RNA.

Benzamidines↗
PubMed1996

2-Iminopiperidine and other 2-iminoazaheterocycles as potent inhibitors of human nitric oxide synthase isoforms.

A series of 2-iminoazaheterocycles have been prepared and shown to be potent inhibitors of human nitric oxide synthase (NOS) isoforms. This series includes cyclic amidines ranging from five- to nine-membered rings, of which 2-iminopiperidine and 2-iminohomopiperidine were the most potent inhibitors, with IC50 values of 1.0 and 2.0 microM, respectively, for human inducible nitric oxide synthase. This series of cyclic inhibitors was further expanded to include analogs with heteroatoms in the 3-position of the six-membered ring. This modification was tolerated for sulfur and oxygen, but nitrogen reduced the inhibitory potency. The oral administration of 2-iminopiperidine in lipopolysaccharide (LPS)-treated rats inhibited the LPS-induced increase in plasma nitrite/nitrate levels in a dose-dependent manner, demonstrating its ability to inhibit inducible NOS activity in vivo. These cyclic amidines represent a new class of potent NOS inhibitors and the foundation for potential therapeutic agents.

Animals↗
PubMed1997

Synthesis and biological characterization of 1,4,5,6-tetrahydropyrimidine and 2-amino-3,4,5,6-tetrahydropyridine derivatives as selective m1 agonists.

Previous studies identified several novel tetrahydropyrimidine derivatives exhibiting muscarinic agonist activity in rat brain. Such compounds might be useful in treating cognitive and memory deficits associated with low acetylcholine levels, as found in Alzheimer's disease. To determine the molecular features of ligands important for binding and activity at muscarinic receptor subtypes, the series of tetrahydropyrimidines was extended. Several active compounds were examined further for functional selectivity through biochemical studies of muscarinic receptor activity using receptor subtypes expressed in cell lines. Several amidine derivatives displayed high efficacy at m1 receptors and lower activity at m3 receptors coupled to phosphoinositide (PI) metabolism in A9 L cells. Four ligands, including 1b, 1f, 2b, and 7b, exhibited marked functional selectivity for m1 vs m3 receptors. Compound 1f also exhibited low activity at m2 receptors coupled to the inhibition of adenylyl cyclase in A9 L cells. Molecular modeling studies also were initiated to help understand the nature of the interaction of muscarinic agonists with the m1 receptor using a nine amino model of the m1 receptor. Several important interactions were identified, including interactions between the ester moiety and Thr192. Additional interactions were found for oxadiazoles and alkynyl derivatives with Asn382, suggesting that enhanced potency and selectivity may be achieved by maximizing interactions with Asp105, Thr192, and Asn382. Taken together, the data indicate that several amidine derivatives display functional selectivity for m1 muscarinic receptors, warranting further evaluation as therapeutic agents for the treatment of Alzheimer's disease. In addition, several amino acid residues were identified as potential binding sites for m1 agonists. These data may be useful in directing efforts to develop even more selective m1 agonists.

Animals↗
PubMed2002

New approach to biomimetic transamination using bifunctional [1,3]-proton transfer catalysis in thioxanthenyl dioxide imines.

A pyridoxamine equivalent, 9-aminothioxanthene 10,10-dioxide, has been designed that is capable of affording transamination in good to excellent yields of natural as well as artificial amino acids. Amidines and guanidines in catalytic amounts were capable of performing [1,3]-proton transfer in the imines under mild conditions, whereas various simple amines failed. The use of chiral catalysts resulted in modest asymmetric induction (ee < or = 45%). The electronic dependence in para-substituted phenyl glyoxylate imines, isotope effects, and computational studies support a stepwise, bifunctional mechanism for amidine and guanidine catalysts. Attempts toward an autocatalytic model system are described.

Amination↗