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PubMed2000

Synthesis of MII[N(SiMe3)2][Me3SiNC(tBu)NSiMe3] (M = Sn, Ge) from amidinate precursors: active catalysts for phenyl isocyanate cyclization.

Mixed amidinato amido complexes [Me3SiNC(tBu)NSiMe3]M[N(SiMe3)2] (M = Sn 2, Ge 3) were prepared by the reaction of [Me3SiNC(tBu)NSiMe3]Li (1a) with SnCl2 and GeCl2(dioxane) in ether. The N(SiMe3)2 ligand in these compounds is derived from the rearrangement of the [Me3SiNC(tBu)NSiMe3]- anion with extrusion of tBuCN. The susceptibility of [Me3SiNC(tBu)NSiMe3]- to rearrangement appears to be dependent on reaction solvent and on the coordinated metal center. Single-crystal X-ray diffraction studies of 2 and 3 are presented. Replacement of Me for tBu in the ligand allowed [Me3SiNC(Me)NSiMe3]2SnII (4) to be isolated, and an X-ray structure of this compound is reported. The isolation of 4 indicates that steric factors also play a role in the stability of [Me3SiNC(tBu)NSiMe3]-. Compounds 2 and 3 are outstanding catalysts for the cyclotrimerization of phenyl isocyanates to perhydro-1,3,5-triazine-2,4,6-triones (isocyanurates) at room temperature. In contrast, complex 4 catalytically reacts with phenyl isocyanate to produce isocyanate dimer and trimer in a 52:35 ratio.

Journal Article↗
PubMed1989

Synthesis and antitumor activity of ribavirin imidates. A new facile synthesis of ribavirin amidine (1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamidine hydrochloride).

Methyl 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboximidate (4) and ethyl 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamidate (6) were synthesized and tested for antitumor and antiviral activity. A new facile synthesis of 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamidine hydrochloride (5), starting with imidate 4, was also developed. The imidates 4 and 6 differed greatly in solubility and dosing requirements. Even so, both compounds exhibited significant activity in vivo against murine leukemia L1210. Nontoxic dosing with 4 also significantly diminished Friend leukemia induced splenomegaly. In contrast, neither imidate was active in vitro.

Animals↗
PubMed1980

Ultraviolet photoelectron spectroscopy of cyclic amidines. 2. Electronic structure of clonidine and some related 2-(phenylimino)imidazolidines with alpha-adrenergic activity.

Ultraviolet photoelectron spectroscopy (UV PES) and CNDO/s molecular orbital calculations have been employed to investigate the electronic structure of clonidine and some other 2-(phenylimino)imidazolidines. The assignment of the bands in the spectra to particular molecular orbitals is based on the CNDO/s results in conjunction with Koopmans' theorem, substituent effects, and differences in intensity between the He (I) and He(II) spectra. The location of the energy levels of orbitals with mainly nN and delta character is not correctly estimated estimated by CNDO/s, while the pi orbital energy levels are satisfactorally predicted. The UV PES and CNDO/s results indicate in contrast investigated 2-(phenylimino)imidazolidines, which may indicate that differences in hypotensive activity cannot be ascribed to variations in steric hindrance within the molecules. The first ionization energies of the pharmacologically active 20-(phenylimino)imidazolidines do not correlate with hypotensive activity based on dosage data after intravenous administration to rats.

Adrenergic alpha-Antagonists↗
PubMed1980

Structure-activity relationships of pyrrole amidine antiviral antibiotics. 2. Preparation of mono- and tripyrrole derivatives of congocidine.

Representatives of three types of congocidine (1) analogues were synthesized. These were tested for cytotoxicity, inhibition of herpes simplex virus (HSV) replication in cultured cells, and effects on the synthesis of HS DNA in isolated nuclei in vitro, as well as on DNA synthesis by purified HSV DNA polymerase. All synthesized tripyrrole derivatives of congocidine were less cytotoxic and more active than the parent drug in all the three ant iviral tests.

Antiviral Agents↗
PubMed1979

Structure--activity relationships of pyrrole amidine antiviral antibiotics. 1. Modifications of the alkylamidine side chain.

Representatives of three types of side-chain analogues of distamycin A (1) were synthesized. These were tested for cytotoxicity, inhibition of herpes simplex virus (HSV) replication in cultured cells, effects on the synthesis of HSV DNA in isolated nuclei in vitro, as well as on DNA synthesis by purified HSV DNA polymerase. Distamycin A was the most active compound in all three antiviral tests, as well as the most toxic. However, several compounds, in particular the aromatic analogues 15 and 16, showed no toxicity under the experimental conditions used but were still very active in the three antiviral tests.

Animals↗
PubMed1998

New platelet fibrinogen receptor glycoprotein IIb-IIIa antagonists: orally active series of N-alkylated amidines with a 6,6-bicyclic template.

The design, synthesis, and pharmacological evaluation of (S)-(-)-ethyl [6-[4-(morpholinoformimidoyl)benzamido]-3, 4-dihydro-2H-1-benzopyran-3-yl]acetate hydrochloride ((S)-4.HCl, MS-180), an orally active glycoprotein IIb-IIIa (GPIIb-IIIa) antagonist, are reported. Pharmacophore mapping of amidino and carboxyl groups of already known GPIIb-IIIa antagonists led to the synthesis of nine amidino acids containing 6,6-bicyclic ring skeletons (10a-i). Among them, the compounds 10a,c,e having an amide bond and 1,2,3,4-tetrahydronaphthalene or 3, 4-dihydro-2H-1-benzopyran skeleton showed marked inhibitions with IC50 values of 46-57 nM in human platelet aggregation assay in vitro, but low oral activities. N-Alkylation of the amidino group coupled with the ester prodrug approach afforded MS-180 ((S)-4.HCl), which generates in vivo the corresponding carboxylic acid (S)-3 as an active species. In vitro, (S)-3 inhibited ADP-induced aggregation of guinea pig, dog, and human platelets (IC50 = 110, 253, and 35 nM, respectively) and inhibited the binding of fibrinogen to immobilized GPIIb-IIIa of human platelets (IC50 = 0.12 nM). After oral administration of MS-180 ((S)-4.HCl) to fasted beagle dog, ex vivo inhibition of platelet aggregation was observed. The maximal inhibitions were observed 2-4 h after dosing with dose dependency (60% inhibition at a dose of 1 mg/kg, 85% at 3 mg/kg, and 100% at 10 mg/kg, respectively) and the extent of the inhibitions paralleled the plasma concentration of the active species (S)-3. On the basis of these studies, we selected MS-180 ((S)-4.HCl) as a candidate for clinical evaluation as a drug for the treatment and prevention of thrombosis in patients.

Acetates↗
PubMed2003

Molecular recognition of amidines in water.

[structure: see text] Tetraphosphonates of the general structure shown above are biomimetic hosts for bisamidinium cations in drugs such as pentamidine and DAPI. Similar to their insertion into DNA's minor groove, these drugs are often sandwiched by two tetraphosphonate hosts (2:1). The alternative binding mode (1:2) produces extremely high association constants in water of approximately 10(8) M(-)(2) ( approximately 12 kcal/mol), which can compete with the biological process.

Journal Article↗
PubMed2006

Unusually weak binding interactions in tetrazole-amidine complexes.

[reaction: see text] Tetrazoles frequently replace carboxylic acids in pharmaceutical drugs. However, while the binding modes of tetrazolate and carboxylate anions in amidinium complexes turns out to be similar, the association constant of the former is 2-3 orders of magnitude smaller in DMSO. Crystal structures revealed that the N...H-N hydrogen bonds in amidinium tetrazolates are bent (162 degrees and 169 degrees ) and noticeably longer (N...N 2.96 A) than corresponding hydrogen bonds in both amidinium carboxylates and ammonium tetrazolates.

Journal Article↗
PubMed2006

Synthesis and characterisation of complexes of Group 13 metal amidinate heterocycles with the CpFe(CO)2 fragment.

The first examples of complexes between a 4-membered amidinato-Group 13 metal(III) heterocycle and a transition metal fragment are formed in salt elimination reactions between Na[CpFe(CO)2] and [MX2(amid)], M=Al, Ga or In; X=Cl or Br; amid-=[(RN)2CBut]-; R=Pri or cyclohexyl (Cy). The formed complexes, [CpFe(CO)2M(X)(amid)] (4 examples) have been crystallographically characterised and subject to halide abstraction reactions. In one case, the cationic complex, [CpFe(CO)2Ga(OEt2){(CyN)2CBut}][BArf4], was isolated and crystallographically characterised. A hydrolysis product of this complex, [{CpFe(CO)2Ga[(CyN)2CBut]}2(micro-OH)][BArf4], was also isolated in low yield from this reaction and structurally characterised.

Journal Article↗