Novel 5-substituted, 2,4-diaminofuro[2,3-d]pyrimidines as multireceptor tyrosine kinase and dihydrofolate reductase inhibitors with antiangiogenic and antitumor activity.

Recent evidence suggests that combination therapy of cancer with receptor tyrosine kinase (RTK) inhibitors, which are usually cytostatic, with conventional chemotherapeutic agents, which are usually cytotoxic, provide an improved treatment option. We have designed, synthesized, and evaluated a series of novel 2,4-diamino-5-substituted furo[2,3-d]pyrimidines with RTK and dihydrofolate reductase (DHFR) inhibitory activity in single molecules, as potential cytostatic and cytotoxic agents with antitumor activity. These compounds were synthesized from 2,4-diamino-5-chloromethyl furo[2,3-d]pyrimidine and aryl methyl ketones using the Wittig reaction to afford the C-8-C-9 unsaturated analogs followed by catalytic reduction to the corresponding saturated compounds. The saturated and unsaturated C-8-C-9 bridged compounds were evaluated as inhibitors of vascular endothelial growth factor receptor (VEGFR-2, Flk, KDR), epidermal growth factor receptor, and platelet-derived growth factor receptor-beta (PDGFR-beta). Selected analogs were also evaluated as antiangiogenic agents in the chicken embryo chorioallantoic membrane (CAM) assay. The compounds were also evaluated as inhibitors of human (h) DHFR and Toxoplasma gondii (tg) DHFR. In each evaluation, a known standard compound was used as a comparison. Of the compounds evaluated, compound 32 was as potent as the standard compounds against VEGFR-2 and PDGFR-beta, showing dual inhibitory activity against RTK. This analog was also highly effective in the CAM assay. A second analog 18 also demonstrated dual VEGFR-2 and PDGFR-beta inhibitory activity as well as potent antiangiogenic activity in the CAM assay. Four additional analogs were also effective against PDGFR-beta and in the CAM assay. An unsaturated C-8-C-9 moiety was necessary for RTK inhibitory activity. Compound 32 also showed inhibitory activity against hDHFR and tgDHFR, illustrating the multitarget inhibitory potential of these analogs. The biological activity of these analogs also suggests the necessity of an unsaturated C-8-C-9 bridge for dual RTK and DHFR inhibitory activity. Compounds 18 and 32 were also evaluated in a B16 melanoma mouse model and were found to be more active as antitumor agents than methotrexate. In addition, both 18 and 32 were also active in decreasing lung metastases in a mouse model of B16 melanomas.

Binding of copper(II) to thyrotropin-releasing hormone (TRH) and its analogs.

Spectroscopy (UV-Vis, (1)H NMR, ESR) and electrochemistry revealed details of the structure of the Cu(II)-TRH (pyroglutamyl-histidyl-prolyl amide) complex. The (1)H NMR spectrum of TRH has been assigned. NMR spectra of TRH in the presence of Cu(II) showed that Cu(II) initially binds TRH through the imidazole. TRH analogs, pGlu-His-Pro-OH, pGlu-(1-Me)His-Pro-amide, pGlu-His-(3,4-dehydro)Pro-amide, pGlu-His-OH, pGlu-Glu-Pro-amide, and pGlu-Phe-Pro-amide provided comparison data. The stoichiometry of the major Cu(II)-TRH complex at pH 7.45 and greater is 1:1. The conditional formation constant (in pH 9.84 borate with 12.0 mM tartrate) for the formation of the complex is above 10(5) M(-1). The coordination starts from the 1-N of the histidyl imidazole, and then proceeds along the backbone involving the deprotonated pGlu-His amide and the lactam nitrogen of the pGlu residue. The fourth equatorial donor is an oxygen donor from water. Hydroxide begins to replace the water before the pH reaches 11. Minority species with stoichiometry of Cu-(TRH)(x) (x = 2-4) probably exist at pH lower than 8.0. In non-buffered aqueous solutions, TRH acts as a monodentate ligand and forms a Cu(II)-(TRH)(4) complex through imidazole nitrogens. All the His-containing analogs behave like TRH in terms of the above properties.

Alkaloids of Thalictrum angustifolium.

Fractionation and chromatography of the ethanolic extract of the roots of Thalictrum angustifolium L. (Ranunculaceae) afforded five alkaloids: noroxyhydrastinine (1), O-methylthalicberine (2), berberine iodide (3), jatrorrhizine iodide (4), magnoflorine iodide (5). In addition, one simple aromatic compound, methyl-4-hydroxybenzoate (6), was also isolated. These compounds were identified via comparison of their spectral data with authentic compounds or spectra available within our laboratory. This is the first reported isolation of these compounds from this species.

15N NMR and Electrochemical Studies of [Ru(II)(hedta)](-) Complexes of NO, NO(+), NO(2)(-), and NO(-).

[Ru(II)(hedta)L](n)()(-) complexes (hedta(3)(-) = N-(hydroxyethyl)ethylenediaminetriacetate; L = NO(+), n = 0; L = NO, n = 1; L = NO(-), n = 2) have been prepared by the displacement of H(2)O/D(2)O via NO(g) or NO(2)(-). This is the first reported entire set of NO(+), NO, and NO(-) as ligands for the same metal center in a constant oxidation state and with a constant ligand environment (here Ru(II) and the amino carboxylate hedta(3)(-)). From the NO stretching frequencies of isolated salts, the net influence of back-donation by Ru(II) and its sigma-withdrawal was observed to be that the bond order for the NO(+) complex is virtually the same (ca. 2.46) as that for the NO complex (ca. 2.48). The back-donation to NO(-) is also small, as is that to NO, but orbital mixing of NO(-) and Ru(II) is sufficiently important to induce a singlet NO(-) complex. Values for the nu(NO) in cm(-)(1) for the (14)N- and (15)N-labeled complexes, respectively, are as follows: NO(+), 1846, 1827; NO, 1858, 1842; NO(-), 1383, 1370. Combined results of (15)N, (13)C, and (1)H NMR spectra of the complexes in D(2)O show that [Ru(II)(hedta)((15)NO(+))] is a single cis-equatorial isomer with its (15)NO(+) resonance at 249.6 ppm vs [(15)N]formamide. The two-electron-reduced [Ru(II)(hedta)((15)NO(-))](2)(-) complex exists as trans- and cis-equatorial isomers having (15)NO(-) resonances at 609.4 and 607.4 ppm. The (15)N resonances appear at 260.0 ppm for the (15)NO(+) ligand and at 348.8 ppm for the bound (15)NO(2)(-) ligand in the [Ru(II)(hedta)((15)NO(2)(-))((15)NO(+))(D(2)O)] complex. Differential pulse voltammetric waves for the [Ru(II)(hedta)L](n)()(-) series occur at -0.37 V for the Ru(II)(NO(-))/Ru(II)(NO) couple, at -0.10 V for the Ru(II)(NO)/Ru(II)(NO(+)) couple, and at +0.98 V for the Ru(II)(NO(+))/Ru(III)(NO(+)) couple. The coordinated nitrosyl ion/nitro equilibrium (L')Ru(II)(NO(+)) + 2OH(-) right harpoon over left harpoon (L')Ru(II)(NO(2)(-)) + H(2)O (K(NO)()2()-) was observed for L' = hedta(3)(-), as for previous examples with L' = violurate, polypyridyl ligands, and (CN(-))(5) and (NH(3))(5) ligand sets. K(NO)()2()- = 1.44 x 10(13) for L' = hedta(3)(-). log(K(NO)()2()-) is linearly related through the ion-pairing equilibrium constant expression to -z(1)z(2), the charge product of the reacting ions (here the (L')Ru(NO(+)) complex and OH(-)) from -4 through +3, excluding the (NH(3))(m)() ammine series with m = 4 and 5. The opposite behavior of the ammines is attributed to strong solvent H-bonding that changes for reactant and product in the nitrosyl/nitro equilibrium. The pK(a) of coordinated nitrous acid in [Ru(II)(hedta)(HONO)](-) is calculated to be -0.80, a 3.85 log unit enhancement over free HONO due to the Ru(II) charge. An MO explanation is presented to interrelate the {Fe(III)-(NO(-) triplet)} complexes, the {Ru(II)-(NO(-) singlet)} type observed for [Ru(II)(hedta)((15)NO(-))](2)(-), and the NO(+) complexes of other strong-field metals. When both d(z)()()2 and d(x)()()2(-)(y)()()2 metal orbitals reside below the NO pi pair, the electronic repulsions favor a bent NO(-) triplet ligand. If both metal orbitals reside above the NO pi pair, the orbital mixing and back-donation induce a coordinated NO(-) singlet ligand, and if the NO pi pair reside between the two sigma-based d orbitals, an NO(+) ligand and reduced metal center obtain.

Crystal and Molecular Structure of a Potential DNA Groove-Spanning Chelate: [MV][Pt(2)(hdta)Cl(2)].4H(2)O (MV(2+) = 1,1'-Dimethyl-4,4'-bipyridinium, hdta(4)(-) = 1,6-Hexanediamine-N,N,N',N'-tetraacetate).

Light yellow crystals of [MV][Pt(2)(hdta)Cl(2)].4H(2)O (1) (MV(2+) = 1,1'-dimethyl-4,4'-bipyridinium, hdta(4)(-) = 1,6-hexanediamine-N,N,N',N'-tetraacetate) were examined by X-ray diffraction. A 0.08 x 0.24 x 0.24 nm crystal was shown to have space group C2/c, having unit cell dimensions of a = 22.757(5) Å, b = 13.566(3) Å, and c = 12.120(2) Å and unit cell angles of alpha = gamma = 90 degrees and beta = 109.07(3) degrees with Z = 4. A total of 3195 independent reflections were refined to R = 0.0454. Each Pt(II) site has the anticipated NO(2)Cl square-planar mer coordination. The Pt-N(1) distance (N(1) is the N donor of the hdta(4)(-) ligand) is 2.001(9) Å, only slightly shorter than typical Pt-N distances (2.04-2.09 Å) for sp(3) donors. The Pt-O distances to the coordinated glycinato donors in 1 are 2.012(7) and 2.000(8) Å, values very similar to those of trans-[Pt(gly)(2)] (gly = glycinate). The Pt-Cl distance of 2.310(3) Å is in the range of 2.27-2.32 Å observed for other Pt(II)-Cl(-) bonds. The bond angles are close to the ideal 90 degrees or 180 degrees value: angleN-Pt-O = 85.4(3) degrees and 83.2(4) degrees; angleN-Pt-Cl = 176.6(2) degrees. The [Pt(2)(hdta)Cl(2)](2)(-) units are packed in an end-to-end fashion such that the [Pt(II)(iminodiacetate)Cl] headgroups are overlapping. This provides square-planar to square-planar stacking of the headgroups. (1)H and (13)C NMR data are presented which show that the [Pt(2)(hdta)Cl(2)](2)(-) coordination of the solid state is maintained in solution. The coordinated glycinato arms of [Pt(2)(hdta)Cl(2)](2)(-) are equivalent, exhibiting only one AB pattern in the (1)H NMR (H(a), 4.31 ppm; H(b), 3.89 ppm; J(ab) = 16.1 Hz) and one type of coordinated carboxylate ((13)C NMR resonance at 189.7 ppm). Time-dependent (1)H and (13)C NMR spectra show that inosine first displaces only Cl(-) in [Pt(2)(hdta)Cl(2)](2)(-) in solutions up to one inosine per Pt(II) center. A higher concentration of inosines (Ino) results in the displacement of one of the glycinato arms, detectable at 175.0 ppm by (13)C NMR. The sequential nature and binding of two Ino ligands, necessarily cis in [Pt(2)(hdta)(Ino)(4)], mimics the steps necessary to allow major groove-spanning ligation of DNA in the manner of the Farrell-type binuclear platinum(II) amine complexes.