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1.
《Inorganica chimica acta》2006,359(5):1650-1658
A series of nickel(II) and palladium(II) complexes containing one or two pentafluorophenyl ligands and the phosphino-amides o-Ph2PC6H4CONHR [R = iPr (a), Ph (b)] displaying different coordination modes have been synthesised. The chelating ability of these ligands and the influence of both coligands and the metal centre in their potential hemilabile behaviour have been explored. The crystal structure of (b) has been determined and reveals N–H⋯O intermolecular hydrogen bonding. Bis-pentafluorophenyl derivatives [M(C6F5)2(o-Ph2PC6H4CO-NHR)] [M = Ni; R = iPr (1a); R = Ph (1b); M = Pd; R = iPr (2a); R = Ph (2b)] in which (a) and (b) act as rigid P, O-chelating ligands were readily prepared from the labile precursors cis-[M(C6F5)2(PhCN)2]. X-ray structures of (1a), (1b) and (2a) have been established, allowing an interesting comparative structural discussion. Dinuclear [{Pd(C6F5)(tht)(μ-Cl)}2] reacted with (a) and (b) yielding the monopentafluorophenyl complexes [Pd(C6F5)Cl{PPh2(C6H4–CONH–R)}] (R = iPr (3a), Ph (3b)) that showed a P, O-chelating behaviour of the ligands, confirmed by the crystal structure determination of (3a). New cationic palladium(II) complexes in which (a) and (b) behave as P-monodentate ligands have been synthesised by reacting them with [{Pd(C6F5)(tht)(μ-Cl)}2], stoichiometric Ag(O3SCF3) and external chelating reagents such as cod [Pd(C6F5)(cod){PPh2(C6H4-CONH-R)}](O3SCF3)(R = iPr (4a), Ph (4b)) and 2,2-bipy [Pd(C6F5)(bipy){PPh2(C6H4-CONH-R)}](O3SCF3) (R = iPr (5a), Ph (5b)). When chloride abstraction in [{Pd(C6F5)(tht)(μ-Cl)}2] is promoted by means of a dithioanionic salt as dimethyl dithiophospate in the presence of (a) or (b), the corresponding neutral complexes [Pd(C6F5){S(S)P(OMe)2}{PPh2(C6H4-CONH-R)}] (R = iPr (6a), Ph (6b)) were obtained.  相似文献   

2.
Vesicular monoamine transporter-2 (VMAT2) is a viable target for development of pharmacotherapies for psychostimulant abuse. Lobeline (1) is a potent antagonist at α4β21 nicotinic acetylcholine receptors, has moderate affinity (Ki = 5.46 μM) for VMAT2, and is being investigated currently as a clinical candidate for treatment of psychostimulant abuse. A series of carboxylic acid and sulfonic acid ester analogs 220 of lobeline were synthesized and evaluated for interaction with α4β21 and α71 neuronal nicotinic acetylcholine receptors (nAChRs), the dopamine transporter (DAT), serotonin transporter (SERT) and VMAT2. Both carboxylic acid and sulfonic acid esters had low affinity at α71 nAChRs. Similar to lobeline (Ki = 4 nM), sulfonic acid esters had high affinity at α4β21 (Ki = 5–17 nM). Aromatic carboxylic acid ester analogs of lobeline (24) were 100–1000-fold less potent than lobeline at α4β21 nAChRs, whereas aliphatic carboxylic acid ester analogs were 10–100-fold less potent than lobeline at α4β21. Two representative lobeline esters, the 10-O-benzoate (2) and the 10-O-benzenesulfonate (10) were evaluated in the 36Rb+ efflux assay using rat thalamic synaptosomes, and were shown to be antagonists with IC50 values of 0.85 μM and 1.60 μM, respectively. Both carboxylic and sulfonic acid esters exhibited a range of potencies (equipotent to 13–45-fold greater potency compared to lobeline) for inhibiting DAT and SERT, respectively, and like lobeline, had moderate affinity (Ki = 1.98–10.8 μM) for VMAT2. One of the more interesting analogs, p-methoxybenzoic acid ester 4, had low affinity at α4β21 nAChRs (Ki = 19.3 μM) and was equipotent with lobeline, at VMAT2 (Ki = 2.98 μM), exhibiting a 6.5-fold selectivity for VMAT2 over α4β2 nAChRs. Thus, esterification of the lobeline molecule may be a useful structural modification for the development of lobeline analogs with improved selectivity at VMAT2.  相似文献   

3.
Central heterocyclic ring size reduction from piperidinyl to pyrrolidinyl in the vesicular monoamine transporter-2 (VMAT2) inhibitor GZ-793A and its analogs resulted in novel N-propane-1,2(R)-diol analogs 11a–i. These compounds were evaluated for their affinity for the dihydrotetrabenazine (DTBZ) binding site on VMAT2 and for their ability to inhibit vesicular dopamine (DA) uptake. The 4-difluoromethoxyphenethyl analog 11f was the most potent inhibitor of [3H]-DTBZ binding (Ki = 560 nM), with 15-fold greater affinity for this site than GZ-793A (Ki = 8.29 μM). Analog 11f also showed similar potency of inhibition of [3H]-DA uptake into vesicles (Ki = 45 nM) compared to that for GZ-793A (Ki = 29 nM). Thus, 11f represents a new water-soluble inhibitor of VMAT function.  相似文献   

4.
5.
《Inorganica chimica acta》2006,359(4):1275-1281
Two new complexes of composition [Cu(2-NO2bz)2(3-pyme)2(H2O)2] (1) and/or [Cu{3,5-(NO2)2bz}2(3-pyme)2] (2) (3-pyme = 3-pyridylmethanol, ronicol or 3-pyridylcarbinol, 2-NO2bz = 2-nitrobenzoate and 3,5-(NO2)2bz = 3,5-dinitrobenzoate) have been prepared and studied by elemental analysis, electronic, infrared and EPR spectroscopy, magnetic susceptibility measurements and the structure of both complexes has been solved. Complex (1) shows an unusual molecular type of structure consisting of the [Cu(2-NO2bz)2(3-pyme)2(H2O)2] molecules held together by hydrogen bonds and van der Waals interactions. Complex (2) exhibits a polymeric chain-like structure [Cu{3,5-(NO2)2bz}2(3-pyme)2]n with copper atoms doubly bridged by two 3-pyridylmethanol molecules and the polymeric molecules are held together by van der Waals interactions. Complex (1) exhibits a magnetic moment μeff = 1.84 B.M. at 300 K that remains nearly constant within the temperature region (5–300 K). Further cooling results in lowering the magnetic moment to μeff = 1.82 B.M. at 1.8 K. The magnetic susceptibility temperature dependence obeys Curie–Weiss law with Curie constant of 0.423 cm3 K mol−1 and with Weiss constant of −0.06 K. The magnetic moment of (2) exhibits a small increase with a decrease in the temperature (μeff = 1.80 B.M. at 300 K and μeff = 1.85 B.M. at 1.8 K) with Curie constant of 0.409 cm3 K mol−1 and with Weiss constant of +1.1 K, which can indicate a very weak ferromagnetic interaction between the copper atoms within the chain. Applying the molecular field model resulted in obtaining zJ′ values −0.08 cm−1 for complex (1), and −0.07 cm−1 for complex (2), respectively, that could characterize intermolecular and interchain interactions transmitted through π–π stacking.  相似文献   

6.
A series of acetato complexes of molybdenum(V), based on the singly metal–metal bonded {Mo2O4}2+ structural fragment, has been prepared. A dinuclear (PyH)3[Mo2O4Cl4(OOCCH3)] · CH3CN (1) (PyH+ = pyridinium cation, C5H5NH+) was obtained upon the reaction of (PyH)5[MoOCl4(H2O)]3Cl2 with the equimolar solution of pyridine and acetic acid in acetonitrile at ambient conditions. The acetato ligand in 1 is coordinated to a pair of molybdenum atoms in a synsyn bidentate bridging manner. (PyH)n[MoOBr4]n afforded in an analogous synthetic procedure a tetranuclear cluster, [Mo4O8(OOCCH3)3(OH)Py4] · 1/2CH 3CN · 1/2H2O (3), with a novel core which may be envisioned as the acetate- and hydroxide-assisted assembly of {Mo2O4}2+ building blocks. Its structure is presented in terms of known tetranuclear clusters which are also composed of two {Mo2O4}2+ units. The acetato ligands in 3 adopted apart from bidentate bridging binding modes also a monodentate one. Partial substitution of chlorido ligands in (PyH)3[Mo2O4Cl4(OOCCH3)] · CH3CN (1) with pyridine resulted in a neutral [Mo2O4Cl(OOCCH3)Py3] · PriOH · Py (2) which retained the original acetate coordination. The title compounds were fully characterized by X-ray diffraction studies and infrared vibrational spectroscopy.  相似文献   

7.
Three classes of novel inhibitors of inosine monophosphate dehydrogenase have been prepared and their anti-proliferative properties were evaluated against several cancer cell lines.(1) Mycophenolic adenine dinucleotide analogues (813) containing a substituent at the C2 of adenine ring were found to be potent inhibitors of IMPDH (Ki’s in range of 0.6–82 nM) and sub-μM inhibitors of leukemic K562 cell proliferation. (2) Mycophenolic adenosine (d and l) esters (20 and 21) showed a potent inhibition of IMPDH2 (Ki = 102 and Ki = 231 nM, respectively) and inhibition of K562 cell growth (IC50 = 0.5 and IC50 = 1.6 μM). These compounds serve both as inhibitors of the enzyme and as a depot form of mycophenolic acid. The corresponding amide analogue 22, also a potent inhibitor of IMPDH (Ki = 84 nM), did not inhibit cancer cell proliferation. (3) Mycophenolic-(l)- and (d)-valine adenine di-amide derivatives 25 (Ki = 9 nM) and 28 (Ki = 3 nM) were found to be very potent enzymatically, but did not inhibit proliferation of cancer cells.  相似文献   

8.
Three series of homologous dendritic amphiphiles—RCONHC(CH2CH2COOH)3, 1(n); ROCONHC(CH2CH2COOH)3, 2(n); RNHCONHC(CH2CH2COOH)3, 3(n), where R = n-CnH2n+1 and n = 13–22 carbon atoms—were assayed for their potential to serve as antimicrobial components in a topical vaginal formulation. Comparing epithelial cytotoxicities to the ability of these homologues to inhibit HIV, Neisseria gonorrhoeae, and Candida albicans provided a measure of their prophylactic/therapeutic potential. Measurements of the ability to inhibit Lactobacillus plantarum, a beneficial bacterium in the vagina, and critical micelle concentrations (CMCs), an indicator of the potential detergency of these amphiphiles, provided additional assessments of safety. Several amphiphiles from each homologous series had modest anti-HIV activity (EC50 = 110–130 μM). Amphiphile 2(18) had the best anti-Neisseria activity (MIC = 65 μM), while 1(19) and 1(21) had MICs against C. albicans of 16 and 7.7 μM, respectively. Two measures of safety showed promise as all compounds had relatively low cytotoxic activity (EC50 = 210–940 μM) against epithelial cells and low activity against L. plantarum, 1(n), 2(n), and 3(n) had MICs ? 490, 1300, and 940 μM, respectively. CMCs measured in aqueous triethanolamine and in aqueous potassium hydroxide showed linear dependences on chain length. As expected, the longest chain in each series had the lowest CMC—in triethanolamine: 1(21), 1500 μM; 2(22), 320 μM; 3(22), 340 μM, and in potassium hydroxide: 1(21), 130 μM; 3(22), 40 μM. The CMC in triethanolamine adjusted to pH 7.4 was 400 μM for 1(21) and 3900 μM for 3(16). The promising antifungal activity, low activity against L. plantarum, relatively high CMCs, and modest epithelial cytotoxicity in addition to their anti-Neisseria properties warrant further design studies with dendritic amphiphiles to improve their safety indices to produce suitable candidates for antimicrobial vaginal products.  相似文献   

9.
The solid state structures of [Ni(1)2][NO3]2 · 2MeOH · 2H2O, [Fe(1)2][ClO4]2 · 2MeOH · 0.5H2O, [Ru(1)2][PF6]2 and [Ru(1)2][PF6][NO3] (1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine) are presented and the structural variation observed for the {M(1)2}2+ unit is discussed. Protonation of the pendant pyridine group in [Ru(1)2]2+ leads to the formation of a hydrogen-bonded, one-dimensional polymer [{Ru(1)(H1)}n]3n+ exemplifed by the solid-state structure of [{Ru(1)(H1)}{Fe(NCS)6} · 1.25H2O]n.  相似文献   

10.
The bimetallic [M1M2(tren)2(CAn?)]m+ series, where M = GaIII or CrIII and CA is the chloranilate ligand which can take on diamagnetic (CAcat,cat)4? or paramagnetic (CAsq,cat)3? forms, comprises an electronically diverse series of compounds ranging from the closed-shell [Ga2(tren)2(CAcat,cat)]2+ to the S = 5/2 ground state of [Cr2(tren)2(CAsq,cat)]3+. This report deals with the interpretation of the EPR and ENDOR spectra of [Ga2(tren)2(CAsq,cat)](BPh4)2(BF4) (2) and the related derivative [Ga2(tren)2(DHBQ)](BPh4)2(BF4) (2a) (where DHBQ is the fully deprotonated trianionic form of 2,5-dihydroxy-1,4-benzoquinone) in an effort to further characterize the electronic structure of this radical species. The X-band (~9.5 GHz) EPR spectrum of complex 2 acquired in a butyronitrile/propionitrile glass at 4 K reveals a rhombic g-tensor with gxx = 2.0100, gyy = 2.0097, and gzz = 2.0060 with hyperfine interactions due to spin delocalization onto the two Ga nuclei (axx = 4.902 G, ayy = 4.124 G, azz = 3.167 G); the origin of the hyperfine coupling was confirmed by analysis of the room temperature spectra of complexes 2 and 2a. The low-temperature spectrum of complex 2 also indicates the presence of a triplet electronic state characterized by a g-value of 2.009 and axial zero-field splitting of D = 150 G (0.012 cm?1) as determined from measurements carried out at both X- and W-band (~95 GHz) frequencies. This triplet state is believed to arise due to a weak intermolecular Heisenberg exchange interaction between two aggregating complexes. ENDOR measurements on complex 2a at 20 K allowed for a determination of the magnitude of hyperfine coupling to the protons associated with the radical bridge as well as providing a rare example of an ENDOR signal arising from coupling to a gallium nucleus. Finally, these results were combined with literature data on the free semiquinone form of the bridging ligand in order to assess the extent to which density functional theory can predict unpaired spin density distribution in a complex molecule of this type. Although differences between theory and experiment were noted, DFT was able to provide a reasonably accurate picture of the electronic structure of this system as well as provide insight into the spin polarization mechanism(s) responsible for the observed hyperfine interactions.  相似文献   

11.
Two tetracyanometalate building blocks, [Fe(5,5′-dmbipy)(CN)4]? (2) and [Fe(4,4′-dmbipy)(CN)4]? (3) (5,5′-dmbipy = 5,5′-dimethyl-2,2′-bipyridine; 4,4′-dmbipy = 4,4′-dimethyl-2,2′-bipyridine), and two cyano-bridged heterobimetallic complexes, [Cu2(bpca)2(H2O)2Fe2(5,5′-dmbipy)2(CN)8] · 2[Cu(bpca)Fe(5,5′-dmbipy)(CN)4] · 4H2O (4) and [Cu(bpca)Fe(4,4′-dmbipy)(CN)4]n (5) (bpca = bis(2-pyridylcarbonyl)amidate), have been synthesized and structurally characterized. Complex 4 contains two dinuclear and one tetranuclear heterobimetallic clusters in an asymmetric unit whereas the structure of complex 5 features a one-dimensional heterobimetallic zigzag chain. The Cu(II) ion is penta-coordinated in the form of a distorted square-based pyramid. Magnetic studies show ferromagnetic coupling between Cu(II) and Fe(III) ions with g = 2.28, J1 = 2.64 cm?1, J2 = 5.40 cm?1 and TIP = ?2.36 × 10?3 for complex 4, and g = 2.17, J = 4.82 cm?1 and zJ = 0.029 cm?1 for complex 5.  相似文献   

12.
We present the synthesis and biological evaluation of a collection of s-triazine derivatives as a novel scaffold of compounds with the capability to inhibit the PGE2 production in LPS-induced RAW 264.7 macrophage cells. A total of 12 derivatives were synthesized and assayed for PGE2 reduction at 10 μM concentration. Two compounds (7b and 7i) exhibiting >90% inhibition of PGE2 production were found to have IC50 values of 5.76 and 5.52 μM, respectively. They were counter screened for inhibition on COX-2 activity in a cell free assay. Specifically, compound 7i (R1 = 4-Bn-Ph, R2 = Cl, R3 = Ph, R5 = CO2Me) was highly active in cells while maintaining little COX-2 inhibition (∼0% at 10 μM). Molecular docking study provides the possibility that compound 7i could inhibit PGE2 production by blocking the PGH2 binding site of mPGES-1 instead of COX-2 enzyme. Based on this result, our synthetic efforts will focus on intensive structure–activity relationship (SAR) study of s-triazine scaffold to discovery a potential PGE2 synthesis inhibitor.  相似文献   

13.
《Inorganica chimica acta》2006,359(11):3639-3648
A series of alkynylgold(I) bis(diphenylphosphino)alkyl- and aryl-amine complexes, [{Ph2PN(R)PPh2}Au2(CCR′)2] [R = nPr, R′ = Ph (1), C6H4OMe-p (2), C6H4Me-p (3), C6H4Cl-p (4); R = C6H4OMe-p, R′ = Ph (5)], has been synthesized. The X-ray crystal structures of 1 and 2 revealed the presence of short intramolecular Au⋯Au contacts with the distances of 2.8404(8) and 3.0708(7) Å. The luminescence behavior of the complexes were studied.  相似文献   

14.
《Inorganica chimica acta》2006,359(9):2896-2909
[RuCl3(NO)(P–P)], [P–P = R2P(CH2)nPR2 (n = 1–3) and R2P(CH2)POR2, PR2–CHCH–PR2, R = Ph and (C6H11)2P-(CH2)2-P(C6H11)2] were obtained and characterized by 31P {1H} NMR, IR spectroscopies and cyclic voltammetry. The structures of fac-[RuCl3(NO)(P–P)], P–P = dppm (1), dppe (2), c-dppen (3) and dppp (4), mer-[RuCl3(NO)(dcpe)] (6a) and mer-[RuCl3(NO)(dppmO)] (7) have been determined by X-ray diffraction. Photochemical isomerization of fac- to mer-[RuCl3(NO)(P–P)] was observed under white light in a CH2Cl2 solution and in solid state. The isomerization processes were followed by IR and 31P {1H} spectra. The mer-[RuCl3(15NO)(dppb)] isomer was used for the definition of the phosphorus atoms in the structure of the complex in solution. The electrochemical study shows that the oxidation/reduction processes observed in these complexes are dependent on both the isomer (fac or mer) and the solvent. In CH2Cl2, the NO+ reduction potentials are less negative for the mer-isomers than for the fac ones, while in CH3CN solvent these potentials are, in general, very close for both isomers.  相似文献   

15.
The synthesis and characterization of homobimetallic palladium and platinum complexes of type [(Me(O)CS-4-NCN–M  NN  M–NCN-4-SC(O)Me](OTf)2 (Me(O)CS-4-NCN = [C6H2(CH2NMe2)2-2,6-SC(O)Me-4]?; NN = 4,4′-bipyridine (bipy); M = Pd, 12; M = Pt, 13) is reported. The required bifunctional thio-acetyl NCN pincer starting compound NC(Br)N-4-SC(O)Me (2) has been synthesized by the consecutive reactions of NC(Br)N–I (I-1-C6H2(CH2NMe2)2-3,5-Br-4) (1) with tBuLi, S8 and Me(O)CCl, respectively. Chemoselective metallation at the Caryl–Br bond was achieved by the reaction of 2 with the palladium(0) source [Pd2(dba)3] (3) (dba = dibenzylidene acetone). Treatment of thus formed [Pd(NCN-4-SC(O)Me)(Br)] (4) with [AgOTf] (8) (OTf = triflate, OSO2CF3) gave [Pd(NCN-4-SC(O)Me)(H2O)][OTf] (9) which was further reacted with 0.5 equiv. of 4,4′-bipyridine (11a) to afford rigid-rod structured 12. When [Pt(tol)2(SEt2)]2 (5) (tol = 4-tolyl) was used instead of 3, then 13 was produced via the in situ formation of [PtBr(NCN-4-SC(O)Me)] (7) and [Pt(NCN-4-SC(O)Me)(H2O)][OTf] (10). Another possibility to synthesize 7 relied upon the subsequent reaction of 1 with 0.5 equiv. of 5 to give [PtBr(NCN-4-I)] (6) which further reacted with tBuLi, 1/8 S8 and Me(O)CCl to afford 7. The cyclic voltammograms of 2, 7, and 13 are discussed.Complex 7 was structurally characterized by single crystal X-ray crystallography. Organometallic 7 crystallizes with three independent molecules in the asymmetric unit and displays a monomeric structure as commonly encountered in d8-metal pincer chemistry.  相似文献   

16.
《Inorganica chimica acta》2006,359(7):2047-2052
Two new coordination polymers, {[Er(5-nip)1.5(2,2′-bipy)](H2O)2}n (1) and {[Er(5-nip)2] (4,4′-H2bipy)0.5}n (2) (5-nip = 5-nitroisophthalic acid, 2,2′-bipy = 2,2′-bipyridyl, 4,4′-bipy = 4,4′-bipyridyl), have been synthesized by the hydrothermal reactions of erbium nitrate, 5-nitroisophthalic acid (5-H2nip) and 2,2′-bipyridyl (for 1), and erbium nitrate, 5-nitroisophthalic acid and 4,4′-bipyridyl (for 2). X-ray diffraction analysis indicates that complex 1 exhibits a two-dimensional layer structure, while complex 2 displays a 3D architecture sustained by the strong hydrogen-bond interactions between the protonated 4,4′-bipyridyl and the carboxyl oxygen atom from [Er2(5-nip)4]2− with 2D layer structure, and 4,4′-bipyridyl as the guest molecules exist in bilayer channel. They are characterized by the elemental analysis and IR spectroscopy. The studies for the thermal stabilities of the two complexes show that complex 2 is more stable than complex 1.  相似文献   

17.
《Inorganica chimica acta》2006,359(5):1549-1558
Reactions of Cp*RhCl2(PPh3) (1) with 1-alkyne and H2O in the presence of KPF6 generated alkenyl ketone complexes [Cp*Rh(CRCHCOCH2R)(PPh3)](PF6) (2) (R = Ph (a), C6H4p-Me (b), C6H4-p-COOMe (c), C6H4-p-NO2 (d)). A similar complex [Cp*Rh(CPhCHCOCH2Ph)(PMePh2)](PF6) (2e) was obtained by use of Cp*RhCl2(PMePh2). It was revealed by X-ray analyses of 2b, 2c and 2e that the complexes 2 consist of the five-membered ring structures bound by the carbon and oxygen atoms of the alkenyl ketone group. Similar reactions of Cp*IrCl2(PPh3) (6) or (C6Me6)RuCl2(PPh3) (7) proceeded with a cleavage of C–C triple bond of 1-alkyne without formation of an alkenyl ketone complex, affording the corresponding carbonyl complexes, [Cp*IrCl(PPh3)(CO)](PF6) (8) or [(C6Me6)RuCl(PPh3)(CO)](PF6) (9). The diphosphine complexes [(Cp*MCl2)2{μ-diphos}] (4: M = Rh, diphos = dppm,; 12a: M = Ir, diphos = dppm; 12b: M = Ir, diphos = dppb) gave a Cl-bridged rhodium complex [{Cp*Rh(μ-Cl)}2{μ-dppm}](PF6)2 (5), mono-carbonyl or dicarbonyl iridium complexes,[(Cp*IrCl2){μ-dppm}{Cp*IrCl(CO)}](PF6)(13a) or [{Cp*IrCl(CO)}2{μ-dppb}](PF6)2 (14b), respectively.  相似文献   

18.
19.
Cyclic tetrapeptide c[Phe-pro-Phe-trp] 2, a diastereomer of CJ-15,208 (1), was identified as a potent dual κ/μ opioid receptor antagonist devoid of δ opioid receptor affinity against cloned human receptors: Ki (2) = 3.8 nM (κ), 30 nM (μ); IC50 ([35S]GTPγS binding) = 140 nM (κ), 21 nM (μ). The d-tryptophan residue rendered 2 ca. eightfold and fourfold more potent at κ and μ, respectively, than the corresponding l-configured tryptophan in the natural product 1. Phe analogs 3–10, designed to probe the effect of substituents on receptor affinity and selectivity, possessed Ki values ranging from 14 to 220 nM against the κ opioid receptor with μ/κ ratios of 0.45–3.0. An alanine scan of 2 yielded c[Ala-pro-Phe-trp] 12, an analog equipotent to 2. Agents 2 and 12 were pure antagonists in vitro devoid of agonist activity. Ac-pro-Phe-trp-Phe-NH2 16 and Ac-Phe-trp-Phe-pro-NH2 17 two of the eight possible acyclic peptides derived from 1 and 2, were selective, modestly potent μ ligands: Ki (16) = 340 nM (μ); Ki (17) = 360 nM (μ).  相似文献   

20.
We report the synthesis and magnetic properties of three hexametallic Mn clusters: [Mn6O2(Et-sao)6(O2C-Naphth)2(EtOH)4(H2O)2] (1) (HO2C-Naphth = 1-naphthoic acid, Et-saoH2 = 2-hydroxyphenylpropanone oxime), [Mn6O2(Et-sao)6(O2C-Anthra)2(EtOH)4(H2O)2] · 0.66EtOH · 0.33H2O (HO2C-Anthra = anthracene-9-carboxylic acid) (2 · 0.66EtOH · 0.33H2O) and [Mn6O2(Et-sao)6(O2CPhCCH)2(EtOH)4(H2O)2] · 1.7EtOH · 0.3H2O (HO2CPhC  CH = 4-ethynylbenzoic acid) (3 · 1.7EtOH · 0.3H2O). Clusters 13 exhibit ferromagnetic exchange between all six MnIII centres resulting in S = 12 ground spin states. Ac magnetic susceptibility and single crystal micro-SQUID measurements on 13 confirm SMM behaviour with barriers to magnetisation reversal of 60.12 (1), 60.10 (2) and 66.79 (3) K.  相似文献   

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