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The cationic ZnII part of aqua(1,4,7,10-tetraazacyclododecane)zinc(II) bis(perchlorate), [Zn(C8H20N4)(H2O)](ClO4)2, exhibits a slightly distorted square-pyramidal coordination environment with a water molecule in the apical position. In the crystal, the macrocyclic ring alternates between two conformations with equal occupancies. Two of the three perchlorate anions are situated about a twofold rotation axis, and one of them shows disorder of the O atoms with occupancies of 0.62 (7) and 0.38 (7). In the crystal, the complexes are connected by intermolecular hydrogen bonding via the perchlorate anions.

Thiolate coordination to zinc(II) ions occurs widely in such functional biomolecules as zinc enzymes or zinc finger proteins. Here, we introduce a simple method for determining the affinity of ligands toward the zinc-enzyme active-center model tetramethylrhodamine (TAMRA)-labeled 1,4,7,10-tetraazacyclododecane (cyclen)–zinc(II) complex (TAMRA–ZnL). The 1 : 1 complexation of TAMRA-labeled cysteine (TAMRA–Cys) with TAMRA–ZnL (each at 2.5 μM), in which the TAMRA moieties approach one another closely, induces remarkable changes in the visible absorption and fluorescence spectra at pH 7.4 and 25 °C. The 1 : 1 complex formation constant (K = [thiolate-bound zinc(II) complex]/[uncomplexed TAMRA–ZnL][uncomplexed TAMRA–Cys], M−1) was determined to be 106.7 M−1 from a Job's plot of the absorbances at 552 nm. By a ligand-competition method with the 1 : 1 complexation equilibrium, analogous K values for thiol-containing ligands, such as N-acetyl-L-cysteine, L-glutathione, and N-acetyl-L-cysteinamide, were evaluated to have similar values of about 104 M−1. As a result of the ligand affinities to TAMRA–ZnL, nonlabeled zinc(II)–cyclen induced remarkable stabilization of the reduced form of L-glutathione and a cysteine-containing enolase peptide to aerial oxidation in aqueous solution at pH 7.4 and 25 °C.

Antioxidant activities of 3-oxygenated and 3,4-dioxygenated carbazole alkaloids and their related carbazoles were comprehensively evaluated. In all assay systems, the 3,8-dihydroxycarbazoles carbazomadurin A (2) and B (3), and their synthetic precursors 2a and 3a exhibited higher antioxidant activities than the 3-monohydroxycarbazoles carazostatin (1), and the synthetic precursors 4a and 4b of carquinostatin A (4). In particular, 2a and 3a exhibited strong scavenging activities due to the reducing ability of formyl group at the C-5 position of carbazoles. The results suggest that these compounds could serve as useful clues for designing and developing novel antioxidants.

A simple and efficient method based on magnetic-bead technology has been developed for the enrichment of thiol-containing biomolecules, such as l-glutathione and cysteine-containing peptides. The thiol-binding site on the bead is a mononuclear complex of zinc(II) with 1,4,7,10-tetraazacyclododecane (cyclen); this is linked to a hydrophilic cross-linked agarose coating on a particle that has a magnetic core. All steps for the thiol-affinity separation are conducted in aqueous buffers with 0.10 mL of the magnetic beads in a 1.5 mL microtube. The entire separation protocol for thiol-containing compounds, from addition to elution, requires less than one hour per sample, provided the buffers and the zinc(II)-cyclen-functionalized magnetic beads have been prepared in advance. The thiol-affinity magnetic beads are reusable at least 15 times without a decrease in their thiol-binding ability, and they are stable for six months at room temperature.

The total syntheses of the neuronal cell-protecting carbazole alkaloids carbazomadurin A and (S)-(+)-carbazomadurin B were achieved. The key step of the synthesis of the polysubstituted carbazole rings included an allene-mediated electrocyclic reaction of the 6π-electron system that involved the indole 2,3-bond. The cleavage of the alkoxy groups of the resulting 3-ethoxy-8-isopropoxycarbazole successfully gave the 3,8-dihydroxycarbazole, which was converted into the 3,8-bis(OSEM)-carbazole (SEM = 2-trimethylsilylethoxymethyl). A Suzuki–Miyaura cross-coupling reaction of the 3,8-bis(OSEM)-carbazole with the corresponding alkenyl pinacol borates afforded the 1-alkenylcarbazoles, which were treated with tetra-n-butylammonium fluoride (TBAF) followed by reduction with NaBH4 to provide carbazomadurin A and (S)-(+)-carbazomadurin B, respectively.

Cysteine-containing biomolecules are attractive targets in the study of thiol biology. Here we introduce a novel method for the selective enrichment of thiol-containing molecules using a thiol-capture zinc(II) complex of 1,4,7,10-tetraazacyclododecane (Zn 2+ –cyclen). Recognition of N -acetylcysteine amide by Zn 2+ –cyclen has been studied by potentiometric pH titration, revealing formation of a 1:1 thiolate-bound Zn 2+ –cyclen complex with a large thiolate-affinity constant of 10 6.2 M −1 at 25 °C and I = 0.10 M (NaCl). The Zn 2+ -bound thiolate anion is unexpectedly stable in aqueous solution at pH 7.8 under atmospheric conditions for a few days. These findings have contributed to the development of a convenient method for separation of thiol compounds by using a micropipette tip. A 200 μL micropipette tip containing 10 μL of hydrophilic cross-linked agarose beads attached to Zn 2+ –cyclen moieties was prepared. All steps for thiol-affinity separation (binding, washing, and eluting) are conducted using aqueous buffers at room temperature. The entire separation protocol requires less than 15 min per sample. We demonstrate practical example separations of cysteine-containing molecules. This micropipette tip method would be used preferentially as an alternative to existing tools for reliable enrichment of thiol-containing molecules.

A new total synthesis of the neuronal cell-protecting carbazole alkaloid carbazomadurin A is described. The key step was an allene-mediated electrocyclic reaction involving an indole [b]-bond for the construction of a highly substituted carbazole ring. The E-alkenyl side chain at the C1 position of carbazole was introduced between O-triflate and alkenyl pinacol borate using the Suzuki–Miyaura reaction. SEM groups were cleaved with TBAF and the formyl group was reduced to provide carbazomadurin A.

A dinuclear zinc(II) complex, m,m-bis(Zn2+–cyclen) was synthesized as a novel host molecule for a malonate dianion. The dizinc(II) complex has two zinc(II)–cyclen moieties (cyclen = 1,4,7,10-tetraa...

A new bis-zinc(II) receptor (Zn2L), which has two macrocyclic 12-membered tetraamine (cyclen) ZnII complexes connected through a p-xylene bridge, has been synthesized as a novel host molecule to recognize barbiturates (such as barbital (bar)) in aqueous solution. Each of the zinc(II) ions in the biszinc(II) receptor was originally intended to match the dianionic barbital anion (bar2−) with supplementary hydrogen bonds between the cyclen NH's and the three carbonyl oxygens in complementary positions to yield a 1:1 complex, Zn2L–bar2−. From an aqueous solution of equimolar Zn2L and barbital at pH 8, however, a cyclic 2:2 complex, (Zn2L-bar2−)2, was isolated and characterized by X-ray crystal analysis. The NMR study in 10% (v/v) D2O/H2O has revealed dissociation of (Zn2L–bar2−)2 solely into the original target 1:1 complex Zn2L–bar2− and established the dimerization constant for 2Zn2L–bar2− → (Zn2L–bar2−)2, Kd ( = [(Zn2L–bar2−)2]/[Zn2L–bar2−]2) to be 103.4 M−1. The thermodynamic parameters were evaluated from the NMR measurements at 25, 35, 45, and 55°C: ΔG = –1.9 × 104 J mol−1, ΔH = – 3.3 × 104 J mol−1, ΔS = – 49 J mol−1 K−1 at 25°C. Potentiometric pH titration of Zn2L (1 mM) and barbital (1 mM) disclosed extremely facile deprotonation of the two imido groups of barbital at pH less than 7 to form the dianionic barbital-bound ZnII complexes Zn2L–bar2− and (Zn2L–bar2−)2, where-by the barbital binding affinity for Zn2L was estimated to be Kbar ( = [Zn2L–bar2−]/[uncomplexed Zn2L][uncomplexed barbital]) = 105.8 M−1 at pH 8 and 25°C with I = 0.10 (NaNO3). The significance of the bis-zinc(II) receptor in stabilizing the dianionic barbital is evident by comparison with the interaction of ZnII–cyclen complex (ZnL) with barbital, which yields only a 1:1 monoanionic barbital complex, ZnL–bar− (Kbar = [ZnL–bar−]/[uncomplexed ZnL][uncomplexed barbital] = 104.2M−1 at pH 8 and 25°C with I = 0.10 (NaNO3)).

Compounds (VII) and (VIII) exhibit selective inhibition of IFN-γ production compared with IL-4 production.

Formation de complexe stable avec le citrate (3−), l'AMP (2−), l'ATP (4−), HPO 4 2− , [Fe(CN) 6 ] 4− et [Fe(CN) 6 ] 3−

1, 1'-(m-Xylenediyl)-bis (1, 4, 7, 10-tetraazacyclododecane)-ZnII2 complex (m-xylenediyl-bicyclen-ZnII2), a potent inhibitor of human immunodeficiency virus (HIV), was obtained from cyclen by a combination of dimerization and metal complexation. The ratio of median cytotoxic concentration against host cells (CC50) and median effective concentration against HIV cytopathogenicity (EC50), referred to as the selectivity index (SI), was regarded to be a measure of anti-HIV activity. These two chemical modifications contributed to a potent, in vitro anti-HIV activity of m-xylenediyl-bicyclen-ZnII2 by respectively increasing the CC50 and decreasing the EC50 in comparison with those of cyclen.

A new 2-(9-anthrylmethylamino)ethyl-appended cyclen, L(3) (1-(2-(9-anthrylmethylamino)ethyl)-1,4,7,10-tetraazacyclododecane) (cyclen = 1,4,7,10-tetraazacyclododecane), was synthesized and characterized for a new Zn(2+) chelation-enhanced fluorophore, in comparison with previously reported 9-anthrylmethylcyclen L(1) (1-(9-anthrylmethyl)-1,4,7,10-tetraazacyclododecane) and dansylamide cyclen L(2). L(3) showed protonation constants log K(a)(i)() of 10.57 +/- 0.02, 9.10 +/- 0.02, 7.15 +/- 0.02,2, and2. The log K(a3) value of 7.15 was assigned to the pendant 2-(9-anthrylmethylamino)ethyl on the basis of the pH-dependent (1)H NMR and fluorescence spectroscopic measurements. The potentiometric pH titration study indicated extremely stable 1:1 Zn(2+)-L(3) complexation with a stability constant log K(s)(ZnL(3)) (where K(s)(ZnL(3)) = [ZnL(3)]/[Zn(2+)][L(3)] (M(-)(1))) of 17.6 at 25 degrees C with I = 0.1 (NaNO(3)), which is translated into the much smaller apparent dissociation constant K(d) (=[Zn(2+)](free)[L(3)](free)/[ZnL(3)]) of 2 x 10(-)(11) M with respect to 5 x 10(-)(8) M for L(1) at pH 7.4. The quantum yield (Phi = 0.14) in the fluorescent emission of L(3) increased to Phi = 0.44 upon complexation with zinc(II) ion at pH 7.4 (excitation at 368 nm). The fluorescence of 5 microM L(3) at pH 7.4 linearly increased with a 0.1-5 microM concentration of zinc(II). By comparison, the fluorescent emission of the free ligand L(1) decreased upon binding to Zn(2+) (from Phi = 0.27 to Phi = 0.19) at pH 7.4 (excitation at 368 nm). The Zn(2+) complexation with L(3) occurred more rapidly (the second-order rate constant k(2) is 4.6 x 10(2) M(-)(1) s(-)(1)) at pH 7.4 than that with L(1) (k(2) = 5.6 x 10 M(-)(1) s(-)(1)) and L(2) (k(2) = 1.4 x 10(2) M(-)(1) s(-)(1)). With an additionally inserted ethylamine in the pendant group, the macrocyclic ligand L(3) is a more effective and practical zinc(II) fluorophore than L(1).

4-(2-Phthalimidyl)benzoyl cyanide (Phibyl-CN) was designed as a fluorescent labeling reagent for primary and secondary alcohols in high-performance liquid chromatography. Reaction conditions were optimized with hexanol, benzylalcohol, cyclopentanol and 1-phenyl-1-propanol as model compounds of primary and secondary alcohols. Phibyl-CN reacted quantitatively with alcohols on heating at 50°C for 30 min in the presence of 4-dimethylaminopyridine to give the corresponding fluorescent esters which were separated on a reversed-phase column with fluorescence detection. The detection limits for alcohols labeled with the reagent were 0.24-0.38pmol per injection. The extents of conversion of primary and secondary alcohols into fluorescent esters were approximately 100%.

We investigated the degradation of angiotensin II by vascular endothelial cells and smooth muscle cells in vitro. When angiotensin II was incubated with confluent culture of endothelial cells or with serum free conditioned medium of the endothelial cells, angiotensin II was destroyed rapidly. When angiotensin II was incubated with cultured vascular smooth muscle cells or their serum free conditioned medium, degradation was not observed. To identify the angiotensin II degradation factor (ADF), we have purified ADF from the conditioned medium of endothelial cells, by column chromatographies, i.e., hydroxyapatite, ion exchange and gel filtration chromatography. The partially purified ADF had apparent molecular masses of 154 kDa on gel filtration chromatography. Its pH optimum was about 7.0. ADF was inhibited by p-chloromercuribenzoic acid, iodoacetamide and high concentration of EDTA, but not by diisopropyl fluorophosphate, bestatin, amastatin or pepstatin A. Of the synthetic substrates examined, ADF degrades human angiotensin II, [Val5]-angiotensin II and [Asn1, Val5]-angiotensin II. It did not degrade angiotensin I.

A new synthesis of the 1-oxygenated 1,3-disubstituted carbazole alkaloids, mukonine (la) and clausine (If) is described. The construction of the carbazole framework is based on an allene-mediated electrocyclic reaction involving the indole 2,3-bond. The 1,3-disubstituted 1-oxygenated carbazoles la and If are derived from the 1,2,3-trisubstituted carbazole.

Formation de complexe stable avec le citrate (3−), l'AMP (2−), l'ATP (4−), HPO 4 2− , [Fe(CN) 6 ] 4− et [Fe(CN) 6 ] 3−

We synthesized 6-methylindole-4,5-quinone (1b) in order to clarify the structure of natural product, 5-methylindole-4,5-quinone (la) isolated from Drupella fragum. The synthesis features the construction of the indole ring based on an electrocyclic reaction of a 3-alkenyl-2-propargylpyrrole intermediate. Two synthetic methylindolequinones and their related compounds were examined in human lung cancer cell line NCI-H460 and human breast cancer cell line MDA-MB-231.

A newly synthesized 18-membered hexaamine carrying an acetate moiety on each nitrogen, L2, has been demonstrated to be a more efficient dissolving agent that ethylenediaminetetraacetic acid for human urinary calculi whose major components are calcium phosphate and magnesium phosphate. L2 is a good chelating agent for Ca2+ and Mg2+, and this chelating action is presumably responsible for the dissolution of inorganic calculi.

The superoxide dismutase (EC 1.15.1.1) activities of new series of macrocyclic complexes with copper(II) have been measured. Chemical modifications in macrocyclic ring size, donor atom, donor atom number, substituents on the macrocyclic skeletons, and length of bridges linking two macrocycles are shown to have profound effects on the superoxide dismutase activities of the metal complexes. The quantitative measurement by the standard xanthine-xanthine oxidase assay, which depends on the conversion of nitroblue tetrazolium to formazan, has been corroborated by a direct assay method using an oxygen electrode.