Catecholamine-Copper Redox as a Basis for Site-Specific Single-Step Functionalization of Material Surfaces.

Realization of robust and facile surface functionalization processes is critical to biomaterials and biotechnology yet remains a challenge. Here, we report a new chemical approach that enables operationally simple and site-specific surface functionalization. The mechanism involves a catechol-copper redox chemistry, where the oxidative polymerization of an alkynyl catecholamine reduces Cu(II) to Cu(I), which in situ catalyzes a click reaction with azide-containing molecules of interest (MOIs). This process enables drop-coating and grafting of two- and three-dimensional solid surfaces in a single operation using as small as sub-microliter volumes. Generalizability of the method is shown for immobilizing MOIs of diverse structure and chemical or biological activity. Biological applications in anti-biofouling, cellular adhesion, scaffold seeding, and tissue regeneration are demonstrated, in which the activities or fates of cells are site-specifically manipulated. This work advances surface chemistry by integrating simplicity and precision with multipurpose surface functionalization.

Building block and rapid synthesis of catecholamines-inorganic nanoflowers with their peroxidase-mimicking and antimicrobial activities.

Protein incorporated flower-shaped hybrid nanostructures have received highly considerable attention due to their greatly enhanced catalytic activities and stabilities. Up to date, proteins, enzymes (mostly considered as proteins), and amino acids (as the building blocks of peptides and proteins) have been used as organic components of the hybrid nanoflowers. Herein, we present a rational strategy to rapidly form catecholamines (dopamine, epinephrine and norepinephrine)-copper ion (Cu2+) incorporated nanoflowers (cNFs) mostly in 3 hours and show their peroxidase-mimic catalytic, dye degradation and antimicrobial activities through Fenton-like reaction mechanism. We systematically studied effects of experimental parameters including catecholamine concentrations, reaction time and reaction pH values, on formation of the cNFs. We also explained that norepinephrine nanoflower (neNF) with its porous structure, high surface area, polar surface property behaves as an efficient Fenton agent by exhibiting highly much catalytic activities compared to dopamine nanoflower (dNF) and epinephrine nanoflower (epNF). We claim that the NFs formed using nonprotein molecules can be used in designing new generation nanobiocatalytics, antimicrobial agents, nanobiosensors and pharmaceutical products.

Hexadentate ß-Dicarbonyl(bis-catecholamine) Ligands for Efficient Uranyl Cation Decorporation: Thermodynamic and Antioxidant Activity Studies.

The special linear dioxo cation structure of the uranyl cation, which relegates ligand coordination to an equatorial plane perpendicular to the O═U═O vector, poses an unusual challenge for the rational design of efficient chelating agents. Therefore, the planar hexadentate ligand rational design employed in this work incorporates two bidentate catecholamine (CAM) chelating moieties and a flexible linker with a ß-dicarbonyl chelating moiety (ß-dicarbonyl(CAM)2 ligands). The solution thermodynamics of ß-dicarbonyl(CAM)2 with a uranyl cation was investigated by potentiometric and spectrophotometric titrations. The results demonstrated that the pUO22+ values are significantly higher than for the previously reported TMA(2Li-1,2-HOPO)2, and efficient chelation of the uranyl cation was realized by the planar hexadentate ß-dicarbonyl(CAM)2. The efficient chelating ability of ß-dicarbonyl(CAM)2 was attributed to the presence of the more flexible ß-dicarbonyl chelating linker and planar hexadentate structure, which favors the geometric arrangement between ligand and uranyl coordinative preference. Meanwhile, ß-dicarbonyl(CAM)2 also exhibits higher antiradical efficiency in comparison to butylated hydroxyanisole. These results indicated that ß-dicarbonyl(CAM)2 has potential application prospects as a chelating agent for efficient chelation of a uranyl cation.

Biomimetic synthesis of the IDO inhibitors exiguamine A and B.

Biomimetic synthesis is an attempt to assemble natural products along biosynthetic lines without recourse to the full enzymatic machinery of nature. We exemplify this with a total synthesis of exiguamine A and the newly isolated natural product exiguamine B. The most noteworthy feature of this work is an oxidative endgame drawing from the complex chemistry of catecholamines, which allows for ready access to a new class of nanomolar indoleamine-2,3-dioxygenase inhibitors.

Asymmetric hydrogenation of alpha-primary and secondary amino ketones: efficient asymmetric syntheses of (-)-arbutamine and (-)-denopamine.

Two beta-receptor agonists (-)-denopamine and (-)-arbutamine were prepared in good yields and enantioselectivities by asymmetric hydrogenation of unprotected amino ketones for the first time by using Rh catalysts bearing electron-donating phosphine ligands. A series of alpha-primary and secondary amino ketones were synthesized and hydrogenated to produce various 1,2-amino alcohols in good yields and with good enantioselectivies. This Rh electron-donating phosphine-catalyzed asymmetric hyderogenation represents one of the most promising and convenient approaches towards the asymmetric synthesis of chiral amino alcohols.

Direct ring conjugation of catecholamines and their immunological interactions.

Catecholamine derivatives were synthesized with potential applications as coating antigens in biosensors or in the raising of specific antibodies. Thioether-bridged derivatives of the catecholamines dopamine, norepinephrine, and epinephrine that attach carboxylic acid functionalities directly to the aromatic ring via an easily incremented linker chain were synthesized by an electrochemical method. These derivatives were purified by convenient ion-exchange chromatography, exact positions of conjugation determined by NMR, and a dopamine derivative immobilized in situ in a BIAcore surface plasmon resonance (SPR) biosensor and its antibody binding studied in comparison with immobilization via the catecholamine primary amine. Binding of an antibody raised to an amine-conjugated protein conjugate showed clear distinction between conjugations at different positions on the catecholamine, illustrating the importance of rational conjugate design in immunosensing of the catecholamines.

Molecular design and biological activities of protein-tyrosine phosphatase inhibitors.

Protein-tyrosine kinase (PTKase) and protein-tyrosine phosphatase (PTPase) regulate the intracellular signal transduction in various biological processes. PTPase often negatively regulates the intracellular protein-tyrosine phosphorylation. PTPases are considered to be involved in the etiology of diabetes mellitus and neural diseases, such as Alzheimer's disease and Parkinson's disease. Therefore, PTPase inhibitors should be useful tools to study the role of PTPases in these diseases and other biological phenomena, and they hopefully may be developed into chemotherapeutic agents. We first discovered a naturally occurring PTPase inhibitor, dephostatin, in 1993. Later, we developed stable and safe dephostatin analogues by a molecular design approach employing the concept of CH/pi interaction. We prepared Et-3,4-dephostatin as a stable analogue and found it to inhibit PTP-1B and SHPTP-1 PTPases selectively. Et-3,4-dephostatin increased the tyrosine phosphorylation of the insulin receptor and insulin receptor substrate-1 (IRS-1), with or without insulin, in differentiated 3T3-L1 mouse adipocytes. It also increased the phosphorylation and activation of Akt. The analogue also enhanced translocation of glucose transporter 4 (GLUT4) from the cytoplasm to the membrane and 2-deoxyglucose transport. It also showed an in vivo antidiabetic effect in terms of reducing the high blood glucose level in KK-Ay mice after oral administration. Since Et-3,4-dephostatin contains a nitrosamine moiety, we designed nitrosamine-free dephostatin analogues employing the concept of CH/pi interaction. Then, we synthesized methoxime- and hexyl-methoxime-3,4-dephostatin as nitrosamine-free analogues. These analogues also showed antidiabetic activity in vivo and illustrate the utility of the CH/pi interaction molecular design approach.

Effect of ligand structure on the zinc-catalyzed Henry reaction. Asymmetric syntheses of (-)-denopamine and (-)-arbutamine.

[reaction: see text] Syntheses of variously modified ligands for the dinuclear zinc catalysts for the asymmetric aldol and nitroaldol (Henry) reactions are reported. Catalytic enantioselective nitroaldol reactions promoted by these modified ligands led to efficient syntheses of the beta-receptor agonists (-)-denopamine and (-)-arbutamine.

A new type of prodrug of catecholamines: an opportunity to improve the treatment of Parkinson's disease.

After decades of research around dopamine agonists, we have found a promising compound in S-PD148903 that represents a new type of prodrug, which in the rat is bioactivated to the catecholamine S-5,6-diOH-DPAT, known to display mixed dopamine D(1)/D(2) receptor agonist properties just like apomorphine. This prodrug has an enone structure which by an oxidative bioactivation mechanism is converted to the corresponding catechol and is delivered enantioselectively into the CNS. This novel concept has the potential to revolutionize the treatment of Parkinson's disease by competing with L-DOPA, the current treatment of choice.

Conformationally restrained analogues of sympathomimetic catecholamines. Synthesis and adrenergic activity of 5,6- and 6,7-dihydroxy-3,4-dihydrospiro[naphthalen-1(2H)-2',5'-morpholines].

The 5,6- (10a) and 6,7-dihydroxy-3,4-dihydrospiro[naphthalen-1(2H)-)-2',5'-morpholine](11a) and their N-isopropyl derivatives (10b and 11b) (DDSNMs), which can be viewed as the result of the combination of the structure of the 2-(3,4-dihydroxyphenyl)morpholine 5a or 5b (DPMs) with the structure of the corresponding 1-(aminomethyl)-5,6-dihydroxy- (8a or 8b) or 1-(aminomethyl)-6,7-dihydroxy-1,2,3,4-tetrahydro-1-naphthalen-ol (9a or 9b) (1-AMDTNs) were synthesised. The new compounds DDSNMs 10a,b and 11a,b were assayed for their alpha- and beta-adrenergic properties by means of binding experiments and functional tests and the results were compared with those obtained for catecholamines 1a, b and the previously described morpholine (5) and tetrahydronaphthalene (8, 9) derivatives. The affinity and activity indices thus obtained indicate in general a low ability of the new compounds 10 and 11 to interact with the alpha- and beta-adrenoceptors, which, in all cases, was lower than that of the corresponding morpholine (5) and tetrahydronaphthalene (8, 9) analogues.

Synthesis and electrochemical studies of a new iron tetra-catecholamide complex.

A new tetra-catecholamide compound N5,N6-thiodipropanoyl-bis[N1,N10-bis(2,3-dihydroxybenzoyl-spermidi ne)] (H8L) has been synthesised as an iron chelator of Fe (III). Cyclic voltammogram of the iron complex H2LFe run under an argon atmosphere shows a quasi-reversible redox process with E0 = -430 mV vs. SCE in CH3OH/H20 (60/40). This value approaches the range of biological reductants and consequently the complex may mimic the release of iron from enterobactin to the agents which are directly involved in cell metabolism.

Conformationally restrained analogs of sympathomimetic catecholamines. Synthesis, conformational analysis, and adrenergic activity of isochroman derivatives.

In previous papers dealing with the study of the conformations and the biopharmacological activity of conformationally restrained analogs of sympathomimetic catecholamines (NE and ISO), proposals were advanced for the three-dimensional molecular models A, B, and C; these models provided information about the steric requirements for the direct activation of alpha 1, alpha 2,beta 1, and beta 2 adrenoceptors, respectively. The 1-(aminomethyl)-6,7-dihydroxyisochromans 11 and 12 and the 1-(aminomethyl)-5,6-dihydroxyisochromans 13 and 14 (1-AMDICs) are two different types of semirigid analogs of NE and ISO. The alpha 1, alpha 2, beta 1, and beta 2 adrenergic properties of the 1-AMDICs 11-14 were evaluated in vitro, both by radioligand binding assays and by functional tests on isolated preparations, and were compared with those of their parent compounds (NE and ISO). The results of a conformational study carried out by means of both 1H NMR spectrometry and theoretical calculations indicated that, in these 1-AMDICs, the presumed active groups (aryl moiety, amine nitrogen and benzylic ethereal oxygen) are in a spatial relationship corresponding to the one found for NE and ISO in their preferred conformations, which also proved to be the pharmacophoric conformation in the models A-C. By means of a comparison of the stereostructures of the 1-AMDICs 11-14 with their biopharmacological properties, it was possible to obtain a further definition of the model B with respect to the activation of the alpha 2 adrenoceptors; the superimposition of the 1-AMDICs 11 and 12 with the molecular model C made it possible to detect an area of the beta-adrenergic receptors which might hinder the fit of adrenergic drugs that are analogs of catecholamines with these receptors.

Synthesis and alpha 2-adrenoceptor effects of substituted catecholimidazoline and catecholimidazole analogues in human platelets.

It is known that the steric requirements for the interactions of catecholamines and catecholimidazolines with alpha 1- and alpha 2-adrenoceptors are different. New analogues of desoxycatecholimidazoline (1), desoxycatecholimidazole (3), benzylic hydroxyl substituted imidazole (4), and the aromatic fluorine substitution analogues of 1 at the 2 (5), 5 (6), and 6 (7) positions, and a set of asymmetric 4-substituted catecholimidazolines, S-8 and R-8, were prepared and tested for interaction with alpha 2-adrenoceptors in human platelets. With the exception of 3, all compounds were selective for alpha-adrenoceptor-mediated responses in human platelets. Introduction of a double bond in imidazoline 1 to give an imidazole 3 or the introduction of a benzylic hydroxyl group to 3, as in 4, reduced the inhibition of platelet aggregation with a rank order potency of 1 greater than 3 greater than 4. Fluorine atom substitution at the 2-, 5-, or 6-positions only slightly modified the inhibitory activity of 1. Each analogue (1, 3-7) produced alpha 2-mediated inhibition of platelet adenylate cyclase and can be classified as a partial agonist. The inhibition potency of S-8 and R-8 against epinephrine-induced aggregatory responses were greatly different, and only R-8 and 4 were alpha 2-agonists on human platelet function. Our studies provide further evidence for the differential interaction of catecholamines and catecholimidazolines in alpha 1- and alpha 2-adrenoceptor systems.

Synthesis and evaluation of the pharmacological activity of rigid analogues of sympathomimetic catecholamines derived from bicyclo[2.2.1]heptane.

endo-3-Amino-exo-2-(3,4-dihydroxyphenyl)-2-hydroxybicyclo[2.2.1]he ptane (4a) and its N-isopropyl derivative (4b) were synthesized and assayed for their adrenergic activity on various isolated preparations. Compounds 4a and 4b, tested up to a dose of 10(-4) M, did not reveal any activity, either stimulant or blocking, on the alpha- and beta-adrenoceptors. Possible rationalizations of the results obtained, however, are suggested.

Conjugates of catecholamines. VII. Synthesis and beta-adrenergic activity of peptide catecholamine conjugates.

A series of novel catecholamine derivatives has been prepared in which one of the N-methyl substituents of isoproterenol has been extended by a spacer consisting of a chain of four methylenes which terminates with an amide linkage to a peptide, the point of attachment being via the aromatic amino group of p-aminophenylalanine. In one of the derivatives, two catecholamines are attached to the same peptide in this manner. The peptides, which range in size from three to eight amino acid residues and contain phenylalanine, glycine, and L-alpha-amino-delta-hydroxyvaleric acid, were synthesized via stepwise and fragment condensation techniques. The beta-adrenergic agonist activities of the derivatives were evaluated in vitro by measuring the intracellular accumulation of cyclic AMP in S49 mouse lymphoma cells.

Conjugates of catecholamines. 6. Synthesis and beta-adrenergic activity of N-(hydroxyalkyl)catecholamine derivatives.

A new series of catecholamines has been prepared in which the N-alkyl substituent of dl-epinephrine or dl-isoproterenol has been extended by a methylene chain terminated by a hydroxyl group or derived functionality (e.g., carbamate or ester). These functionalized catecholamines (congeners) and model compounds were prepared with the goal of eventual attachment to polymeric carrier molecules. The beta-adrenergic agonist activity of the derivatives was evaluated in vitro by measuring the intracellular accumulation of cyclic AMP in S49 mouse lymphoma cells and by the displacement of iodocyanopindolol (ICYP). A n-butylcarbamate derivative (compound 15) was the most active compound in this series with a potency 190 times greater than dl-isoproterenol in the S49 assay. The biological results indicate that minor modifications in structure in the N-alkyl substituent of the catecholamine can influence the pharmacologic activity.

Affinity-dependent cross-linking to neurotoxin sites of the acetylcholine receptor mediated by catechol oxidation.

The choline homologue 3-[(trimethylammonio)methyl]catechol (TMC) has been synthesized, and the controllable features of its complex oxidation have been examined spectroscopically and correlated with its toxin binding inactivating reactions with the acetylcholine receptor (AcChR) from Torpedo californica electroplax. Affinity-dependent reactions of early intermediates in the oxidation of TMC are suggested to intercede covalently in this inactivation. At pH 7.4, where the oxidative polymerization of catechols proceeds spontaneously, pyrocatechol produced no effect on the toxin binding function of AcChR, whereas comparable concentrations of TMC led to inactivation of half of all available sites. Lower concentrations of TMC converted via oxidation with ceric salts to an in situ mixture of monohydroxylated catechols were shown to be effective in short-term incubations in inactivating approximately half of the toxin binding sites by covalent labeling of the receptor. Mixtures of dihydroxycatechol intermediates, hydroxy-p-quinones, and polymeric products led to nonspecific toxin binding site inactivation of AcChR in excess of half of all available sites. Collectively, the results suggest that both covalent labeling and oxygen reduction product inactivating mechanisms are operative in these model macromolecular site reactions and that catechol-containing affinity reagents may be useful in elucidating the molecular features of sites to which they are directed.

Conjugates of catecholamines. 1. N-alkyl-functionalized carboxylic acid congeners and amides related to isoproterenol.

A series of functionalized catecholamines (congeners) has been synthesized in which, formalistically, the N-isopropyl group of isoproterenol has been extended by a linear alkyl chain of varying length, terminated by a carboxy group or a substituted amide. The compounds were prepared generally via the reductive amination of norepinephrine with a keto acid or a preformed keto amide. An alternate synthesis of the model amide derivatives, involving activation of the carboxylic acid congeners and coupling with amines, was complicated in the case of short-chain derivatives by facile cyclization to lactams. In vitro evaluation of these compounds as potential beta-adrenergic agonists has shown that, while the carboxylic acid congeners have relatively low potencies, the model amide derivatives have potencies that are highly dependent on both the length of the alkyl chain and also the nature of the substituent on the amide. In general, aromatic amides are the most potent, although the nature and position of substituents on the aromatic group dramatically influences their potency. The implications of these studies, in terms of general beta-adrenergic drug design and also the attachment of the carboxylic acid congeners to carriers, are discussed.

alpha 2-Adrenoceptor agonist properties of exo- and endo-isomers of 2-amino-6,7,dihydroxybenzonorbornene designed as rigid catecholamines.

A series of N-substituted exo- and endo-isomers of 2-amino-6,7-dihydroxybenzonorbornene, designed as rigid catecholamines, have been studied in the pithed rat in-vivo, as vasoconstrictor agents, and as inhibitors of the twitch response in the transmurally stimulated guinea-pig ileum. The exo-isomers examined were vasoconstrictor agonists in the pithed rat and inhibited the twitch response of the ileum. The corresponding endo-isomers were inactive in both preparations. The exo-isomers were less potent than the alpha 2-receptor agonist TL99, but were all directly acting vasoconstrictor agents, since they were still effective in reserpine-pretreated animals. Responses induced by members of the exo-series were selectively antagonized by the alpha 2-receptor antagonist rauwolscine, but were not antagonized by the alpha 1-receptor antagonist, prazosin, or the dopamine-receptor antagonist alpha-flupenthixol. The results demonstrate important conformational requirements for the interaction of catecholamines at presynaptic or postsynaptic alpha 2-receptors, and suggest that a fully extended or anti-conformation of the noradrenaline molecule is involved in alpha 2-receptor-agonist interaction.