Mehmet Serdar Gültekin

Ni/Pd core/shell nanoparticles supported on graphene as a highly active and reusable catalyst for Suzuki-Miyaura cross-coupling reaction

AbstractMonodisperse Ni/Pd core/shell nanoparticles (NPs) have been synthesized by sequential reduction of nickel(II) acetate and palladium(II) bromide in oleylamine (OAm) and trioctylphosphine (TOP). The Ni/Pd NPs have a narrow size distribution with a mean particle size of 10 nm and a standard deviation of 5% with respect to the particle diameter. Mechanistic studies showed that the presence of TOP was essential to control the reductive decomposition of Ni-TOP and Pd-TOP, and the formation of Ni/Pd core/shell NPs. Using the current synthetic protocol, the composition of the Ni/Pd within the core/shell structure can be readily tuned by simply controlling the initial molar ratio of the Ni and Pd salts. The as-synthesized Ni/Pd core/shell NPs were supported on graphene (G) and used as catalyst in Suzuki-Miyaura cross-coupling reactions. Among three different kinds of Ni/Pd NPs tested, the Ni/Pd (Ni/Pd = 3/2) NPs were found to be the most active catalyst for the Suzuki-Miyaura cross-coupling of arylboronic acids with aryl iodides, bromides and even chlorides in a dimethylformamide/water mixture by using K2CO3 as a base at 110 °C. The G-Ni/Pd was also stable and reusable, providing 98% conversion after the 5th catalytic run without showing any noticeable Ni/Pd composition change. The G-Ni/Pd structure reported in this paper combines both the efficiency of a homogeneous catalyst and the durability of a heterogeneous catalyst, and is promising catalyst candidate for various Pd-based catalytic applications.

Secondary/tertiary benzenesulfonamides with inhibitory action against the cytosolic human carbonic anhydrase isoforms I and II.

Carbonic anhydrase inhibitors of primary sulfonamide type, RSO2NH2, have clinical applications as diuretics, antiglaucoma, antiepileptic, antiobesity and antitumor drugs. Here we investigated inhibition of two human cytosolic isozymes, hCA I and II, with a series of secondary/tertiary sulfonamides, incorporating tosyl moieties (CH3C6H4SO2NR1R2). Most compounds inhibited both isoforms in low micromolar range, with inhibition constants between 0.181–6.01 μM against hCA I, and 0.209–0.779 μM against hCA II, respectively. These findings point out that substituted benzenesulfonamides may be used as leads for generating interesting CAIs probably possessing a distinct mechanism of action compared to primary sulfonamides. Indeed, classical RSO2NH2 inhibitors bind in deprotonated form to the Zn(II) ion from the CA active site and participate in many other favorable interactions with amino acid residues lining the cavity. The secondary/tertiary sulfonamides cannot bind to the zinc due to steric hindrance and probably are accommodated at the entrance of the active site, in coumarin binding-site.

A novel and one-pot synthesis of new 1-tosyl pyrrol-2-one derivatives and analysis of carbonic anhydrase inhibitory potencies

Here we propose a novel one-pot synthesis of new tosyl-pyrrole derivatives. By means of the new developed method, pyrrole derivatives were synthesized at room temperature in a single step, and a useful method is proposed for the synthesis of similar compounds. Moreover, inhibitions of two human cytosolic carbonic anhydrase (hCA, EC 4.2.1.1) isozymes I and II by 1-tosyl-pyrrole and 1-tosyl-pyrrol-2-on derivatives were investigated. 1-Tosyl-pyrrole, 1-tosyl-1H-pyrrol-2(5H)-one, 5-hydroxy-1-tosyl-1H-pyrrol-2(5H)-one and 5-oxo-1-tosyl-2,5-dihydro-1H-pyrrol-2-yl acetate showed inhibitory action with K(i) values in the range of 14.6-42.4 microM for hCA I and 0.53-37.5 microM for hCA II, respectively. All pyrrole derivatives were competitive inhibitors with 4-nitrophenylacetate as substrate. Some new synthesized pyrrole derivatives showed very effective hCA II inhibitory effects, in the same range as the clinically used sulfonamide acetazolamide, and might be used as leads for generating enzyme inhibitors targeting other CA isoforms.

The synthesis of some β-lactams and investigation of their metal-chelating activity, carbonic anhydrase and acetylcholinesterase inhibition profiles

Abstract β-Lactam antibiotics are a broad class of antibiotics, consisting of all antibiotic agents that contain a β-lactam ring in their molecular structures. Synthesis of β-lactam analogs, which are containing dichloride atoms and N-methyl, N-aromatic rings, was achieved by Schiff bases and dichloroketene compounds. All the synthesized imines and β-lactam analogs were tested against two physiologically relevant carbonic anhydrase isozymes (hCA I and II) and acetylcholinesterase (AChE). They demponstrated effective inhibitory profiles with Ki values in ranging of 3.22-11.18 nM against hCA I, 3.74-10.41 nM against hCA II, and 0.50-1.57 nM against AChE. On the other hand, acetazolamide and dorzolamide clinically used as CA inhibitors, showed Ki value of 170.34 and 129.26 nM against hCA I, and 115.43 and 135.67 nM against hCA II, respectively. Also, tacrine used as standard AChE inhibitor showed Ki value of 5.70 nM against AChE.

Sulfapyridine-like benzenesulfonamide derivatives as inhibitors of carbonic anhydrase isoenzymes I, II and VI

The inhibition of two human cytosolic carbonic anhydrase (hCA, EC 4.2.1.1) isozymes I, II and human serum isozyme VI, with a series of tosylited aromatic amine derivatives was investigated. The KI ranges of compounds 1–14 and acetazolamide against hCA I ranged between 1.130 and- 448.2 μM, against hCA II between 0.103 and- 14.3 μM, and against hCA VI ranged between 0.340 and- 42.39 μM. Tosylited aromatic amine derivatives are thus interesting hCA I, II and VI inhibitors, and might be used as leads for generating enzyme inhibitors eventually targeting other isoforms which have not been assayed yet for their interactions with such agents.

9,10-Dibromo-N-aryl-9,10-dihydro-9,10-[3,4]epipyrroloanthracene-12,14-diones: Synthesis and Investigation of Their Effects on Carbonic Anhydrase Isozymes I, II, IX, and XII.

N‐substituted maleimides were synthesized from maleic anhydride and primary amines. 1,4‐Dibromo‐dibenzo[e,h]bicyclo‐[2,2,2]octane‐2,3‐dicarboximide derivatives (4a–f) were prepared by the [4+2] cycloaddition reaction of dibromoanthracenes with the N‐substituted maleimide derivatives. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory effects of the new derivatives were assayed against the human (h) isozymes hCA I, II, IX, and XII. All tested bicyclo dicarboximide derivatives exhibited excellent inhibitory effects in the nanomolar range, with Ki values in the range of 117.73–232.87 nM against hCA I and of 69.74–111.51 nM against hCA II, whereas they were low micromolar inhibitors against hCA IX and XII.

FePd alloy nanoparticles assembled on reduced graphene oxide as a catalyst for selective transfer hydrogenation of nitroarenes to anilines using ammonia borane as a hydrogen source

Addressed herein is a facile protocol for the synthesis and assembly of FePd alloy nanoparticles (NPs) on reduced graphene oxide (rGO) to catalyze transfer hydrogenation of nitroarenes to anilines under ambient conditions. 3.5 nm FePd NPs were synthesized by using a surfactant-assisted co-reduction method that allowed NP composition control. FePd NPs were then assembled on rGO via a liquid-phase self-assembly method and studied as catalysts to promote hydrogen transfer from ammonia borane (AB) to numerous nitroarenes in aqueous methanol solutions at room temperature. Among three different rGO–FePd, the commercial C–Pd and rGO–Pd catalysts tested, rGO–Fe48Pd52 showed the highest efficiency in converting nitroarenes to anilines, achieving >90% yields within 10–20 min of reactions. Our work demonstrates an efficient and selective approach to transfer hydrogenation of nitroarenes to anilines.

Dihydroxylation of olefins catalyzed by zeolite-confined osmium(0) nanoclusters: an efficient and reusable method for the preparation of 1,2-cis-diols

Addressed herein is a novel, eco-friendly, recoverable, reusable and bottleable catalytic system developed for the dihydroxylation of various olefins yielding 1,2-cis-diols. In our protocol, zeolite-confined osmium(0) nanoclusters (zeolite-Os0) are used as reusable catalyst and H2O2 served as a co-oxidant. Zeolite-Os0 are found to be highly efficient and selective catalysts for the dihydroxylation of a wide range olefins in an aqueous acetone mixture at room temperature. In all of the olefins surveyed, the catalytic dihydroxylation reaction proceeds smoothly and the corresponding 1,2-cis-diols are obtained in excellent chemical yield under the optimized conditions. The present heterogeneous catalyst system provides many advantages, such as being eco-friendly and industrially applicable over the traditional homogenous OsO4–NMO system for the dihydroxylation of olefins.

The synthesis of (Z)-4-oxo-4-(arylamino)but-2-enoic acids derivatives and determination of their inhibition properties against human carbonic anhydrase I and II isoenzymes

Abstract The synthesis of (Z)-4-oxo-4-(arylamino)but-2-enoic acid (4) derivatives containing structural characteristics that can be used for the synthesis of several active molecules, is presented. Some of the butenoic acid derivatives (4a, 4c, 4e, 4i, 4j, 4k) are synthesized following literature procedures and at the end of the reaction. In addition, structures of all synthesized derivatives (4a–4m) were determined by 1H-NMR, 13C-NMR and IR spectroscopy. Carbonic anhydrase is a metalloenzyme involved in many crucial physiologic processes as it catalyzes a simple but fundamental reaction, the reversible hydration of carbon dioxide to bicarbonate and protons. Significant results were obtained by evaluating the enzyme inhibitory activities of these derivatives against human carbonic anhydrase hCA I and II isoenzymes (hCA I and II). Butenoic acid derivatives (4a–4m) strongly inhibited hCA I and II with Kis in the low nanomolar range of 1.85 ± 0.58 to 5.04 ± 1.46 nM against hCA I and in the range of 2.01 ± 0.52 to 2.94 ± 1.31 nM against hCA II.

Synthesis of 3-chloro-1-substituted aryl pyrrolidine-2,5-dione derivatives: discovery of potent human carbonic anhydrase inhibitors

Carbonic anhydrase isoenzymes are important metalloenzymes that are involved in many physiologic processes, in which they catalyze the reversible hydration of carbon dioxide (CO2) to bicarbonate (HCO3–) and protons (H+) via a metal hydroxide nucleophilic mechanism. Because of their known biological activities and potential as carbonic anhydrase inhibitors, the present study focused on developing of a convenient route to synthesize 3-chloro-1-aryl pyrrolidine-2,5-diones (2b). This synthetic route started with (Z)-4-oxo-4-(arylamino)but-2-enoic acid (3b) and sulfurous dichloride (SOCl2) and resulted in a ring closing reaction that produced a series of 3-chloro-N-aryl maleimide derivatives (20–29) in good yields. This is the first report of the syntheses of 3-chloro-1-aryl pyyrolidine-2,5-diones 20–23 and 27–29 by ring-closing reactions of (Z)-4-oxo-4-(arylamino)but-2-enoic acid. The structures of all of the products were determined by 1H-NMR, 13C-NMR and infrared spectroscopy. Their biological activities were studied against human carbonic anhydrase I, and II. The 3-chloro-1-aryl pyrrolidine-2,5-diones strongly inhibited the activity of human carbonic anhydrase I and II, with Ki values in the low nanomolar range of 23.27–36.83 nmol/L against human carbonic anhydrase I and 10.64–31.86 nmol/L against human carbonic anhydrase II.