Özdemir Dogan

Auxiliary mediated synthesis of aziridine-2-carboxylic acid derivatives

Abstract Synthetically useful aziridine-2-carboxylic acid derivatives can be prepared in a stereodefined manner from readily available α,β-unsaturated acyl camphor sultams via an asymmetric Gabriel-Cromwell reaction sequence.

A promising combination of benzotriazole and quinoxaline units: A new acceptor moiety toward synthesis of multipurpose donor–acceptor type polymers

By combining benzotriazole and quinoxaline units in an acceptor unit, three novel monomers, 2-dodecyl-6,7-diphenyl-4,9-di(thiophen-2-yl)-2H-[1,2,3]triazolo[4,5-g]quinoxaline (M1), 2-dodecyl-4,6,7,9-tetra(thiophen-2-yl)-2H-[1,2,3]triazolo[4,5-g]quinoxaline (M2) and 6,7-bis(4-tert-butylphenyl)-2-dodecyl-4,9-di(thiophen-2-yl)-2H-[1,2,3]triazolo[4,5-g]quinoxaline (M3), were synthesized and polymerized electrochemically. All polymers revealed both p- and n-type doping properties under ambient conditions. As found by spectroelectrochemical studies they have small band gaps, ca. 1.00 eV. The polymers revealed two distinct absorption bands as all green coloured neutral state donor–acceptor–donor type polymers should have. Besides this, all have broad absorptions covering the region between 700 nm and 1000 nm which is rarely seen in electrochromic polymers. Due to these promising features, they are considered to be potential materials for optoelectronics.

Synthesis of 2-aziridinyl phosphonates by modified Gabriel—Cromwell reaction and their antibacterial activities

A set of new aziridinyl phosphonates (4a-g) were synthesized by using the Gabriel-Cromwell reaction and its modified version developed in this study and their structures confirmed by HRMS, IR, and NMR spectra. All the compounds were screened for their antibacterial activity. They all showed comparable moderate to good growth inhibitory activity in reference to ampicillin and streptomycin.

Diethylzinc-mediated 1,3-dipolar cycloaddition reaction of chiral azomethine ylides: asymmetric synthesis of ferrocenyl-substituted pyrrolidine derivatives

Asymmetric synthesis of ferrocenyl-substituted pyrrolidine derivatives was successfully achieved by diethylzinc-mediated 1,3-dipolar cycloaddition reactions of chiral azomethine ylides with a number of electron-deficient dipolarophiles. Chiral azomethine ylides were formed by condensing glycyl sultam with ferrocenecarboxaldehyde via imine tautomerization and complexation with diethylzinc. All of the cycloaddition reactions gave ferrocenyl-substituted pyrrolidine derivatives with very high regio- and diastereoselectivity in reasonable yields.

Synthesis of ferrocene substituted pyrrolidine derivatives via Et2Zn catalyzed 1,3-dipolar cycloaddition reactions of azomethine ylides

Abstract Synthesis of ferrocene substituted pyrrolidine derivatives via diethylzinc catalyzed 1,3-dipolar cycloadditions of azomethine ylides is described. Azomethine ylides were generated from glycine methyl ester and ferrocenecarboxaldehyde by the ‘imine tautomerization’ method and trapped with dipolarophiles to give the corresponding cycloadducts in reasonable yields and high regio- and stereoselectivity.

Comparison of chemical fractionation method and 1H-NMR spectroscopy in measuring the monomer block distribution of algal alginates

Abstract Alginates are composed of β-D-mannuronic acid (M) and α-L-guluronic acid (G). In this study, block distributions of alginate samples were measured by a chemical fractionation method and 1H-NMR spectroscopy, to compare the usefulness of the two methods. Block distribution results obtained from the two methods were found to be statistically different from each other; the chemical fractionation method gave consistently lower estimates for the amount of homopolymeric blocks. The repeatability of the results was also lower in the chemical fractionation method. By contrast, 1H-NMR spectroscopy was found to be a reproducible and a faster method for determining the distribution of monomeric blocks in alginates.

Enantiomerically pure β-dipeptide derivative induces anticancer activity against human hormone-refractory prostate cancer through both PI3K/Akt-dependent and -independent pathways

The use of peptides that target cancer cells and induce anticancer activities through various mechanisms is developing as a potential anticancer strategy. KUD983, an enantiomerically pure β-dipeptide derivative, displays potent activity against hormone-refractory prostate cancer (HRPC) PC-3 and DU145 cells with submicromolar IC50. KUD983 induced G1 arrest of the cell cycle and subsequent apoptosis associated with down-regulation of several related proteins including cyclin D1, cyclin E and Cdk4, and the de-phosphorylation of RB. The levels of nuclear and total c-Myc protein, which could increase the expression of both cyclin D1 and cyclin E, were profoundly inhibited by KUD983. Furthermore, it inhibited PI3K/Akt and mTOR/p70S6K/4E-BP1 pathways, the key signaling in multiple cellular functions. The transient transfection of constitutively active myristylated Akt (myr-Akt) cDNA significantly rescued KUD983-induced caspase activation but did not blunt the inhibition of mTOR/p70S6K/4E-BP1 signaling cascade suggesting the presence of both Akt-dependent and -independent pathways. Moreover, KUD983-induced effect was enhanced with the down-regulation of anti-apoptotic Bcl-2 members (e.g., Bcl-2, and Mcl-1) and IAP family members (e.g., survivin). Notably, KUD983 induced autophagic cell death using confocal microscopic examination, tracking the level of conversion of LC3-I to LC3-II and flow cytometric detection of acidic vesicular organelles-positive cells. In conclusion, the data suggest that KUD983 is an anticancer β-dipeptide against HRPCs through the inhibition of cell proliferation and induction of apoptotic and autophagic cell death. The suppression of signaling pathways regulated by c-Myc, PI3K/Akt and mTOR/p70S6K/4E-BP1 and the collaboration with down-regulation of Mcl-1 and survivin may explain KUD983-induced anti-HRPC mechanism.The use of peptides that target cancer cells and induce anticancer activities through various mechanisms is developing as a potential anticancer strategy. KUD983, an enantiomerically pure β-dipeptide derivative, displays potent activity against hormone-refractory prostate cancer (HRPC) PC-3 and DU145 cells with submicromolar IC50. KUD983 induced G1 arrest of the cell cycle and subsequent apoptosis associated with down-regulation of several related proteins including cyclin D1, cyclin E and Cdk4, and the de-phosphorylation of RB. The levels of nuclear and total c-Myc protein, which could increase the expression of both cyclin D1 and cyclin E, were profoundly inhibited by KUD983. Furthermore, it inhibited PI3K/Akt and mTOR/p70S6K/4E-BP1 pathways, the key signaling in multiple cellular functions. The transient transfection of constitutively active myristylated Akt (myr-Akt) cDNA significantly rescued KUD983-induced caspase activation but did not blunt the inhibition of mTOR/p70S6K/4E-BP1 signaling cascade suggesting the presence of both Akt-dependent and -independent pathways. Moreover, KUD983-induced effect was enhanced with the down-regulation of anti-apoptotic Bcl-2 members (e.g., Bcl-2, and Mcl-1) and IAP family members (e.g., survivin). Notably, KUD983 induced autophagic cell death using confocal microscopic examination, tracking the level of conversion of LC3-I to LC3-II and flow cytometric detection of acidic vesicular organelles-positive cells. In conclusion, the data suggest that KUD983 is an anticancer β-dipeptide against HRPCs through the inhibition of cell proliferation and induction of apoptotic and autophagic cell death. The suppression of signaling pathways regulated by c-Myc, PI3K/Akt and mTOR/p70S6K/4E-BP1 and the collaboration with down-regulation of Mcl-1 and survivin may explain KUD983-induced anti-HRPC mechanism.

Use of laboratory-grown bacterial alginate in copper removal

Industrial production leads to toxic heavy metal pollution in water bodies. Copper is one of the examples that requires removal from effluents before being discharged. It is difficult and sometimes very expensive to remove toxic heavy metals by conventional treatment techniques. This study aims to remove copper by the use of bacterial alginate as a non-conventional technique. Bacterial alginates (natural polymers composed of mannuronic and guluronic acid monomers) were synthesized by Azotobacter vinelandii ATCC(®) 9046 in a laboratory fermentor under controlled environmental conditions. The alginates produced, with a range of different characteristics in terms of monomer distribution and viscosity, were investigated for maximum copper uptake capacities. The average copper uptake capacities of alginates produced were found to be about 1.90 mmol/L Cu(2+)/g alginate. Although the GG-block amount of alginates was varied from 12 to 87% and culture broth viscosities were changed within the range of 1.47 and 14 cP, neither the block distribution nor viscosities of alginate samples considerably affected the copper uptake of alginates.

Synthesis of 3-Azabicyclo[3.3.0]octane Framework and a Novel Tricyclicaminoether

Abstract The efficient synthesis of 3-azabicyclo[3.3.0]octane derivative 1 and a novel tricyclicaminoether 11 has been achieved in seven steps using commercially available starting materials and commonly used reagents. The key steps are the intramolecular ring opening of epoxide 7 providing tricyclic aminoalcohol 3 and Baeyer-Villiger oxidation of ketone 8 providing the corresponding lactone 2. Both reactions proceeded regiospecifically.

Synthesis of β-chloro-α-aminophosphonate derivatives via the regioselective ring opening of unactivated aziridine-2-phosphonates

Abstract A series of unactivated racemic and chiral aziridine-2-phosphonates were synthesized by modified Gabriel-Cromwell reaction. Ring opening reaction of the synthesized phosphonates by gaseous HCl provided access to a wide range of biologically interesting novel β-chloro-α-aminophosphonates. All reactions toward each of the above-mentioned products can be conducted regioselectively in high yields. GRAPHICAL ABSTRACT