Nitrogen Position Research Articles

Study of the effect of plasma current density on the formation of titanium nitride and titanium oxynitride thin films prepared by reactive DC magnetron sputtering

Titanium nitride and titanium oxynitride films were deposited by varying the plasma current density from 10 mA/cm 2 to 40 mA/cm 2 using DC magnetron sputtering at constant gas flow rate and deposition time. Samples were characterized by Grazing Incidence X-Ray Diffraction, XPS, Nanoindentation and colorimetric analysis. Different coloured films like golden, blue, pink and green were obtained at different current densities. At lower current density (10 mA/cm 2), golden coloured stoichiometric titanium nitride film was formed. At higher current densities (20, 30 and 40 mA/cm 2), non stoichiometric Titanium oxynitride films of colour blue, pink and green were formed respectively. The thickness of the films increased with plasma current density from 43 nm to 117 nm. It was found that the colour variation was not only due to thickness of the film but also due to oxygen atoms replacing the nitrogen positions in TiN lattice. Hardness and Young Modulus of the films were found to decrease from 17.49 GPa to 7.05 GPa and 319.58 GPa–246.77 GPa respectively with increasing plasma current density. This variation of hardness and Young Modulus of the films can be speculated due to change in crystal orientation caused by oxygen incorporation in the films. The film resistivity increased from 16.46 × 10 −4 to 3.28 × 10 −1 Ω cm for increasing plasma current density caused due to oxygen incorporation in the crystal lattice.

Superbasicity of a Bis-guanidino Compound with a Flexible Linker: A Theoretical and Experimental Study

The bis-guanidino compound H(2)C{hpp}(2) (I; hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) has been converted to the monocation [I-H](+) and isolated as the chloride and tetraphenylborate salts. Solution-state spectroscopic data do not differentiate the protonated guanidinium from the neutral guanidino group but suggest intramolecular "-N-H...N=" hydrogen bonding to form an eight-membered C(3)N(4)H heterocycle. Solid-state CPMAS (15)N NMR spectroscopy confirms protonation at one of the imine nitrogens, although line broadening is consistent with solid-state proton transfer between guanidine functionalities. X-ray diffraction data have been recorded over the temperature range 50-273 K. Examination of the carbon-nitrogen bond lengths suggests a degree of "partial protonation" of the neutral guanidino group at higher temperatures, with greater localization of the proton at one nitrogen position as the temperature is lowered. Difference electron density maps generated from high-resolution X-ray diffraction studies at 110 K give the first direct experimental evidence for proton transfer in a poly(guanidino) system. Computational analysis of I and its conjugate acid [I-H](+) indicate strong cationic resonance stabilization of the guanidinium group, with the nonprotonated group also stabilized, albeit to a lesser extent. The maximum barrier to proton transfer calculated using the Boese-Martin for kinetics method was 2.8 kcal mol(-1), with hydrogen-bond compression evident in the transition state; addition of zero-point vibrational energy values leads to the conclusion that the proton transfer is barrierless, implying that the proton shuttles freely between the two nitrogen atoms. Calculations determining the gas-phase proton affinity and the pK(a) in acetonitrile both indicate that compound I should behave as a superbase. This has been confirmed by spectrophotometric titrations in MeCN using polyphosphazene references, which give an average pK(a) of 28.98 +/- 0.05. Triadic analysis indicates that the dominant term causing the high basicity is the relaxation energy.

Phosphonylation of 2‐Amino‐ and 2‐Amido‐3‐bromopyridines and 2‐Amino‐3‐chloroquinoxalines with Triethyl Phosphite

AbstractThe Tavs reaction of 2‐amino‐ and 2‐acylamido‐3‐bromopyridines 1 and 2 with triethyl phosphite in the presence of palladium acetate or chloride allows the synthesis of 2‐amino‐ and 2‐acylamidopyridine‐3‐phosphonates 3 and 4. A second ring nitrogen atom causes strong activation and leads to excellent yields in the phosphonylation of 2‐amino‐3‐chloroquinoxalines. 2,3‐Dichloroquinoxaline does not need a catalyst and undergoes double phosphonylation with sodium diethyl phosphite under Michaelis–Becker conditions. The results show an activating influence of pyridine nitrogen (–M) and deactivating influence of the amino group (+M). The reactivity of 1 and 2 in the Tavs coupling is compared with that of the 3‐NH‐2‐bromopyridine position isomers and 2‐bromoanilines and discussed in terms of the opposite effects of pyridine and amino(amido) nitrogen and different position of the N atoms towards the reaction site. The advantage of the Tavs reaction is the easy optimization because neither auxiliary ligands are required nor a base to trap the halide or a solvent. Triethyl phosphite itself acts as ligand and forms Pd0{P(OEt)3}n in the initial phase of the reaction. The structures of the products and the expected intramolecular N–H···O=P hydrogen bridging bonds were proven by solution NMR and by X‐ray crystal structure analysis of single crystalline 3c.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Double-Bridged 1-D Chain Polymers of Zinc and Cadmium Constructed by a Flexible Dipyridyl-Type Linking Ligand: {[ML1.5(NO3)2].(CH3OH)}∞ {M = Zn or Cd; L = (3-py)-CH2-NH-(CH3)C6H3-C6H3(CH3)-NH-CH2-(3-py)}

36 Ligand L3 is a reduced form of L2, and coordination polymers based on ligand L3 have novel intriguing topologies, consistent with our expectation that free rotations about the Ar-NH, NH-CH2, and CH2-(4-py) bonds may be possible. In other words, our previous work demonstrated that reduced species of diimine ligands possess a greatly enhanced structural flexibility, which may create novel polymers that cannot be obtained from the original rigid diimine ligands. As an extension of that work, we decided to reduce ligand L1 and to prepare coordination polymers by employing the resulting reduced ligand. It is worth noting that ligand L1 is a structural isomer of ligand L2 due to the different nitrogen positions in the terminal pyridyl rings. We report herein the preparation of ligand L, (3-py)-CH2-NH-(CH3)C6H3-C6H3(CH3)NH-CH2-(3-py), and structures of its zinc and cadmium coordination polymers.

Spin‐coupling and hyperfine interaction of the nitrogen donors in 6H‐SiC

AbstractThe X‐, Q‐band field‐sweep electron spin echo (FS ESE) study of n‐type 6H‐SiC wafers shows besides the well known hyperfine (hf) triplet lines of14N on two quasi‐cubic (Nc1, Nc2) and hexagonal (Nh) sites additional triplet lines (Nx) of comparatively low intensity with ag‐tensor of about the average value of the Nc2and Nhspectrum at 4.2 K. The Nxtriplet has half of the hf splitting with respect to the nitrogen residing at cubic sites Nc2. Pulsed electron nuclear double resonance (ENDOR) measurements performed on the NxEPR triplet line demonstrate that there is an efficient spin‐coupling between Nhand Nxnitrogen related centers. The Nxtriplet lines were attributed to distant donor Nc–Nhpairs between nitrogen atoms residing at quasi‐cubic and hexagonal sites having a total electron spinS= 1, which were found before in n‐type 4H‐SiC. Based on Q‐band FS ESE and X‐band pulsed ENDOR measurements the values of the hf interaction for Nc1, Nc2were reassigned with respect to the assignment accepted hitherto.The super hyperfine (shf) interaction with neighboring atoms of nitrogen on the quasi‐cubic lattice sites was studied by FS ESE and pulsed ENDOR. The new shf lines due to29Si and13C atoms with large shf interaction which were not observed previously were found in nitrogen FS ESE and ENDOR spectra. One of them, with the largest shf splitting (23.12 MHz), were attributed to the29Si atoms along thec‐axis in nearest‐neighbor positions of nitrogen on the quasi‐cubic sites which unambiguously confirms that nitrogen substitute carbon lattice site in 6H‐SiC. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The nitrogen position effect on the selectivity of diazacrown ethers to metal ion

In this paper, the nitrogen position isomers of diaza-18-crown-6, diaza-15-crown-5, diaza-12-crown-4, and their complexes with Na + ion are studied by the density functional theory. Their stable structures are identified by geometry optimization without strict for their geometry. The binding capability that reflects the selectivity of these diazacrown ethers to metallic ions is estimated by the binding energy. The position effects of nitrogen on the stability of these complexes are also investigated by the explicit natural bond orbital and atoms-in-molecule analysis. It is found that different nitrogen position in crown ring will result in different relative energy. To those diazacrown ethers under consideration, the calculation results show that 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane, 1,4-diaza-7,10,13-trioxacyclopentadecane, and 1,7-diaza-4,10-dioxacyclododecane exhibit higher metal binding selectivity than their corresponding nitrogen position isomers, respectively. Clearly, the position of nitrogen plays an important role in the selectivity of diazacrown ethers to metal ions in the system involved. This work will be help for the material design of ionic recognition and other related fields.

Quantum chemical calculations of flexible opiate narcotics: Methadone, meperidine, and prodines

Using the pcilo method, the conformational behavior and charge distribution of two types of flexible opiate narcotics—acyclic methadone and the 4-phenyl piperidines, meperidine and prodine—have been made and the extent to which they mimic rigid opiates such as morphine determined. While the charge distribution around the protonated amine nitrogen is similar for the three classes of compounds, low energy conformers of meperidine, prodine, and methadone did not resemble morphine in the relative position of the amine nitrogen, the phenyl ring, and polar oxygen groups, three common structural features assumed important in analgesic activity. Evidence is presented that the flexible 4-phenyl piperdine narcotics act at the morphine receptor in a Φ-equatorial conformation with the same cationic receptor site as morphine. On this basis, the relative potencies of meperidine and desmethyl prodine have been accounted for and the potency difference from (+) to (—) isomers of prodine satisfactorily explained. We have also shown that methadone cannot readily assume a conformation which maximally resembles morphine, such conformers being high energy forms, and that a conformer with direct interaction between the protonated amine and carbonyl group is most favored. This minimum energy conformer of methadone can also act at the receptor with the same nitrogen atom contact as morphine. In such an orientation it resembles the minimum energy meperidine conformer, making similar polar group and phenyl ring receptor contact possible for these two structurally different classes of opiate analgesics.

Inclusion Properties, Polymorphism and Desolvation Kinetics in a New 2-Pyridyl Iminophenol Compound with 1D Nanochannels

The syntheses, crystal structures and solid-state inclusion properties of 3- and 2-pyridyl 3,5-diphenyl-4-hydroxy iminophenols are reported. Their solid-state organization is based on supramolecular head-to-tail chains sustained by O−H···N hydrogen bonds. It is shown that the position of the pyridinic nitrogen is crucial to determine the inclusion propensity. Although formation of nonsolvated close packed networks is observed for both compounds, the 2-pyridyl iminophenol derivative is also able to form nanochannels hosting arrays of guest molecules (toluene, acetone, chloroform). Most interestingly the toluene solvate occurs in two concomitant polymorphs, presenting different channel arrangements, whose properties are studied also by means of high-pressure X-ray diffraction. Thermal analyses are used to determine the kinetics of desolvation of all solvates, whose thermal behavior is correlated with their supramolecular structures.

14N nuclear quadrupole resonance and proton spin–lattice relaxation study of phase transition in pyridazine perchlorate

The temperature dependence of the 14N nuclear quadrupole resonance frequencies in pyridazine perchlorate has been measured by double resonance. The results show that in the low temperature phase the pyridazinium ions are static, while in the high temperature phase the ions reorient around the normal to the plane of the ring between six equivalent orientations in agreement with the X-ray data. The 14N NQR data have been obtained for the protonated nitrogen position in the pyridazine ring for the first time. Temperature and frequency dependence of the proton spin–lattice relaxation time T 1 has been measured in both crystallographic phases. The results show the ionic mobility dominates T 1 in the low temperature phase. The activation energy for the ionic mobility is 240 meV. In the high temperature phase the pyridazine ring reorientation dominates the proton spin–lattice relaxation.

Chirality-dependent hydrogen bond direction in jet-cooled (S)-1,2,3,4-tetrahydro-3-isoquinoline methanol (THIQM): IR-ion dip vibrational spectroscopy of the neutral and the ion

The structural modifications of (S)-1,2,3,4-tetrahydro-3-isoquinoline methanol (THIQM) upon ionisation have been investigated in jet-cooled conditions, by means of laser-induced fluorescence, REMPI, and IR-UV ion-dip spectroscopy of the neutral ground state and the ion. These results combined with ab initio calculations, support the presence in the jet of two low-energy conformers of THIQM. In the most stable Conformer I, the CH(2)OH substituent acts as a hydrogen bond donor to the nitrogen lone pair in the equatorial position. In this case, the nitrogen atom is in (S) configuration. Conformer II shows the opposite NHO hydrogen bond from the hydrogen atom in the equatorial position of nitrogen to the OH group. In this case, the nitrogen atom is in (R) configuration. This chirality dependence of the hydrogen bond direction is lost upon ionisation. While ionisation of Conformer II reinforces the NHO hydrogen bond, ionisation of Conformer I induces its isomerisation to the same ion as Conformer II, i.e. a change in hydrogen bond direction.

Theoretical Study on N Doping in Carbon Materials for Hydrogen Storage

AbstractInteraction between nitrogen-substituted graphene-like compounds and hydrogen was investigated using ab initio molecular orbital method in the aspect of hydrogen storage. We adopted coronene as a model compound for fragmented graphene-like carbon materials and compared the interaction between hydrogen and pure or N-substituted coronenes by changing nitrogen positions. Among the assumed 19 N-substituted models, polarozabilities and HOMO–LUMO gaps were compared to evaluate physisorption and chemisorption energies. As for chemisorption, two N-substituted models were selected and closely examined to reveal the dependence on both nitrogen-substitution and hydrogen-adsorption positions. Potential energy surfaces as a function of H–H bond length and H2–coronen distance showed that the barrier height for hydrogen chemisorption strongly depends on N-substitution positions. The chemisorbed products of N-substituted coronenes are stabilized or destabilized compared with the pure carbon case depending on the sites of N-substitution and H-adsorption. These results suggest that N-substitution at certain positions possibly improve hydrogen storage properties of graphene-like materials.

Specificity of Pyrrolysyl-tRNA Synthetase for Pyrrolysine and Pyrrolysine Analogs

Pyrrolysine, the 22nd amino acid, is encoded by amber (TAG = UAG) codons in certain methanogenic archaea and bacteria. PylS, the pyrrolysyl-tRNA synthetase, ligates pyrrolysine to tRNA Pyl for amber decoding as pyrrolysine. PylS and tRNA Pyl have potential utility in making tailored recombinant proteins. Here, we probed interactions necessary for recognition of substrates by archaeal PylS via synthesis of close pyrrolysine analogs and testing their reactivity in amino acid activation assays. Replacement of the methylpyrroline ring of pyrrolysine with cyclopentane indicated that solely hydrophobic interactions with the ring-binding pocket of PylS are sufficient for substrate recognition. However, a 100-fold increase in the specificity constant of PylS was observed with an analog, 2-amino-6-(( R)-tetrahydrofuran-2-carboxamido)hexanoic acid (2Thf-lys), in which tetrahydrofuran replaced the pyrrolysine methylpyrroline ring. Other analogs in which the electronegative atom was moved to different positions suggested PylS preference for a hydrogen-bond-accepting group at the imine nitrogen position in pyrrolysine. 2Thf-lys was a preferred substrate over a commonly employed pyrrolysine analog, but the specificity constant for 2Thf-lys was 10-fold lower than for pyrrolysine itself, largely due to the change in K m. The in vivo activity of the analogs in supporting UAG suppression in Escherichia coli bearing genes for PylS and tRNA Pyl was similar to in vitro results, with l-pyrrolysine and 2Thf-lys supporting the highest amounts of UAG translation. Increasing concentrations of either PylS substrate resulted in a linear increase in UAG suppression, providing a facile method to assay bioactive pyrrolysine analogs. These results illustrate the relative importance of the H-bonding and hydrophobic interactions in the recognition of the methylpyrroline ring of pyrrolysine and provide a promising new series of easily synthesized pyrrolysine analogs that can serve as scaffolds for the introduction of novel functional groups into recombinant proteins.

Effects of Solute Structure on Local Solvation and Solvent Interactions: Results from UV/Vis Spectroscopy and Molecular Dynamics Simulations

Solvation of heterocyclic amines in CO(2)-expanded methanol (MeOH) has been explored with UV/vis spectroscopy and molecular dynamics (MD) simulations. A synergistic study of experiments and simulations allows exploration of solute and solvent effects on solvation and the molecular interactions that affect absorption. MeOH-nitrogen hydrogen bonds hinder the n-pi* transition; however, CO(2) addition causes a blue shift relative to MeOH because of Lewis acid/base interactions with nitrogen. Effects of solute structure are considered, and very different absorption spectra are obtained as nitrogen positions change. MD simulations provide detailed solvent clustering behavior around the solute molecules and show that the local solvent environment and ultimately the spectra are sensitive to the solute structure. This work demonstrates the importance of atomic-level information in determining the structure-property relationships between solute structure, local salvation, and solvatochromism.

Synthesis andin vitroanticancer activity of water-soluble cationic pyridylporphyrins and their metallocomplexes

Tetrapyrrolic compounds such as porphyrins are known to be prospective chemotherapeutics and photosensitizers for cancer treatment and diagnosis. In this work, water-soluble, meso-substituted cationic pyridyl-porphyrins and their metallocomplexes bearing various central metal atoms ( Ag , Zn , Co , and Fe ) in the porphine ring and various functional groups (allyl, oxyethyl, butyl, and methallyl) at the nitrogen atom in the pyridine ring were synthesized and characterized by1H and13C NMR and UV-visible spectroscopy. Cytotoxic and photodynamic activities of new porphyrins and their metal derivatives were investigated in vitro (KCL-22 cancer cell line of human chronic myeloid leukemia). The cytotoxicity of porphyrins was shown to be dependent on the presence and type of the central metal atom in the porphine ring. Ag -derivatives were more cytotoxic than Co −, Zn −, and Fe − metallocomplexes. The porphyrins bearing allyl-functional groups were evidenced to be more cytotoxic than those which included butyl-, oxyethyl-, and methallyl-groups. The change of nitrogen position in the pyridine ring of Ag -metalloporphyrins from 3(3-N-pyridylporphyrins) to 4(4-N-pyridylporphyrins) induced an increase in the cytotoxic activity of metallocomplexes. All synthesized Ag-metalloporphyrins, except, the oxyethyl-containing one were more cytotoxic than cisplatin. Allyl containing free porphyrin and its Zn -metallocomplex had higher phototoxicity than Ag −, Co −, and Fe -metalloporphyrins. The results obtained can be useful for further investigation of new porphyrins as potential chemotherapeutics and photosensitizers.

Nickel 2-Iminopyridine N-Oxide (PymNox) Complexes: Cationic Counterparts of Salicylaldiminate-Based Neutral Ethylene Polymerization Catalysts

2-Iminopyridine N-oxides (PymNox) constitute a promising class of ligands that can be considered as the neutral counterparts of the well-known salicylaldiminate system. A series of nickel PymNox complexes displaying different substitution patterns in the ligand have been synthesized, and their activity as ethylene polymerization catalysts has been studied. While an electron-donor group (OMe) at the remote position 4 of the pyridine ring causes a moderate decrease of the catalytic activity and increase of the polyethylene molecular weight, a strongly electron-withdrawing group (NO2) in this position shifts the catalyst selectivity from ethylene polymerization to oligomerization. The introduction of a phenyl substituent next to the pyridine nitrogen (position 6) causes a significant increase of the catalytic activity and the polymer molecular weight. Although aldimino PymNox catalysts are inactive in ethylene−methyl acrylate copolymerization, we observed that acetaldimino (displaying the Me-C═NAr group) catalysts display a small but significant activity on this account, giving rise to copolymers incorporating ca. 1% methyl acrylate in their structure. The trends observed in the PymNox catalytic system are strongly reminiscent of those of nickel salicylaldiminates (although the former are considerably more active), demonstrating for the first time that substitution of the widely used phenoxo anionic group by the neutral pyridine N-oxide fragment is a useful possibility in the design of late transition metal catalysts for olefin polymerization.

Investigation on copper phthalocyanine/multiwalled carbon nanotube interface

The electronic and structural properties of copper phthalocyanine deposited onto multiwalled carbon nanotubes were studied as a function of the deposition thickness. The valence band and core level spectra were investigated using photoemission spectroscopy. A shift of the organic highest occupied molecular level toward the Fermi level was observed for very thin film, together with a small shift of the nitrogen and copper core level peak positions. Scanning electron microscope images showed the formation of small particles around the nanotubes, forming a thin overlayer decorating the nanotube walls. An x-ray diffraction analysis reported that these particles present both the α and β crystalline phases.

Influence of the chemical and electronic structure on the electrical behavior of zirconium oxynitride films

This work is devoted to the investigation of decorative zirconium oxynitride, ZrOxNy, films prepared by dc reactive magnetron sputtering, using a 17:3 nitrogen-to-oxygen-ratio gas mixture. The color of the films changed from metallic-like, very bright yellow pale, and golden yellow, for low gas mixture flows [from 0 to about 9SCCM (SCCM denotes cubic centimeter per minute at STP)] to red brownish for intermediate gas flows (values up to 12SCCM). Associated to this color change there is a significant decrease of brightness. With further increase of the reactive gas flow, the color of the samples changed from red brownish to dark blue (samples prepared with 13 and 14SCCM). The films deposited with gas flows above 14SCCM showed only apparent colorations due to interference effects. This change in optical behavior from opaque to transparent (characteristic of a transition from metallic to insulating-type materials), promoted by the change in gas flow values, revealed that significant changes were occurring in the film structure and electronic properties, thus opening new potential applications for the films, beyond those of purely decorative ones. Taking this into account, the electrical behavior of the films was investigated as a function of the reactive gas flow and correlated with the observed chemical, electronic, and structural features. The variations in composition disclosed the existence of four different zones, which were correlated to different crystalline structures. For the so-called zone I, x-ray diffraction revealed the development of films with a B1 NaCl face-centered cubic zirconium nitride-type phase, with some texture changes. Increasing the reactive gas flow, the structure of the films is that of a poorly crystallized overstoichiometric nitride phase, which may be similar to that of Zr3N4, but with some probable oxygen inclusions within nitrogen positions. This region was characterized as zone II. Zone III was indexed as an oxynitride-type phase, similar to that of γ-Zr2ON2 with some oxygen atoms occupying some of the nitrogen positions. Finally, occurring at the highest flow rates, zone IV was assigned to a ZrO2 monoclinic-type structure. The composition∕structure variations were consistent with the chemical bonding analysis carried out by x-ray photoelectron spectroscopy, which showed oxygen doping in both Zr3N4- and ZrN-type grown films. The electronic properties of the films exhibited significant changes from zone to zone. Resistivity measurements revealed a very wide range of values, varying from relatively highly conductive materials (for zone I) with resistivity values around few hundreds of μΩcm to highly insulating films within zones III and IV, which presented resistivity values in the order of 1015μΩcm. Regarding zone II, corresponding to oxygen doped Zr3N4-type compounds, the observed behavior revealed resistivity values increasing steeply from about 103 up to 1015μΩcm, indicating a systematic transition from metallic to insulating regimes.

Temperature dependence of nonequivalent potential wells for pyridinium ion reorientation in pyridinium tetrachloroiodate(III), PyHICl4, studied by 1H14N nuclear quadrupole double resonance

The reorientation of a pyridinium ion in the paraelectric and antiferroelectric phase of PyHICl(4) is investigated using (1)H-(14)N nuclear quadrupole double resonance (NQDR). The (14)N nuclear quadrupole resonance frequencies are measured. The temperature variations of the principal values of the time-averaged electric-field-gradient (EFG) tensor at the nitrogen position are used to determine the occupation probabilities of the six orientations of a pyridinium ion in both crystallographic phases. The energy difference between various orientations is determined. The molar transition entropy associated with the reorientation of the pyridinium ions is calculated and compared to the experimental value.

Synthesis of 1-/2-substituted-[1,2,3]triazolo[4,5- g]phthalazine-4,9-diones and evaluation of their cytotoxicity and topoisomerase II inhibition

Studies on antitumor heterocyclic quinones containing nitrogens revealed that the number and position of nitrogens on the heterocyclic ring have significance on cytotoxicity of quinones. In our continuous effort to find more cytotoxic quinone compounds, we designed triazolophthalazine analogues in order to introduce more nitrogens on the heterocyclic quinones. 1-/2-Substituted-[1,2,3]triazolo[4,5- g]phthalazine-4,9-diones were synthesized by 1,3-dipolar addition of phthalazine-5,8-dione and 4-methoxybenzyl azide by modification of previously reported method. The cytotoxicity of the synthesized compounds was evaluated by a SRB (sulforhodamine B) assay against nine types of human cancer cell lines and inhibition against topoisomerase II (Topo II) of them was assessed by a decatenation assay. Most of the synthesized compounds showed considerably higher cytotoxicity than that of doxorubicin. Also, topoisomerase II inhibitory activity of the tested compounds was higher than that of etoposide and IC 50 values of the compounds were 19.4–64.5 μM.

β-Amino alcohols derived from (1 R,2 S)-norephedrine and (1 S,2 S)-pseudonorephedrine as catalysts in the asymmetric addition of diethylzinc to aldehydes

A family of N-alkylnorephedrine and N-alkylpseudonorephedrine derived ligands were prepared and applied in the asymmetric alkylation of benzaldehyde using diethylzinc. The absolute configuration of the addition product was directed primarily by the benzylic position of the Ephedra alkaloid, while the magnitude of the enantiomeric ratio was heavily influenced by the nitrogen substituent. However, sterically demanding substituents at the nitrogen position caused the enantioselectivity to be the same for the two diastereomeric systems. Among the ligands that were prepared, it was determined that the N-cyclooctylpseudonorephedrine derivative 7b yielded the highest enantiomeric ratios (87.5:12.5 to 91.0:9.0) when applied in the catalytic asymmetric addition of diethylzinc to aldehydes.