Chiroptical properties of (R)-3-chloro-1-butene and (R)-2-chlorobutane

Coupled cluster and density functional models of specific rotation and vacuum UV (VUV) absorption and circular dichroism spectra are reported for the conformationally flexible molecules (R)-3-chloro-1-butene and (R)-2-chlorobutane. Coupled cluster length- and modified-velocity-gauge representations of the Rosenfeld optical activity tensor yield significantly different specific rotations for (R)-3-chloro-1-butene, with the latter providing much closer comparison (within 3%) to the available gas-phase experimental data at 355 and 633 nm. Density functional theory overestimates the experimental rotations for (R)-3-chloro-1-butene by approximately 80%. For (R)-2-chlorobutane, on the other hand, all three models give reasonable comparison to experiment. The theoretical specific rotations of the individual conformers of (R)-3-chloro-1-butene are much larger than those of (R)-2-chlorobutane, in disagreement with previous studies of the temperature dependence of the experimental rotations in solution. Simulations of VUV absorption and circular dichroism spectra reveal large differences between the coupled cluster and density functional excitation energies and the rotational strengths. However, while these differences lead to very different specific rotations for (R)-3-chloro-1-butene, they have much less impact on the computed specific rotations for (R)-2-chlorobutane. In addition, the coupled cluster VUV absorption spectrum of (R)-2-chlorobutane compares well to experiment.     

Chiroptical properties of S-alanine conformational isomers

The chiroptical properties of several S-alanine (zwitterionic and nonzwitterionic), S-alanine cation, and S-alanine anion structural isomers are calculated from LCAO-MO-SCF-CI wave functions constructed on the semiempirical CNDO MO model. Electronic excited states are constructed in the virtual orbital-configuration interaction approximation. We calculate and report the transition energies, dipole strengths, reduced rotatory strengths, and dissymmetry factors for the four lowest energy singlet-singlet transitions as a function of a single conformational variable (the angle between the C_αCOO′ plane and the CC_αN plane, where C ≡ carboxylate C atom, N ≡ ammonium or amino N atom, and C_α ≡ α-carbon atom) for zwitterionic and nonzwitterionic S-alanine, the S-alanine anion, and the S-alanine cation. The ground state dipole moments and first three ionization potentials are also computed and reported for the various S-alanine species. Electric dipole transition integrals are calculated in the dipole velocity formalism and all two-center contributions to these and the magnetic dipole transition integrals are included. The calculated rotatory strengths are compared with experimental circular dichroism spectra reported for S-alanine and with predictions based on sector rules which have been proposed for α-amino acids.     

New (S)-1-phenylethylamine N-arylidene derivatives as chiral dopants to liquid crystalline systems

New chiral N-arylidene (S)-1-phenylethylamines with a 4,4'-biphenylene group in the central path of the rigid core were synthesized and their mesomorphic properties investigated. The helical twisting power and the temperature dependences of the helical pitch and the selective light reflection were analysed for several liquid crystalline systems based on 4-pentyl-4'-cyanobiphenyl, E63 (Merck) and 4-(n-hexyloxy)phenyl 4'-(n-butyl)benzoate containing new chiral components. The chiral compounds investigated induce helical ordering effectively in all the host materials and have significant potential for applications. The results obtained for the new chiral compounds are compared with those for some previously studied similar chiral additives.     

Approaches to (R)- and (S)-1′-(1-aminoethyl)ferrocene-1-carboxylic acid derivatives

Lipase-catalyzed esterification of (±)-methyl 1′-(1-hydroxyethyl)ferrocene-1-carboxylate 4 afforded its (R)-acetate (−)-5 (ee = 99%) and (S)-(+)-4 (ee = 90%). Stereoretentive azidation/amination/acetylation of (R)-(−)-5 gave (R)-(+)-methyl 1′-(1-acetamidoethyl)ferrocene-1-carboxylate (R)-3 (ee = 98%). In a similar manner (S)-(+)-4 was converted into (S)-(−)-3 (ee = 84%). Both enantiomers of 3 were obtained in high chemical yields without a loss of enantiomeric purity. The title compounds can be coupled with natural amino acids and peptides on both C- and N-termini.     

Efficient racemization of 1-phenylethylamine and its derivatives

We report on simple and efficient procedure for the racemization of 1-phenylethylamine and its derivatives. In the presence of trichloroisocyanuric acid, N-chloroimine derivative is formed as the intermediates, with subsequent hydrogenation catalyzed by Pd-C leading to the racemic product.     

Electronic properties of hydrogen-bonded complexes of benzene(HCN)(1-4): comparison with benzene(H2O)(1-4)

The electronic properties, specifically, the dipole and quadrupole moments and the ionization energies of benzene (Bz) and hydrogen cyanide (HCN), and the respective binding energies, of complexes of Bz(HCN)(1-4), have been studied through MP2 and OVGF calculations. The results are compared with the properties of benzene-water complexes, Bz(H(2)O)(1-4), with the purpose of analyzing the electronic properties of microsolvated benzene, with respect to the strength of the CH/π and OH/π hydrogen-bond (H-bond) interactions. The linear HCN chains have the singular ability to interact with the aromatic ring, preserving the symmetry of the latter. A blue shift of the first vertical ionization energies (IEs) of benzene is observed for the linear Bz(HCN)(1-4) clusters, which increases with the length of the chain. NBO analysis indicates that the increase of the IE with the number of HCN molecules is related to a strengthening of the CH/π H-bond, driven by cooperative effects, increasing the acidity of the hydrogen cyanide H atom involved in the π H-bond. The longer HCN chains (n ≥ 3), however, can bend to form CH/N H-bonds with the Bz H atoms. These cyclic structures are found to be slightly more stable than their linear counterparts. For the nonlinear Bz(HCN)(3-4) and Bz(H(2)O)(2-4) complexes, an increase of the binding energy with the number of solvent molecules and a decrease of the IE of benzene, relative to the values for the Bz(HCN) and Bz(H(2)O) complexes, respectively, are observed. Although a strengthening of the CH/π and OH/π H-bonds, with increasing n, also takes place for the Bz(H(2)O)(2-4) and Bz(HCN)(3-4) nonlinear complexes, Bz proton donor, CH/O, and CH/N interactions are at the origin of this decrease. Thus CH/π and OH/π H-bonds lead to higher IEs of Bz, whereas the weaker CH/N and CH/O H-bond interactions have the opposite effect. The present results emphasize the importance of both aromatic XH/π (X = C, O) and CH/X (X = N, O) interactions for understanding the structure and electronic properties of Bz(HCN)(n) and Bz(H(2)O)(n) complexes.     

Synthesis and characterization of novel chiral calix[4]arene bearing (R)-(+)-1-phenylethylamine bonded silica particles

Two novel chiral di- and tri-amide derivatives of p-tert-butylcalix[4]arene were synthesized by (R)-(+)-1-Phenylethylamine via convenient reactions and then immobilized on aminopropyl functionalized silica particles. The prepared chiral calix[4]arenes and their silica polymers (Calix-SP1 and Calix-SP2) were characterized using ¹H NMR, ¹³C NMR, FT-IR, and thermal and elemental analysis techniques.     

Isopropylidene glycerol hydrogen phthalate as a resolving agent: a study of its diastereomeric salts with (S)- and (R)-1-phenylethylamine

An insight into the mechanism of the highly efficient resolution of 1-phenylethylamine with enantiomerically pure isopropylideneglycerol hydrogen phthalate is provided by comparison of physicochemical and X-ray crystallographic data of the two diastereomeric salts formed by the amine with the S acid. In the nearly identical structures of these salts, the different disposition of the isopropylidene glycerol moiety stands out drawing attention to the critical role played by the chiral part of the acid in the discrimination between the amine enantiomers.     

Synthesis and properties of aminomethoxy derivatives of 1-(butylsulfanyl)pentane

New aminomethoxy derivatives of 1-(butylsulfanyl)pentane have been synthesized. The structure of the synthesized compounds was studied by elemental analysis, IR and ¹Н NMR spectroscopy, and mass spectrometry. Some specimens of the synthesized compounds were tested as antimicrobial additives to lubricant oil, and as aseptic compounds against bacteria and fungi.     

Synthesis and properties of methyleneoxyamine derivatives of 1-(propylthio)octane

Synthesis of new methyleneoxyamine derivatives of 1-(propylthio)octane by condensation of 1-(propylthio)octane with secondary amines and formaldehyde was carried out. Structure of the synthesized compounds was proved by elemental analysis, IR, ¹H NMR, and mass spectra. Compounds were tested as antimicrobial additives to lubricating oils. They were found to suppress effectively the activity of microorganisms.     

Synthesis and properties of aminomethoxy derivatives of 1-(ethylsulfanyl)alkanes

Mannich condensation of 1-(ethylsulfanyl)alkan-2-ols, formaldehyde, and secondary amines taken in equimolar amounts was used to obtain new amino derivatives of 1-(ethylsulfanyl)alkanes. The structure of the thus synthesized compounds was confirmed by elemental analysis, IR and ¹H NMR spectroscopies, and mass spectrometry. It is shown that the obtained compounds can be used as antimicrobial additives to lubricating oils and antiseptic substances against bacteria and fungi.     

Synthesis and antiproliferative activity of (1R,2R)-N1-(2-butyl)-1,2-cyclohexanediamine platinum(II) complexes with malonate derivatives

Three new platinum(II) complexes of (1R,2R)-N¹-(2-butyl)-1,2-cyclohexanediamine with malonate derivatives as leaving groups have been synthesized and spectrally characterized. They were tested in vitro against four human cancer cell lines. [(1R,2R)-N¹-(2-butyl)-1,2-cyclohexanediamine-N,N′](2-ethylmalonato-O,O′)platinum(II) turned out to be more active (IC₅₀ = 4.65 μM) than oxaliplatin (IC₅₀ = 6.55 μM) against the MCF-7 cell line and is superior to its parent complex, [(1R,2R)-N¹-(2-butyl)-1,2-cyclohexanediamine-N,N′](malonato-O,O′)platinum(II). In addition, agarose gel electrophoresis study revealed that the interaction of the complex with pET22b plasmid DNA had a different behavior from that of cisplatin or oxaliplatin.     

Synthesis and properties of Β-(1-uracilyl)-α-hydroxypropionic acid derivatives

-(1-Uracilyl)--substituted propionitriles were obtained by cyanohydrin synthesis from 1-uracilylacetaldehydes. Their hydrolysis, bromination, and amination were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 954–959, July, 1990.     

Synthesis and electrocatalytic properties of a dinuclear palladium(I) 1-[(2-bromo)benzene]-3-[(2-carboxymethyl)benzene]triazenide complex

The reaction of 1-[(2-bromo)benzene]-3-[(2-carboxymethyl)benzene]triazene and [Pd(CH₃CN)₄]Cl₂ gave a new dinuclear triazenido complex [Pd₂L₂] 1, which has been characterized by NMR spectra and X-ray crystallography. Electrochemical studies showed that complex 1 is capable of generating hydrogen from acetic acid in CH₂Cl₂.     

Resolution of methyl-1-phenylethylamines by acidic derivatives of 1-phenylethylamine

Methyl-1-phenylethylamines were resolved by phenylethylamine derivatives formed with a homologous series of dicarboxylic acids. The structure of the 4-methyl-1-phenylethylamine N-(1-phenylethylamine) succinic acid monoamide diastereoisomeric salt was investigated by single crystal X-ray diffraction.     

Asymmetric syntheses of (1r,3R,4S)- and (1s,3R,4S)-(3,4-difluorocyclopentyl)-alanine derivatives

By employing a sequence of epoxide opening, asymmetric alkylation, and fluorination, polyfluorinated cyclopentylamino acids with defined stereochemistries were prepared.