Synthesis of stereoisomeric 1,3-dimethyl- and 1,2,5-trimethyl-4-acyl(benzoyl)-4-piperidinols

In order to synthesize stereoisometric 4-acyl(benzoyl)-1, 3-dimethyl and-1, 2, 5-trimethyl-4-piperidinols, the reaction of the geometrical isomers of 4-cyano-1, 3-dimethyl- and -1, 2, 5-trimethyl-4-piperidinols and the amines and imidic esters corresponding to them with some alkyl- and arylmagnesium halides, leading to the corresponding isomeric piperidinic α-ketols, has been studied. The dependence of the reactivity of the geometrical isomers of the compounds studied on the spatial orientation of their functional groups has been shown.     

Light- and temperature-assisted spin state annealing: accessing the hidden multistability

Among responsive multistable materials, spin crossover (SCO) systems are of particular interest for stabilizing multiple spin states with various stimulus inputs and physical outputs. Here, in a 2D Hofmann-type coordination polymer, [Fe(isoq)₂{Au(CN)₂}₂] (isoq = isoquinoline), a medium-temperature annealing process is introduced after light/temperature stimulation, which accesses the hidden multistability of the spin state. With the combined effort of magnetic, crystallographic and Mössbauer spectral investigation, these distinct spin states are identified and the light- and temperature-assisted transition pathways are clarified. Such excitation-relaxation and trapping-relaxation joint mechanisms, as ingenious interplays between the kinetic and thermodynamic effects, uncover hidden possibilities for the discovery of multistable materials and the development of multistate intelligent devices.

Two new two-stage manipulation protocols, namely light- and temperature-assisted spin state annealing (LASSA/TASSA), are applied to a spin crossover coordination polymer, [Fe(isoq)₂{Au(CN)₂}₂], revealing the hidden multistability of spin states.     

Synthesis and spatial structure of the geometrical isomers of 4-substituted 1-tert-butyl-3-methyl-piperidin-4-ols and 4-acyloxy-1-tert-butyl-3-methylpiperidines

In order to study the interrelationship between the structure, reactivity, and spectroscopic characteristics of the stereoisomeric piperidines, starting from 1-tert-butyl-3-methylpiperidin-4-one the synthesis has been performed of the geometric isomers of some 4-substituted 1-tert-butyl-3-methylpiperidin-4-ols and 4-acyloxy-1-tert-butyl-3-methylpiperidines. The spatial structures of the compounds obtained have been determined by IR and PMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1056–1061, August, 1973.     

Synthesis and three-dimensional structures of geometrical isomers of some 4-substitute d 1,2,5-trimethyl-4-acetoxy- and 1,2,5-trimethyl-4-benzoxypiperidines

Stereoisomers of the corresponding 4-substituted 1,2,5-trimethyl-4-acetoxy- and 1,2,5-trimethyl-4-benzoxypiperidines were obtained by acylation of the geometrical isomers of 1,2, 5-trimethyl-4-piperidol and its 4-ethynyl, 4-ethyl, and 4-phenyl-substituted derivatives. The preferred conformations of the investigated esters were elucidated by means of the PMR and IR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No.1, pp. 50–55, January, 1973.     

Cubic splines and the Lippmann-Schwinger equation

The Galerkin method of solution of integral equations using splines is proposed. This method is applied to the Lippmann-Schwinger equation. Bound state energies and correspondingt-matrices are calculated for various potentials. This method can also be applied to reduce the Faddeev equation to the one-dimensional ones.The authors are grateful to Doc. J.Kvasnica for number of useful discussions and to M.erný for help with numerical calculations.     

Mutagenic effects of near ultraviolet and visible radiant energy on continuous cultures of escherichia coli

Abstract— –The induction of mutation to phage T5 resistance by near ultraviolet (u.v.) and visible light was studied in chemostat cultures of Escherichia coli strains B/r and B/r/1, trp. The visible light mutation rate to phage T5 resistance was independent of growth rate over the range studied. This result is consistent with a photochemical mechanism of mutagenesis. Changeovers, in which a faster growing subpopulation takes over the culture, usually causing the mutant frequency to decline sharply, occur more frequently in chemostat cultures irradiated with visible light than in cultures treated with far u.v. or caffeine. A preliminary action spectrum was obtained with aerated chemostats that revealed effective wavelengths to be between 330 nm and 500 nm. Wavelengths longer than 500 nm were not effective. Wavelengths longer than 340 nm were not mutagenic in anaerobic chemostats. This oxygen requirement for mutagenesis between 340 nm and 500 nm is consistent with a photodynamic mechanism of action. In aerated cultures, wavelengths between 400 nm and 500 nm were as effective as wavelengths between 330 nm and 400 nm. A number of naturally occurring compounds, including riboflavin and vitamin K, are consistent with the data as candidates for the chromophore responsible for near u.v. and visible light mutagenesis.     

The Thermodynamics of Translesion DNA Synthesis Past Major Adducts of Enantiomeric Analogues of Antitumor Cisplatin

The Pt^II-coordination complex [PtCl₂(DAB)] (DAB=2,3-diaminobutane) belongs to a class of cytotoxic cisplatin analogues that contain chiral diamine ligands. Enantiomeric pairs of these compounds have attracted particular interest because they have different effects on different DNA conformations, which, in turn, influences the binding of damaged-DNA-processing enzymes that control downstream effects of the adducts, and thus exhibit different biological activities of the enantiomers. Herein, we studied the translesion synthesis across the major 1,2-d(GG) intrastrand cross-link formed by the R,R and S,S enantiomers of [Pt(DAB)]²⁺ in the TGGT sequence by using the enzyme that catalyzes the polymerization of deoxyribonucleotides into a DNA strand. We also employed differential scanning calorimetry (DSC) to measure the thermodynamic changes associated with replication-bypass past 1,2-d(GG) adducts of the [Pt(DAB)]²⁺ enantiomers. In the sequence TGGT, the 1,2-d(GG) intrastrand cross-links that were formed by the enantiomeric pairs of [Pt(DAB)]²⁺ inhibited DNA polymerization in a chirality-dependent manner. The thermodynamic data helped to understand the effect of the alterations in thermodynamic stability of DNA caused by the Pt-d(GG) adducts upon DNA polymerization across these lesions. Moreover, these data can possibly explain the influence of these alterations on the ability of many DNA polymerases to bypass adducts of antitumor platinum drugs. These results also highlighted the usefulness of DSC in evaluating the impact of DNA adducts of platinum-coordinated compounds on the processing of these lesions by damaged-DNA processing-enzymes.     

Impact of the Type of Crosslinking Agents on the Properties of Modified Sodium Alginate/Poly(vinyl Alcohol) Hydrogels

Here, we report on studies on the influence of different crosslinking methods (ionic and chemical) on the physicochemical (swelling ability and degradation in simulated body fluids), structural (FT-IR spectra analysis) and morphological (SEM analysis) properties of SA/PVA hydrogels containing active substances of natural origin. First, an aqueous extract of Echinacea purpurea was prepared using a Soxhlet apparatus. Next, a series of modified SA/PVA-based hydrogels were obtained through the chemical crosslinking method using poly(ethylene glycol) diacrylate (PEGDA, M_n = 700 g/mol) as a crosslinking agent and, additionally, the ionic reaction in the presence of a 5% w/v calcium chloride solution. The compositions of SA/PVA/E. purpurea-based hydrogels contained a polymer of natural origin—sodium alginate (SA, 1.5% solution)—and a synthetic polymer—poly(vinyl alcohol) (PVA, M_n = 72,000 g/mol, 10% solution)—in the ratio 2:1, and different amounts of the aqueous extract of E. purpurea—5, 10, 15 or 20% (v/v). Additionally, the release behavior of echinacoside from the polymeric matrix was evaluated in phosphate-buffered saline (PBS) at 37 °C. The results indicate that the type of the crosslinking method has a direct impact on the release profile. Consequently, it is possible to design a system that delivers an active substance in a way that depends on the application.     

Constituents of the root of Dictamnus albus L.

In addition to several known constituents and their artefacts, the root of Dictamnus albus L. has yielded the new natural products, isomaculosidine (9) and preskimmianine (15, R== Me).²¹