Methods for preparation of 5′-substituted spiropyrans, their chemical properties, and the effects of various factors on the relative stabilities of the spiropyrans and their isomeric merocyanine ...forms are examined, reviewed, and discussed.
Objectives.
To develop the procedures for synthesis of hybrid molecules with potential anti-tubercular activity containing heterocyclic cores of 4-nitroimidazole and 1,3,4-thiadiazole within the ...framework of a double-drug strategy and predict bioactivity of target structures and drug-likeness physicochemical parameters.
Methods.
Target compounds were prepared by classical organic synthesis methods. The structure of the obtained compounds was characterized by melting points,
1
H and
13
C nuclear magnetic resonance spectroscopy, and high-resolution mass spectrometry. The calculation of the physicochemical parameters of the target compounds and prediction of their biological activity were carried out using publicly available software for cheminformatics and molecular modeling.
Results.
Acylation of propargylamine with (2-methyl-4-nitro-1H-imidazol-1-yl)acetic and (4-nitro-1H-imidazol-1-yl)acetic acids provided the corresponding amides, which were cyclized with seven different benzylamines in the presence of zinc triflate. In this way, seven new compounds were obtained at 20–30% yields. Ten arylamines were acylated with chloroacetyl chloride and the resulting chloroacetamides were converted into corresponding thio-oxahydrazides by the Willgerodt–Kindler reaction. Following acylation by (4-nitro-1H-imidazol-1-yl)acetic acid, these compounds were converted into the target hybrid imidazolyl-thiadiazoles at 29–54% yields.
Conclusions.
Two series of new heterocyclic compounds with a hybrid structure including a privileged 4-nitroimidazole moiety linked to the second heterocycle, imidazole, or thiadiazole, were obtained. The synthesis and characterization of compounds by physicochemical methods was aimed at searching for anti-tuberculosis activity. The bioactivity potential of target compounds was demonstrated by preliminary calculations performed using public prognostic programs.
Display omitted
Isosteric replacement of the oxadiazole ring by amide bond in the structure of new non-β-lactam antibiotics led to compounds with higher activity against Gram-positive pathogens of ...ESKAPE panel. A series of 17 compounds were synthesized by acylation of 4-(4-fluorophenoxy)aniline with various amino acids. The spirocyclic derivative with 6-methylsulfonyl-2,6-diazaspiro3.4octane moiety showed excellent minimum inhibitory concentrations of 0.093–0.75 μg ml−1 against a number of methicillin-resistant Staphylococcus aureus strains.
•New 6-nitro-substituted spiropyrans have been synthesized.•We studied spectral-kinetic properties of intermediates of spiropyran vinylogs.•Nanosecond laser flash photolysis techniques were used for ...investigation.•Relative quantum yields of different intermediates formation have been measured.
The absorption spectra and decay kinetics of the ground and triplet states of merocyanine (MC) form of spiropyran vinylogs have been investigated by nanosecond laser flash photolysis techniques in toluene and ethanol. The 3MC decays to the ground state MC either by quenching with O2 or due to the intersystem crossing. Relative quantum yield of both 3MC and MC drastically decreases when the terminal polar group is separated from the indoline moiety by the CC-linker. In the presence of the CC-linker the replacement of terminal CN by CHO has no effect. The yield of 3MC and corresponding MC in ethanol is 5 times smaller than that in toluene solution.
Height changes of the ice surface above subglacial Lake Vostok, East Antarctica, reflect the integral effect of different processes within the subglacial environment and the ice sheet. Repeated GNSS ...(Global Navigation Satellite Systems) observations on 56 surface markers in the Lake Vostok region spanning 11 years and continuous GNSS observations at Vostok station over 5 years are used to determine the vertical firn particle movement. Vertical marker velocities are derived with an accuracy of 1 cm/yr or better. Repeated measurements of surface height profiles around Vostok station using kinematic GNSS observations on a snowmobile allow the quantification of surface height changes at 308 crossover points. The height change rate was determined at 1 ± 5 mm/yr, thus indicating a stable ice surface height over the last decade. It is concluded that both the local mass balance of the ice and the lake level of the entire lake have been stable throughout the observation period. The continuous GNSS observations demonstrate that the particle heights vary linearly with time. Nonlinear height changes do not exceed ±1 cm at Vostok station and constrain the magnitude of spatiotemporal lake‐level variations. ICESat laser altimetry data confirm that the amplitude of the surface deformations over the lake is restricted to a few centimeters. Assuming the ice sheet to be in steady state over the entire lake, estimates for the surface accumulation, on basal accretion/melt rates and on flux divergence, are derived.
Key Points
Ice surface height above Lake Vostok has been stable between 2001 and 2013Water volume in subglacial Lake Vostok has remained unchanged over a decadeSurface and marker height changes are derived with accuracies better than 1 cm/a
► We studied spectral-kinetic properties of intermediates of spiropyran retinal analogs. ► Nanosecond laser flash photolysis techniques were used for investigation. ► Relative quantum yields of ...different intermediates formation have been measured. ► Formation of merocyanine form upon photolysis depends on polyenic chain length.
Spectral-kinetic properties of intermediates of spiropyran retinal analogs (SRA), which molecules contain spiropyran and retinoid (with different polyenic chain length and aldehyde terminal group) fragments, have been investigated by nanosecond laser flash photolysis techniques using excitation wavelengths 337 and 380–450nm in toluene. Relative quantum yields of different SRA intermediates formation relative to those of model compounds, namely triplet excited state and merocyanine form generated upon pyran cycle cleavage have been measured. It has been found that merocyanine form does not form upon photolysis of SRA with polyenic chain length of 5 and 9 using excitation wavelengths of 380–450nm, the triplet state of retinoid fragment is observed exclusively. The yield of merocyanine (MC) form is the largest one upon SRA photolysis with excitation wavelength of 337nm for 6′-formylsubstituted spiropyran (it exceeds that of unsubstituted analog in 8 times and forms mainly from the triplet state). The yields of MC for SRA with polyenic chain length of 3, 5 and 9 carbon atoms are 5–10 times smaller than that for unsubstituted spiropyran.
Display omitted
The effects of chromophoric group structures on the functional properties of bacteriorhodopsin (BR) and proteorhodopsin from E. sibiricum (ESRh) were compared. ESRh retinal binding ...site was found as preserving the similar stereo- and spatial restrictions on the chromophore structure during the retinal protein reconstitution process (except for C25-analog AR8). It was revealed that the structure peculiarities of the chromophore analog molecules affect the optical parameters of ESRh and BR pigment families in similar ways.
Two new photochromic labels of spirochromene-2,2’-indole series supplied with 5-positioned maleimide moieties suitable for labelling macromolecules with sulfhydryl groups were synthesized.
A new 5,10,15,20-tetrasubstituted porphyrin containing four 6’-nitro-1,3,3-trimethylspiro(indolino-2,2’-2H-chromene) substituents and its complexes with Zn2+ and Cu2+ ions were prepared and ...characterized by physicochemical methods of analysis.
Properties of nanoparticles are significantly different from their bulk counterparts, including their biological and toxic activity. The properties of silver nanoparticles governing their ...toxicological effects are summarized. These basic characteristics can be used as descriptors for modelling the toxic properties of nanoparticles.
PDF