The Crystal Structure of 3-Epismilagenin Acetate and 23-Oxo-3-epismilagenin Acetate

Abstract  

The crystal structure together with unambiguous assignation of ¹H and ¹³C NMR signals of 3-epismilagenin acetate 4 and 23-oxo-3-epismilagenin acetate 5 are described. Compound 4, crystallized as orthorhombic system a = 10.535(1) ?, b = 13.775 (1) ?, c = 18.347 (1) ?, α = β = γ = 90°; with space group P2 ₁ 2 ₁ 2 ₁ ; while compound 5 crystallized as a monoclinic system a = 10.380(1) ?, b = 7.327(1) ?, c = 17.881(1) ?, α = γ = 90°, β = 99.56(1)°, with a space group P2 ₁ . The presence a carbonyl group at C(23) in compound 5 produces a significant deviation from the chair conformation observed in compound 4. The effects of the side chain modifications on the puckering parameters derived from are discussed.     

Sorption study of 25 volatile organic compounds in several Mediterranean soils using headspace-gas chromatography-mass spectrometry

A sorption study of 25 volatile organic compounds (VOCs) in different agricultural soils was carried out by using headspace-gas chromatography-mass spectrometry. The extraction of the VOCs from soil samples was carried out following the EPA method with some differences such as addition of potassium chloride and different instrumental conditions which provide higher sample throughput. In addition, a complementary study on several procedures for soil fortification with VOCs was also assayed, fortification with minimal sample handling was selected in order to minimise evaporation losses of the VOCs. The effect of clay minerals (7.0-69.7%) and organic carbon (0.2-3.5%) contents on acid and alkaline (pH 5.3-8.8) soils were evaluated. Based on the results, all compounds assayed were more sorbed in alkaline soils than acid ones; chlorobenzenes interact more strongly with agricultural soils than do alkylbenzenes. The organic carbon content affects the sorption of 25 VOCs in alkaline soils (the highest sorption was found for the most organic soil), while in acid soils VOC sorption increases as the organic carbon content decreases. The clay mineral fraction plays an important role in the sorption of VOCs in acid soil owing to pi-/n-electron interactions, this effect being more marked for chlorobenzenes.     

Conjugate additions of sulfur-stabilized anions to unsaturated lactams. Synthesis of polyfunctionalized benzo[a]quinolizinone systems

Conjugate addition reactions of sulfur-stabilized nucleophiles to the delta-lactam unit of tetrahydrobenzo[a]benzoquinolizines have been studied. The stereochemical outcome of the conjugate addition reaction depends on the nature of the substituent at the angular position, thus 2,11b-cis or 2,11b-trans diastereomers could be obtained selectively. The tandem conjugate addition-alkylation also takes place in good yields and with high diastereoselectivity. The polyfunctionalized hexahydrobenzo[a]quinolizinone systems obtained could be further elaborated toward emetine-like structures.     

GC-MS Study of Mono- and Bishaloethylphosphonates Related to Schedule 2.B.04 of the Chemical Weapons Convention: The Discovery of a New Intramolecular Halogen Transfer

A new class of compounds, mono- and bis-haloethylphosphonates (HAPs and bisHAPs, respectively), listed in Schedule 2.B.04 of the Chemical Weapons Convention (CWC), has been synthesized and studied by GC-MS with two aims. First, to improve the identification of this type of chemicals by the Organization for the Prohibition of Chemical Weapons, (OPCW). Second, to study the synergistic effect of halogen and silicon atoms in molecules undergoing mass spectrometry. Fragmentation patterns of trimethylsilyl derivatives of HAPs were found to depend on the nature of the halogen atom; this was in agreement with DFT-calculations. The data suggest that a novel intramolecular halogen transfer takes place during the fragmentation process.

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Recent Insights Into the Biomedical Applications of Shape‐memory Polymers

Shape‐memory polymers (SMP) are versatile stimuli‐responsive materials that can switch, upon stimulation, from a temporary to a permanent shape. This advanced functionality makes SMP suitable and promising materials for diverse technological applications, including the fabrication of smart biomedical devices. In this paper, advances in the design of SMP are discussed, with emphasis on materials investigated for medical applications. Future directions necessary to bring SMP closer to their clinical application are also highlighted.

     

Multiplexed immunoassay to detect anabolic androgenic steroids in human serum

A multianalyte enzyme-linked immunosorbent assay (ELISA) has been developed for the simultaneous detection of anabolic androgenic steroids (AAS) in human serum. The multiplexed method was developed according to a planar strategy in which the analytes are identified by their location in the microtiter plate. In the immunochemical procedure established here, human serum samples are mixed with a cocktail of antibodies and added to the distinct sections of a microplate biofunctionalized with different haptenized biomolecules. The cocktail of antibodies consists of a mixture of polyclonal antibodies raised against stanozolol (ST), boldenone (B), and tetrahydrogestrinone (THG). The whole immunochemical analytical procedure takes around 2 h including sample preparation, and many samples can be processed simultaneously to screen for the presence of the three AAS in a single run. Using this ELISA, ST, B, and THG can be detected and quantified individually. When used as a screening method, due to the cross-reactivity profiles of the immunoreagents used, the presence of up to 11 AAS can be detected simultaneously. The detectabilities achieved by this method in human serum are below the MRPLs (minimum required performance limits) proposed by WADA (World Anti-Doping Agency) and reference laboratories of the European Community.     

Monitoring of chicken meat freshness by means of a colorimetric sensor array

A new optoelectronic nose to monitor chicken meat ageing has been developed. It is based on 16 pigments prepared by the incorporation of different dyes (pH indicators, Lewis acids, hydrogen-bonding derivatives, selective probes and natural dyes) into inorganic materials (UVM-7, silica and alumina). The colour changes of the sensor array were characteristic of chicken ageing in a modified packaging atmosphere (30% CO(2)-70% N(2)). The chromogenic array data were processed with qualitative (PCA) and quantitative (PLS) tools. The PCA statistical analysis showed a high degree of dispersion, with nine dimensions required to explain 95% of variance. Despite this high dimensionality, a tridimensional representation of the three principal components was able to differentiate ageing with 2-day intervals. Moreover, the PLS statistical analysis allows the creation of a model to correlate the chromogenic data with chicken meat ageing. The model offers a PLS prediction model for ageing with values of 0.9937, 0.0389 and 0.994 for the slope, the intercept and the regression coefficient, respectively, and is in agreement with the perfect fit between the predicted and measured values observed. The results suggest the feasibility of this system to help develop optoelectronic noses that monitor food freshness.     

Reversible Double C?H Bond Activation of Linear and Cyclic Ethers To Form Iridium Carbenes

The double C? H bond activation of a series of linear and cyclic ethers by the iridium complex [Tp^tol′Ir(C₆H₅)(N₂)] ( 2? N₂), which features a cyclometalated hydrotris(3‐p‐tolylpyrazol‐1‐yl)borate ligand (Tp^tol′) coordinated in a κ⁴‐N,N′,N′′,C manner, has been studied. Two methyl ethers, namely, Me₂O and MeOtBu, along with diethyl ether and the cyclic ethers tetrahydrofuran, tetrahydropyran (THP), and 1,4‐dioxane have been investigated with formation in every case of the corresponding hydride carbene complexes 3 – 8 , which are stabilized by κ⁴‐coordination of the ancillary Tp^tol′ ligand. Five of the compounds have been structurally authenticated by X‐ray crystallography. A remarkable feature of these rearrangements is the reversibility of the double C? H bond activation of Me₂O, MeOtBu, Et₂O, and THP. This has permitted catalytic deuterium incorporation into the methyl groups of the two methyl ethers, although in a rather inefficient manner (for synthetic purposes). Although possible in all cases, C? C coupling by migratory insertion of the carbene into the Ir? C σ bond of the metalated linkage has only been observed for complex 8 that contains a cyclic carbene that results from α,α‐C? H activation of 1,4‐dioxane. Computational studies on the formation of iridium carbenes are also reported, which show a role for metalated Tp ligands in the double C? H activation and account for the reversibility of the reaction in terms of the relative stability of the reagents and the products of the reaction.     

Ultraviolet to infrared refractive indices of tetragonal double tungstate and double molybdate laser crystals

Sellmeier parameters of thirteen tetragonal (space group $I\overline{4}$ ) double tungstate and double molybdate laser crystals with M⁺T³⁺(X⁶⁺O₄)₂ composition have been calculated using the room temperature refractive indices determined from the ultraviolet band gap of the crystals to ????2 ??m. All considered crystals are uniaxial but only crystals with Bi in their composition show a significant birefringence (??n>10^?2). The refractive index value increases for the sequence T³⁺=La, Y, Gd, Lu, and Bi independently of the M⁺ and X⁶⁺ cation pair. Implications for the design of laser waveguides and laser pulse dispersion are discussed.