Ester Carbonyl Group Research Articles

Structure–Activity Relationships in Toll-Like Receptor 2-Agonists Leading to Simplified Monoacyl Lipopeptides

Toll-like receptor 2-agonistic lipopeptides typified by S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-R-cysteinyl-S-serine (PAM(2)CS) compounds are potential vaccine adjuvants. In continuation of previously reported structure-activity relationships on this chemotype, we have determined that at least one acyl group of optimal length (C(16)) and an appropriately oriented ester carbonyl group is essential for TLR2-agonistic activity. The spacing between one of the palmitoyl ester carbonyl and the thioether is crucial to allow for an important H-bond, which observed in the crystal structure of the lipopeptide:TLR2 complex; consequently, activity is lost in homologated compounds. Penicillamine-derived analogues are also inactive, likely due to unfavorable steric interactions with the carbonyl of Ser 12 in TLR2. The thioether in this chemotype can be replaced with a selenoether. Importantly, the thioglycerol motif can be dispensed with altogether and can be replaced with a thioethanol bridge. These results have led to a structurally simpler, synthetically more accessible, and water-soluble analogue possessing strong TLR2-agonistic activities in human blood.

Characterization of Tribofilm from Sulfurized Mohwa Oil

The reaction products of sulfurized Mohwa oil with iron powder in hydrocarbon medium at 150°C for 8 h were studied to investigate the type of lubricant films formed during their application as antiwear and extreme pressure additives. The main reaction product was isolated on the basis of its solubility in mixed solvent. Surface characterization was carried out using ultraviolet-visible spectroscopy (UV), fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), X-ray diffraction spectroscopy (XRD), scanning electron microscope (SEM), and high frequency reciprocal rig (HFRR). An examination of their elemental analysis and instrumental analysis data reveals that there is reduction in the length of the alkyl chains and carbonyl ester groups with formation of inorganic iron sulfides. Polymerized product with a number of ketonic and aldehydic groups containing iron and sulfur in the polymeric films in the form of unsaturated cyclic rings was also formed. The films are organo-inorganic in nature, unlike the purely inorganic iron sulfide type. The load-carrying characteristic of this product is strongly influenced by the type of the film formed on the iron surfaces.

Structure–activity relationship of novel juvenile hormone, JHSB3, isolated from the stink bug, Plautia stali

The structure–activity relationship of JHSB3 isolated from the pentatomid bug, Plautia stali, was studied. Various synthetic analogs were synthesized and subjected to the juvenilizing activity tests using the last instar nymphs of P. stali. These studies indicated that the coexistence of the ester carbonyl group, two epoxides at C2,3 and C10,11 were proved to be crucial for the potent juvenilizing activity. Among the tested analogs, we found highly potent analogs in which the C6,7 double bond of JHSB3 was saturated (0.1μg/insect). The methoxy analogs in which the epoxide moiety at C10,11 was substituted with a methoxy group exerted a moderate juvenilizing activity.

Effects of chemical modification on the structure and mechanical properties of starch-based biofilms

In this work, chemically modified corn starch and plasticized corn starch biofilms were obtained and characterized in four steps: (1) preparation of corn starch microparticles, (2) preparation of malic acid-modified corn starch microparticles (MA–SM), (3) preparation of corn starch biofilms and MA–SM-plasticized corn starch biofilms, and (4) characterization of the biofilms. The effects of MA–SM concentration (4, 8, and 12% based on the amount of corn starch) on the structural characteristics and mechanical properties of the biofilms were investigated. Changes in the starch granules after chemical modification were studied by X-ray diffraction, FT-IR spectroscopy, and scanning electron microscopy. The presence of ester carbonyl group stretching vibration at 1,720 cm−1 in FT-IR spectra was evidence of reaction of the starch microparticles with malic acid. The tensile yield strength and Young’s modulus of the films increased with increasing MA–SM content. Water uptake decreased from 69.8% for biofilm without MA–SM to 52.7% for biofilm with MA–SM. The improvement of these properties in the plasticized product could be attributed to the good interaction between the MA–SM filler and the corn starch.

Effect of Moisture on the Orientation Birefringence of Cellulose Esters

Orientation birefringence and its wavelength dispersion are studied for hot-drawn films of cellulose esters such as cellulose triacetate (CTA), cellulose diacetate (CDA), and cellulose acetate propionate (CAP) exposed to three different humidities of environments. Hot-drawn CTA films show negative birefringence that decreases with increasing wavelength. On the other hand, CDA and CAP films show positive birefringence that increases with increasing wavelength, i.e., the so-called extraordinary wavelength dispersion of birefringence. Upon exposure to high humidity environment, the orientation birefringence of CDA and CAP decreases. The decrease is prominent for the samples containing a large amount of water. CTA, however, shows an increase in magnitude of its negative orientation birefringence with increasing moisture content. The results can be explained by the increase of the polarizability anisotropy perpendicular to the stretching direction in the cellulose esters. It is found from ATR-FTIR measurements that hydrogen bonds are formed between carbonyl groups of cellulose esters and water molecules. Considering that orientation birefringence of cellulose esters is determined mainly by ester groups, the formation of hydrogen bonds contributes to the polarizability anisotropy, thus affecting the orientation birefringence.

Effect of Poly(methyl Methacrylate) Modified Water Hyacinth Fiber on Properties of Low Density Polyethylene/Natural Rubber/Water Hyacinth Fiber Composites

The effect of poly(methyl methacrylate) modified water hyacinth fiber on properties of low density polyethylene (LDPE)/natural rubber (NR)/water hyacinth fiber (WHF) composites were investigated. The composites were prepared with Z-blade mixer at 180°C and rotor speed of 50 rpm. The poly(methyl methacrylate) modified water hyacinth fibers in LDPE/NR composites (LDPE/NR/WHF-PMMA) gave a greater value of tensile strength, Young's modulus, glass transition temperature (Tg), melting temperature (Tm), and % crystallinity compared to unmodified water hyacinth fibers in LDPE/NR composites (LDPE/NR/WHF). FTIR analysis shows the presence of ester carbonyl group and C-O ester group in poly (methyl methacrylate) modified water hyacinth fiber. The SEM micrograph also shows a better interfacial adhesion between the fibers and LDPE/NR matrixes for LDPE/NR/WHF-PMMA composites than LDPE/NR/WHF composites. LDPE/NR/WHF-PMMA composites had a lower value of interparticle spacing compared to LDPE/NR/WHF composites thatenhanced the interparticle interaction between fiber and LDPE/NR matrixes.

ChemInform Abstract: Spiro Heterocyclization of Methyl 3‐Aroyl‐1‐aryl‐4,5‐dioxo‐4,5‐dihydro‐1H‐pyrrole‐2‐carboxylates by the Action of Diphenylguanidine.

Reactions of monocyclic 1H-pyrrole-2,3-diones with guanidines were not reported. We examined reactions of methyl 1-aryl-3-aroyl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates Ia and Ib with 1,3-diphenylguanidine (II) at a molar ratio of 1 : 1 in boiling anhydrous 1,2-dichloroethane (reaction time 1–2 h; TLC monitoring) and isolated 6-aryl-9-aroyl-8-hydroxy-2-imino-1,3-diphenyl-1,3,6-triazaspiro[4.4]non8-ene-4,7-diones IIIa and IIIb whose structure was confirmed by X-ray analysis. Presumably, compounds IIIa and IIIb are formed via addition of one secondary amino group in diphenylguanidine II at the C atom of pyrroledione Ia or Ib, followed by closure of imidazole ring as a result of intramolecular attack by the second secondary amino group in II on the ester carbonyl group and elimination of methanol molecule. and 1 mmol of diphenylguanidine II in 10 ml of anhydrous 1,2-di-chloroethane was heated for 1 h under reflux. The mixture was cooled, and the precipitate was filtered off. Yield 79%, mp 243–244°C (from 1,2-dichloroethane). IR spectrum, ν, cm: 3070 br (OH, NH), 1790 (C=O), 1730, 1700 (C=O), 1615 br (9-C=O). H NMR spectrum, δ, ppm: 2.41 s (3H, Me), 7.10–7.69 m (19H, Harom), 9.44 br.s (2H, NH, OH). Found, %: C 72.73; H 4.50; N 10.67. C32H24N4O4. Calculated, %: C 72.72; H 4.58; N 10.60. 9-(4-Ethoxybenzoyl)-8-hydroxy-2-imino-6(4-methylphenyl)-1,3-diphenyl-1,3,6-triazaspiro[4.4]non-8-ene-4,7-dione (IIIb) was synthesized in a similar way. Yield 75%, mp 251–252°C (from 1,2-dichloroethane). IR spectrum, ν, cm: 3050 br (OH, NH), 1790 (C=O), 1730, 1700 (C=O), 1610 br (9-C=O). H NMR spectrum, δ, ppm: 1.35 t (3H, CH3CH2, J = 7.0 Hz), 2.40 s (3H, Me), 4.08 q (2H, CH2O, J = 7.0 Hz), 6.85–7.81 m (18H, Harom), 9.28 br.s (2H, NH, OH). Found, %: C 71.38; H 4.88; N 9.70. C34H28N4O5. Calculated, %: C 71.32; H 4.93; N 9.78. The IR spectra were recorded on an FMS-1201 spectrometer from samples dispersed in mineral oil. The H NMR spectra were measured on a Bruker WP400 instrument from solutions in DMSO-d6 using tetramethylsilane as internal reference. The purity of the products was checked by TLC on Silufol plates using ethyl acetate as eluent; spots were visualized by treatment with iodine vapor. This study was performed under financial support by the Russian Foundation for Basic Research (project no. 07-03-96 036). Ar = Ph (a), 4-EtOC6H4 (b). ISSN 1070-4280, Russian Journal of Organic Chemistry, 2010, Vol. 46, No. 12, p. 1891. © Pleiades Publishing, Ltd., 2010. Original Russian Text © N.V. Bubnov, E.S. Denislamova, Z.G. Aliev, A.N. Maslivets, 2010, published in Zhurnal Organicheskoi Khimii, 2010, Vol. 46, No. 12, p. 1876.

Oligo(p‐phenylene‐ethynylene)s with Backbone Conformation Controlled by Competitive Intramolecular Hydrogen Bonds

A series of conjugated oligo(p-phenylene-ethynylene) (OPE) molecules with backbone conformations (that is, the relative orientations of the contained phenylene units) controlled by competitive intramolecular hydrogen bonds to be either co-planar or random were synthesised and studied. In these oligomers, carboxylate and amido substituents were attached to alternate phenylene units in the OPE backbone. These functional groups were able to form intramolecular hydrogen bonds between neighbouring phenylene units. Thereby, all phenylene units in the backbone were confined in a co-planar conformation. This planarised structure featured a more extended effective conjugation length than that of regular OPEs with phenylene units adopting random orientation due to a low rotational-energy barrier. However, if a tri(ethylene glycol) (Tg) side chain was appended to the amido group, it enabled another type of intramolecular hydrogen bond, formed by the Tg chain folding back and the contained ether oxygen atom competing with the ester carbonyl group as the hydrogen-bond acceptor. The outcome of this competition was proven to depend on the length of the alkylene linker joining the ether oxygen atom to the amido group. Specifically, if the Tg chain folded back to form a five-membered cyclic structure, this hydrogen-bonding motif was sufficiently robust to overrule the hydrogen bonds between adjacent phenylene units. Consequently, the oligomers assumed non-planar conformations. However, if the side chain formed a six-membered ring by hydrogen bonding with the amido NH group, such a motif was much less stable and yielded in the competition with the ester carbonyl group from the adjacent phenylene unit. Thus, the hydrogen bonds between the phenylene units remained, and the co-planar conformation was manifested. In our system, the hydrogen bonds formed by the back-folded Tg chain and amido NH group relied on a single oxygen atom as the hydrogen-bond acceptor. The additional oxygen atoms in the Tg chain made a negligible contribution. A bifurcated hydrogen-bond motif was unimportant. From our results, in combination with the results from an independent study by Meijer et al., it is evident that intramolecular hydrogen bonds involving back-folded oligo(ethylene glycol) moieties may differ in their structural details. Absorption spectroscopy served as a convenient yet sensitive technique for analysing hydrogen-bonding motifs in our study.

Graphical Abstract: Eur. J. Org. Chem. 15/2011

AbstractThe cover picture shows a synthetic n‐puzzle, a game that challenges players to move tiles along unbending routes in order to establish a certain end configuration. Our templated 1,3,9‐decatrienoate precursors, advanced synthetic tiles, were designed on the basis of a chiral 1,3‐dioxane tether and paved the way for stereodirected intramolecular Diels–Alder reactions, leading to asymmetric cyclohexene rings. The 1,3‐dioxane tether was expected to rigidify the decatrienoate system for efficient stereocontrol, with the ester carbonyl group strongly favoring endo‐boat transitions states. Thanks to this method we succeeded in synthesizing valuable intermediates towards the total synthesis of the diterpene harringtonolide originating from the plum yew shown in the background and the fungal polyketide pyrrocidine A. Details of this work are described in the article by B. Nay et al. on p. 2789 ff.

Synthesis of Naturally Occurring Cyclohexene Rings Using Stereodirected Intramolecular Diels–Alder Reactions Through Asymmetric 1,3‐Dioxane Tethering (Eur. J. Org. Chem. 15/2011)

AbstractThe cover picture shows a synthetic n‐puzzle, a game that challenges players to move tiles along unbending routes in order to establish a certain end configuration. Our templated 1,3,9‐decatrienoate precursors, advanced synthetic tiles, were designed on the basis of a chiral 1,3‐dioxane tether and paved the way for stereodirected intramolecular Diels–Alder reactions, leading to asymmetric cyclohexene rings. The 1,3‐dioxane tether was expected to rigidify the decatrienoate system for efficient stereocontrol, with the ester carbonyl group strongly favoring endo‐boat transitions states. Thanks to this method we succeeded in synthesizing valuable intermediates towards the total synthesis of the diterpene harringtonolide originating from the plum yew shown in the background and the fungal polyketide pyrrocidine A. Details of this work are described in the article by B. Nay et al. on p. 2789 ff.

An infrared study of solute-solvent interactions of testosterone propionate.

Abstract Interactions between testosterone propionate and 10 different organic solvents have been investigated by observing the shifts of the stretching frequencies of the ketone and ester carbonyl groups. The shifts are shown to be approximately proportional to the degree of deviation from regular solution behaviour. The solvents are classified into three groups and the possible interactions in each discussed.

Production and Physicochemical Properties of 2‐Octen‐1‐Ylsuccinic Derivatives from Waxy Corn Starch

Waxy corn starch was esterified with 2-octen-1-ylsuccinic anhydride (OSA) using response surface methodology. The molecular structure and paste properties were also investigated. Results indicated that the optimum parameters for esterification were as follows: reaction period 4 h, temperature 36.7 °C, pH of reaction system 8.3, concentration of starch slurry 36.9%, and amount of OSA 3%. The degree of substitution was 0.0187 and the reaction efficiency was 80.6%. The ester carbonyl group in OSA starch was characterized by Fourier Transform Infrared Spectroscopy at 1723 cm(-1). Compared with native starch, OSA derivative had higher peak viscosity, better freeze-thaw stability, and decreased gelatinization temperature and digestibility by porcine pancreatic alpha-amylase. Scanning electron microscopy showed that the gels from OSA starch had less and smaller pores; however, the native starch gels changed to sponge-like structure after 4 freezing/thawing cycles. The OSA modified waxy corn starch offered a potential to be used in frozen foods. (a) To optimize operating conditions to achieve OSA modified waxy corn starch with a high degree of substitution; (b) to give a deeper insight into the physicochemical properties of OSA modified waxy corn starch, which offered a potential to be used in frozen foods.

Effect of mesophilic and thermophilic conditions on changes of physicochemical characteristics of smooth cordgrass via dry digestion process

In this study, the changes on physicochemical characteristics of pretreated and digested smooth cordgrass were investigated by the composition, X-ray, FTIR and 13C NMR, and TG analyses. Simultaneous lime treatment and dry digestion could be successfully carried out in leaching bed reactor at thermophilic condition with highest breakage of lignocellulose and higher biogas yield. Comparing with mesophilic condition, thermophilic condition brought a greater change of lignocellulosic structure, thus making holocellulose more accessible to anaerobic bacteria and benefiting to biogas production. The removal of lignin and hemicellulose at pretreatment phase was shown by the cleavage of ester linkage or carbonyl groups and the reducing intensity of lignin from FTIR and 13C NMR spectra analysis. The removal of polysaccharide mainly happened at digestion phase, as shown by the results of composition, FTIR and 13C NMR analysis. The crystalline index obviously decreased at pretreatment and digestion phases, as indicated by the intensity change of hydrogen bonding. The results of TG analysis showed that pretreatment and digestion had an obvious impact on the distribution of volatile matter, rate of weight loss and kinetic parameters of pyrolysis.

Doubly Activated Supramolecular Reaction: Transesterification of Acyclic Oligoether Esters with Metal Alkoxides

Transesterification reactions of acyclic oligoether esters E3-E10 with metal alkoxides were accelerated upon noncovalent complexation of the esters with metal ions. In the reaction of monovalent alkaline metal alkoxides, CH(3)ONa and CH(3)OK, plots of the observed rate constants k(obs) with respect to the chain length of E3-E10 showed selective acceleration of the transesterification. Compared with the shortest E3, which can hardly bind metal ion, 4.3- and 6.6-fold accelerations in the maxima were achieved in the combinations of E5/CH(3)ONa and E6/CH(3)OK, respectively. Supramolecular intermediate complex could be spectrometrically visualized by ESI-FT-ICR-MS in the course of reaction. Kinetic experiments, together with structural analyses by means of NMR, mass spectrometry, and DFT calculations of the intermediate complexes, indicate that a size-fit complex of host substitute with alkali metal ion allows strong electron withdrawing due to the close contact of the carbonyl oxygen to the metal ion, resulting in the selective rate enhancement of the reaction, while in the reaction of E3-E10 with a divalent alkaline earth metal alkoxide, (CH(3)CH(2)O)(2)Ba, the k(obs) values increased stepwise with elongation of the side arm to attain an dramatic large acceleration. In comparison with the k(obs) of E3, 4610-fold acceleration was achieved in the reaction of E10. The double activation of the host substrate and guest counter nucleophile at once brings about this extraordinary rate acceleration. The strong wrapping complexation of long oligoether ester with barium ethoxide allows for the effective electron withdrawal from the ester carbonyl group (host activation) as well as separation of the accompanying guest alkoxide anions (guest activation).

Spiro heterocyclization of methyl 3-aroyl-1-aryl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates by the action of diphenylguanidine

Reactions of monocyclic 1H-pyrrole-2,3-diones with guanidines were not reported. We examined reactions of methyl 1-aryl-3-aroyl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates Ia and Ib with 1,3-diphenylguanidine (II) at a molar ratio of 1 : 1 in boiling anhydrous 1,2-dichloroethane (reaction time 1–2 h; TLC monitoring) and isolated 6-aryl-9-aroyl-8-hydroxy-2-imino-1,3-diphenyl-1,3,6-triazaspiro[4.4]non8-ene-4,7-diones IIIa and IIIb whose structure was confirmed by X-ray analysis. Presumably, compounds IIIa and IIIb are formed via addition of one secondary amino group in diphenylguanidine II at the C atom of pyrroledione Ia or Ib, followed by closure of imidazole ring as a result of intramolecular attack by the second secondary amino group in II on the ester carbonyl group and elimination of methanol molecule. and 1 mmol of diphenylguanidine II in 10 ml of anhydrous 1,2-di-chloroethane was heated for 1 h under reflux. The mixture was cooled, and the precipitate was filtered off. Yield 79%, mp 243–244°C (from 1,2-dichloroethane). IR spectrum, ν, cm: 3070 br (OH, NH), 1790 (C=O), 1730, 1700 (C=O), 1615 br (9-C=O). H NMR spectrum, δ, ppm: 2.41 s (3H, Me), 7.10–7.69 m (19H, Harom), 9.44 br.s (2H, NH, OH). Found, %: C 72.73; H 4.50; N 10.67. C32H24N4O4. Calculated, %: C 72.72; H 4.58; N 10.60. 9-(4-Ethoxybenzoyl)-8-hydroxy-2-imino-6(4-methylphenyl)-1,3-diphenyl-1,3,6-triazaspiro[4.4]non-8-ene-4,7-dione (IIIb) was synthesized in a similar way. Yield 75%, mp 251–252°C (from 1,2-dichloroethane). IR spectrum, ν, cm: 3050 br (OH, NH), 1790 (C=O), 1730, 1700 (C=O), 1610 br (9-C=O). H NMR spectrum, δ, ppm: 1.35 t (3H, CH3CH2, J = 7.0 Hz), 2.40 s (3H, Me), 4.08 q (2H, CH2O, J = 7.0 Hz), 6.85–7.81 m (18H, Harom), 9.28 br.s (2H, NH, OH). Found, %: C 71.38; H 4.88; N 9.70. C34H28N4O5. Calculated, %: C 71.32; H 4.93; N 9.78. The IR spectra were recorded on an FMS-1201 spectrometer from samples dispersed in mineral oil. The H NMR spectra were measured on a Bruker WP400 instrument from solutions in DMSO-d6 using tetramethylsilane as internal reference. The purity of the products was checked by TLC on Silufol plates using ethyl acetate as eluent; spots were visualized by treatment with iodine vapor. This study was performed under financial support by the Russian Foundation for Basic Research (project no. 07-03-96 036). Ar = Ph (a), 4-EtOC6H4 (b). ISSN 1070-4280, Russian Journal of Organic Chemistry, 2010, Vol. 46, No. 12, p. 1891. © Pleiades Publishing, Ltd., 2010. Original Russian Text © N.V. Bubnov, E.S. Denislamova, Z.G. Aliev, A.N. Maslivets, 2010, published in Zhurnal Organicheskoi Khimii, 2010, Vol. 46, No. 12, p. 1876.

Characteristics and application of octenyl succinic anhydride modified waxy corn starch in sausage

AbstractNative and acid‐hydrolyzed wx corn starches were modified by octenyl succinic anhydride (OSA) in aqueous slurry systems. The characteristics of the modified wx corn starches and their effects on chicken meat sausages were evaluated by means of FT‐IR, rapid visco analyser, SEM, and texture profile analysis. FT‐IR spectroscopy indicated that the ester carbonyl groups in the OSA modified native and acid‐hydrolyzed starches were characterized at 1725 cm−1. The process of OSA modification could achieve starch derivatives, which had higher viscosities, better paste clarity and freeze–thaw stability than the native counterparts. Texture results showed that the hardness, springiness, cohesiveness, and chewiness of the sausage increased as OSA‐H0 was added (p < 0.05). SEM revealed that the sausages with native wx corn starch had larger and uneven pores, while it was comparatively compact for the sausages with OSA starches. The OSA modified wx corn starch offered a great potential to be used in meat products to enhance textural quality.

The Role of Intercalated Water in Multilayered Graphene Oxide

A detailed in situ infrared spectroscopy analysis of single layer and multilayered graphene oxide (GO) thin films reveals that the normalized infrared absorption in the carbonyl region is substantially higher in multilayered GO upon mild annealing. These results highlight the fact that the reduction chemistry of multilayered GO is dramatically different from the single layer GO due to the presence of water molecules confined in the ∼1 nm spacing between sheets. IR spectroscopy, XPS analysis, and DFT calculations all confirm that the water molecules play a significant role interacting with basal plane etch holes through passivation, via evolution of CO(2) leading to the formation of ketone and ester carbonyl groups. Displacement of water from intersheet spacing with alcohol significantly changes the chemistry of carbonyl formation with temperature.

Evidence of lipid peroxidation and protein phosphorylation in cells upon oxidative stress photo-generated by fullerols

An oxidative stress (OS) state is characterized by the generation of Reactive Oxygen Species (ROS) in a biological system above its capacity to counterbalance them [1]. Exposure to OS induces the accumulation of intracellular ROS, which in turn causes cell damage in the form of protein, lipid, and/or DNA oxidations. Such conditions are believed to be linked to numerous diseases or simply to the ageing of tissues. However, the controlled generation of ROS via photosensitizing drugs or photosensitizers (PS) is now widely used to treat various tumors and other infections [2,3]. Here we present a method to track the chemical changes in a cell after exposure to oxidative stress. OS is induced via fullerols, a custom made water soluble derivative of fullerene (C 60), under visible light illumination. Synchrotron-based Fourier Transform InfraRed Microspectroscopy (S-FTIRM) was used to assess the chemical makeup of single cells after OS exposure. Consequently, a chemical fingerprint of oxidative stress was probed in this study through an increase in the bands linked with lipid peroxidation (carbonyl ester group at 1740 cm −1) and protein phosphorylation (asymmetric phosphate stretching at 1240 cm −1).

Selective Reductions of Cyclic 1,3‐Diesters by Using SmI2 and H2O

SmI(2)/H(2)O reduces cyclic 1,3-diesters to 3-hydroxyacids with no over reduction. Furthermore, the reagent system is selective for cyclic 1,3-diesters over acyclic 1,3-diesters, and esters. Radicals formed by one-electron reduction of the ester carbonyl group have been exploited in intramolecular additions to alkenes. The ketal unit and the reaction temperature have a marked impact on the diastereoselectivity of the cyclizations. Cyclization cascades are possible when two alkenes are present in the starting cyclic diester and lead to the formation of two rings and four stereocenters with excellent stereocontrol.

ChemInform Abstract: Synthetic Application of Lithiated Tris(methylthio)methane: Preparation of Aliphatic Methyl Thiolcarboxylates from the Corresponding Halides. Convenient Synthesis of Tris(methylthio)methane.

A thorough study directed towards the synthesis of methyl thiolcarboxylates was made on the basis of the following steps: (i) conversion of alkyl halides into the corresponding trimethyl trithioorthocarboxylates by using tris(methylthio)methyllithium in THF at –78 °C; (ii) selective hydrolysis of the intermediates to methyl thiolcarboxylates by using 35% aq. HBF4 in DMSO or, in some cases, in THF. The overall yields of the two stages are, usually, between 70 and 88%. By this procedure it is also possible to incorporate 8O in the carbonyl group of thiol esters (∼98% isotopic purity). Furthermore, a new, convenient method for the preparation of tris(methylthio)methane as the precursor of tris(methylthio)methyllithium was developed.