Methylthio Substituents Research Articles

Electrospray ionization collision induced dissociation of thieno[3,2-d]pyrimidine derivatives

2,4-substituted thieno[3,2-d]pyrimidines, with different l-amino acid methyl ester substituent on 4-C and methyl or methylthio substituent on 2-C, showed a complex and analytically valuable fragmentation behaviour under positive ion electrospray ionization collision-induced dissociation ((+)-ESI-CID) mass spectrometry. Protonated 2,4-substituted thieno[3,2-d]pyrimidines firstly lose a neutral fragment C2H4O2 (MS2) and the ion [M + H - 60]+ thus formed, then dissociates by losing of extended series of neutral molecule fragmentation from amino acid methyl ester substituent, in competition with the expulsion of CS or CH3SH and other direct bond scissions. Moreover, losing of NH3, CHN and CH2NH from the precursor ions of [M + H - 60]+ were proposed to occur via rearrangements. The formation of diagnostic product ions and the series neutral eliminations provided information about the properties of substituents, assisting their characterization via MS/MS, high-resolution mass spectrometry, the hydrogen/deuterium exchange experiment and density functional theory (DFT) calculations. The proposed fragmentation patterns of these compounds give an insight into the understanding of gas-phase reactions in mass spectrometric studies of thieno[3,2-d]pyrimidine derivatives.

Supramolecular Block Copolymers by Seeded Living Polymerization of Perylene Bisimides.

Living covalent polymerization has been a subject of intense research for many decades and has culminated in the synthesis of a large variety of block copolymers (BCPs) with structural and functional diversity. In contrast, the research on supramolecular BCPs is still in its infancy and their generation by living processes remains a challenge. Here we report the formation of supramolecular block copolymers by two-component seeded living polymerization of properly designed perylene bisimides (PBIs) under precise kinetic control. Our detailed studies on thermodynamically and kinetically controlled supramolecular polymerization of three investigated PBIs, which contain hydrogen-bonding amide side groups in imide position and chlorine, methoxy, or methylthio substituents in 1,7 bay-positions, revealed that these PBIs form kinetically metastable H-aggregates, which can be transformed into the thermodynamically favored J-aggregates by seed-induced living polymerization. We show here that copolymerization of kinetically trapped states of one PBI with seeds of another PBI leads to the formation of supramolecular block copolymers by chain-growth process from the seed termini as confirmed by UV/vis spectroscopy and atomic force microscopy (AFM). This work demonstrates for the first time the formation of triblock supramolecular polymer architectures with A-B-A and B-A-B block pattern by alternate two-component seeded polymerization in a living manner.

Synthesis and application of methylthio-substituted BODIPYs/aza-BODIPYs

A series of new BODIPYs/aza-BODIPYs with a methylthio group were Herein prepared. Introduction of the electron-donating methylthio substituent into such dyes could reduce the fluorescence quantum yield, red-shift its emission spectra, provide higher extinction coefficients and larger Stokes' shift. Oxidation of the thioether of BODIPY 4 into the corresponding electron-withdrawing sulfoxide by HClO can restore the quantum yield and blue-shift its emission spectra, and dye 4 was highly sensitive and selective to HClO.

ChemInform Abstract: Synthesis of N2‐Arylaminopyrimidine‐5‐carbonitrile Derivatives via SNAr Amination Reaction.

Abstractscope and limitations of the new protocol

Synthesis of N2-arylaminopyrimidine-5-carbonitrile derivatives via SNAr amination reaction

Abstract An efficient and high-yielding synthesis of N 2 -arylaminopyrimidine-5-carbonitrile derivatives starting from arylamines and 2-methylthio-pyrimidine-5-carbonitrile derivatives has been developed in the presence of cesium carbonate as basic reagent. This new protocol showed high chemical tolerance for a range of functional groups, and only the methylthio substituent on C2 of the pyrimidine ring was replaced with arylamine derivatives under the reaction conditions.

Effect of Substituents on the Structure, Stability, and π-Dimerization of Dithienylpyrrole Radical Cations

A series of 2,5-di(2-thienyl)-N-methylpyrrole derivatives 1a-1d with methylthio end-capping groups and electron-donating substituents at the 3-position of the thiophene rings was synthesized, and the effects of the substituents on the structure, stability, and π-dimerization ability of the radical cation were investigated using UV-vis-NIR and electron spin resonance spectra and density functional theory (DFT) calculations. Among the electron-donating methyl, methoxy, and methylthio substituents, the methoxy derivative 1c gave the most stable radical cation, which persisted in dichloromethane at room temperature under nitrogen for several hours without any apparent decomposition. In addition, 1c(•+) had the largest π-dimerization enthalpy among 1a(•+)-1d(•+). DFT calculations with the M06-2X method revealed that methyl and methylthio derivatives 1b(•+) and 1d(•+) as well as 1c(•+) adopt a cis-cis conformation, in contrast to the trans-trans conformer of unsubstituted 1a(•+), while the π-dimers of all of these compounds were shown to have a cis-cis conformation. On the basis of further detailed analyses, the preformed cis-cis conformation and the weaker intramolecular and intermolecular steric repulsions were considered to explain why 1c(•+) has the largest π-dimerization enthalpy.

Enantioselective total syntheses of plectosphaeroic acids B and C.

Evolution of the synthetic strategy that culminated in the first total syntheses of the structurally unique plectosphaeroic acids B (2) and C (3) is described. The successful enantioselective route to (+)-2 and (+)-3 proceeds in 6 and 11 steps from the known hexahydro-2H-pyrazinopyrrolo[2,3-b]indole-1,4-dione 39, which in turn is available in enantiomerically pure form by chemical synthesis. The central challenge in this synthesis endeavor was uniting the hexahydro-2H-pyrazinopyrrolo[2,3-b]indole-1,4-dione and cinnabarinic acid fragments of these marine alkaloids. Critical for achieving this successful C-N bond formation was the use of an iodocinnabarinic acid diester in which the amino group was masked with two Boc substituents, a Cu(I) carboxylate complex and the weak base KOAc. The highly congested C-N bond generated in this coupling, in conjunction with the delicate nature of the densely functionalized coupling partners, provided a striking testament to the power of modern copper-mediated amination methods. Two approaches, one stereoselective, for introducing the methylthio substituents of (+)-plectosphaeroic acid B were developed. The epitrisulfide ring of (+)-plectosphaeroic acid C was formed by ring expansion of an epidisulfide precursor.

Aryl Nitrene Rearrangements: Spectroscopic Observation of a Benzazirine and Its Ring Expansion to a Ketenimine by Heavy-Atom Tunneling

In the photodecompositions of 4-methoxyphenyl azide (1) and 4-methylthiophenyl azide (5) in argon matrixes at cryogenic temperatures, benzazirine intermediates were identified on the basis of IR spectra. As expected, the benzazirines photochemically rearranged to the corresponding ketenimines and triplet nitrenes. Interestingly, with the methylthio substituent, the rearrangement of benzazirine 8 to ketenimine 7 occurred at 1.49 × 10(-5) s(-1) even in the dark at 10 K, despite a computed activation barrier of 3.4 kcal mol(-1). Because this rate is 10(57) times higher than that calculated for passing over the barrier and because it shows no temperature dependence, the rearrangement mechanism is interpreted in terms of heavy-atom tunneling.

Enantioselective Total Synthesis of Plectosphaeroic Acid B

The first total synthesis of a member of the plectosphaeroic acid family of fungal natural products is reported. Key steps include the late-stage formation of the hindered N6-C9" bond and stereoselective introduction of the two methylthio substituents.

Design, synthesis and evaluation of the inhibitory selectivity of novel trans-resveratrol analogues on human recombinant CYP1A1, CYP1A2 and CYP1B1

A series of trans-stilbene derivatives containing 4′-methylthio substituent were synthesized and evaluated for inhibitory activities on human recombinant cytochrome P450(s): CYP1A1, CYP1A2, and CYP1B1. CYP1A2-related metabolism of stilbene derivatives was estimated by using NADPH oxidation assay. Additionally, for CYP1A2 and CYP1B1 molecular docking analysis was carried out to provide information on enzyme–ligand interactions and putative site of metabolism.3,4,5-Trimethoxy-4′-methylthio-trans-stilbene, an analogue of DMU-212 (3,4,5,4′-tetramethoxy-trans-stilbene) was an effective inhibitor of all CYP1 enzymes. On the other hand, 2,3,4-trimethoxy-4′-methylthio-trans-stilbene, appeared to be the most selective inhibitor of the isozymes CYP1A1 and CYP1B1, displaying extremely low affinity towards CYP1A2. Molecular modeling suggested that the most probable binding poses of the methylthiostilbene derivatives in CYP1A2 active sites are those with the methylthio substituent directed towards the heme iron. Products of CYP1A2-catalyzed oxidation of 2,4,5-trimethoxy-4′-methylthiostilbene and 3,4,5-trimethoxy-4′-methylthiostilbene were identified as monohydroxylated compounds. Other studied derivatives appeared to be poor substrates of CYP1A2. Structure–activity relationship analysis rendered better understanding of the mechanism of action of xenobiotic-metabolizing enzymes crucial at the early stage of carcinogenesis.

Cobalt-Catalyzed C-SMe Bond Activation of Heteroaromatic Thioethers

N-Heterocycles bearing methylthio substituents can be activated by CoBr2, enabling cross-coupling reactions as electrophiles with aryl or benzylzinc reagents. At the same time, the ­reaction conditions allow the generation of hetero-aryl-ZnSMe compounds that can be used as nucleophiles for subsequent cross-couplings.

ChemInform Abstract: Comparison of Bipolaron-Like Charge State Generation in the Oxidative Doping of α,ω-Dithienyl and α,ω-Diphenyl Polyenes Stabilized by Methoxy and Methylthio Substituents.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Triflupromazine: a microbicide non-antibiotic compound

The antipsychotic phenothiazine triflupromazine, possessing a methyl-thio substituent at position 10 and a fluorine moiety at position 2, exhibited significant antibacterial activity against 279 strains of Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration (MIC) of the drug, according to the agar dilution method, was between 2 and 50 microg/ml for Staphylococcus aureus, and 5 and 100 microg/ml for shigellae and vibrios. Triflupromazine, when injected intraperitoneally into Swiss albino mice at a concentration of 30 microg/mouse (20 g), manifested a significant protection to the mice (p<0.001) when they were challenged with 50 median lethal dose (MLD) of Salmonella typhimurium NCTC 74. Moreover, there was a statistically significant reduction in the number of viable bacteria in organ homogenates and blood of mice treated with this phenothiazine compound.

Triazolylbenzimidazolthiones and Derivatives of the New 1,2,3‐Triazolo[1,5‐a][1,3,5]benzotriazepine Heterocycle.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Triazolylbenzimidazolthiones and derivatives of the new 1,2,3‐triazolo[ 1,5‐a][ 1,3,5]benzotriazepine heterocycle

AbstractFour new triazolylbenzimidazolthione derivatives (2a‐d), analogous to triazolylbenzimidazolone derivatives previously tested as activators of the BKCa potassium channels, were prepared and assayed without success. Some derivatives of a new tricyclic nitrogen heterocycle, 1,2,3‐triazolo[1,5‐a][1,3,5]benzo‐triazepine, bearing a carboxamido group in the 3 position, other substituents in the 8 position and a carbonyl (5a‐d) or thione (6a‐c) or methylthio (7a‐c) function in the 5 position were synthesised. The nucleophilic displacement of the methylthio substituent with morpholine or cyclopentylamine provided the 5‐amino‐substituted tricyclic derivatives 8a‐d. Starting from the l‐(2‐nitrophenyl)‐4‐cyano‐5‐amino‐1,2,3‐triazole (9), the 3‐cyano‐triazolobenzotriazepin‐5‐one derivative 12 was also obtained. The majority of the new compounds were tested towards the BKCa potassium channels, the benzodiazepine and adenosine A1 and A2a receptors, but no remarkable activity was detected.

3-Cyano-5-(4-methoxybenzyl)-6-(4-methoxyphenyl)-4-methylthio-2H-pyran-2-one

The synthesis of the title compound, C 22 H 19 NO 4 S, is described. The methyl group of the methylthio substituent points towards the CN group, as has been noted before when bulky substituents occupy the 5-position. The phenyl groups in the 5- and 6-positions are twisted at angles of 75.7 (1) and 36.5 (1)°, respectively, from the plane of the pyrone ring.

Syntheses of Batzelline A, Batzeline B, Isobatzelline A, and Isobatzelline B

Batzellines A and B (1a, b) and isobatzellines A and B (2a, b) are 1,3,4,5-tetrahydropyrrolo[4,3,2-de]quinoline-containing marine alkaloids characterized by the presence of a methylthio substituent at C-2 of the tricyclic system. We describe here the total synthesis of these natural compounds following the synthetic strategy that we have used previously for the synthesis of damirones A and B, batzelline C, isobatzelline C, discorhabdin C, and makaluvamines A, B, C, and D. The introduction of the methylthio group by electrophilic substitution of a pyrrolo[4,3,2-de]quinoline, appropriately substituted and in a suitable oxidation state, is the key step in the success of these syntheses.

ChemInform Abstract: Altering the Acidity and Solution Properties of Bilirubin. Methoxy and Methylthio Substituents.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Altering the Acidity and Solution Properties of Bilirubin. Methoxy and Methylthio Substituents

Substitution of electron-withdrawing groups at the alpha-position of an aliphatic carboxylic acid can be expected to increase the acidity of the acid. Methoxy and methylthio groups are especially effective; they increase the acidity of acetic acid by approximately 1.1 pK(a) units. Bilirubin, the water-insoluble pigment of jaundice, has two propionic acids, and an alpha-methoxy or alpha-methylthio substituent in each propionic acid can be expected to lower the pK(a) similarly and thus alter its solubility properties. (A previously synthesized analogue, alpha,alpha'-difluororubin (4), is soluble in water.) Two new analogues of bilirubin, alpha,alpha'-dimethoxyrubin (1) and alpha,alpha'-bis(methylthio)rubin (2), have been synthesized, separated into diastereomers, and analyzed. The isomers are shown by NMR to adopt intramolecularly hydrogen-bonded ridge-tile-shaped conformations. Like bilirubin, both 1 and 2 are insoluble in water. Unlike bilirubin, 1 is soluble in dilute aqueous bicarbonate, but 2 is insoluble, which would not be predicted from the expectation that 1 and 2 have the same pK(a). The data hint at a much larger steric size of SCH(3) relative to OCH(3).

β,β-Disubstituted oligothiophenes, a new oligomeric approach towards the synthesis of conducting polymers

Abstract The electropolymerization of methylthio-substituted oligothiophenes 2 – 4 has been studied. Theoretical and experimental results reveal that only 4,4′-disubstituted derivatives yield polymeric films. The reason for this is that electron-donating methylthio (=methylsulphonyl) substituents in the ‘outer’ β -positions of the starting compounds 2 – 4 , which cause high spin densities at the corresponding α -C atoms, favour fast coupling steps between the reacting oligomers during all stages of the electropolymerization. All data clearly indicate that the electropolymerization of donor-substituted thiophenes is not a chain propagation process but a series of successive ‘dimerization’ steps. The resulting polymers have been characterized by voltammetric measurements, in situ conductivity experiments and spectroelectrochemistry.