A Diaminodiacid (DADA) Strategy for the Development of Disulfide Surrogate Peptides

Disulfide bond‐containing peptides are useful molecular scaffolds with diagnostic and therapeutic applications due to their good biological activity and good target selectivity, but their utility is sometimes limited by the lability of the disulfide moiety under reducing conditions and in the presence of disulfide bond isomerase. The development of disulfide surrogates with improved redox stability has been an area of ongoing research; and one possible strategy is based on a diaminodiacid (DADA) moiety, which can be used to synthesize the disulfide bond replacement peptides with precise structures and enhanced stability through automated solid‐phase peptide synthesis (SPPS). This review summarizes recent developments in the DADA‐based SPPS of peptide disulfide surrogates. Some representative applications and structural studies on the DADA‐based disulfide surrogates are described.     

Intercalation of molybdenum disulfide with chlorobis(phenanthroline)copper(II)

An intercalation compound of molybdenum disulfide with the copper complex Cu^II(phen)₂Cl⁺ was found to form by the interaction of the MoS₂ single-layer dispersions with the complex and by the treatment of the phenanthroline intercalation compound with CuCl₂. The compositions and structures of the compounds formed were determined by powder diffractometry and electron microscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2648–2654, December, 2005.     

Synthesis and Structure of { (Tab-Tab) [Ag2(μ-Cl)4]·2MeCN}n (Tab = 4-(Trimethylammonio)benzenethiolate)

In the presence of Et4NCl?H2O,reaction of AgCl with TabHPF6 in MeCN afforded the title complex {(Tab-Tab)[Ag2(μ-Cl)4]·2MeCN}n 1.1 crystallizes in the orthorhombic space group Pbcn with a=16.782(3),b=6.8358(14),c=26.194(5) ,V=3004.9(10) 3,Z=8,μ= 1.817 mm-1,Dc=1.711 g/cm3,T=223 K,C11H16AgCl2N2S,Mr=387.10,F(000)=1544,S=1.160,R=0.0528 and wR=0.0896 for 2732 observed reflections with I > 2σ(I).1 contains a 1D linear [Ag2Cl4]n2n-chain coupled with the [Tab-Tab]2+ dications.Intermolecular hydrogen bonding interac-tions between the protons of methyl groups from the Tab-Tab dications and the chlorides result in the formation of a 2D hydrogen-bonded network.     

Reactivity of Cyclic (Alkyl)(amino)carbenes (CAACs) and Bis(amino)cyclopropenylidenes (BACs) with Heteroallenes: Comparisons with their N‐Heterocyclic Carbene (NHCs) Counterparts

Similarly to NHCs, CAAC_a and BAC_a react with CO₂ to give the corresponding betaines. Based on the carbonyl stretching frequencies of cis‐[RhCl(CO)₂(L)] complexes, the order of electron donor ability was predicted to be CAAC_a≈BAC_a>NHCs. When the betaines ν_asym(CO₂) values are used, the apparent ordering is BAC_a>NHCs≈CAAC_a that indicates a limitation for the use of IR spectroscopy in the ranking of ligand σ‐donating ability. Although all carbenes react with carbon disulfide to give the corresponding betaines, a second equivalent of CS₂ reacts with the BAC‐CS₂ leading to a bicyclic thieno[2,3‐diamino]‐1,3‐dithiole‐2‐thione, which results from a novel ring expansion process. Surprisingly, in contrast to NHCs, CAAC _a does not react with carbodiimide, whereas BAC_a exclusively gives a ring expanded product, analogous to that obtained with CS₂. The intermediate amidinate can be trapped, using the lithium tetrafluoroborate adduct of BAC_b as a carbene surrogate.     

Crystal Structure of Bis(3-hydroxy-2-pyridyl)disulfide

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THE EPR SPECTRA OF TETRADENTATE SCHIFF BASE COMPLEXES OF COPPER (II) II. N,N'-bis(salicylidene)ethylenediimine and 7-methyl-N,N'-bis (salicylidene)ethylenediimine

Abstract

The EPR spectra of single crystals of ⁶³Cu(II) doped N, N'-bis(salicylidene)ethylenediimine Ni(II), [Ni(sal)₂en] and 7-methyl-N, N'-bis(salicylidene)ethylenediimine Ni(II), [Ni(7-me sal)₂en] have been studied. The usual doublet spin-Hamiltonian parameters for the complexes have been found to be: Cu(II)[(sal)₂en]; g _z =2.192 ± 0.002; g _x =2.046 ± 0.004; g _y =2.049 ± 0.004; A _z =201.0 × 10^?4 cm^?1; A _x =29.3 × 10^?4 cm^?1; A _y =31.3 × 10^?4 cm^?1; A^N _z =12.6 × 10^?4 cm^?1; A ^N _x =14.5 × 10^?4 cm^?1; A ^N _y =15.7 × 10^?4 cm^?1; A ^H _z =6.3 × 10^?4 cm^?1; A ^H _x =7.3 × 10^?4 cm^?1; A ^H _y =7.9 × 10^?4 cm^?1; Cu(II)[(7-me sal)₂en]; g _z =2.189 ± 0.002; g _x =2.037 ± 0.004; g _y =2.046 ± 0.004; A _z =203.0 × 10^?4 cm^?1; A _x =36.9 × 10^?4 cm^?1; A _y =22.7 × 10^?4 cm^?1; A ^N _z =12.6 × 10^?4 cm^?1; A ^N _x =13.3 × 10^?4 cm^?1; A ^N _y =14.0 × 10^?4 cm^?1. Values of molecular orbital coefficients calculated for these complexes show that their bonding properties are similar to those of other compounds of this type. There is considerable covalency in the metal-ligand [sgrave]-bonds, and significant in-plane pi-bonding is present.     

Kinetic analyses of disulfide formation between thiol groups attached to linear poly(acrylamide)

Kinetic analyses were carried out for formation of disulfide crosslinkages between thiol groups on linear polymers, poly(acrylamide‐co‐N‐acrylcysteamine) (P‐SH). Disulfide crosslinkages were formed by auto‐oxidation of pendant thiol groups or through the thiol‐disulfide exchange reaction induced by addition of disulfide compounds gluthathione. In the auto‐oxidation reaction, the rate constant for disulfide formation highly depended on pH values of the reaction mixtures and the P‐SH concentrations. Gelation rate is too slow to enclose living cells into hydrogel under physiological pH 7.4. The hydrogel formation rate can be accelerated by addition of disulfides, such as oxidized glutathione. In the later case, oxygen in the reaction mixture is not consumed. The thiol‐disulfide exchange reaction is much more suitable for the cell encapsulation than the thiol auto‐oxidation reaction. These findings give a basis for enclosure of living cells in a hydrogel. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Crystallographic report: Dichloro[bis(1‐methylimidazole‐2)disulfide]zinc(II)

The Zn center in [ZnCl₂(L‐S‐S‐L)], where L‐S‐S‐L = bis(1‐methylimidazole‐2)disulfide, adopts a tetrahedral configuration defined by two Cl atoms and two N atoms from L‐S‐S‐L, which was obtained by in situ oxidation of 1‐methylimidazole‐2‐thione. Copyright © 2005 John Wiley & Sons, Ltd.     

Reductive Cleavage of Te-Te Bond in Ditellurides by Sm / ZrCl4 System : a Novel Method for the Synthesis of β-Telluroesters (and Nitriles)

Diaryl ditellurides were conveniently reduced by a system consisting of samarium and zirconium tetrachloride in tetrahydrofuran to produce samarium aryltellurolates. This new tellurolate anion species reacted smoothly with α, β-unsaturated esters (and nitriles) to give β-telluroesters (and nitriles) in good yields.     

含钴(Ⅱ)配阳离子的MoS2基嵌入化合物

本文测量了表面ζ电位随pH值的变化关系，表明MoS₂单分子层表面吸附的是OH^-离子，其等电点在pH=2附近。在pH=5～10范围内，ζ电位在-22到-24 mV之间，较为稳定。在pH=7.2条件下，利用MoS₂单分子层与钴(Ⅱ)配位阳离子基团反应合成了3个嵌入化合物[Co(H₂O)_z]_y/2MoS₂、[Co(bpy)₃]_y/2MoS₂和[Co(phen)₃]_y/2MoS₂。X-射线衍射、元素分析和热重分析研究表明前一个化合物中每10个{MoS₂}单元约嵌入一个水合钴离子，层间距增大了0.893nm，水合钴离子在基体层间按双层错开排列。后两个化合物中每20个{MoS₂}单元约嵌入一个钴有机配阳离子，层间距分别增大了0.953和1.018 nm，配位阳离子则单层排列于MoS₂基体层间，[Co(bpy)₃]²⁺和[Co(phen)₃]²⁺离子中CoN₆配位八面体的三次对称轴近于垂直于MoS₂基体层板。     

Synthesis and healing properties of poly(arylene ether sulfone)‐poly(alkyl disulfide) multiblock copolymers

A multiblock copolymer consisting of hard (poly(arylene ether sulfone)) and soft (poly(alkyl disulfide)) segments was successfully synthesized by oxidative coupling of the corresponding thiol‐terminated oligomers. Its structure was confirmed by ¹H and ¹³C NMR spectroscopy. The GPC data (M_w = 82,000, M_w/M_n = 2.7) and inherent viscosity (0.67 dL g⁻¹) indicated the formation of a high‐molecular‐weight multiblock copolymer, while AFM and DSC indicated a microphase‐separated morphology. Tensile testing of the multiblock copolymer films showed a large elongation at break, which is characteristic of microphase‐separated hard/soft multiblock copolymers. Over 90% of the elongation at break of damaged samples (notched or cut) was recovered by UV irradiation. The elongation recovery was proportional to the UV irradiation energy, and the high recovery was achieved by relatively weak irradiation (<170 J cm⁻²). The high content of disulfide bonds in the multiblock copolymer resulted in a lower self‐healing energy. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1358–1365     

Determination of tetramethylthiuram disulfide (thiram) for residual analysis in food using spectrophotometry coupled with a solid-phase reactor (SPR) in a flow system

An analytical method was developed for quantification of the fungicide thiram (tetramethylthiuram disulfide), based on its capacity to complex Cu²⁺ ions. A solid-phase reactor (SPR) was coupled in a flow system containing a spectrophotometer as detector. The SPR consisted of a tube filled with finely ground resin, in which copper(II) phosphate was immobilised prior to polymerisation. Contact of thiram with the Cu²⁺ ions immobilised in the resin resulted in the formation of a strongly coloured Cu²⁺/thiram complex. Maximum absorbance of the Cu²⁺/thiram complex was obtained at a wavelength of 439 nm. The usefulness of the methodology has been evidenced by the determination of thiram residues in corn and bean grains. Previously, a variety of transition metal cations which would form coloured complexes with tetramethylthiuram disulfide were tested.     

Synthesis and healing properties of poly(arylether sulfone)–poly(alkylthioether) multiblock copolymers containing disulfide bonds

Thermoplastic elastomers composed of soft and hard segments are important elastic and processable synthetic polymers. The microphase‐separated soft domains show low glass transition temperature and possess sufficient chain mobility at room temperature. In this study, we report the synthesis and healing properties of multiblock copolymers containing disulfide bonds as dynamic covalent bonds. The multiblock copolymers composed of poly(arylether sulfone) and poly(alkylthioether) segments were synthesized by oxidative coupling polymerization of the corresponding thiol‐terminated oligomers. Atomic force microscopy phase images, differential scanning calorimetry, and dynamic mechanical analysis curves indicated the microphase‐separated morphology of the multiblock copolymer. Self‐healing properties of the polymer were evaluated by changes in the elongation at break of the cut/adhered samples. The elongation recovery increased with UV irradiation time, and the multiblock copolymer showed a 93% recovery after UV irradiation for 5 h. The healing efficiency induced by UV irradiation, determined by subtracting the recovery without UV irradiation, was calculated to be 51%. According to the UV spectra and solubility changes after UV irradiation, the main healing factor in this study was the crosslinking reactions caused by thiyl radicals generated from UV irradiation instead of disulfide exchange reactions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3545–3553     

SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF TRIS(DIMETHYLDITHIOCARBAMATE) INDIUM(III), In[S2CN(CH3)2]3

Abstract

The synthesis and structure of the indium dithiocarbamate, In[S₂CN(CH₃)₂]₃·(1/2) 4-mepy (4-mepy=4-methylpyridine), is described. Indium metal was oxidized by tetramethylthiuram disulfide in 4-methylpyridine at 25°C to form a new, homoleptic indium(III) dithiocarbamate in yields exceeding 60%. In[S₂CN(CH₃)₂]₃ exists as a discrete molecule with a distorted-octahedral geometry. The compound crystallizes in the P 1 (No. 2) space group with a=9.282(1)Å, b=10.081(1)Å, c=12.502Å, α=73.91(1)°, β=70.21(1)°, γ=85.84(1)°, Z=2, V(Å)=1057.3(3), R=0.046 and R_w =0.061.     

Trichloroisocyanuric Acid (TCCA) and N-Chlorosuccinimide (NCS) as Efficient Reagents for the Direct Oxidative Conversion of Thiols and Disulfides to Sulfonyl Chlorides

Abstract

Trichloroisocyanuric acid (TCCA) and N-chlorosuccinimide (NCS) were found to be mild and efficient reagents for the direct oxidative conversion of sulfur compounds to the corresponding arenesulfonyl chlorides in good-to-excellent yields through the oxidative chlorination. The overall process is simple and practical, and it provides convenient access to a variety of aryl or heteroarylsulfonyl chlorides. The mild reaction conditions and the broad substrate scope render this method attractive and complementary to existing syntheses of aryl or heteroarylsulfonyl chlorides.     

Structural diversity in poly(disulfide)s

This article reports a synthetic methodology for single step preparation of telechelic poly(disulfide)s (PDS) by step‐growth polymerization between a di‐thiol and a commercially available monomer 2,2′‐dithiodipyridine in presence of a functional group appended pyridyl disulfide moiety as the “mono‐functional impurity” (MFI). Redox‐destructible well‐defined segmented PDSs with functional chain terminal, predicted and tunable degree of polymerization and narrow polydispersity index (<2.0) could be synthesized under a mild reaction condition. Using an appropriate MFI, PDS could be synthesized with trithiocarbonate chain terminals in a single step, which could be further used as macro chain‐transfer agent (CTA) for chain growth polymerization under RAFT mechanism producing ABA type tri‐block copolymer wherein the B block consists of the degradable PDS chain. By copolymerization between a hydrophobic di‐thiol monomer and a hydroxyl group appended di‐thiol monomer, PDS could be prepared with pendant hydroxyl functional group which was utilized to initiate ring opening polymerization of cyclic lactide monomers producing well‐defined degradable graft‐copolymer. The pendant hydroxyl groups were further utilized to anchor a polar carboxylic group to the degradable PDS backbone which under basic condition showed aqueous self‐assembly generating micelle‐like structure with hydrophobic guest encapsulation ability and glutathione responsive sustained release. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 194–202     

A Bio‐Inspired Switch Based on Cobalt(II) Disulfide/Cobalt(III) Thiolate Interconversion

Disulfide/thiolate interconversion supported by transition‐metal ions is proposed to be implicated in fundamental biological processes, such as the transport of metal ions or the regulation of the production of reactive oxygen species. We report herein a mononuclear dithiolate Co^III complex, [Co^IIILS(Cl)] ( 1 ; LS=sulfur containing ligand), that undergoes a clean, fast, quantitative and reversible Co^II disulfide/Co^III thiolate interconversion mediated by a chloride anion. The removal of Cl^? from the Co^III complex leads to the formation of a bis(μ‐thiolato) μ‐disulfido dicobalt(II) complex, [Co₂^II,IILSSL]²⁺ ( 2 ²⁺). The structures of both complexes have been resolved by single‐crystal X‐ray diffraction; their magnetic, spectroscopic, and redox properties investigated together with DFT calculations. This system is a unique example of metal‐based switchable Mⁿ₂‐RSSR/2 M⁽ⁿ⁺¹⁾‐SR (M=metal ion, n=oxidation state) system that does not contain copper, acts under aerobic conditions, and involves systems with different nuclearities.