Study of the reaction of chalcone analogs of dehydroacetic acid and o-aminothiophenol: synthesis and structure of 1,5-benzothiazepines and 1,4-benzothiazines

Treatment of α,β-unsaturated carbonyl compounds, obtained by the reaction of DHA and aromatic (or heteroaromatic) aldehydes, with o-aminothiophenol results in the formation of 1,5-benzothiazepines and/or 1,4-benzothiazines depending upon the reaction conditions and structure of the aldehydes. The products were characterized by the combined use of multinuclear 1D and 2D NMR and GIAO/DFT calculations of ¹H, ¹³C and ¹⁵N chemical shifts. The tautomerism of these compounds in solution was determined, they have an exocyclic CC double bond.     

Trifluoroacetic acid: a more effective and efficient reagent for the synthesis of 3-arylmethylene-3,4-dihydro-1H-quinolin-2-ones and 3-arylmethyl-2-amino-quinolines from Baylis-Hillman derivatives via Claisen rearrangement

Trifluoroacetic acid has been discovered to be a highly effective and efficient reagent for the tandem Claisen rearrangement and cyclization reaction to yield 3-arylmethylene-3,4-dihydro-1H-quinolin-2-ones from compounds obtained from the S_N2 reaction between anilines and acetyl derivatives of Baylis-Hillman adducts of acrylates in the presence of DABCO. In contrast, similar compounds obtained from the acetyl derivatives of Baylis-Hillman adduct of acrylonitrile on treatment with trifluoroacetic acid directly furnish 3-arylmethyl-2-amino-quinoline via tandem Claisen rearrangement, cyclization and isomerization.     

Photooxidized products of recombinant alpha A-crystallin and W9F mutant

Human lenses contain many photosensitizers that absorb light at wavelengths above 300 nm, most notably UVA light (320-400 nm). Kynurenine (Kyn) and 3-hydroxykynurenine (HK), two of the best-known photosensitizers in the human lens, may play a significant role in photooxidation-related changes in lens proteins, such as conformational change and aggregation. In vitro irradiation experiments with proteins indicate that the Trp residue (with maximal absorption at 295 nm) is more susceptible to photooxidation by UVB light (280-320 nm) than by UVA light, but most UVB light below 300 nm is screened by the cornea and little reaches the lens, especially the nuclear region where nuclear color develops. Therefore, if photooxidation is an important contributor to nuclear color or nuclear cataract, it must arise from a photosensitized reaction. In the present study, we use recombinant alpha A- and its Trp-deficient mutant W9F as models to study the effects of UVA irradiation in the presence of HK or Kyn and of UVB (300 nm) irradiation on alpha-crystallins. alpha A-crystallin showed a large decrease in Trp fluorescence and a large increase in non-Trp (blue) fluorescence after the HK-sensitized or 300 nm photooxidation. For the W9F mutant, a smaller decrease in protein fluorescence (lambda ex at 280 nm) and a smaller increase in blue fluorescence than for the wild-type alpha A-crystallin were observed. A decrease in the near-UV CD was also observed for both photooxidized alpha A and the W9F mutant. The effect of Kyn sensitization is smaller than that of HK sensitization. A study of chaperone-like activity indicated that only 300 nm photooxidized alpha A and the W9F mutant increased the ability to protect insulin from dithiothreitol-induced aggregation. Thus, sensitized photooxidation can occur in amino acids other than Trp by UVA in the presence of HK or Kyn with effects similar to, albeit smaller than, those of direct UVB (300 nm) photooxidation.     

Substituted Diorganotin(IV) O,O’-Alkylene Dithiophosphates: Synthesis and Spectral Aspects

Six new substituted diphenyltin(IV) O,O′-alkylene dithiophosphates, (C₆H₅)₂Sn(X)S(S) POGO [G = —CH₂C(CH₃)₂CH₂—, X = Cl (1), SCN (3), ClO₄ (5); G = —CH₂C (C₄H₉)(C₂H₅)CH₂—, X = Cl (2), SCN (4), ClO₄ (6)], were synthesized by the reaction of the corresponding ammonium salts of the O,O’-alkylene dithiophosphates with an appropriate organotin(IV) chloride. The compounds were characterized on the basis of elemental and spectral analyses (ESI mass spectrometry, IR, ¹H, ¹³C, ³¹P, and ¹¹⁹Sn NMR). The presence of a four-coordinated Sn atom and monodentate O,O’-alkylene dithiophosphate moiety in compounds 1–4 as well as bidentate O,O’-alkylene dithiophosphate unit in compounds 5,6 is established.     

Comparative Antioxidant Study of Stem and Stem Induced Callus of Phyllanthus fraternus Webster—An Important Antiviral and Hepatoprotective Plant

Phyllanthus fraternus is widely used in the cure of various liver diseases and possess antiviral properties especially against hepatitis virus. In the present study, evaluation of the antioxidant activity of stem and calli induced from stem has been done by different assays. Extraction was done by standard method in water and ethanol. Total antioxidant capacity was measured by 1, 1-diphenyl-2-picrylhydrazyl free radical scavenging method. Lipid peroxidation was measured in terms of thiobarbituric acid-reactive substances (TBARS) by using egg yolk homogenates as lipid-rich media, and superoxide radical scavenging activity was measured using riboflavin–light–nitro blue tetrazolium assay. Reducing power was determined on the basis of Fe³⁺–Fe²⁺ transformation in the presence of the extract. In addition to the antioxidant activity, polyphenolic compounds like total phenolics and flavonoids were also measured by spectroscopic method. Results showed that the ethanolic extract of stem is more potent in antioxidant activity than its aqueous extract and ethanolic extract of calli. A significant correlation between antioxidant capacity and polyphenolic content and reducing potential was observed, indicating that phenolic compounds and reducers present in extract are major contributors to the antioxidant potential. Thus, this plant extract could be used as a potent natural antioxidant.     

Novel Tripod Amphiphiles for Membrane Protein Analysis

Integral membrane proteins play central roles in controlling the flow of information and molecules across membranes. Our understanding of membrane protein structures and functions, however, is seriously limited, mainly due to difficulties in handling and analysing these proteins in aqueous solution. The use of a detergent or other amphipathic agents is required to overcome the intrinsic incompatibility between the large lipophilic surfaces displayed by the membrane proteins in their native forms and the polar solvent molecules. Here, we introduce new tripod amphiphiles displaying favourable behaviours toward several membrane protein systems, leading to an enhanced protein solubilisation and stabilisation compared to both conventional detergents and previously described tripod amphiphiles.     

Inversion of the Kirkwood–Buff theory of solutions: application to binary systems

Kirkwood–Buff (K–B) integrals play an important role in characterizing the properties and interactions of various liquid mixtures. However, there exists no method to calculate directly the K–B integrals from the easily available experimental data of ultrasonic velocity and density. An attempt has been made to evaluate the same using these initial parameters. A statistical mechanical theory advanced by Arakawa et al. has been used here, in combination with a semi-empirical formula to compute K–B parameters in the whole concentration range for six binary systems at atmospheric pressure and at 298.15 K.