Sheet-forming abiotic hetero foldamers

Abiotic hetero oligomers, adopting a well-defined extended self-assembled sheet-like structure, derived from conformationally constrained aliphatic and aromatic amino acid residues repeating at regular intervals are reported.     

Stereoselective total synthesis of paecilomycin E and F and its two congeners Cochliomycin C and 6-epi-Cochliomycin C

An efficient and concise approach to the total synthesis of Paecilomycins E (1) and F (2), Cochliomycin C (4) and 6-epi-Cochliomycin C (3) is described. The synthesis involves novel route to the synthesis of Paecilomycin E and F and further conversion to Cochliomycin C and 6-epi-Cochliomycin C. Olefin metathesis and base promoted macro lactonization being the key reactions followed by chlorination to achieve target Cochliomycin C and 6-epi-Cochliomycin C.     

Electrospun PVDF/Cloisite-30B and PVDF/BaTio3/graphene nanofiber mats for development of nanogenerators

The research work mainly focusses on the preparation of nanogenerators based on PVDF/Cloisite-30B and PVDF/BaTiO₃/Graphene polymer nano composites using electrospinning technique. The process parameters were designed and optimized by applying Taguchi's Design of Experiments with L₄ array. Morphology of the polymer composites were studied using Scanning Electron Microscopic images. β-phase Crystallinity of PVDF/Cloisite-30B and PVDF/BaTiO₃/Graphene was 85% and 80% respectively when it is estimated using FTIIR spectroscopic technique. The nanogenerator with PVDF/BaTiO₃/Graphene produced 3.65 V and the same was 3.5 V in case of PVDF/Cloisite-30B nano composites. Better crystallinity was observed in PVDF/Cloisite-30B fiber mats but improved sensitivity of PVDF/BaTiO₃/Graphene resulted in slight enhancement of output voltage. The result indicates the ability of polymer composites as nanogenerator for development of wearable self-powered electronic devices for smart sensing applications.     

Novel silaproline (Sip)-incorporated close structural mimics of potent antidepressant peptide drug rapastinel (GLYX-13)

Rapastinel (GLYX-13) is a C-amidated tetrapeptide drug under clinical development for adjunctive treatment of major depressive disorder (MDD). Rapastinel features two consecutive proline residues centered at the peptide sequence (Thr-Pro-Pro-Thr-NH₂), which are detrimental to its biological activity. In this communication, we report the synthesis of very close structural analogues of rapastinel comprising silaproline (Sip) as proline surrogate. By virtue of its enhanced lipophilicity and metabolic stability, Sip introduction in the native rapastinel sequence is expected to improve its pharmacokinetic profiles.     

Simultaneous LC Estimation of Glimepiride and Metformin in Glimepiride Immediate Release and Metformin Sustained Release Tablets

In the present study, a simple, rapid and precise liquid chromatographic method was developed and validated for the simultaneous determination of glimepiride and metformin in sustained release formulation. The separation was achieved on a Nucleosil 100-5SA column, 250 × 4.6 mm i.d., 5 μm using a mobile phase composed of 1.7 % ammonium dihydrogen phosphate buffer pH 3.0: acetonitrile (70:30 v/v).The instrumental settings were a flow rate of 1.0 ml min⁻¹ and a detector wavelength of 230 nm. The retention time of glimepiride and metformin were 5.1 and 11.3, respectively. The developed method was validated in terms of specificity, sensitivity, linearity, range, accuracy, precision and ruggedness. The proposed method was successfully applied to the sustained release pharmaceutical dosage form for the simultaneous determination of glimepiride and metformin without any interference by excipients.

     

Sugar–amino acid cyclic conjugates as novel conformationally constrained hydroxyethylamine transition-state isosteres

Hydroxyethylamine (HEA) isosteres have previously been shown to display a multitude of biomedical applications. In fact, the first protease inhibitor, saquinavir is an HEA based peptidomimetic. Herein we describe an easy-to-operate synthetic route to a series of carbohydrate-based conformationally constrained hydroxyethylamine (HEA) isosteres featuring amino acid side chains, starting from d-glucose. This class of novel sugar–amino acid-tethered conformationally restricted HEA systems may have bearing in practical application, particularly in the development of conformationally restricted protease inhibitors.     

Silica supported lanthanum triflate mediated synthesis of 5-substituted-1H tetrazoles

Silica supported lanthanum triflate (Ln(OTf)₃-SiO₂) promoted synthesis of 5-substituted 1H-tetrazoles via [3+2] cycloaddition between aromatic/heteroaromatic nitriles and sodium azide is a high product yielding, facile, and straightforward procedure. Non toxicity, recovery, and reusability for three continuous cycles are the noteworthy features of the currently employed heterogeneous catalyst.     

Grafting Vinyl Monomers onto Silk Fibers: Graft Copolymerization of Vinyl Monomers onto Silk Using the Vanadyl Acetylacetonate Complex

Abstract

The graft copolymerization of methyl methacrylate (MMA) onto mulberry silk fibers was studied in aqueous solution using the acetylacetonate oxovanadium (IV) complex. The rate of grafting was investigated by varying the concentration of the monomer and the complex, the acidity of the medium, the solvent composition of the reaction medium, the surfactants, and the inhibitors. The graft yield increases with increasing concentration of the initiator up to 8.75 × 10^?5 mol/L, of the monomer up to 0.5634 mol/L, and thereafter it decreases. Among the various vinyl monomers studied, MMA was found to be most suitable for grafting. Grafting increases with increasing concentration of HCIO₄ and with increasing temperature. Inhibitors like picryl chloride and hydroquinone significantly decrease the extent of grafting. Alcoholic solvents at a solvents/water ration of 10:90 seem to constitute the most favorable medium for grafting. A suitable reaction scheme has been proposed, and the activation energy calculated from the Arrhenius plots.     

Bicyclic amino acid-carbohydrate-conjugates as conformationally restricted hydroxyethylamine (HEA) transition-state isosteres

This communication describes a general synthetic route to bicyclic amino acid-carbohydrate-conjugates, which would be useful as conformationally restricted hydroxyethylamine (HEA) transition-state isosteres. The synthesis was achieved in 12 steps starting from D-glucose. The striking features of this system are the bicyclic rigid core displaying an α-amino acid side chain and hydroxyethylamine moiety--both of which would be potentially important for receptor interactions, leading to various biomedical responses, as described in the literature. Crystal structure investigation suggested extensive intermolecular hydrogen-bonding interactions in this system, involving the backbone amide and hydroxyl groups.     

Concise total synthesis of antiarrhythmic drug dronedarone via a conjugate addition followed intramolecular heck cyclization

A concise, scalable, and an efficient total synthesis for dronedarone ( 2 ) was described using conjugate addition followed by intramolecular Heck cyclization. The other key reaction includes selective reduction of nitro functionality and addition of lithiated terminal alkyne to the aldehyde. The overall yield of this approach is 44% in six steps.