A New Kinetic Method of Processing TA Data

A new method of investigating the kinetic parameters and mechanism functions of a solid phase reaction is presented. This method is to analyze the data based on the use of these data at the same temperature and the same degree of conversion on a series of TA curves with different heating rates, so that the kinetic triplet--the activation energy E, the pre-exponential factor A and the analytical form of the function of conversionf(α) can be obtained. The main advantage of this method is that the values of E and f(α) are obtained respectively, and the determination of f(α) is not under the influence of the value of E and the calculation of the value of E is not influenced by thef(α) either.     

A Conjugate Addition Approach to Diazo-Containing Scaffolds with β Quaternary Centers

Structurally complex diazo-containing scaffolds are formed by conjugate addition to vinyl diazonium salts. The electrophile, a little studied α-diazonium-α,β-unsaturated carbonyl compound, is formed at low temperature under mild conditions by treating β-hydroxy-α-diazo carbonyls with Sc(OTf)₃. Conjugate addition occurs selectively at the 3-position of indole to give α-diazo-β-indole carbonyls, and enoxy silanes react to give 2-diazo-1,4-dicarbonyl products. These reactions result in the formation of tertiary and quaternary centers, and give products that would be otherwise difficult to form. Importantly, the diazo functional group is retained within the molecule for future manipulation. Treating an α-diazo ester indole addition product with Rh₂(OAc)₄ caused a rearrangement to occur to give a 2-(1H-indol-3-yl)-2-enoate. In the case of diazo ketone compounds, this shift occurred spontaneously on prolonged exposure to the Lewis acidic reaction conditions.     

A Facile Convergent Approach to Octopus Polyestrone

IntroductionDendrimersarehighlybranchedlnonodispersepolymers'.ThroughjudiciouschoiceofbranchedbuiIdingblocksandftnctionalgroup,onecanpreciseIycontroltheirshape,dimension,density,polarity,flexibilityandsolubility,givingrisetouniquephysicalandchemicalproperties'.Inthelastdecadedendrimershaveattractedeverincreasingattentioninorganic.super-molecular'polymerchemistryandcoordinationchemistry.andhavebeenwide]yusedascatalyst'-micellemimicry',immuno-diagnostics',andgene-deliveringvectors'etc.Theconnec…     

A New Approach to α—Bromochalcones

α-Bromo benzolymethylene triphenylphosphorane 3 has been synthesized by the reaction of benzoylmethylene triphenylphosphorane 1 with N-bromosuccinimide in the yield of 87% and can react with aromatic aldehydes 4 to give α-bromochalcones 5 in good yields.     

A “Multi-Heavy-Atom” Approach toward Biphotonic Photosensitizers with Improved Singlet-Oxygen Generation Properties

Two trispicolinate 1,4,7-triazacyclonane (TACN)-based ligands bearing three picolinate biphotonic antennae were synthetized and their Yb³⁺ and Gd³⁺ complexes isolated. One series differs from the other by the absence ( L¹ )/presence ( L² ) of bromine atoms on the antenna backbone, offering respectively improved optical and singlet-oxygen generation properties. Photophysical properties of the ligands, complexes and micellar Pluronic suspensions were investigated. Complexes exhibit high two-photon absorption cross-section combined either with NIR emission (Yb) or excellent ¹O₂ generation (Gd). The very large intersystem crossing efficiency induced by the combination of bromine atom and heavy rare-earth element was corroborated with theoretical calculations. The ¹O₂ generation properties of L² Gd micellar suspension under two-photon activation leads to tumour cell death, suggesting the potential of such structures for theranostic applications.     

The Reaction of Phosphoryl Chlorides with Enamines - A New Approach to β-Ketophosphonates

Abstract

Several approaches are available for the preparation of β-ketophosphonate esters. A Michaelis-Arbuzov approach using the reaction of an α-halo ketone with a trialkyl phosphite may in certain instances be controlled to favor the preparation of the target materials. However, an alternative pathway leading to the formation of vinyl phosphate esters often predominates. (This reaction system has recently been reviewed by Borowitz and Borowitz.¹) An alternative approach is that developed in recent years by Wiemer, et al.² involving the rearrangement of vinyl phosphate esters to the β-ketophosphonates.     

A Novel Approach to Synthesis of Tricyclic Diterpenoid

A novel approach has been found and the first total synthesis of (±)-Salvirecognine was accomplished by using it. In which intramolecular cyclization and Friedel-Crafts alkylation took place simultaneously to afford key intermediates for synthesis of aromatic tricyclic diterpenoids OMe PPA O O O OMe 1 2 Scheme 1 As shown in Scheme 1 intramolecular cyclization and Friedel-Crafts alkylation took place simultaneously when compound 1 was treated by PPA at 125 ℃. In which the i-pr…     

A “Low-Molecular” Approach to the Identification of Microorganisms by MALDI Mass Spectrometry

A new approach to the identification of microorganisms is presented. It includes the transformation of their MALDI mass spectra aimed at reducing mass scale by one order of magnitude and the use of standard software for building mass spectral libraries of low-molecular compounds and library searches. A library of 728 transformed (“rescaled”) mass spectra of 182 strains for some Streptococcus species was built. With this library, the rate of true microorganism identification was estimated by cross-comparison between library mass spectra (internal validation of the approach). The true identification rate was 84% for three Streptococcus species, which corresponds to the average trueness of species identification by MALDI as found in the literature. The proposed approach to identification can be considered as a method of choice for solving identification problems under consideration.     

A Scalable Approach to Obtaining Orthogonally Protected β-d-Idopyranosides

A practical method to obtain orthogonally protected d-idopyranose from d-galactose has been developed, which is the first method to enable synthesis of the challenging β-d-idopyranoside linkage. The method relies on a key double inversion at O-2 and O-3 in an easily prepared d-galactose derivative, which proceeds regio- and stereoselectively through a 2,3-anhydrotalopyranoside; reaction using a selection of alkoxides affords exclusively the 3-O-alkylidopyranoside, which can be used to generate an orthogonally protected monosaccharide. The process is scalable and requires minimal purification, so it could be used to produce building blocks to aid in the synthesis of various β-idopyranose-containing oligosaccharide targets to further probe their biological functions.     

A Novel Approach to the Prediction of Transmembrane Proteins

A novel method based on continuous, wavelet transform (CWT) for predicting the number and location of helices in membrane proteins is presented. The PDB code of lyst is chosen as an example to describe the prediction of transmembrane helices (HTM) by using CWT. The results indicate that CWT is a promising approach for the prediction of HTM.     

A Facile Approach to γ,δ-Unsaturated Amides

A convenient synthesis of γ-substituted γ,δ-unsaturated amides by modified Horner-Wadsworth-Emmons reaction of γ-diethoxyphosphorylbutyric acid (1) with aldehydes is described.     

A Concise Approach to the Synthesis of L-and D-Deoxyribose

2 Ｄｅｏｘｙ Ｄ ｒｉｂｏｓｅ (1) ,ｔｈｅｓｕｇａｒｐａｒｔｏｆＤＮＡ ,ｉｓｏｎｅｏｆｔｈｅｍｏｓｔｉｍｐｏｒｔａｎｔｓｔａｒｔｉｎｇｍａｔｅｒｉａｌｎｏｔｏｎｌｙｆｏｒｔｈｅｐｒｅｐａｒａｔｉｏｎｓｏｆｎｕｃｌｅｏｓｉｄｅｓ ,ｎｕｃｌｅｏｔｉｄｅｓ ,ＤＮＡａｎｄｔｈｅｉｒａｎａｌｏｇｓ,ｂｕｔａｌｓｏｆｏｒｔｈｅｓｙｎｔｈｅｓｅｓｏｆａｎｕｍｂｅｒｏｆｏｔｈｅｒｂｉｏ ａｃｔｉｖｅｃｏｍｐｏｕｎｄｓ .1Ｒｅｃｅｎｔｌｙｉｔｓａｎｔｉｐｏｄｅ 2 ｄｅｏｘｙ Ｌ ｒｉｂｏｓｅ (2 )ｗａｓａｌｓｏａｔｔｒａ…     

A Novel Stereoseletive Approach to (E)-Vinylic Selenides

Vinylicselenidesareimportantintermediatesinorganicsynthesis.andtheirpromisingpotentialcouldbeanticipatedbythecombinationofthespecialreactivityofseleniumandthereactivit}'associatedwithcarbon-carbondoublebond.particularly'the}'areextremely"set'ulinhighlystereoselectiveC-Cbondformationprocess'.Variouspreparationsofthesecompoundshavebeenreported,butmostofthesemethodsinvolvedthedisposalofhighlytoxicselenides,suchasRSeX,RSeSeRandRSeH.Futhermore,manyofthesemethodsarenotstereocontrolledandgivemixt…     

A Facile Approach to Regioselective 1-O-Deacylation of Peracylated Glycopyranoses

The regioselective 1-O-deacylation of peracylated glycopyranoses 1a-d with zinc chloride and zinc oxide in THE/MeOH gave the corresponding tetra-O-acylglycopyranoses 2a-d in good yields.     

Chemometrics Assisted Formulation of Glimepiride Nanosuspension for Solubility Enhancement in Diabetic Therapy—A Systematic Approach

Glimepiride (GLM), a third-generation sulfonylurea oral hypoglycemic medication, is used to treat type II diabetes. Admittedly, it has a low bioavailability, a relatively short half-life (t_1/2), and high toxicity. To address the issue, a nanosuspension of poorly soluble GLM is designed using a Quality-by-Design (QbD) method, to enhance its solubility. Prospective risk factors are identified and assessed using Critical Material Attribute (CMAs) and Critical Processing Parameter (CPPs) to evaluate the targets by Taguchi orthogonal array (OA) design and to study the effects of formulation and process variables on dependent variables. The amount of Polyvinylpyrrolidone (PVP) (X2), agitation time (X5), and concentration of Poloxamer (X7) are found as significant parameters (p < 0.05), and are further optimized using the Box Behnken Design as response surface methodology model. The optimized GLM nanosuspension 1) has mean particle size (PS), zeta potential, viscosity (VS), and percentage cumulative drug release (CDR%) of 258.17 nm, −25.2 mV, 1.087cPs, and 98.52%, respectively. The pattern of drug release is fitted to Non-Fickian kinetics. The study results in an economic and efficient nano formulation with enhanced solubility.     

A Simple Approach to Control the Growth of Non-spherical Gold Nanoparticles

A simple method to prepare the non-spherical gold particles was developed. The result solution included trigonal, truncated trigonal, hexagonal layers, and a pseudo-pentagonal shaped gold nanocrystals. The key factor is to control the relative rates of nucleation and cluster growth in this method. These attributes make seeding growth method as a useful tool in the fabrication of colloidal metal materials. A longitudinal plasmon resonance of 866 nm was observed, which is in the near-IR spectral regions (600-1000 nm). The excellent optical properties as near-IR labels are used to develop highly sensitive analvsis method.     

A Facile,Sequential Multicomponent Approach to N-Aminoamidinothioureas—Versatile Synthons to Bioactive Heterocycles

A sequential, three-component approach for the rapid and convenient one-pot synthesis of N-aminoamidinothioureas is reported. The improved synthetic strategy involves the selective blocking of amino functionality in aminoguanidine by Schiff base formation with carbonyl compounds to generate corresponding N-(alkylidene/arylidene)aminoguanidines and their subsequent in situ condensation with isothiocyanate. The structural motif incorporates three points for diversity multiplication, making it a suitable candidate for combinatorial synthesis. The generality of the improved procedure was established by synthesizing a series of diverse compounds through solution phase parallel synthesis by varying the carbonyl and isothiocyanate components. The newly synthesized compounds were characterized by spectral methods. The developed synthetic procedure employs mild reaction conditions, and individual steps are carefully optimized for easy automation.     

Reaction of 1-Iodoalkynes with Tin Metal: A New Approach to the Sn–Csp Bond Formation

Russian Journal of General Chemistry - Tin iodoalkynylides were synthesized by the reaction of 1-iodoalkynes with tin metal. The scope of the reaction and the composition of the resulting mixtures...     

Hydrophobicity Measurements by HPLC: A New Approach to π Constants

Abstract

A classical HPLC method of measuring log P_o/w has been reevaluated and applied to 107 different mono- and disubstituted benzenes. The contribution of several functional groups has been estimated through multiple regression analysis, obtaining statistically significant mean π?_m values.

Deviations of experimentally determined log P? values for a set of ortho-, meta-, and para- disubstituted isomers from the “simple additive” model have been evaluated, and interpretations are suggested.