A tactical approach for the synthesis of novel β-lactam-substituted,polycyclic-fused isoxazolidine derivatives via an intramolecular [3+2] cycloaddition reaction

The synthesis of functionalized β-lactam-substituted, tricyclic chromenoisoxazolidine and tetracyclic naphthopyranoisoxazolidine derivatives by intramolecular nitrone cycloaddition reaction is described. The O-allyl hydroxyaldehyde derivatives, obtained from Baylis–Hillman adducts (BHA) derived from β-lactam aldehyde underwent intramolecular cycloaddition reaction to give β-lactam-substituted, polycyclic isoxazolidine derivatives in good yield. All the products were confirmed by spectral analysis. The products with a β-lactam substituent may find good applications in biological chemistry.     

Silica sulfuric acid mediated synthesis of naphtho[2,1-b]furan derivatives and development of one-pot multicomponent synthesis of substituted pyrazole derivatives

Silica sulfuric acid (SSA) mediated synthesis of naphtho[2,1-b]furan derivatives starting from β-nitrostyrene derivatives and β-naphthol derivatives under solvent-free conditions have been developed. The scope of SSA as a heterogeneous catalyst is extended to one-pot multicomponent reaction for the synthesis of functionalized pyrazole derivatives under solvent-free conditions from readily available β-nitrostyrene derivatives, acetyl acetone, and hydrazine hydrate. The synthetic methods have significant advantages such as solvent-free conditions, simple operation, shorter reaction times, ease and clean isolation procedures, and very good yields of products.     

Diastereoselective synthesis of β-amino ketone and acid derivatives by palladium-catalyzed conjugate addition

The first diastereoselective synthesis of β-amino ketone and β-amino acid derivatives by palladium-catalyzed conjugate addition of arylboronic acids to chiral β-enamino ketones and β-enamino esters is reported. The catalytic system employing (S)-4-(tert-butyl)oxazolidin-2-one as the chiral auxiliary in water under an air atmosphere provides β-amino ketone and β-amino acid derivatives in high yields with excellent diastereoselectivity.     

New β-cyclodextrin derivatives possessing biologically active saccharide antennae

Abstract

The synthesis of monosubstituted β-cyclodextrin derivatives having the monosaccharides, β-D-glucose, β-D-galactose, α-D-mannose, β-L and β-D-fucose linked to the macrocycle via a C9 spacer chain is described. The approach is based on the highly efficient coupling of the NCS sugar derivatives to monomethyl nonanedicarboxylate to generate a stable amido linkage. The NMR studies show the saccharide antennae to be oriented into the environment and not towards the CD cavity.     

“Three-in-one” Complexes Formed by Anionic Guests and Monosubstituted Cationic Alkyldiamino β-Cyclodextrin Derivatives

The effect of electrostatic interactions on the complexation of ionic guests by charged β-cyclodextrin (βCD) derivatives is reviewed. Special attention is paid to the numerous studies concerning the effect of electrostatic interactions on (i) the complexation of fluorescent and UV probes; (ii) the catalytic and chiral recognition properties of βCD derivatives; and (iii) the complexation of two bile salts (sodium cholate, NaC, and sodium deoxycholate, NaDC). The formation of three-in-one complexes between NaC and alkyldiamino βCD derivatives is also presented.     

A method for determining absolute configuratiom of β-amino acids by CD spectra of their DNP derivatives

Aromatic β-amino acids were converted to the Dnp derivatives, and aliphatic ones to Dnp-pMA derivatives. The sign of the Cotton effect near 400 nm reflected the configuration at the β-position without exception. Thus, the relation seems to afford a new reliable method for determining the absolute configuration of β-amino acids.     

Competitive growth of α- and β-crystals in isotactic polypropylene with versatile nucleating agents under shear flow

Sorbitol derivatives, the conventional α-nucleating agents of isotactic polypropylene (iPP), are discovered to induce β-phase iPP under normal crystalline conditions. Combined effects of shear flow and sorbitol derivatives on the crystallization of iPP were investigated by using differential scanning calorimetry, wide-angle X-ray diffraction, and small-angle X-ray scattering. In the nucleation stage, sorbitol derivatives induce both α- and β-nuclei, while shear flow and the interactions between shear and sorbitol derivatives enhance the amount of α-nuclei. In the growth stage, the epitaxial growth of β-crystals on shear-induced α-row nuclei occurs. As the shear rate increases, more epitaxial β-crystals form due to the increase of α-row nuclei, further increasing the content of β-crystals. Under high shear rate, the presence of sorbitol derivatives and shear flow exhibit a synergistic interaction on increasing the content of β-crystals. Moreover, α-nuclei, which arise from the interaction between shear and sorbitol derivatives, emerge earlier than shear-induced α-row nuclei.

β-环糊精流动相添加剂在手性分离中的应用综述

介绍了β-环糊精的基本性质,综述了β-环糊精及其衍生物作为流动相添加剂在高效液相色谱和高效毛细管电泳手性分离中的应用,并探讨了其作为手性流动相添加剂的特点.指出β-环糊精是良好的手性识别体,不仅可作为色谱手性固定相,还可作为流动相添加剂,用于手性对映体的拆分.     

GC and MS Properties of β-Blockers as tert-Butyldimethylsilyl Derivatives and as Ethoxycarbonyl/Trimethylsilyl Derivatives

Fourteen β-blockers in pre-dried free base forms were simultaneously converted into tert-butyldimethylsilyl (TBDMS) derivatives in one-step. As a different approach, β-blockers were directly transformed into N-ethoxycarbonyl (EOC) derivatives in aqueous solution, followed by extraction and trimethylsilyl (TMS) derivatization. The retention index sets measured by DB-5 and DB-17 dual-column GC were characteristic for each β-blocker as TBDMS- and EOC/TMS derivatives. Their characteristic fragmentation patterns obtained by GC–MS facilitated easier peak identification of each β-blocker. The overall EOC/TMS method for assays of 14 β-blockers in aqueous solution was linear with acceptable precision and accuracy.     

Preparation and chromatographic evaluation of β-cyclodextrin derivative CSPs bearing substituted phenylcarbamate groups for HPLC

Five β-cyclodextrin (β-CD) derivatives bearing substituted phenylcarbamate/3-(triethoxysilyl)propylcarbamate groups at the 2-, 3-, and 6-positions of glucose unit and another five derivatives containing benzoate at the 2-position and substituted phenylcarbamate/3-(triethoxysilyl)propylcarbamate groups at the 3- and 6-positions were synthesized using the regioselective esterification method. The obtained β-CD derivatives were efficiently immobilized onto the silica gel through the intermolecular polycondensation of a small amount of the triethoxysilyl groups, which were used as the chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). The chiral separation properties of these CSPs were evaluated under the normal-phase HPLC. The effects of solvent polarity and the side chain structures of β-CD derivatives on the chiral recognition ability of the immobilized CSPs were investigated. Among these β-CD derivative CSPs, 2,3,6-tris(3,5-dichlorophenylcarbamate)-β-CD CSP showed a relatively high chiral recognition ability for the studied racemates. The regioselective esterification at the 2-position of glucose unit in the β-CD decreased the chiral recognition ability at the same conditions. For some racemates, the β-CD derivative CSPs showed chiral recognition abilities comparable or better to some chemical bonded β-CD derivative CSPs and 3,5-dichloro- and 3,5-dimethylphenylcarbamates of cellulose and amylose CSPs.     

Determination of Enantiomeric Purity and Absolute Configuration of β-Lactams by High-Performance Liquid Chromatography on Chiral Columns

Enantiomers of β-lactams bearing aryl, furyl or styryl substituents in the 4-position were chromatographically separated by means of high-performance liquid chromatography on chiral column packed with amino acid-derived chiral stationary phase. Separation factors are generally modest. To improve further the resolution of enantiomers, the rings of these β-lactams were opened with octanol in acidic conditions and converted into N-3,5- dinitrobenzoyl ester derivatives of the resulting β-amino acids. Enantiomers of these derivatives are efficiently separated on an amide-derived chiral stationary phase. The chromatographic separations enable accurate determination of optical purity of the chiral β- lactams, prepared from homochiral ester enolate-imine condensation. The absolute configuration of the major enantiomer of the β-amino acid derivatives was determined from elution order on a chiral column.     

Microwave-assisted novel and efficient one-pot synthesis of fused steroidal and non-steroidal isothiazoles

An efficient microwave promoted one-pot synthesis of steroidal and non-steroidal isothiazole derivatives from corresponding β-bromo-α,β-unsaturated aldehydes has been described using a sodium thiocyanate-urea system. The β-bromo-α,β-unsaturated aldehydes derivatives are efficiently synthesized from corresponding cyclic ketones using Vilsmeir formylation reaction. The synthetic protocol is also applied for the synthesis of antifungal brassilexin.     

The Knoevenagel-Doebner reaction on 1,2-O-(2,2,2-trichloroethylidene) derivatives of D-gluco- and D-manno-furanose

The synthesis of new α,β-unsaturated furanuronic acid derivatives of α-gluco-, β-gluco- and β-manno-chloraloses via a convenient one pot procedure using the Knoevenagel-Doebner reaction approach are described. The dialdofuranose derivatives were reacted with malonic acid under Knoevenagel-Doebner reaction conditions and (E)-α,β-unsaturated furanuronic acid derivatives were obtained.     

Cyclodextrin derivatives in the GC separation of racemic mixtures of volatile compounds: Part IV

This paper reports the chromatographic performance of columns coated with 2,3,6-trimethyl-α-, β-, and γ-cyclodextrins (2,3,6-TriMe-α,- β-, and γ-CD) and their derivatives 2,6-dimethyl-3-trifluoroacetyl-α-, β-, and γ-cyclodextrins (2,6-DiMe-3-TFA-α-, β-, and γ-CD), all six diluted in polysiloxane, for the separation of the enantiomers of volatile compounds. The influence of column length and film thickness on separation is reported. Phenomena related to reproducibility and consistency, over a period of time, of columns prepared with these CD derivatives are also discussed, and a possible solution to some drawbacks reported here is proposed.     

Catalytic asymmetric synthesis of stereoisomers of 1-C-n-butyl-LABs for the SAR study of α-glucosidase inhibition

We achieved synthesis of seven stereoisomers of 1-C-n-butyl-L-iminofuranose derivatives using catalytic asymmetric alkylation and Negishi coupling as key reactions. The synthetic strategy based on these key reactions was quite useful, since both α- and β-iminofuranoses could be obtained by switching the chirality of the ligand employed for the AAA reaction. The common intermediates for α- and β-isomers were subjected to further manipulations to install a diol unit at C2 and C3 to give the desired stereoisomers of L-iminofuranose derivatives. We achieved the preparation of all stereoisomers of 1-C-n-butyl-L-iminofuranose derivatives, with the exception of β-lyxo type iminofuranose. It is noteworthy that a synthetic route for many stereoisomers of iminofuranose derivatives was developed. Unfortunately, none of the L-iminofuranoses obtained showed inhibitory activity against the α-glycosidases examined—e.g., maltase, sucrase, and isomaltase.     

Kinetic resolution of N-acyl-β-lactams via benzotetramisole-catalyzed enantioselective alcoholysis

The first nonenzymatic kinetic resolution of β-lactams has been achieved. Alcoholysis of their N-aroyl derivatives in the presence of a simple chiral acyl transfer catalyst, benzotetramisole, produces β-amino acid derivatives with excellent enantioselectivity.     

Synthesis and characterization of copolymers of β-cyclodextrin derivatives

Cyclodextrins (CDs) are cyclic oligosaccharides made up of d-glucose units connected by 1,4-glucosidic linkages. β-CD is a cyclical starch derivative containing seven glucopyranose units. β-CD derivatives have characteristic property of larger surface area, robust mechanical strength, high surface to volume ratio, electrical and optical properties for analyte determination, good dispersion, easy removal of the template, surface modification, functionalization and handling capacity. In this work, an attempt is made to prepare succinyl-β-CD-acrylamide (S-β-CD-AA) copolymer and β-CD-malic anhydride (β-CD-MAH) copolymer. For the synthesis of S-β-CD-AA, S-β-CD derivative is prepared and further, acrylamide (AA) along with cross-linker undergoes free radical copolymerization for the formation of gel like product. The degree of succinylation (DS) of β-CD derivative is estimated. S-β-CD-AA copolymer showed potential swelling, and deswelling characteristic. Another copolymer is prepared from β-CD malic anhydride derivative. Further, the derivative is treated with cellulose and ethylene diamine tetra acetate (EDTA) to form β-CD-MAH copolymer. The two derivatives are characterized by several techniques. Thermal stability of these copolymers is estimated with the help of thermogravimetric analysis. The basic characterization of the presence of functional groups is done using UV–visible spectroscopy, and infrared spectroscopy. The elemental analysis helped to estimate C, H, N, S in the synthesized compounds. The surface morphology characterization is done with the help of scanning electron microscopy. X-ray diffraction analysis helped in determination of crystal structure of β-CD-MAH. β-CD derivatives prepared may be potential candidate to prepare inclusion complex, in drug delivery, drug loading and several similar applications.     

Asymmetric synthesis of chiral β-hydroxy-α-amino acid derivatives by organocatalytic aldol reactions of isocyanoesters with β,γ-unsaturated α-ketoesters

The first organocatalytic asymmetric aldol reaction of isocyanoesters with various β,γ-unsaturated α-ketoesters has been described. Using cinchona alkaloid-derived bifunctional thiourea as the catalyst, chiral β-hydroxy-α-amino acid derivatives can be obtained in excellent yields and enantioselectivities (up to 95% yield and 92% ee) after acidic hydrolysis. This protocol provides a straightforward method to access multiple substituted β-hydroxy-α-amino acid derivatives with high enantiomeric purity.     

不对称二苯乙炔系列衍生物的二阶非线性光学性质的ZINDO-SOS 研究

在ZINDO方法基础上,按完全态求和(SOS)公式编制了计算分子二阶非线性光学系数β~i~j~k,β~μ的程序;研究了不对称二苯乙炔系列衍生物的结构和非线性光学性质;计算了不对称二苯乙炔系列衍生物的UV光谱,偶极矩,β~μ,β~0,μβ,μβ~0,及激发态电荷转移;考察了分子共轭链长、给电子基团对β~μ的影响。并对上述结果在微观上给予了解释。     

Synthesis of β-Amino Acid Derivatives

In recent years, β-amino acids and their derivatives have attracted considerable attention due to their occurrence in biologically active natural products, such as dolastatins,cyclohexylnorstatine and Taxol. β-Amino acids also find application in the synthesis of β-lactams,piperidines, indolizidines. Moreover, the peptides consisting of β-amino acids, the so-called β-peptides, have been extensively studied recently. Consequently, considerable efforts have been directed to the synthesis of β-amino acids and their derivatives1. In particular, stereoselective synthesis of β-amino acids has been a challenging project, and there are only limited methods available. In this presentation, we report our efforts in this area.