Synthesis of 8‐Desoxythunberginol A and (±)‐8‐Desoxy‐3,4‐Dihydrothunberginol A

A two step synthesis of title isocoumarin isolated from Homalium longifolium and its conversion into corresponding 3,4‐dihydroisocoumarin has been described. 3,4‐Dimethoxybenzoyl chloride on condensation with homophthalic acid afforded 3‐(3′,4′‐dimethoxyphenyl)isocoumarin which was demethylated to furnish the 8‐desoxythunberginol A, whereas its sequential saponification, reduction and demethylation yielded the (±)‐8‐desoxy‐3,4‐dihydrothunberginol A. The synthesized compounds were examined in vitro for antibacterial activity.     

Simultaneous Determination of Metformin Hydrochloride, Cyanoguanidine and Melamine in Tablets by Mixed-Mode HILIC

A simple and specific hydrophilic interaction liquid chromatography (HILIC) procedure for the quantification of metformin hydrochloride (MFH) and its impurities in bulk pharmaceuticals and finished dosage forms has been developed. The method is based on hydrophilic interaction of the analytes with silica. The influence of the weaker solvent, acetonitrile, pH and the nature and ionic strength of the buffer was studied. Linearity range and percent recoveries for MFH were 100–400 μg mL⁻¹ and 100.62%, respectively. Good validation data were obtained for all compounds. The method separates impurities cyanoguanidine (CGD), melamine (MLN) and other degradation products with a run time of less than 13 min. Degradation studies involved thermal stress, hydrolysis at various pHs and chemical and photolytic oxidation.     

Review on asymmetric synthetic methodologies for chiral isoquinuclidines; 2008 to date

Isoquinuclidines constitute the central structural nucleus of numerous biologically active natural products, for example, iboga alkaloids such as ibogamine and catharanthine as well as non-indole-containing alkaloids such as the dioscorine and the cannivonines. Furthermore, in medicinal and pharmaceutical chemistry, the isoquinuclidine core is commonly employed as a rigid azabicyclic scaffold, thus providing significant precursors in the synthesis of numerous valuable alkaloids. Summarizing well-organized approaches to access the chiral isoquinuclidine structural centerpiece signifies a significant endeavor not only for developing biologically active natural products but also enhancing biological researches that can lead to possible drug discovery. Over time, the values and methodologies for the asymmetric synthesis of chiral isoquinuclidines are increasing; hence to advance asymmetric synthesis, this review combines and discusses the pros and cons of each synthesis techniques from 2008. This review should be helpful for promoting further developments of asymmetric synthetic methodologies and for medicinal chemistry.     

Synthesis and Crystal Structure of N-(Biphenyl-2-thiocarbamoyl)-4-(1,3-dichlorophenyl) Carboxamide

The synthesis of the title molecule was achieved by the reaction of 2,4-dichlorobenzoyl chloride with potassium thiocyanate in 1:1 molar ratio in dry acetonitrile to afford the corresponding isothiocyante in situ followed by the treatment with 2-aminobiphenyl. The structure of the target compound was established by elemental analysis, FTIR, 1H, 13 C NMR and mass spectroscopy and unequivocally confirmed by the crystallographic data. The title compound crystallizes in the monoclinic space group P21/n with a = 13.356(2), b = 7.0761(11), c = 20.539(3) , β = 105.723(4)°, V = 1868.5(5) 3 and Z = 4.     

Synthesis and Crystal Structure of 3,5-Dichloro-N-(2-methoxyphenyl)benzamide

<正>The title compound was synthesized by the direct reaction of 3,5-dichlorobenzoic acid with 2-methoxyaniline in the presence of DCC and HOBT. The structure was supported by the spectroscopic data and unambiguously confirmed by the single-crystal X-ray diffraction studies. It crystallizes from a methanol solution in the monoclinic space group P2_1/c with unit cell dimensions of a = 4.9369(16), b = 13.351(5), c = 20.168(7), β = 96.755(8)°, V = 1320.1(8)~3 and Z = 4.     

New N‐(Aryl)‐5‐((quinolin‐8‐yloxy)methyl)‐1,3,4‐oxa/Thiadiazol‐2‐amines and 4‐Aryl‐5‐((quinolin‐8‐yloxy)methyl)‐2H‐1,2,4‐triazole‐3(4H)‐thiones,Synthesis and Characterization

In this study, methyl 2‐(quinolin‐8‐yloxy) acetate ( 2 ) obtained by reaction of 8‐hydroxyquinoline ( 1 ) with methyl chloroacetate was condensed with hydrazine hydrate to afford the carbohydrazide ( 3 ). Thio/semicarbazide derivatives ( 4a , 4b , 4c , 4d , 4e , 4f , 4g ) were obtained by treatment of the 3 with substituted phenyl iso/thioisocyanates. The 4a , 4b , 4c , 4d , 4e , 4f , 4g on acidic and basic intramolecular cyclization led to N‐(aryl)‐5‐((quinolin‐8‐yloxy)methyl)‐1,3,4‐oxa/thiadiazol‐2‐amines ( 5a , 5b , 5c , 5d , 5e , 5f , 5g ) and 4‐aryl‐5‐((quinolin‐8‐yloxy)methyl)‐2H‐1,2,4‐triazole‐3(4H)‐thiones ( 6a , 6b , 6c , 6d , 6e , 6f , 6g ), respectively. All the synthesized compounds were characterized by spectroscopic techniques and elemental analyses. The thiosemicarbazide ( 4c ) was also confirmed by X‐ray crystallography.     

An efficient synthesis of 3,5‐dimethoxyhomophthalic acid,a key intermediate for synthesis of natural isocoumarins

3,5‐Dimethoxyhomophthalic acid was prepared efficiently in three steps, from 3,5‐dimethoxybenzyl bromide via rhodium‐catalyzed direct carbonylation to 3,5‐dimethoxyphenylacetic acid followed by successive o‐formylation and oxidation. Isocoumarins related to agrimonolide and achlisocoumarin 1 were prepared in single step by condensation of the homophthalic acid with appropriate acid chlorides.     

The adaptive synchronization of fractional-order Liu chaotic system with unknown parameters

In this paper, the chaos control and the synchronization of two fractional-order Liu chaotic systems with unknown parameters are studied. According to the Lyapunov stabilization theory and the adaptive control theorem, the adaptive control rule is obtained for the described error dynamic stabilization. Using the adaptive rule and a proper Lyapunov candidate function, the unknown coefficients of the system are estimated and the stabilization of the synchronizer system is demonstrated. Finally, the numerical simulation illustrates the efficiency of the proposed method in synchronizing two chaotic systems.     

Reduction of Methylene Green by EDTA:Kinetic and Thermodynamic Aspects

The reduction of methylene green (MG) into protonated leuco dye with ethylenediamine tetraacetic acid (EDTA) in aqueous alkaline medium was studied spectrophotometrically at λ_max 660 nm. EDTA behaved as an effective electron donor during the reduction of MG in an aerobic condition. Consumption of EDTA in the reduction of MG means that it is oxidized. This is an unexpected result since EDTA does not normally function as a reducing agent. The nitrogen-containing chelating agents with secondary or tertiary nitrogen behaved as an electron donor in photochemical reaction of dye. The rate of reduction depends upon pH in the same way as the base titration of EDTA. Effects of salt and temperature have been investigated for the reduction process. The salting agent KNO₃ has been found to uniquely enhance the rate of reduction of MG by EDTA in the aerobic condition. Detailed kinetic and thermodynamic aspects have been discussed to realize the interaction between MG and EDTA. Kinetic studies revealed that reaction was sensitive and regeneration of oxidized form of the dye was observed. Reversible first order reaction kinetics with respect to EDTA, MG and NaOH was found.