聚L-赖氨酸修饰电极循环伏安法测定药剂中的多巴胺

用循环伏安法制备了聚L-赖氨酸修饰玻碳电极,研究多巴胺在聚L-赖氨酸修饰电极上的电化学行为,建立了循环伏安法测定多巴胺的新方法。实验结果表明,在pH7.0的磷酸盐缓冲溶液中,扫描速率为150mV/s,循环扫描电位在-0.3~0.6V时,多巴胺在聚L-赖氨酸修饰玻碳电极上出现一对灵敏的氧化还原峰,峰电位分别为Epa=0.175V,Epc=0.146V(相对饱和甘汞电极);测定多巴胺的线性范围为1.0×10-3~1.0×10-5mol/L和1.0×10-5~8.0×10-9mol/L,方法检出限1.0×10-9mol/L。用于药剂中多巴胺的测定。     

银掺杂聚L-天冬氨酸修饰电极的制备及对多巴胺的测定

利用循环伏安法将银与L-天冬氨酸聚合修饰在玻碳电极表面,制成银掺杂聚L-天冬氨酸修饰电极,研究了多巴胺在此电极上的电化学行为,建立了循环伏安法测定多巴胺的新方法.在磷酸盐缓冲溶液(PBS, pH 7.0)中,扫描速率为50 mV/s时,多巴胺在修饰电极上产生一对氧化还原峰,Epa=0.191 V,Epc=0.161 V.用循环伏安法进行测定时,峰电流与多巴胺浓度分别在3.0×10-7 ～1.0×10-5 mol/L和1.0×10-5 ～5.0×10-4 mol/L内呈良好的线性关系; 检出限为5.0×10-8 mol/L.用于药物和尿样中多巴胺的测定,结果满意.     

聚L-谷氨酸修饰电极的制备及对多巴胺的测定

用循环伏安法制备了聚L-谷氨酸修饰玻碳电极,研究了多巴胺在聚L-谷氨酸修饰电极上的电化学行为,建立了测定多巴胺的新方法。在pH 7.5的磷酸盐缓冲溶液中,用循环伏安法测定多巴胺的线性范围为1.0×10-4~4.0×10-8mol.L-1,检出限为5.0×10-9mol.L-1。该法用于药剂中多巴胺的测定,结果满意。     

聚L-色氨酸修饰电极的制备及对多巴胺的测定

研究了聚L 色氨酸修饰玻碳电极的制备及其多巴胺在该修饰电极上的循环伏安特性,建立了循环伏安法测定多巴胺的电化学分析新方法。在pH7.0的磷酸盐缓冲溶液中,用该电极测定多巴胺的线性范围为:2.0×10-6～5.0×10-4mol L,检测限为1.5×10-7mol L。已用于药剂中多巴胺的测定。     

聚L-精氨酸修饰电极存在下同时测定多巴胺和肾上腺素

用循环伏安法制备了聚L-精氨酸修饰玻碳电极,研究了多巴胺和肾上腺素在修饰电极上的电化学行为,建立了同时测定多巴胺和肾上腺素的新方法。在pH7.5的磷酸盐缓冲溶液中,多巴胺在修饰电极上产生一对氧化还原峰,峰电位分别为0.276V和0.059V;肾上腺素在修饰电极上产生3个氧化峰和一个还原峰,峰电位分别为0.262V、0.121V、-0.126V和-0.316V(对Ag/AgCl电极)。多巴胺和肾上腺素同时存在时ΔEpc=375mV,用还原峰对多巴胺和肾上腺素同时测定的线性范围分别为8.0×10-7~5.0×10-4mol/L和5.0×10-7~5.0×10-5mol/L;检出限分别为3.0×10-7mol/L和1.0×10-7mol/L。大量的抗坏血酸和尿酸不干扰测定,用于人尿液中多巴胺和肾上腺素样品的同时测定,结果满意。     

聚L-酪氨酸修饰电极的制备及对多巴胺的测定

用循环伏安法制备了聚L 酪氨酸修饰玻碳电极,研究了多巴胺在聚L 酪氨酸修饰电极上的电化学行为,建立了循环伏安法测定痕量多巴胺的新方法。多巴胺在pH7.0的磷酸盐缓冲溶液中,在聚L 酪氨酸修饰玻碳电极上产生一对灵敏的氧化还原峰,峰电位分别为Epa=189mV,Epc=131mV。循环伏安法测定多巴胺的线性范围为1.0×10-3～1.0×10-8mol/L,检出限:1.0×10-9mol/L。方法可用于药剂中多巴胺的测定。     

银掺杂聚L-甲硫氨酸修饰电极同时测定对苯二酚和邻苯二酚

用循环伏安法制备了银掺杂聚L-甲硫氨酸修饰玻碳电极,研究了对苯二酚和邻苯二酚在该修饰电极上的电化学行为,建立了同时测定对苯二酚和邻苯二酚的新方法.研究发现,在pH=5.0的磷酸盐缓冲溶液中,扫速为100 mV/s时,对苯二酚和邻苯二酚在银掺杂聚L-甲硫氨酸修饰玻碳电极上均出现1对氧化还原峰,峰电位分别为:Epa=0.228 V、Epc =0.162 V和Epa=0.347 V、Epc =0.287 V,二者的氧化峰电位差达119 mV,还原峰差达125 mV.在最佳的条件下,用差分脉冲伏安法同时测定邻苯二酚和对苯二酚的线性范围为3.00 ×10-6～1.00 ×10-4mol/L,检出限为8.0×10-7 mol/L(对苯二酚)和5.0×10-7 mol/L(邻苯二酚).此法用于废水样中对苯二酚和邻苯二酚的测定,获得满意结果.     

聚甲基蓝修饰电极的制备及对多巴胺的测定

研究了聚甲基蓝修饰电极的制备及其多巴胺在聚甲基蓝修饰电极上的循环伏安特性,建立了循环伏安法测定多巴胺的新方法。在pH7.0磷酸盐缓冲溶液中,峰电流与多巴胺浓度在8.0×10-7～5.0×10-4mol L范围内呈良好的线性关系,检出限为5.0×10-8mol L。已用于药剂中多巴胺的测定。     

尿酸在聚L-苯丙氨酸修饰电极上的伏安测定

采用循环伏安法制备了聚L-苯丙氨酸薄膜修饰玻碳电极,研究了尿酸在该修饰电极上的电化学行为,循环伏安法测定了尿酸. 研究发现,在pH=5.6的磷酸盐缓冲溶液中,尿酸在聚L-苯丙氨酸修饰电极上于0.43 V处产生1灵敏的氧化峰;循环伏安法测定其氧化峰电流与尿酸的浓度在2.0×10-6～3.0×10-4 mol/L呈良好的线性关系,检出限为1×10-6 mol/L. 对1.0×10-5 mol/L尿酸平行测定5次,相对标准偏差为3.0%. 该聚合物修饰电极制作简单,重现性好,可用于尿液中尿酸的测定,结果令人满意.     

聚钙羧酸修饰玻碳电极差分脉冲伏安法同时测定多巴胺和尿酸

采用电化学方法将钙羧酸(CCA)聚合修饰在玻碳电极(GCE)表面制备了聚钙羧酸指示剂修饰玻碳电极(PCCA/GCE),并用循环伏安法和交流阻抗法研究了电极的电化学性能。结果表明:在pH 6.0的磷酸盐缓冲溶液中,多巴胺(DA)和尿酸(UA)在聚钙羧酸修饰电极上的氧化峰得以分开,峰电位差为0.14V,据此提出了聚钙羧酸修饰电极差分脉冲伏安法同时测定多巴胺和尿酸的方法。DA和UA的浓度分别在5.0～43.8μmol.L-1和5.0～50.0μmol.L-1范围内与其氧化峰电流呈线性关系,检出限(3S/N)分别为0.2μmol.L-1和0.5μmol.L-1。方法可用于多巴胺注射液样品中DA和UA的测定,测定值的相对标准偏差(n=5)依次为2.43%和2.35%。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.