High-performance liquid chromatographic method for direct separation of 5-(p-hydroxyphenyl)-5-phenylhydantoin enantiomers using a chiral tris(4-methylbenzoate) column.

After simple purification of the incubation mixture of phenytoin in isolated rat hepatocytes, 5-(p-hydroxyphenyl)-5-phenylhydantoin (p-HPPH), which formed as a major metabolite, was readily resolved to each enantiomer by direct high-performance liquid chromatography on a cellulose tris(4-methylbenzoate) column, with a mobile phase of ethanol-water. It was also observed that the formation of S-(-)-p-HPPH was dominant, and the S/R ratio was 11.5.     

5-(对-羟基苯基):-5-苯基乙内酰脲的反相高效液相手性分离测定法

以β－ＣＤ为手性流动相添加剂、苯巴比妥为内标,于ＦＬＣ－Ｃ８反相柱上建立了鼠肝微粒体中５－（对－羟基苯基）－５－苯基乙内酰脲（ｐ－ＨＰＰＨ）外消旋体的拆分方法。测得ｐ－ＨＰＰＨ对映体的线性范围为０．５～１１０ｍｇ／Ｌ（ｒ＝０．９９９６）;最低检出量为５ｎｇ（Ｓ／Ｎ＝３）;Ｓ－ｐ－ＨＰＰＨ的回收率为９３．６％±２．８％,Ｒ－ｐ－ＨＰＰＨ的回收率为９４．７％±１．８％;日内和日间精密度ＲＳＤ值均小于２％。所建立的方法具有结果准确、操作方便等特点。     

Gas chromatographic determination of m- and p-hydroxyphenytoin in the urine of epileptic patients

An analytical method for determining phenytoin and its metabolites in the urine of epileptic patients is described. The analysis was performed for the m- and p-isomers of hydroxyphenytoin, the oxidative products of phenytoin, using gas chromatography. As an internal standard, 5-(4-methylphenyl)-5-phenylhydantoin was chosen; the extraction solvent from human urine was ether-chloroform (3:7). Phenytoin and its hydroxy isomers were satisfactorily determined by the modified on-column methylation technique on a 2% OV-17 column using temperature programming from 180 degrees C to 240 degrees C at 5 degrees C/min.     

Stereocontrolled Syntheses of (4S, 5R)- and (4S, 5S)-Dihydroxy-N-Decanoic Acid-4-Lactones Via Biochemical Methods

(4S-5R)- and (4S-5S)-dihydroxy-n-decanoic acid-4-lactones have been synthesized in a stereocontrolled manner by a chemomicrobiological approach.     

Synthesis of the optical isomers of 4-[1-(4-tert-butylphenyl)-2-oxo- pyrrolidine-4-yl]methyloxybenzoic acid (S-2) and their biological evaluation as antilipidemic agent

The enantiomers of (+/-)-4-[1-(4-tert-butylphenyl)-2-oxo-pyrrolidine- 4-yl]methyloxybenzoic acid (S-2), a new antilipidemic agent having dual action on the plasma triglyceride (TG) and cholesterol (Cho) lowering effects, were prepared via separation by Chiralcel OJ column chromatography of their methyl ester and also by the same method as the described racemate's synthesis from optically active 1-(4-tert-butylphenyl)-2-oxo-pyrrolidine-4-carboxylic acid respectively. These optically active carboxylic acids were prepared by the resolution of diastereomeric N-[(S)-(-)-[4-methyl-(alpha-methyl)benzyl]]-1-(4-tert-butylphenyl)-2-oxo - pyrrolidine-4-carboxyamide using silica gel column chromatography, followed by deamination with N2O4. The absolute configurations for the enantiomers of S-2 were indirectly determined using X-ray analysis of the 4-bromo-2-fluorobenzamide of the (+)-4-[1-(4-tert-butylphenyl)-2- oxo-pyrrolidine-4-yl]-methyloxybenzoic acid. S-2 and its enantiomers showed an essentially equipotent activity on the fatty acid- and sterol-biosynthesis inhibition in vitro. On the other hand, in the in vivo activity, (S)-(+)-4-[1-(4-tert-butylphenyl)-2-oxo-pyrrolidine- 4-yl]methyloxybenzoic acid (S-2E) was superior in the lowering abilities of the plasma TG and phospholipid(PL) and was chosen as a candidate for a novel antilipidemic agent. The difference in the in vivo activity among S-2 and its enantiomers was explained from the pharmacokinetics after administration p.o.     

Chemical ligation of S-scylated cysteine peptides to form native peptides via 5-, 11-, and 14-membered cyclic transition states

Cysteine-containing dipeptides 3a-l, (3b+3b') (compound numbers in parentheses are used to indicate racemic mixtures; thus (3b+3b') is the racemate of 3b and 3b'), and tripeptide 13 were synthesized in 68-96% yields by acylation of cysteine with N-(Pg-α-aminoacyl)- and N-(Pg-α-dipeptidoyl)benzotriazoles (where Pg stands for protecting group in the nomenclature for peptides throughout the paper) in the presence of Et(3)N. Cysteine-containing peptides 3a-l and 13 were S-acylated to give S-(Pg-α-aminoacyl)dipeptides 5a-l and S-(Pg-α-aminoacyl)tripeptide 14 without racemization in 47-90% yields using N-(Pg-α-aminoacyl)benzotriazoles 2 in CH(3)CN-H(2)O (7:3) in the presence of KHCO(3). (In our peptide nomenclature, the prefixes di-, tri-, etc. refer to the number of amino acid residues in the main peptide chain; amino acid residues attached to sulfur are designated as S-acyl peptides. Thus we avoid use of the prefix "iso".) Selective S-acylations of serine peptide 3k and threonine peptide 3l containing free OH groups were thus achieved in 58% and 72% yield, respectively. S-(Pg-α-aminoacyl)cysteines 4a,b underwent native chemical ligations to form native dipeptides 3f,i via 5-membered cyclic transition states. Microwave irradiation of S-(Pg-α-aminoacyl)tripeptide 15 and S-(Pg-α-aminoacyl)tetrapeptide 17 in the presence of NaH(2)PO(4)/Na(2)HPO(4) buffer solution at pH 7.8 achieved chemical ligations, involving intramolecular migrations of acyl groups, via 11- and 14-membered cyclic transition states from the S-atom of a cysteine residue to a peptide terminal amino group to form native peptides 19 and 20 in isolated yields of 26% and 23%, respectively.     

Characterization of interaction kinetics between chiral solutes and human serum albumin by using high-performance affinity chromatography and peak profiling

Peak profiling and high-performance columns containing immobilized human serum albumin (HSA) were used to study the interaction kinetics of chiral solutes with this protein. This approach was tested using the phenytoin metabolites 5-(3-hydroxyphenyl)-5-phenylhydantoin (m-HPPH) and 5-(4-hydroxyphenyl)-5-phenylhydantoin (p-HPPH) as model analytes. HSA columns provided some resolution of the enantiomers for each phenytoin metabolite, which made it possible to simultaneously conduct kinetic studies on each chiral form. The dissociation rate constants for these interactions were determined by using both the single flow rate and multiple flow rate peak profiling methods. Corrections for non-specific interactions with the support were also considered. The final estimates obtained at pH 7.4 and 37°C for the dissociation rate constants of these interactions were 8.2-9.6 s(-1) for the two enantiomers of m-HPPH and 3.2-4.1 s(-1) for the enantiomers of p-HPPH. These rate constants agreed with previous values that have been reported for other drugs and solutes that have similar affinities and binding regions on HSA. The approach used in this report was not limited to phenytoin metabolites or HSA but could be applied to a variety of other chiral solutes and proteins. This method could also be adopted for use in the rapid screening of drug-protein interactions.     

5-(5-氯-2-吡啶偶氮)-2,4-二氨基甲苯的电分析特性研究

本文采用多种电化学方法研究了5-Cl-PADAT的电分析特性,求得了该化合物的电极反应电子转移数,扩散系数及电极反应标准速率常数,研究了其在滴汞电极上的吸附性质,提出了可能的电极还原过程。并且应用光度法测定了化合物的酸离解常数。     

N,N′-二[3-氯-5S-(l-孟氧基)-2(5H)-4-呋喃酮基]-1,4-丁二胺的合成及晶体结构(英文)

合成了N,N′-二[3-氯-5S-(l-孟氧基)-2(5H)-4-呋喃酮基]-1,4-丁二胺,并通过IR,1H NMR,MS和X射线单晶衍射对其进行了表征.X射线单晶衍射结果表明:标题化合物的不对称结构单元中包含一个平面的呋喃酮环和一个椅式的环己烷环,四个手性中心.标题化合物通过N—H…O分子间氢键作用实现空间堆积.     

Kinetics and mechanism of ring transformation of S-[1-(4-methoxyphenyl)pyrrolidin-2-on-3-yl]isothiuronium bromide to 2-methylimino-5-[2-(4-methoxyphenylamino)ethyl]thiazolidin-4-one

The kinetics and mechanism of transformation reaction of S-[1-(4- methoxyphenyl)pyrrolidin-2-one-3-yl]-N-methyl-isothiuronium bromide into 2-methylimino-5-[2-(4-methoxyphenylamino) ethyl)]thiazolidin-4-one have been studied in aqueous solutions of amine buffers (pH 8.1-11.5) and sodium hydroxide solutions (0.005-0.5 mol l-1) at 25 degrees C and at I = 1 mol l-1 at pseudo-first-order reaction conditions. The kinetics observed shows that the transformation reaction is subject to general base, general acid, and hydroxide-ion catalyses. The rate-limiting step of transformation is the splitting-off a proton from the tetrahedral intermediate In. The value of pKa for S-[1-(4-methoxyphenyl)- pyrrolidin-2-one-3-yl]-N-methylisothiuronium bromide has been determined from the kinetic data (pKa = 8.75 +/- 0.10) and by potentiometric titration (pKa = 8.90 +/- 0.05). With increasing pKa value of the acid buffer component, the value of Br?nsted coefficient beta gradually decreases from about 0.7 to almost zero. The value of pKa approximately 10 for the intermediate to base-catalysed transformation has been found from this dependence. In the N-methylpyrrolidine and triethylamine buffers, the rate-limiting step of transformation is changed into ring opening of In-, and the general-base-catalysed reaction changes into a specific-base-catalysed one.     

Total synthesis of (+/-)-culmorin and (+/-)-longiborneol: an efficient construction of Tricyclo[6.3.0.0(3,9)]undecan-10-one by intramolecular double Michael addition

The treatment of 4-[(5E)-6-methoxycarbonyl-5-hexenyl]-3, 4-dimethyl-2-cyclopenten-1-one (5) with LHMDS, TMSI-HMDS, Bu(2)OTf-HMDS, or TMSCl-NEt(3)-ZnCl(2) caused the intramolecular double Michael addition to afford tricyclo[6.3.0.0(3, 9)]undecan-10-one 12 in high yields with perfect stereoselectivity. The methodology was further elaborated to achieve efficient total syntheses of (+/-)-culmorin (1) and (+/-)-longiborneol (2). The common precursor 13 of them was obtained from 14 in 94% yield as a single isomer by the treatment with LHMDS. After the conversion of 13 into the corresponding acid 24 by hydrolysis, oxidative decarboxylation using S-(1-oxido-2-pyridinyl)-1,1,3, 3-tetramethylthiouronium hexafluorophosphate (HOTT, 27), followed by the Birch reduction, stereoselectively afforded (+/-)-culmorin (1). (+/-)-Longiborneol (2) was synthesized from 24 by the standard transformation. Additionally, the treatment of 24 with Pb(OAc)(4) led to 28 via uncommon migration. Its structure was determined by X-ray analysis after the transformation into the diketone 29.     

Isotachophoretic determination of 2-5A phosphodiesterase

Together with 2-5A synthetase and ribonuclease L, 2-5A phosphodiesterase belongs to the 2-5A system, which plays an important role in the action of interferon. Analytical capillary isotachophoresis was used for the determination of 2-5A phosphodiesterase activity. Enzyme assay was optimized using snake venom phosphodiesterase as a source of 2-5A phosphodiesterase activity. The 2-5A trimer core was used as a substrate. Enzyme activity was determined in time- and concentration-dependent reactions. In addition, 2-5A phosphodiesterase activity was determined in lysates of mononuclear blood cells.     

Direct determination of S-(-)- and R-(+)-propranolol glucuronide in rat hepatic microsomes by RP-HPLC

Propranolol, available commercially as a racemic mixture, is a non-selective beta-adrenergic blocking agent used in the treatment of hypertension, angina pectoris and cardiac arrhythmias. We have developed and validated an RP-HPLC assay method for direct determination of R-(+)- and S-(-)-propranolol glucuronide in rat hepatic microsomes to investigate the enantioselectivity of propranolol glucuronidation metabolism. A baseline separation of propranolol glucuronide enantiomers was achieved on a 5 microm reversed-phase ODS column, with a mixture of phosphate buffer (pH 3.5, 0.067 mol/L) and methanol (55:45, v/v) as mobile phase. Ultraviolet detection was set at 220 nm, and p-nitrobenzoic acid was used as internal standard. The standard curve of assay for R-(+)- and S-(-)-propranolol glucuronide in spiked microsomal incubate showed good linearity throughout the concentration range from 0.50 to 20.0 micromol/L. The analytical method affords average recovery of 99.8 and 100.1% for R-(+)- and S-(-)-propranolol glucuronide, respectively. The method provides a high sensitivity and good precision for R-(+)- and S-(-)-propranolol glucuronide (RSD < 10%). The LOD was 0.15 micromol/L and the LOQ was 0.5 micromol/L (RSD < 8%, n = 5) for both R-(+)- and S-(-)-propranolol glucuronide. The method is simple, precise and accurate, and is suitable for quantifying the propranolol glucuronides enantiomers in rat hepatic microsomes.     

Spectrophotometric determination of cadmium(II) using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

The complex of cadmium with the reagent 2-(-5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) has been studied. The composition, stability constant, and free energy change of formation of the complex have been determined. A sensitive spectrophotometric method for the determination of cadmium has been developed and applied for a range of concentration of 0.4–4.0 μg/ml cadmium using the complex Cd-5-Br-PADAP. The optimum conditions for maximum sensitivity of determination such as standing time, pH, wavelength, and order of addition have been determined. The effect of foreign ions on this method has been also studied.     

Synthesis of ethyl 4-(1,2,3-thiadiazol-4-yl)-5-(bromomethyl)furan-2-carboxylate and its reactions with nucleophiles

By cyclization of carboethoxyhydrazone of ethyl 4-acetyl-5-methylfuran-2-carboxylate under the conditions of Hurd–Mori reaction ethyl 4-(1,2,3-thiadiazol-4-yl)-5-methylfuran-2-carboxylate was synthesized. The ester obtained was brominated with N-bromosuccinimide at the methyl group in the furan ring. This bromide reacts with various N-, S-, O-, and P-nucleophiles to form the corresponding substitution products. Furylthiadiazole fragment remains stable in the course of these transformations.     

手性-3, 5-二取代-1', 2', 4'-三唑-[3', 4'-b]-2, 4-二氢间 噻二嗪的合成及 生物活性

以3-芳基-5-巯基-1,2,4-均三唑为原料,和甲醛及S-(-)-α-苯乙胺在酸催化作用下合成了6种新的化合物。研究了合成反应的条件。通过元素分析、IR、^1HNMR、和MS确证了其结构,测定了比旋光度和生物活性。结果表明,一些化合物具有一定的抗菌活性。     

Synthesis and properties of 5-(5-nitro-2-furyl)thiazolines

The reactions of 2-amino-4-methyl-5-(5-nitro-2-furyl)thiazole with excess methyl iodide leads to 3,4-dimethyl-2-methylamino-5-(5-nitro-2-furyl)thiazolium iodide, which is converted to 2-imino-3,4-dimethyl-5-(5-nitro-2-furyl)thiazoline under the influence of bases. The iminothiazoline structure was proved by comparison of the spectral characteristics of its acetyl derivative and the isomeric 2-(N-acetyl-N-methyl) amino-4-methyl-5-(5-nitro-2-furyl)thiazole. The pKa values of 2-amino-4-methyl-5-(5-nitro-2-furyl)thiazole and 3,4-dimethyl-2-imino-5-(5-nitro-2-furyl)-thiazoline were determined, and the constant of the aminothiazole-iminothiazoline tautomeric equilibrium was calculated.Translated from Khimiya Geterosiklicheskikh Soedinenii, No. 10, pp. 1337–1340, October, 1985.     

Facile Synthesis of Enantiomerically Pure 1-（5-Bromo-2-chlorophenyl）-1-（4-ethoxyphenyl）ethane

A facile 7-step procedure for the synthesis of enantiomerically pure 1-（5-bromo-2-chlorophenyl）-1-（4-ethoxyphenyl）ethanes[（R）-2 and（S）-2] that started from （5-bromo-2-chlorophenyl）（4-ethoxyphenyl）methanone 3 was developed.The key step was the resolution of 2-（5-bromo-2-chlorophenyl）-2-（4-ethoxyphenyl）acetic acid 6 by crystallizations of its L-and D-menthyl esters 7 and 8 from petroleum ether to give optically pure enantiomers 9 and 10,respectively.The absolute configurations of the products were unambiguously determined by single-crystal X-ray diffractions of four key intermediates,9,10,13 and 14.This procedure is characterized by inexpensiveness,scalability and ability to produce two individual enantiomers of a diarylethane with unambiguously determined absolute configurations and high enantiomeric purities.     

Structural isomers in a 2-(5-bromo-2-pyridylazo)-5diethylaminophenolatochloropalladium(II) crystal.

Crystal structure of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenolatochloropalladium(II) (PdLCl) has been determined by X-ray diffraction. A crystal of PdLCl was constructed by two structural isomers of PdLCl molecules, which were particularly different in the positions of the carbon atoms at the diethylamino group, having cis-like or trans-like conformation for the carbon atoms. The molecules of PdLCl in the crystal were warped by a steric hindrance of the diethylamino group.     

A sensitive LC-MS/MS method for quantification of phenytoin and its major metabolite with application to in vivo investigations of intravenous and intranasal phenytoin delivery

Phenytoin is a powerful antiseizure drug with complex pharmacokinetic properties, making it an interesting model drug to use in preclinical in vivo investigations, especially with regards to formulations aiming to improve drug delivery to the brain. Moreover, it has a major metabolite, 5-(4-hydroxyphenyl)-5-phenylhydantoin, which can be simultaneously studied to achieve a better assessment of its behaviour in the body. Here, we describe the development and validation of a sensitive LCMS/MS method for quantification of phenytoin and 5-(4-hydroxyphenyl)-5-phenylhydantoin in rat plasma and brain which can be used in such preclinical studies. Calibration curves produced covered a range of 7.81 to 250 ng/mL (plasma) and 23.4 to 750 ng/g (brain tissue) for both analytes. The method was validated for specificity, sensitivity, accuracy, and precision and found to be within the acceptable limits of ±15% over this range in both tissue types. The method when applied in two in vivo investigations: validation of a seizure model and to study the behaviour of a solution of intranasally administered phenytoin as a foundation for future studies into direct nose-to-brain delivery of phenytoin using specifically developed particulate systems, was highly sensitive for detecting phenytoin and 5-(4-hydroxyphenyl)-5-phenylhydantoin in rat plasma and brain.