Silica–Sulfuric Acid Catalyzed Nitrodeiodination of Iodopyrazoles

Abstract

We report here the synthesis of nitropyrazoles in good to excellent yields from iodopyrazoles over silica–sulfuric acid catalyst for the first time. The present procedure require less acid, offers a simplified workup procedure, and may be applied for the nitration of a wide variety of iodoazoles in drug and pharmaceutical industries.     

High Performance Liquid Chromatographic Procedure for Retinoic Acid in Ophthalmic Solution

Abstract

A fast and simple procedure has been developed for the quantitation of retinoic acid in ophthalmic solutions. the procedure involves the use of reverse phase high performance liquid chromatography with a mobile phase containing an amine modifier. This procedure is specific for retinoic acid in the presence of its degradation products and formulation excipients. the method is linear over a wide range of concentrations.     

赖氨酸衍生氮杂大环化合物的固相合成

基于固相载体的假稀释效应, 设计并合成了由赖氨酸为前体结构衍生的氮杂大环化合物8, 9, 10, 12及13. 合成中的关键构件是在固相树脂上肽链的N端键合的二个相邻的赖氨酸残基, 并以溴乙酸为桥连组份, 先后经酰化及亲核取代(S_N2)反应完成三氮杂十六元环骨架的构建. 5种粗产物的总收率在68.9%～86.1%之间, 并全部经氨基酸组成分析及ESI-MS分析表征.     

Isoliquiritigenin extracted from licorice <Emphasis Type="Italic">Glycyrrhiza uralensis</Emphasis> roots by a facile conversion technique

Isoliquiritigenin (1), one of the major constituents of licorice, is a natural pigment with a simple chalcone structure 4,2',4'-trihydroxychalcone. This study was performed to determine whether liquiritin, isoliquiritin, and liquiritigenin can be converted into isoliquiritigenin using alkaline conversion after acid hydrolysis. An orthogonal L₉ (3)⁴ test design was used in the extraction mode and used for optimization of the extract conditions, and the yield from the conventional procedure and from the optimum procedure to extract 1 was compared. The results demonstrated that the yield of the novel procedure was increased about 27 times compared with the conventional procedure, which indicated that the novel procedure is powerful in separating and purifying isoliquiritigenin.     

An Efficient Synthesis of Isofraxidin

An improved procedure for the preparation of isofraxidin 1 a well known natural coumarin, through transformation of syringaldehyde is reported. The cyclization of 7 to the coumarinic carboxylic acid 8 is readily performed by cold concentrated sulfuric acid. The overall yield to 1 by this convenient route is near 50%.     

Preparation of N,N-Bis[2-[N',N'-Bis[(Tert-Butoxycarbonyl)Methyl]-Amino]Ethyl-L-Aspartic Acid: An Intermediate in the Synthesis of MRI Contrast Agents

A preparation of DTPA carboxylic acid 1, a suitable intermediate in the synthesis of MRI contrast agents 2, is described starting from α-tert-butyl-β-benzyl-L-aspartate hydrochloride. In addition, an alternative procedure for the synthesis of bromide 3b is presented.     

New and Concise Approach to (R)-α-Lipoic Acid

A concise enantiospecific synthesis of (S)-6,8-bis(methylsulfonyloxy)-octanoic acid (2), a ready precursor of (R)-(+)-α-lipoic acid (1), is reported. The key step of the synthesis is the coupling of the tosylate derived from (R)-malic acid with phenylpropyl magnesium bromide. A recently reported green procedure was used for the oxidative unmasking of the phenyl group, used as a latent carboxyl group.     

Two Efficient Syntheses of Protected 4‐Deoxy‐D‐lyxo‐hexose (4‐Desoxy‐D‐mannose)

The formation of four differently protected 4‐deoxy‐D‐lyxo‐hexose derivatives 7, 8, 12, and 14 is described. In the first procedure, a nucleophilic displacement of the allylic mesylate 4 by hydride was combined with a highly stereoselective osmylation of olefin 6 to afford diol 7. In the second radical procedure, tributyl tin hydride was substituted by the cheap and environmentally friendly hypophosphorous acid as a hydrogen donor in the reduction of xanthate 13 to 4‐deoxy lyxo‐hexose 14.     

Glc Determination of Valproic Acid in Plasma

Abstract

A one-step glc procedure was developed for the quantitative determination of valproic acid in plasma. After addition of internal standard (4-methyl valeric acid), plasma is buffered at pH 4.5 to avoid hydrolysis of valproic acid conjugate (s). Evaporation is avoided by extraction into a chloroform bead. The method is sufficiently sensitive to quantitate 0.8 μg of the drug in 0.2 ml of plasma. The procedure has been thoroughly tested for precision and reproducibility through the determination of over two thousand samples.     

<Emphasis Type="Italic">N</Emphasis>-Alkoxy-3,5-dinitro-4-aminobenzoic acid derivatives with controlled physico-chemical properties

Starting from 4-chloro-3,5-dinitrobenzoic acid 1, compounds 2–10 (N-alkoxy-3,5-dinitro-4-aminobenzoic acid esters where alkoxy stands for methoxy, carboxymethoxy, triphenylmethoxy, or corresponding amides) have been obtained, from which compounds 3–5 and 7–10 are new, and for the known compounds 2 and 6 the synthetic procedure has been improved. The new derivatives have been characterized by appropriate means (IR, UV–Vis, ¹H- and ¹³C-NMR, fluorescence) and their properties were studied. Thus, depending on their structure, the compounds have acid properties, fluorescence and complexing properties with alkaline cations.     

Amino Acid Profiling of Protein Hydrolysates Using Liquid Chromatography and Fluorescence Detection

Abstract

A liquid chromatography procedure is described for separating the amino acids in protein hydrolysates. The proteins are hydrolyzed with hydrochloric acid and an aliquot of the hydrolysate is derivatized with dansyl chloride reagent. The derivatization procedure takes only 2 minutes using a reaction temperature of 100°C. The dansylated amino acids are chromatographed using a reversed-phase C₈ column and a multi-step, nonlinear gradient elution solvent program which is readily achieved using a microprocessor-controlled liquid chromatograph. Chromatography is complete in approximately 40 min. The procedure is useful for characterizing proteins and may also be used to analyse intact dansylated polypeptides. Chromatograms showing the amino acid profile of chymotrypsin, albumin and histone are given.     

Semiquantitative and Quantitative Determination of Trace Amount of Phosphate Ion in Water Using Polyurethane Foam Thin -Layer Colorimetry

Abstract

A simple, sensitive and fast method for the colorimetric determination of phosphate ion in water is described.

The method is based on spectrophotometric measurement of the blue molybdoantimony phosphoric acid species sorbed in a polyurethane foam thin-layer for quantitative determination of phosphate ion, or the visual color comparison technique for rapid semiquantitative determination.

The detection limit for the quantitative procedure is 5 μg/1 and for semiquantitative procedure 20 μg/1 for sample volumes of 100 ml and 25 ml, respectively.     

The Design and Synthesis of a Hapten for 1192U90, a Potential Atypical Antipsychotic Agent

The design and synthesis of a hapten for a radioimmunoassay procedure for the potential atypical antipsychotic agent 1192U90 (1) is described. The hapten, a butyric acid derivative of ortho-amino benzamide 1192U90, was prepared in five steps starting from 5-hydroxy-2-nitrobenzaldehyde.     

A Phosphoric Acid Treated Reactive GLC Column for the Analysis of Long Chain Amides

Abstract

The conversion of nonvolatile amides to more volatile nitriles on a reactive column was studied. It was found that pyrophosphoric acid was necessary for the conversion, that the amide reacts 100% on the first 6 inches of the column to produce one nitrile and 3 carboxylic acid groups for every 4 amide groups injected and that a quantitative analytical procedure is possible.     

A Fast and Large-Scale Synthesis of 3-Formyl-2-mercaptoquinolines

A convenient, efficient, and inexpensive procedure for the synthesis of 3-formyl-2-mercaptoquinolines 2a–l has been developed by a simple one-pot reaction of 3-formyl-2-chloroquinolines 1a–l with sodium sulfide and hydrochloric acid in ethanol. The structures of all the synthesized compounds were elucidated on the basis of elemental analyses and IR, ¹ H NMR, and mass spectral data.     

Synthesis of Trichlorophenol Derivatives

An expedient three‐step procedure for the synthesis of trichlorophenol derivatives based on the acid‐catalyzed rearrangement of the bicyclic ketone precursors 6a–e in high overall yield is described. The bicyclic ketone precursors 6a–e were obtained from Diels–Alder cycloadducts of β‐substituted vinyl acetates with tetrachloro‐5,5‐dimethoxycyclopentadiene in two steps.     

HPLC analysis of aspartame and saccharin in pharmaceutical and dietary formulations

Summary A reversed-phase HPLC method has been developed suitable for a reliable quality control of pharmaceutical and dietary formulations containing the synthetic sweeteners aspartame and saccharin. The proposed method is able to separate acesulfame, aspartame and saccharin, and their impurities such as 5-benzyl-3,6-dioxo-2-piperazineacetic acid (the major degradation product of aspartame) and 4-sulphamoylbenzoic acid,o- andp-toluenesulphonamides (the synthesis impurities of saccharin). A convenient solid-phase extraction (SPE) procedure using C-18 sorbent, was also developed for the determination of potential saccharin impurities.     

A Novel Approach to the Synthesis of 1-Substituted-3,6-diaryl-imidazo[1,5-b]pyridazines

A simple and efficient procedure for the preparation a new type of 1-substituted-3,6-diaryl-imidazo[1,5-b]pyridazines was described. This synthesis was carried out by the following three steps: Aryl methyl ketone 3 was condensed with 1-amino-2-subsatiuted-4-arylimidazole 2 in ethanol with catalytic glacial acetic acid to afford enamines 4 a–k. Treatment with t-butoxybis(dimethylamino)methane in DME at room temperature gave enamine (5a-k) which was cyclized to compound (1a–k) in 84–96% yield in trifluoroacetic acid.     

Volumetric Microdetermination of Hydrazines and Hydrazides

Abstract

A micro procedure for the determination of hydrazines, hydrazides and their derivatives is described using bromine monochloride in acetic acid as the reagent. The results obtained showed a maximum deviation of about 3. 64% in most cases.     

Non-Aqueous Titrimetric Determination of Sulphadimidine Sodium and Sulphadiazine Sodium in Injections

Abstract

The behaviour of sodium salts of two heterocyclic sulphonamide derivatives (Sulphadimidine and sulphadiazine) in non-aqueous titrimetry was studied. Accordingly a simple and accurate procedure for their determination, based on their titration in acetic anhydride-acetic acid solvent system (5:1) with acetous perchloric acid solution is proposed. Results obtained agreed with those of a pharmacopoeial method.