Brian A. Dawson

Fenofibrate raw materials: HPLC methods for assay and purity and an NMR method for purity

HPLC methods for drug content and HPLC and NMR methods for related compounds in fenofibrate raw materials were developed. The HPLC methods resolved 11 known and six unknown impurities from the drug. The HPLC system was comprised of a Waters Symmetry ODS column (100 x 4.6 mm, 3.5 microm), a mobile phase consisting of acetonitrile water trifluoroacetic acid 700/300/l (v/v/v) at a flow rate of 1 ml min(-1). and a UV detector set at 280 nm. Minimum quantifiable amounts were about 0.1% for three of the compounds and less than 0.05% for the other eight. Individual impurities in 14 raw materials ranged from trace levels to 0.25%, and total impurities from 0.04 to 0.53% (w/w). Six unknown impurities were detected by HPLC, all at levels below 0.10%, assuming the same relative response as fenofibrate. An NMR method for related compounds was also developed and it was suitable for 12 known and several unknown impurities. It requires an NMR of 400 MHz, or greater, field strength. Individual impurities in the raw materials analyzed ranged from trace levels to 0.24%, and total impurities from trace levels to 0.59%. Several lots contained small amounts of unknown impurities at trace levels. Three lots, all from the same manufacturer, contained an unknown impurity, not detectable by HPLC, which was not present in the other raw materials. It was estimated to be present at a level greater than 0.2%. The results for related compounds by the two techniques were consistent. The main differences stem from the low sensitivity of the HPLC method for some of the related compounds at 280 nm, or from the higher limits of quantitation by the NMR method for several other impurities using the conditions specified. A fifteenth raw material was not homogeneous in its content of impurity VI, a synthetic intermediate and possible degradation product. The HPLC/MS results provided information on the peak purity (number of components) for minor HPLC peaks, as well as structural data such as the molecular ions and diagnostic fragment ions. The HPLC/MS results showed that there were five unknown drug related impurities, for which there were no standards available. Results for the assay of 15 raw materials by HPLC were within the range 98.5-101.5%.

Mouse hepatic metabolites of ketoconazole: Isolation and structure elucidation

Oxidation, cleavage and degradation of the imidazole and piperazine rings, O-dealkylation, and aromatic hydroxylation are the reported pathways of ketoconazole (KC) metabolism. Metabolites were examined in hepatic extracts from male Swiss Webster mice treated with KC (350 mg kg-1 po x 7 days) in a 0.25% gum tragacanth suspension at 10 ml kg-1. Livers were collected 24 h after the last dose and stored at -70 degrees C. A mixture of chloroform/methanol extracts of liver homogenates were dried under vacuum and methanol extracts of the residue were chromatographed by a series of preparative and analytical HPLC techniques. Structure assignments were made by NMR and MS/MS techniques. It was demonstrated that KC was biotransformed to a number of products. Nine were isolated and seven identified as exclusive products of the biotransformation of the 1-acetylpiperazine moiety of KC. This substituent was biotransformed to the following: piperazine (de-N-acetyl ketoconazole, DAKC), N-carbamylpiperazine, N-formylpiperazine, 2,3-piperazinedione, 2-formamidoethylamine, ethylenediamine and amine. The 1H-NMR and MS data suggested that the remaining two metabolites were products resulting from the oxidation of the imidazole ring.

Deacetylated ketoconazole: A major ketoconazole metabolite isolated from mouse liver

This paper describes the isolation and characterization of a novel metabolite of ketoconazole from hepatic tissue following a treatment regimen associated with ketoconazole induced phospholipidosis

Synthesis and Spectral Properties of 2,5-Dimethoxy-4-Ethoxyamphetamine and Its Precursors

2,5-Dimethoxy-4-ethoxyamphetamine (MEM) was synthesized by two routes. The gas liquid chromatographic data and ultraviolet, infrared, proton magnetic resonance, carbon-13 magnetic resonance, and mass spectra are presented for this amphetamine as well as its precursors. This amphetamine was found to be identical to the sample submitted by the police.

Identification of 4-Ethoxy-2,5-Dimethoxy Amphetamine by an Nmr Shift Reagent Study

ABSTRACTAn NMR shift reagent study was carried out on a 2,4,5-trisubstituted amphetamine (with one ethoxy and two methoxy groups), showing that the ethoxy is in the 4-position. Shift reagent studies were also performed for two model compounds (2,4,5-trimethoxyamphetamine and 4-ethyl-2,5-dimethoxyamphetamine) to illustrate the validity of this approach. For all three amphetamines the magnitude of the lanthanide induced shifts for the aromatic substituents decreased with distance from the nitrogen atom.

Identification of Two New “Designer” Amphetamines by NMR Techniques

ABSTRACTTwo new designer amphetamines (4-chloro-2, 5-dimethoxyamphetamine and 2, 5-dimethoxy-4-methylthioamphetamine) were identified by nuclear magnetic resonance (NMR) techniques. Nuclear Overhauser Effect (NOE) difference spectra provided all the necessary structural information to identify the unknowns. Lanthanide shift reagent (LSR) studies provided an alternate method to prove positional substitution for the structures.

Structural Elucidation of Unusual Police Exhibits. II. Identification and Spectral Characterization of N-(2-Hydroxyethyl)amphetamine Hydrochloride

An unusual police exhibit having the physical appearance, color, and odor of methamphetamine hydrochloride was identified unequivocally on the basis of combined evidence from 1H- and 13C-NMR, mass, and infrared spectroscopic examination as N-(2-hydroxyethyl)amphetamine hydrochloride (HEA·HCl). A minor contaminant of the exhibit was similarly identified as ethanolamine hydrochloride (HE·HCl), suggesting synthesis via reductive amination of phenylacetone. Relevant spectroscopic data (1H-, 13C-NMR, mass, and FT-IR) and spectra are presented.

Preparative liquid chromatographic separation of the oligomers of nonoxynol-9 and their characterization by 1H-NMR and mass spectroscopy

Conditions are described for the preparative LC separation of a bulk nonoxynol-9 material into 16 components. 1H-NMR analyses of these fractions provided evidence for all but the first of the components to be oligomers of nonylphenoxypolyethoxyethanol (nonoxynol) with n-values for (OCH2CH2)n ranging consecutively from 3 to 17, corresponding to the LC fractions 2-16. Mass spectral analysis of the separated LC fractions confirmed the oligomeric sizes deduced from 1H-NMR spectral data, and provided EI fragmentation information for these oligomeric substances.

Synthesis and Characterization of Monoethoxymethamphetamines

ABSTRACTThe monoethoxymethamphetamines were synthesized from the (E)-monoethoxy-1-(2-nitro-1-propenyl)benzenes via the corresponding 1-phenyl-2-propanones. The gas-liquid chromatographic (GLC) data, and ultraviolet (UV), infrared (IR), proton magnetic resonance (1H-NMR), carbon-13 magnetic resonance (13C-NMR) and mass spectra (MS) are presented for the 1-phenyl-2-propanones as well as the methamphetamines.

Chromatographic and spectroscopic characterization of sulphur-bound dimetridazole and ronidazole derivatives

The 5-nitroimidazoles, dimetridazole and ronidazole, two important veterinary drugs, were reacted under reductive conditions with the sulfhydryl-containing substrates cysteine and glutathione to yield 5-amino-4-S-substituted imidazoles. After purification by reversed-phase liquid chromatography (RP-LC), the four adducts were characterized by RP-LC with photodiode array detection using conditions where their parent drugs were not eluted from the column. Structural identification was conducted by spectroscopic techniques, mainly 1-dimensional and 2-dimensional NMR. While the dimetridazole adducts were found to be monosubstituted at the C-4 position, the two ronidazole products contained two units of the sulfhydryl substrate, located at the C-4 and C-6 positions.