Search

A liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) method has been developed and validated to detect and confirm the marker residue of eprinomectin (B1a component) in bovine liver when present at levels ≥2400 ng/g. Sample extracts prepared for assay by the LC/fluorescence determinative method (prior to the derivatization step) and standard solutions were used to validate the confirmatory method. The chromatographic retention time of the eprinomectin B1a component and the relative ion intensities of the parent ion ([M + H]+ at m/z 914) and three product ions (m/z 896, 468, and 330) generated by fragmentation of the parent ion are compared to those determined from standards. Keywords: Eprinomectin; residue; confirmatory; bovine liver; LC/MS/MS

A simple, selective, sensitive, accurate and relatively inexpensive method for the determination of palladium in bulk pharmaceutical chemicals (BPC) and their synthetic intermediates by graphite furnace atomic absorption spectroscopy has been developed and validated. Sample preparation by direct dissolution of sample in 70% nitric acid is simple and effective without adverse effects. The limit of detection and the limit of quantitation of the method were determined to be 0.7 ppm and 2 ppm respectively in BPC.

The existence of an isomeric form in equilibrium with the major component of FK-520 in polar solutions has been demonstrated. This minor component has been isolated in high yield and purity by a novel crystallization strategy and preparative HPLC. The equilibrium product was characterized by NMR and MS.

The existence of an isomeric form in equilibrium with the major component of FK-520 in polar solutions has been demonstrated. This minor component has been isolated in high yield and purity by a novel crystallization strategy and preparative HPLC. The equilibrium product was characterized by NMR and MS.

A method has been developed for the determination of abamectin in tomatoes. Sample homogenization and extraction are performed simultaneously with acetonitrile/water/hexane. Abamectin and its isomer are selectively concentrated and derivatized by an instantaneous reaction with trifluoroacetic anhydride (TFAA)/1-methylimidazole. Quantification is achieved by HPLC with fluorescence detection

An analytical method has been developed for the extraction, derivatization, and fluorescence HPLC determination of MK-0244 [4"-deoxy-4"-(epimethylamino)avermectin B1 benzoate salt] and its delta 8,9-isomer from lettuce and celery at trace (parts per billion) levels. MK-0244 and its delta 8,9-isomer are extracted with methanol, and the extract is cleaned up on a reverse-phase C8 cartridge followed by a liquid-liquid extraction with ethyl acetate before passing through a propyl sulfonyl cation-exchange cartridge. MK-0244 and its delta 8,9-isomer are then derivatized with trifluoroacetic anhydride/1-methylimidazole/acetonitrile reagent system to form a fluorescent derivative which is separated on a reverse-phase HPLC system and detected with a fluorescence detector. The average recoveries were 95 +/- 10% for celery and 96 +/- 8% for lettuce. For both lettuce and celery matrix, concentrations as low as 2 ppb (S/N = 10) can be detected in a 10-g sample. This method was used to determine the MK-0244 levels in samples from a lettuce field trial.

A multi-element inductively coupled plasma-mass spectrometry (ICP-MS) survey method has been demonstrated as an alternative to the antiquated 'heavy metals limit test' prescribed by United States Pharmacopoeia (USP), European Pharmacopoeia (EP), and British Pharmacopoeia (BP), for drug substances, intermediates, and raw materials. The survey method is simple, fast, sensitive, semi-quantitative to quantitative, and includes all the elements which can be analyzed by atomic spectroscopy.

We have developed an FT-IR method, using a Spectra-Tech Monit-IR 400 systems, to monitor off-line the completion of a reaction in real-time. The reaction is moisture-sensitive and analysis by more conventional methods (normal-phase HPLC) is difficult to reproduce. The FT-IR method is based on the shift of a diazo band when a conjugated beta-diketone is transformed into a silyl enol ether during the reaction. The reaction mixture is examined directly by IR and does not require sample workup. Data acquisition time is less than one minute. The method has been validated for specificity, precision and accuracy. The results obtained by the FT-IR method for known mixtures and in-process samples compare favorably with those from a normal-phase HPLC method.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The preparation of 4-de-N-methylfortimicin A analogs as well as the preparation of 4-de-N-methyl-4-N-(beta-aminoethyl)-4-N-ethylfortimicin B is reported. It was shown that the 4-N-methyl group in fortimicin analogs is essential for antibacterial activity since neither the 4-de-N-methylfortimicin A nor the 4-de-N-methyl-4-N-(beta-aminoethyl)-4-N-ethylfortimicin B exhibited useful biological activity.

The reaction of 4-t-butylpyridine 1-oxide (1) with t-butyl or 1-adamantyl mercaptan in acetic anhydride yielded the expected 2- and 3-alkylthio-4-t-butylpyridines and 1-acetyl-2,6-bis-(alkylthio)-3-acetoxy-4-t-butyl- and the unexpected 1-acetyl-2-acetoxy-3,6-bis(alkylthio-4-t-butyl-1,2,3,6-tetrahydropyridines. The addition of t-butyl mercaptan to a solution of 1 in acetic anhydride containing triethylamine produced the expected 1-acetyl-2-t-dmtylthio-3-acetoxy-4-t-butyl-6-hydroxy-1,2,3,4-tetrahydropyridine (6a) and the unexpected 1-acetyl-2,6-bis(hydroxy)-3-t-butylthio-4-t-butyl-1,2,3,6-tetrahydropyridine. Mild alkaline hydrolysis of 6a yielded predominantly 2-[(acetamido) (t-butylthio)methyl]-3-t-butyl-5-hydroxy-2,5-dihydrofuran. The latter was converted by very mild acidic reagents to the corresponding furan and with 2,4-dinitrophenylhydrazine and sulfuric acid furnished 3-t-butylfurfural 2,4-dinitrophenyl-hydrazone.

The reaction of pyridine 1-oxide with 1-adamantanethiol in acetic anhydride produced a mixture of 2- and 3-(1-adamantanethio)pyridines, 1-aeetyl-2-(1-adamantanethio)-3-hydroxy-4-acetoxy-1,2,3,4-telrahydropyridine and the corresponding 3-acetoxyderivative. Pure substances were separated by means of column chromatography on alumina. The tetrahydropyridines were identified by means of their proton magnetic and mass spectra. 4-(1-Adamantanethio)pyridine was synthesized from 4-chloropyridinc and 1-adamantanethiol. The three isomeric (1-adamantanethio)-pyridines were, each, cleaved by concentrated hydrochloric acid to give 1-chloroadamantane and the corresponding pyridinethiol.

Erythromycin A is slowly metabolized to a new antibiotic, erythromycin E (5), when incubated with fermentations of certain strains of the producing organism Streptomyces erythreus. Erythromycin E contains a novel ortho ester grouping not previously encountered in macrolide antibiotics. The isolation of erythromycin E extends and further delineates the latter stages of the erythromycin biogenetic pathway.

A further examination of the products from fermentation broths of Streptomyces violaceoniger has yielded small quantities of several lankamycin related antibiotics and metabolites. One of the antibiotics has been characterized as 3″-de-O-methyl-2″,3″-anhydro-lankamycin. The anhydro sugar of the new lankamycin, 3-methyl-4-O-acetyl-2,3,6-trideoxy-α-L-threo-hex-2-enepyranoside was also isolated as the ethyl glycoside from fermentation broths of the same organism.

The nature of the products obtained from the reaction of chelocardin (1) and the model compound 2-acetyldimedone (5) with a variety of amines was investigated. It was observed that amines react with β-triketones having an exocyclic carbonyl side-chain to give exclusively β,β′-diketoenamines with substitution at the side-chain carbonyl.

Proton magnetic resonance spectra at 100 MHz were obtained for water-soluble and water-insoluble glucans from 11 strains of Streptococcus mutans . The percentages of α- D -(1→6) and non-α- D -(1→6)-, namely, α- D -(1→3)-, linkages were calculated from the anomeric-proton resonances in the 4.7-4.8 and 5.0-5.1 p.p.m. range, respectively. The average content of α- D (1→6) linkages in the polymer fractions precipitating from solution during synthesis of the glucans was generally much lower than that of fractions remaining in solution. The frequent appearance of the α- D -(1→3) resonances as doublets in the spectra suggested neighboring-group effects among the possible α- D -(1→3) and α- D -(1→6) linkage-configurations. These effects were confirmed from 100-MHz spectra of products of a dextranase-degraded, water-insoluble glucan, and a 270-MHz spectrum of an undegraded glucan. It was thus possible to assign the doublet resonances to α- D -(1→3), homogeneous, heterogeneous, and branch configurations, although complete differentiation among proportions of each configuration in the glucan chains could not be achieved.

7-Deoxy-4(R)-dihydrospectinomycin (7) has been prepared and its structure firmly established by proton magnetic resonance and high resolution mass spectrometry. This spectinomycin analog is devoid of antibiotic activity.

3-O-(2″,6″-Dideoxy-α- l -ribo-hexopyranosyl)erythronolide B (6) and 3-O-(2″,6″-dideoxy-α- l -arabino-hexopyranosyl)erythronolide B (7), aberrant metabolites of erythromycin biosynthesis, have been isolated from the fermentation broth of a blocked mutant of the erythromycin producing organism Streptomyces erythreus. The defective glycosidesm, when incubated with early blocked mutants of S. erythreus capable of converting authentic erythromycin progenitors to the complete antibiotic, were unmetabolized. The probable origin of the metabolite is discussed.

The structures of fortimicins A and B have been determined by PMR, CMR, mass spectra and CD combined with chemical degradations. Both antibiotics are pseudodisaccha-rides and incorporate a novel aminocyclitol, fortamine. Incontrast to the diaminocyclitol moieties of known aminoglycosides, fortamine is a 1, 4-diamine, contains both N- and O-methyl groups and possesses chiro stereochemistry. Both antibiotics are glycosides of 6-epi-pur-purosamine B, but fort imicin A differs from fortimicin B by being a glycyl amide.

A new series of tetrahydropyridines was isolated when 1-adamantyl or t-butyl mercaptan was added last to a solution of pyridine N-oxide and triethylamine in acetic anhydride. Under these conditions, the predominant tetrahydropyridines proved to be 1-acetyl-2-alkylthio-3-acetoxy-6-hydroxy-1,2,3,6-tetrahydropyridines. These carbinolamides were isomerized in part during silica gel column chromatography to trans-4-acetoxy-5-alkylthio-5-acetamido-2-pentenals.

The proton magnetic resonance spectra of all the 2-amino-, 2-chloro-, 2-nitropicolines were determined. Long-range coupling of the methyl groups to all available ortho (four bonds) and para (six bonds) ring protons was found in these picolines. The p.m.r. spectra of all of the ring methyl substituted 2-pyridones and 2-pyridthiones were analyzed. In 4- and 5-methyl-2-pyridones and the corresponding thiones, selective ring coupling was observed to only one ortho ring proton, viz., to H-3 and H-6 respectively. However, in 3- and 6-methyl-2-pyridones and analogous thiones, long-range coupling was visible to both ortho and para ring protons. These long-range spin-spin interactions are interpreted in terms of the structures of 2-pyridones and their thione analogs.

The isolation and structure elucidation of a shunt metabolite of erythromycin biosynthesis, (8S)-8-hydroxy-5,6-dideoxy-5-oxoerythronolide B ( 1a ), is described. NMR and CD data reveal that the title compound and related 5-oxo derivatives ( 5 and 6 ) are conformationally homogeneous with erythronolide B ( 2 ). Consistent with this observation is the hydroxyketone-hemiacetal equilibrium present in the case of 5 . The spectroscopic data further show that 1a , (8S)8)hydroxyerythronolide B ( 12 ), and lankolide ( 13 ) have identical 8S stereochemistry.

Facile isomerization of molecular diethylstilbestrol (DES) occurs by a second order reaction on solution in organic solvents. The isomerization of the disodium salt of DES which occurs in basic methanolic solutions is a reversible first order reaction. Mechanisms of the isomerization processes of molecular and anionic DES are proposed. The estrogenic response of isolated disodium salt of cis -DES was determined to be approximately 45% of the activity observed for trans -DES using a mouse uterine weight assay. Since the trans isomer is believed to be considerably more active biologically because of its structural similarity with estradiol, it appears that the observed appreciable activity of the cis -DES test solution is a consequence of the isomerization in vivo to the trans isomer. These results may have significance in the use of DES as a ruminant growth promoter since estrogenic response appears not to be restricted solely to the amount of trans isomer content.

8- epi -erythronolide B ( 4 ) has been isolated as a product formed from the acid treatment of erythronolide B ( 3 ). When this compound was fed to a blocked mutant of the erythromycin producing organism, Streptomycetes erythreus (Abbott 2NU153), nearly quantitative yields of 3- O -(α- l -mycarosyl)-8- epi -erythronolide B ( 10 ) were obtained. The much desired 8- epi -erythromycins ( 2 ) were not realized.

We have shown previously that the esters of adenosine-5'-carboxylic acid (10) represent a new class of potent nontoxic coronary vasodilators. For example, the ethyl ester (12), which is active by an intraduodenal or intravenous route in dogs, causes a large increase in coronary sinus PO2 and coronary blood flow. Because of the pronounced vasoactive properties of the esters of adenosine-5'-carboxylic acid, a systematic study of the corresponding amides (14--50) was undertaken. In addition, several other analogues containing the N1-oxide function (51--52) or 2',3' substituents (3--9, 53--54) were studied.

The structures of seldomycin factors 1 and 2 have been determined by consideration of chemical degradation and spectral properties. Factor 1, also known as XK-88-1, is shown to be 6-O-(2-amino-2-deoxy-alpha-D-xylopyranosyl) paromamine (1) and factor 2, also known as XK-88-2, is shown to be 4'-deoxy-neamine (2). Mass spectral evidence has been obtained that suggests the most probable structure for seldomycin factor 3, also known as XK-88-3, is 6'-amino-6'-deoxyseldomycin factor 1 (12).

The biotransformation of lankamycin and congeners darcanolide and 11-acetyllankolide by a blocked mutant of the erythromycin-producing organism Streptomyces erythreus, which cannot synthesize erythromycin without supplementation with erythromycin precursors, was investigated. Darcanolide and 11-acetyllankolide were converted into the corresponding 15-deoxy-15-oxo derivatives. Lankamycin was transformed to 15-deoxy-15-oxolankamycin, 4"-deacetyl-l5-deoxy-15-oxolankamycin and 3'-de-O-methyllankamycin. None of the derivatives possessed high antimicrobial activity.

We have shown previously that the esters of adenosine-5'-carboxylic acid (10) represent a new class of potent nontoxic coronary vasodilators. For example, the ethyl ester (12), which is active by an intraduodenal or intravenous route in dogs, causes a large increase in coronary sinus PO2 and coronary blood flow. Because of the pronounced vasoactive properties of the esters of adenosine-5'-carboxylic acid, a systematic study of the corresponding amides (14--50) was undertaken. In addition, several other analogues containing the N1-oxide function (51--52) or 2',3' substituents (3--9, 53--54) were studied.

13C-NMR studies have confirmed the structures of (8S)-8-hydroxyerythromycins A- and B-6, 9;9, 11-acetal proposed by KROWICKI and ZAMOJSKI2, 3) for the products of the m-chloroperbenzoic acid oxidation of 8, 9-anhydroerythromycins A- and B-6, 9-hemiacetal. The preparations of (8S)-8-methylthiomethoxy- and (8S)-8-methoxyerythromycin B-6, 9;9, 11-acetals are described. The latter are stable in aqueous acetic acid under conditions which convert (8S)-8-hydroxyerythromycin B-6, 9;9, 11-acetalinto (8S)-8-hydroxyerythromycin B. In a paper describing the preparation of the C8-epimeric 8-hydroxyerythromycins B, we reported1) that buffered m-chloroperbenzoic acid oxidation of 8, 9-anhydroerythromycin B-6, 9-hemiacetal (1), followed by catalytic reduction of the resulting N-oxide to the free amine, gave (8S, 9S)-8, 9-anhydroerythromycin B-6, 9-hemiacetal-8, 9-epoxide (2). Our assignment of structure 2 was based on the expected course of olefin epoxidation with peracids and with apparently compatible spectral properties. In addition, the facile conversion of 2 to (8S)-8-hydroxyerythromycin B (3) in aqueous acetic acid was expected for the strained epoxy spiroacetal structure (2).