Isolation and identification of three urinary metabolites of retinoic acid in the rat.

After the intraperitoneal administration of high doses of ¹⁴C- and ³H-labelled retinoic acid ( 1 ) to rats three major urinary metabolites have been isolated in microgram amounts by use of column, thin-layer and high-pressure liquid chromatography. Their structures were elucidated by mass spectroscopy and Fourier transform ¹H-NMR. spectroscopy as 2 (5-methyl-5-[2-(2,6,6-trimethyl-3-oxo-1-cyclohexen-1-yl)vinyl]-2-tetrahydrofuranone), 3 (5-[2-(6-hydroxymethyl-2,6-dimethyl-3-oxo-1-cyclohexen-1-yl)vinyl]-5-methyl-2-tetrahydrofuranone) and 4 (6-(6-hydroxymethyl-2,6-dimethyl-3-oxo-1-cyclohexen-1-yl)-4-methyl-4-hexenoic acid). In these metabolites the tetraene side chain of 1 is shortened and the cyclohexene ring oxidized. The radioactivity of 2 and 3 accounted for about 10% (0.9% of the dose) each, metabolite 4 for about 6% (0.5% of the dose) of the total urinary radioactivity.     

Interactions intramoleculaires. XXI—Constantes de couplage et interactions gauches avec un groupement t-butyle (molécules cyclohexaniques deutériées)

Different isotopic modifications of deuterated products of 1-t-butlyl-4-methoxycarbonyl cyclohexene (d₄-3,3,6,6), cis- and trans-3-methyl-4-cyanocyclohexene (d₃-3,6,6), cis- and trans-3-methyl-4-cyanocyclohexene (d₃,6,6), cis- and trans-3-t-butyl-4-methoxycarbonylcyclohexene (d₃,-3,6,6) are shown by nuclear magnetic resonance spectral analysis. By comparison of ³J and ⁴J coupling constants of model molecules and molecules with large gauche interactions, we obtain proof that the latter are in a chair conformation with moderate cycle deformations.     

Stereospecific syntheses of all four stereoisomers of 4-fluoroglutamic acid

(+)- -threo-4-Fluoroglutamic acid [(+)-(2S, 4S)-fluoroglutamic acid] has been synthesizedstarting with the natural (−)-4-trans-hydroxy- -proline. Its acetylation at nitrogen followedby esterification with diazomethane afforded methyl 1-acetyl-trans-4-hydroxy- -prolinatewhich was converted to methyl 1-acetyl-cis-4-fluoro- -prolinate by means of diethylaminosulfurtrifluoride (DAST) or 2-chloro-1,1,2-trifluorotriethylamine. The mixture wasoxidized by ruthenium tetroxide to methyl 1-acetyl-cis-4-fluoro- -pyrrolidin-5-one-2-carboxylate,whose acid hydrolysis yielded the title compound. A similar sequence of reactionsconverted cis-4-hydroxy- -proline to (−)- -erythro-4-fluoroglutamic acid [(−)(2R, 4S)-fluoroglutamic acid]. (−)- -threo-4-Fluoroglutamic acid [(−)-(2R, 4R)-floroglutamicacid] was prepared analogously from trans-4-hydroxy- -proline, obtained from its diastereomerby inversion of configuration at carbon 4 of the pyrrolidine ring using thediethyl azodicarboxylate-triphenylphosphine procedure. cis-4-Hydroxy- -proline, necessaryfor the synthesis of (+)- -erythro-4-fluoroglutamic acid [(+)-(2S, 4R)-fluoroglutamicacid], was prepared from trans-4-hydroxy- -proline by benzyloxycarbonylation at thenitrogen, oxidation of the 1-benzyloxycarbonyl-trans-4-hydroxy- -proline to 1-benzyloxy-carbonyl-4-oxo- -proline, its reduction to 1-benzyloxycarbonyl-cis-4-hydroxy- -proline anddeprotection of the latter at the nitrogen. (−)-cis-4-Fluoro- -proline and (+)-trans-4-fluoro- -proline were isolated after the hydrolysis of incompletely oxidized methyl 1-acetyl-cis-4-fluoro- -prolinate and methyl 1-acetyl-trans-4-fluoro- -prolinate, respectively.     

Compounds with bridgehead nitrogen. 44—the conformational analysis of perhydropyrido[1,2-c] [1,3]thiazine

The 270 MHz NMR data on trans- and cis-(H-4a, H-7)-7-ethylperhydropyrido[1,2-c][1,3]thiazine show heavy conformational bias to the trans- and S-inside cis-fused conformations, respectively. Comparison of the ¹³C NMR spectra of these anancomeric systems with the ¹³C NMR spectrum of perhydropyrido[1,2-c][1,3]thiazine indicates a trans-?S-inside cis-conformational equilibrium for the latter compound in CDCl₃ at 25°C, containing ca 75% trans-fused conformer. The ¹³C NMR spectrum of perhydropyrido[1,2-c][1,3]-thiazine at ?75°C showed 64% trans-fused conformer and 36% S-inside cis-conformer.     

Saturated heterocycles. 254 . synthesis and stereochemistry of saturated or partially saturated pyridazino-[6,1-b]- and phthalazino[1,2-b]quinazolinones

By the reaction of anthranilic hydrazide 1 with cis-2-(p-methylbenzoyl)-1-cyclohexanecarboxylic acid 2a or diendo-3-(p-methylbenzoyl)bicyclo[2.2.1]heptane-2-carboxylic acid 2b , fused tetra- and pentacyclic ring systems 3a, b were prepared, trans-2-Amino-1-cyclohexanecar-bohydrazide 4b was reacted with 3-(p-chlorobenzoyl)propionic acid 5 to yield the pyridazino[6,1-b]quinazolinone 6 . From the reaction of cis-2-amino-1-cyclohexanecarbohydrazide 4a with 2a , three isomeric partially saturated 8H-phthalazino[1,2-b]quinazolin-8-ones 7a-c were formed. The reaction of diexo-2-aminobicyclo[2.2.1]heptane-3-carbohydrazide 4c and 2a furnished the pentacyclic derivatives 8 and 9 containing a 3-aryl-4,5-dihydropyridazine or 3-arylhexahydropyridazine ring C with cis annelated C/D rings. The formation of 8 and 9 involving different ring systems can be rationalized by two reaction pathways: (i) in the bislactam 9 the carboxyl group acylates the hydrazide, while (ii) in 8 it forms a pyridazine ring with the cyclic amino group by cyclocondensation. The structures of the products were elucidated by ¹H and ¹³C nmr methods, including DEPT, DNOE and 2D-HSC measurements.     

Proton magnetic resonance studies of compounds with bridgehead nitrogen. 37–a comparison of the positions of conformational equilibria in 1-methylperhydro-oxazolo[3,4-a]pyridines and in 1-methylperhydrothiazolo [3,4-a]pyridines

cis(1-H, 8a-H)-1-Methylperhydro-oxazolo[3,4-a]pyridine and cis(1-H, 8a-H)-1-methylperhydrothiazolo[3,4-a]pyridine both adopt exclusively the trans-fused conformation in carbon tetrachloride solution at room temperature. Both parent unsubstituted systems exist under similar conditions as equilibria containing c. 67% (oxazolo compound) and 64% (thiazolo compound) of the trans-fused conformation. In marked contrast to these similar positions of conformational equilibria in both systems the trans(1-H,8a-H)-1-methylperhydrooxazolo[3,4-a]pyridine exists as c. 73% trans-fused in equilibrium with a cis-fused conformation whereas the trans(1-H, 8a-H)-1-methylperhydrothiazolo[3,4-a]pyridine exists almost exclusively in a cis-fused ring conformation. These differences in conformational equilibria are explained in terms of changes in non-bonded interactions.     

Stereochemistries of electron impact induced hydrogen abstraction reactions proceeding through 6-membered transition states

The stereochemistries of nine electron-impact induced eliminations proceeding from derivatives of the cis-4-t-butyl system have been determined. The predominant cis elimination observed in every case is consistent with the substantial integrity of the cyclohexyl ring prior to fragmentation, and with a cyclic transition state for hydrogen abstraction. The stereochemistries of electron impact induced eliminations from 11 derivatives of the trans-4-t-butylcyclohexyl system exhibit a dichotomy. The predominatn trans stereochemistry observed in six electron impact induced eliminations, and the nonstereospecific electron impact induced dehydration of trans-4′-t-butylcyclohexyl-ethanol are consistent with nonconcerted elimination from a chair-like cyclohexyl ring. Conversely, the McLafferty rearrangement of trans-4′-t-butyl-cyclohexyl-2-propanone proceeds nonstereospecifically. trans-4-t-Butylcyclohexyl acetaldehyde, 2-methyl-3-(trans-4′-t-butylcyclohexyl)-1-propane and trans-4-t-butylcyclohexyl-S-methyl xanthate exhibit predominant cis McLafferty rearrangement stereochemistry. This result may be due to fragmentation through boat-like conformers in these compounds.     

1H-NMR.-, 13C-NMR.-, UV.- und CD.-Daten von synthetischem (3S, 3′S)-Astaxanthin,seinem 15-cis-Isomeren und einigen analogen Verbindungen

¹H-NMR., ¹³C-NMR., UV. and CD. spectral data of synthetic (3S, 3′S)-astaxanthin, its 15-cis isomer, and some related compounds ¹H-NMR., ¹³C-NMR., UV. and CD. spectra are reported for synthetic (3S, 3′S)-astaxanthin ( 1 ), its 15-cis isomer ( 2 ), its diacetate ( 3 ), and the 15, 15′-didehydro compound ( 5 ). These data prove the identity of the synthetic and the naturally occuring compound 1 . A full interpretation of the ¹H- and ¹³C-NMR. spectra is given and confirms the configuration of all the double bonds. The conformation of the cyclohexene end group of all the compounds is shown to be identical. The signs of the different CD. maxima of 15-cis-astaxanthin are found to be opposite to those of the all-trans compound.     

Synthese von threo-cis/threo-trans- und erythro-cis/erythro-trans-Dihydropalustrin. 17. Mitteilung über Schachtelhalmalkaloide

Synthesis of threo-cis/threo-trans- and erythro-cis/erythro-trans-dihydropalustrin The first synthesis of a threefold protected spermidine, namely ³-benzyloxycarbonyl-N¹-phthaloyl-N²-tosylspermidin ( 9 ) is presented. Each of the protecting groups can be removed selectively. After hydrazinolysis the resulting N³-benzyloxy-carbonyl-N²-tosylspermidine ( 10 ) has been condensed with methyl (2 E)-cis-7,8-epoxy-2-decenoate to the threo-cis/trans piperidines 17 , and with methyl (2 E)-trans-7,8-epoxy-2-decenoate to the erythro-cis/trans piperidines 17 , respectively. After catalytic removal of the Z group, the resulting aminoesters 13 and 18 , in a melt with imidazole, underwent ring closure to the 13-membered lactames 14 and 19 , respectively. reductive deprotection of the N-tosyl group with sodium/ammonia led to the stereoisomeric palustrines 15 and 20 , respectively.     

Synthesis,separation, and resolution of cis- and trans-3-ethylproline

The synthesis, separation, and optical resolution of cis- and trans-3-ethylproline are described. Two different approaches were employed: (1) The Michael addition reaction of 2-pentenal with diethyl-N-carbobenzyloxyaminomalonate gave the intermediate 3-ethyl-5-hydroxy-N-benzyloxypyrrolidine. Hydrogenolysis of this intermediate followed by acid hydrolysis gave a mixture of cis- and trans-3-ethylproline. Separation of the isomers was accomplished by selective saponification of N-(p-toluenesulfonyl)-cis- and trans-3-ethylproline methyl esters using 0.25N methanolic sodium hydroxide. (2) The Michael condensation of diethyl acetamidomalonate with 2-pentenoic acid ethyl ether produced the intermediate 5,5-bis(ethoxycarbonyl)-4-ethylpyrrolidine. Partial saponification followed by decarboxylation afforded a mixture of cis- and trans-isomers of ethyl-3-ethylpyroglutamate. The diastereoisomers were separated using low temperature fractional crystallization. Reduction of these isomers and tosylation in situ afforded the corresponding N-(p-toluenesulfonyl)-cis- and trans-3-ethylprolinols. Chromic acid oxidation gave N-(p-toluenesulfonyl)-cis- and trans-3-ethylproline. Reaction of these tosylates with 30% hydrogen bromide in acetic acid gave cis- and trans-3-ethylproline. Both optically active isomers of D(+)-and L(-)-trans-3-ethylproline were successfully resolved using (+)-dibenzoyl-D -tartaric acid and (-)-dibenzoyl-L -tartaric acid as resolving agents. The absolute configurations of the optically active isomers were determined by circular dichroism spectroscopy.     

Die thermische Umlagerung von 2-(Buta-1′,3′-dienyl)-phenolen in 2-Alkyl-2H-chromene; Beispiele für aromatische [1,7a]- und [1,5s]sigmatropische Wasserstoffverschiebungen

2-(1′-cis,3′-cis-)- and 2-(1′-cis,3′-trans-Penta-1′,3′-dienyl)-phenol (cis, cis- 4 and cis, trans- 4 , cf. scheme 1) rearrange thermally at 85–110° via [1,7 a] hydrogen shifts to yield the o-quinomethide 2 (R ? CH₃) which rapidly cyclises to give 2-ethyl-2H-chromene ( 7 ). The trans formation of cis, cis- and cis, trans- 4 into 7 is accompanied by a thermal cis, trans isomerisation of the 3′ double bond in 4. The isomerisation indicates that [1,7 a] hydrogen shifts in 2 compete with the electrocyclic ring closure of 2 . The isomeric phenols, trans, trans- and trans, cis- 4 , are stable at 85–110° but at 190° rearrange also to form 7 . This rearrangement is induced by a thermal cis, trans isomerisation of the 1′ double bond which occurs via [1, 5s] hydrogen shifts. Deuterium labelling experiments show that the chromene 7 is in equilibrium with the o-quinomethide 2 (R ? CH₃), at 210°. Thus, when 2-benzyl-2H-chromene ( 9 ) or 2-(1′-trans,3′-trans,-4′-phenyl-buta1′,3′-dienyl)-phenol (trans, trans- 6 ) is heated in diglyme solution at >200°, an equilibrium mixture of both compounds (～ 55% 9 and 45% 6 ) is obtained.     

Der Metabolismus des Retinoids Ro 10-9359. Isolierung und Identifizierung der Hauptmetaboliten aus Plasma,Urin und Faeces des Menschen sowie aus der Galle der Ratte Synthese von drei Urinmetaboliten

The Metabolism of the Retinoid Ro 10-9359. Isolation and Identification of the Major Metabolites in Human Plasma, Urine and Feces Synthesis of Three Urinary Metabolites After oral administration of therapeutic doses of the ³H-labelled aromatic retinoic acid analog (retinoid) Ro 10-9359 (ethyl all-trans-9-(4-methoxy-2,3,6-trimethyl-phenyl)-3,7-dimethyl-2,4,6,8-nonatetraenoate) to humans 75 and 15% of the ³H-dose were excreted within the first five days in the feces and the urine, respectively. Using chromatographic procedures including high pressure liquid chromatography 18 metabolites could be isolated from human urine. Their structures were elucidated by mass spectrometry and FT–¹H-NMR. spectroscopy. In these urinary metabolites the tetraene side chain of the parent compound Ro 10-9359 is shortened. The radioactivity of the identified urinary metabolites accounted for about 11% of the dose. Three urinary metabolites were synthesized. The main part of the radioactivity excreted within the first five days in the feces consisted of unchanged drug (60% of the dose). A smaller (amount 15% of the dose) could not be identified. The unchanged drug and a major metabolite, the corresponding acid, were found in human plasma. In an experiment with bile-duct cannulated rats the radioactively labelled retinoid Ro 10-9359 was injected intravenously. About 70% of the ³H-dose was excreted in the bile, within the first 48 hours. The whole radioactivity of the rat bile consisted of polar metabolites. No unchanged drug could be found. After enzymatic hydrolysis of the bile conjugates three metabolites were isolated. The main metabolite (49% of the i.v. dose) was a conjugate of the corresponding acid of the parent drug, already found as free compound in human plasma. The other bile metabolites (9 and 7% of the i.v. dose) had an intact side chain, too. An enterohepatic recycling of the bile metabolites was observed in the rat.     

Synthesis, 1H- and 13C-NMR spectra,crystal structure and ring openings of 1-methyl-6,9-epoxy-9-aryl-5,6,9,10-tetrahydro-1H-imidazo [3,2-e] [2H-1,5] oxazocinium methanesulfonate

The methanesulfonic acid catalyzed reaction of 1-(4-chloro- and 2,4-dichlorophenyl)-2-(1-methyl-2-imida-zolyl)ethanones 1a and 1b with glycerol produced cis- and trans-{2-haloaryl-2-[(1-methyl-2-imidazolyl)methyl]-4-hydroxymethyl}-1,3-dioxolanes 2a and 2b with a 2:1 cis/trans ratio. Besides these five-membered ketals, the reaction of 1a with glycerol afforded a small amount of trans-{2-(4-chlorophenyl)-2-[(1-methyl-2-imidazolyl)methyl]-5-hydroxy}-1,3-dioxane ( 3a , 7%). The reaction of methanesulfonyl chloride with cis-1 formed the corresponding methanesulfonates, cis- 4 , which rapidly cyclized to the title compounds 5 . Base-catalyzed ring opening of 5 furnished 1-methyl-5,6-dihydro-6-hydroxymethyl-8-(4-chloro- and 2,4-dichlorophenyl)-1H-imidazo[3,2-d][1,4]oxazepinium methanesulfonates 7 . Acid-catalyzed hydrolyses of 5 or 7 provided 1-methyl-2-[(4-chloro- and 2,4-dichloro)phenacyl]-3-[(2,3-dihydroxy)-1-propyl]imidazolium salts 12 . Structure proofs were based on extensive ¹H and ¹³C chemical shifts and coupling constants and structures of 3a and 5a were confirmed by single crystal X-ray crystallography.     

Stereospezifische Synthese und Isomerisierung der 10-Chlor-decahydroisochinoline. Decahydroisochinoline. IV. Teil

Treatment of cis- and trans-10-hydroxy-N-methyl-decahydroisoquinoline, ( 3a ) and ( 10a ) respectively, or N-methyl-Δ^9,10-octahydroisoquinoline ( 4 a ) with hydrogen chloride in acetic acid affords the thermodynamically more stable trans-isomer of 10-chloro-N-methyl-decahydroisoquinoline ( 1a ). On the other hand ring closure of β-(cyclohexen-1-yl)-ethylamines 11a or 11b with aqueous formaldehyde in the presence of chloride ions leads to the 10-cis-chlorides 2a or 2b in a kinetically controlled reactions.     

Syntheses of Unique Bicyclophostones and Unexpected Difference in the Reaction of Lawesson's Reagent vs. P2S5 with Cis-Bicyclophostone (1)

Abstract

The purpose of this study was to synthesize trans-l and determine the equilibriurr constant with cis-1. Oniy the synthesis¹ and x-ray structure² of the cis isomer have bcen reported. Four prior synthetic routes to make the vans isomer³ gave only cis product. For example, intrarmolecular ring closure of the cis or trains isomers of 4 (R= (CH₂)₃OH) with LiH or thermal closure of the cis or trans 4 (R= (CH₂)₂) gave only cis-1. Since both iosmers of 1,8-dioxabicyclo[4.4.0] decane are known and readily equilibrate (57% cis and 43% trans), the apparent inaccessibility of trans-1 attracted our attention. Thc preparation of trans-1 was achieved by treatment of cis-1 with Lawesson's reagent (LR) to provide cis-2. followed by oxidation with m-chloroperbenzoic acid/trifluoroacetic acid to give a 5:1 mixture of cis:trans 1, respectively. An unexpected formation of the sulfur analogue of 1 was observed on treatment of cis-1 with P₂S₅/pyridine at reflux temperatures to give a 1.6:1 mixture of cis:trans 3, respectively. Thermal quilibration of 1 at 204°C provided an equilibrium ratio of 99.5% cis and 0.5% of the trans isomer. However, equilibration of 3 at 250°C led to 82.2:17.8 ratio in favor of the cis isomr. These results are consistent with semiemperical MO calculations. The stereochemical outcome on treatment of 4 with LR was also investigated. X-ray structures for six compounds: trans-1, cis-2, cis and trans-3; cis-4 (R=Ph), and cis-5, (R = Ph) wen determined.     

Separation of new antidiabetic agent,N-(trans-4-isopropylcyclohexylcarbonyl)-d-phenylalanine and three related compounds by RP-HPLC

Summary A high-performance liquid chromatographic method is proposed for the simultaneous separation of two pairs of isomers:N-(trans-4-isopropylcyclohexylcarbonyl)-d-phenylalanine, (Nateglinide) andN-(cis-4-isopropylcyclohexylcarbonyl)-d-phenylalanine,trans-4-isopropylcyclohexane-carboxylic acid andcis-4-isopropyl-cyclohexanecarboxylic acid using a C₁₈ column. The mobile phase is a ternary mixture of acetonitrile-methanol-0.1 M ammonium dihydrogen phosphate buffer, pH 3.0 (5:2:4 v/v/v) and UV detection at 210 nm. Precision, linearity, limit of detection and recovery were also evaluated for each compound. Satisfactory results were obtained.     

Separation of 5-Lipoxygenase Metabolites Using Cyclodextrin-Modified Microemulsion Electrokinetic Chromatography and Head Column Field-Amplified Sample Stacking

A cyclodextrin-modified microemulsion electrokinetic chromatography method employing head column field-amplified sample stacking was developed for the analysis of arachidonic acid metabolites of the lipoxygenase pathways. The influence of the concentration of boric acid, the surfactant sodium dodecyl sulfate, the co-surfactant 1-butanol and the oil phase octane as well as the pH of the background electrolyte, the separation voltage and the separation temperature was studied. The optimized microemulsion consisting of 20 mM boric acid buffer, pH 9.0, 3.0 % (m/v) sodium dodecyl sulfate, 0.5 % (v/v) octane, 5.0 % (v/v) 1-butanol and 15 mM α-cyclodextrin enabled the separation of 20-hydroxy-leukotriene B₄, leukotriene B₄, 6-trans-leukotriene B₄, 6-trans-12-epi-leukotriene B₄, 5(S)-hydroxy-6-trans-8,11,14-cis-eicosatetraenoic acid, 12(S)-hydroxy-5,8,14-cis-10-trans-eicosatetraenoic acid, 15(S)-hydroxy-5,8,11-cis-13-trans-eicosatetraenoic acid as well as the internal standard prostaglandin B₁ in <10 min employing a separation voltage of 17.5 kV at a temperature of 23 °C. A matrix peak from solid-phase extraction sample workup co-migrated with 5(S)-hydroxy-6-trans-8,11,14-cis-eicosatetraenoic acid affecting peak integration. The addition of 5 % (v/v) 2-propanol to the microemulsion resulted in the separation of this eicosatetraenoic acid and the matrix components at the expense of analysis time and peak resolution between the diastereomers 6-trans-leukotriene B₄ and 6-trans-12-epi-leukotriene B₄. In summary, the MEEKC method appeared to be especially suitable for the more polar arachidonic acid metabolites.     

Synthesis and Reactions of 4-cis- and 4-trans-Hydroxy-2e-methyl-4-ethynyl-trans-decahydroquinolines

By treating 2e-methyl-4-oxo-trans-decahydroquinoline with lithium acetylide a mixture of stereoisomeric 4-cis-hydroxy-2e-methyl- and 4-trans-hydroxy-2e-methyl-4-ethynyl-trans-decahydroquinolines was obtained in 3:2 ratio. Their reaction with acetonitrile in the presence of sulfuric acid (Ritter's reaction) results in a mixture of stereoisomeric 4-cis-acetylamino-2e-methyl- and 4-trans-acetylamino-2e-methyl-4-ethynyl-trans-decahydroquinolines in the same ratio. The ethynyl group of alcohols synthesized is not hydrated under conditions of Kuchrerov's reaction. The boiling of the alcohols with formic acid furnished a mixture of 4-acetyl-2e-methyl and 2e-methyl-4-ethynyl-1,2,3,6,7,8,9,10-octahydroquinolines in 1:7 ratio. The former of these compounds under conditions of Ritter's reaction yielded a mixture (1:1.4) of stereoisomeric 4-acetyl-4-trans-acetylamino- and 4-acetyl-4-cis-acetylamino-2e-methyl-trans-decahydroquinolines. From 2e-methyl-4-ethynyl-1,2,3,6,7,8,9,10-octahydroquinoline under the same conditions were obtained both already mentioned stereoisomeric 4-acetylamino-2e-methyl-4-ethynyl-decahydroquinolines (53% of cis-isomer and 35% of trans-isomer in the mixture) and 4-acetyl-4-acetylamino-2e-methyldecahydroquinolines (7% of cis-isomer and 5% of trans-isomer).     

Determination of trace levels of pyrethroid metabolites in human urine by capillary gas chromatography-high resolution mass spectrometry with negative chemical ionization

Summary Applications of high-resolution gas chromatography and high-resolution mass spectrometry (GC-MS) for identification and quantitation of trace amounts of pyrethroid metabolites in human urine samples are demonstrated. The method covers the pyrethroid metabolitescis- andtrans-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropane carboxylic acid (cis- andtrans-DCCA),cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DBCA), 4-fluoro-3-phenoxybenzoic acid (FPBA), and 3-phenoxybenzoic acid (3-PBA). After acid-induced hydrolysis of urine samples and exhaustive solvent extraction, a carbodiimide-coupled esterification of the free carboxylic acids with hexafluoroisopropanol (HFIP) is applied. Identification of the derivatives formed is achieved by low-resolution electron-impact mass spectrometry (EIMS) using an ion-trap detector. Quantitation was by capillary gas chromatography—high-resolution mass spectrometry using negative chemical ionization (GC-NCIMS). 2-Phenoxybenzoic acid (2-PBA) served as internal standard. The limits of detection forcis- andtrans-DCCA,cis-DBCA, FPBA and 3-PBA were 0.03 μg L⁻¹ or below. The applicability of the presented method was tested on urine samples of persons exposed to low levels of pyrethroids.     

An ab initio study of some structural features and the rotational barriers in performic acid,formic acid and hydrogen peroxide

Calculations on performic acid at the 4-31G level, with and without bond functions with complete geometry optimization, and at the (9, 5) level, with and without polarization functions and rigid rotation, all give no sign of a well in the potential energy curve for rotation about the O/O bond axis in the region of 50° – 90° ; and all but the unaugmented 4-31G basis set find the cis-cis planar conformer to be the most stable form. Calculations at the (9,5) level with rigid rotation find the energies of the other planar conformers, relative to the cis-cis conformer, to be 0.94, 1.50 and 14.80 kcal mol^?1 for the trans-trans, cis-trans and trans-cis structures respectively. These energies and also that for the barrier separating the cis-cis and cis-trans conformers, 1–2 kcal mol^?1, are discussed in relation to corresponding data for formic acid, hydrogen peroxide and several planar four heavy-atom molecules. Dipole moment calculations using the same basis sets would seem to favor a skew conformation as the most stable for performic acid, but comparisons between calculated and experimental values for formic acid and for hydrogen peroxide cast doubt on the validity of such results.