Determination of a novel selective inhibitor of type 1 5α-reductase in human plasma by liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry

A sensitive and specific assay of human plasma for the determination of (5α,7β,16β)-16[(4-chlorophenyl)oxy]-4,7-dimethyl-4-aza-andronstan-3-one (I), a selective inhibitor of human type 1 5α-reductase, has been developed. The method is based on high-performance liquid chromatography (HPLC) with tandem mass spectrometric (MS–MS) detection. The analyte (I) and internal standard, Proscar (II), were isolated from the basified biological matrix using a liquid–liquid extraction with methyl-tert.-butyl ether (MTBE). The organic extract was evaporated to dryness, the residue was reconstituted in mobile phase and injected into the HPLC system. The MS–MS detection was performed on a PE Sciex API III Plus tandem mass spectrometer using a heated nebulizer interface. Multiple reaction monitoring using the precursor→product ion combinations of m/z 430→114 and 373→305 was used to quantify I and internal standard (II), respectively. The assay was validated in the concentration range of 0.5 to 500 ng/ml in human plasma. The precision of the assay, expressed as coefficient of variation (C.V.), was less than 7% over the entire concentration range, with adequate assay specificity and accuracy. The HPLC–MS–MS method provided sufficient sensitivity to completely map the 24 h pharmacokinetic time-course following a single 0.5 mg dose of I.     

Simultaneous determination of a potassium channel opener and its metabolite in rat plasma with column-switching liquid chromatography using atmospheric pressure chemical ionisation

A specific LC–MS assay was developed for simultaneous determination of Ro 31-7837 (I) and its metabolite Ro 31-6930 (II) in rat plasma, using on-line SPE by column-switching reversed-phase HPLC combined with atmospheric pressure chemical ionization (APCI) tandem mass spectrometry for detection in the selected reaction monitoring mode. The method involved precipitation of plasma proteins with ethanol and automatic injection of a 1-ml aliquot of the supernatant onto a standard bore trapping column (LC-ABZ, 20×4.6 mm) for compound retention. Using the backflush mode, the analytes were transferred onto the analytical column (Kromasil C₁₈, 125×4.0 mm) for chromatographic separation and mass spectrometric detection. The mean precision and accuracy for I and II in the concentration range 0.25–100 ng/ml were found to be 3.7% and 101%, and 3.5% and 106%, respectively. The data were assessed from QC samples during the validation phase of the assay. The lower limit of quantification for both I and II was 0.25 ng/ml, using a 0.5-ml plasma aliquot. This LC–MS method provided the requisite specificity, sensitivity, accuracy and precision to assess the pharmacokinetics of the compounds in the rat.     

Chemical analysis of the female sex pheromone in Palpita nigropunctalis (Lepidoptera: Crambidae)

The lilac pyralid, Palpita nigropunctalis Bremer (Lepidoptera: Crambidae), is a common pest of Oleaceae plants. A crude extract of the female sex pheromone glands was examined by gas chromatography-electroantennogram detection (GC-EAD) and GC coupled to a mass spectrometer (GC/MS). The GC-EAD analysis revealed three EAG-active components (I–III) in a ratio of 1:0.2:0.01 (I: II: III). GC/MS analysis successfully recorded the mass spectra of I and II. For I, ions at m/z 238 (M⁺) and 220 ([M-18]⁺) indicated the structure of a monoenyl aldehyde with a 16-carbon chain. For II, M⁺ was not detected, but ions at m/z 222 ([M-60]⁺) and 61 ([AcOH+1]⁺) suggested that II was a monoenyl acetate with a 16-carbon chain. Further GC/MS analysis of the extract treated with dimethyl disulfide revealed that the double bonds in both I and II are located at the same position of 11th-carbon. In addition, the pheromone extract was examined by GC/Fourier transform-infrared spectrophotometer (GC/FT-IR). An IR spectrum of I showed characteristic absorption at 1716 and 966?cm^?1, indicating a formyl group and E configuration of the double bond, respectively. In the case of II, absorption at 1745 and 968?cm^?1 indicated an ester carbonyl and E configuration, respectively. Taken together and by comparison with authentic standards, I and II were confirmed as (E)-11-hexadecenal and (E)-11-hexadecenyl acetate, respectively; while III was speculated as (E)-11-hexadecen-1-ol. The synthetic I, II and III all coincided well with those of the natural components in chemical data, and elicited strong electroantennographic activity in male P. nigropunctalis.     

1-trans-Parinaroyl phospholipids: Synthesis and fast atom bombardment/electron impact mass spectrometric characterization

1-trans-Parinaroyl-2-linoleoyl-sn-glycero-3-phosphocholine (1–18:4-2-18:2-GPC) was synthesized from lecithin and parinaric acid by the following route: $\text{diacyl-GPC}\text{→}\text{GPC}\text{→ 1,2-}\text{di}\text{-18:4-}\text{GPC}\text{(}\text{I}\text{) → 1–18:4-}\text{GPC}\text{(}\text{II}\text{) → 1–18:4-2-18:2-}\text{GPC}\text{(}\text{III}\text{)}$. The identity of I, II and III was established by fast atom bombardment (FAB) mass spectrometry of the intact molecules as well as electron impact (E1) mass spectrometry of the corresponding O-TMS derivatives obtained after phospholipase C treatment and silylation. Temperature dependent phase transition of phospholipid liposomes was performed in the presence of III.     

Determination of a cyclic hexapeptide, a novel antifungal agent, in human plasma by high-performance liquid chromatography with ion spray and turbo ion spray tandem mass spectrometric detection

Methods for the determination of a semi-synthetic cyclic hexapeptide (I, MK-0991) in human plasma based on high-performance liquid chromatography (HPLC) with tandem mass spectrometric (MS–MS) detection using pneumatically assisted electrospray (ion spray, ISP) and turbo ion spray (TISP) interfaces were developed. Drug and internal standard (II, an isostere of I) were isolated from plasma by solid-phase extraction (SPE). The eluent from SPE was evaporated to dryness, the residue was reconstituted in mobile phase and injected into the HPLC system. The use of ISP, TISP and heated nebulizer (HN) interfaces as sample introduction systems were evaluated and showed that the heated nebulizer was not adequate for analysis due to thermal instability and/or adsorption of I and II to glass surfaces of the interface. Compounds I and II were chromatographed on a wide pore (300 Å), 150×4.6 mm C₈ analytical column, and the HPLC flow-rate of 1.2 ml/min was split 1:20 prior to introduction to the ISP or TISP interface of the mass spectrometric system. The MS–MS detection was performed on a PE Sciex API III Plus tandem mass spectrometer operated in selected reaction monitoring mode (SRM). The precursor→product ion combinations of m/z 1093.7→1033.6 and 1094.7→1033.6 were used to quantify I and II, respectively, after chromatographic separation of the analytes. The assay was validated in the concentration range of 10–1000 ng/ml using ISP, and 2.5–500 ng/ml of plasma using TISP with good precision and adequate accuracy. The effects of HPLC mobile-phase components on the ionization efficiency and sensitivity of detection in the positive ionization mode, the evaluation of the matrix effect, and limitations in sensitivity of detection of I due to the formation of multiply charged species are presented.     

Determination of imidapril and imidaprilat in human plasma by high-performance liquid chromatography–electrospray ionization tandem mass spectrometry

A sensitive and specific assay of imidapril and its active metabolite, imidaprilat, in human plasma has been developed. This method is based on rapid isolation and high-performance liquid chromatography (HPLC)–electrospray ionization (ESI)-tandem mass spectrometry (MS–MS). Imidapril and imidaprilat were isolated from human plasma using OASIS HLB (solid-phase extraction cartridge), after deproteinization. The eluent from the cartridge was evaporated to dryness, and the residue was reconstituted in mobile phase and injected into the HPLC–ESI-MS–MS system. Each compound was separated on a semi-micro ODS column in acetonitrile–0.05% (v/v) formic acid (1:3, v/v). The selected ion monitoring using precursor→product ion combinations of m/z 406→234 and 378→206, was used for determination of imidapril and imidaprilat, respectively. The linearity was confirmed in the concentration range of 0.2 to 50 ng/ml in human plasma, and the precision of this assay, expressed as a relative standard deviation, was less than 13.2% over the entire concentration range with adequate assay accuracy. The HPLC–ESI-MS–MS method correlates well with the radioimmunoassay method, therefore, it is useful for the determination of imidapril and imidaprilat with sufficient sensitivity and specificity in clinical studies.     

The kinetics of ligand substitution in bis(N-alkylsalicylaldiminato)nickel(II) Complexes: a study on the reactivity of square-planar versus octahedral coordination

The bis(N-alkylsalicylaldiminato)nickel(II) complexes Ni(R-sal)₂ with R = CH(CH₂OH)CH(OH)Ph (I), R = CH(CH₃)CH(OH)Ph (II) and R = CH₂CH₂Ph (III; Ph = phenyl) were prepared and characterized. In the solid state I and II are paramagnetic (μ = 3.2 and 3.3 BM at 20 °C, respectively), whereas III is diamagnetic. It follows from the UV-Vis spectra that in acetone solution I is six-coordinate octahedral and III is four-coordinate planar, the spectrum of II showing characteristics of both modes of coordination. Vis spectrophotometry and stopped-flow spectrophotometry were applied to study the kinetics of ligand substitution in I–III by H₂salen (= N,N′-disalicylidene-ethylenediamine) in the solvent acetone at different temperatures. The kinetics follow a second-order rate law, rate = k[H₂-salen] [complex]. At 20 °C the sequence of rate constants is k(III):k(II):k(I) = 11 850:40.6:1. The activation parameters are ΔH^≠(I) = 112, ΔH^≠(II) = 40.7, ΔH^≠(III) = 35.7 kJ mol⁻¹ and ΔS^≠(I) = 92, ΔS^≠(II) = −103, ΔS^≠(III) = −89 J K⁻¹ mol⁻¹. The enormous difference in rate between complexes I, II and III, which is less pronounced in methanol, is attributed to the existence of a fast equilibrium planar ⇌ octahedral, which is established in the case of I and II by intramolecular octahedral coordination through the hydroxyl groups present in the organic group R. An A-mechanism is suggested to control the substitution in the sense that the entering ligand attacks the four-coordinate planar complex, the octahedral complex being kinetically inert.     

Interactions of five- and six-membered cyclic esters with α-chymotrypsin: Kinetic evidence for covalent enzyme intermediates

Interactions of α-chymotrypsin with 2-coumaranone (I), 3,4-dihydrocoumarin (II), o-hydroxy-α-toluenesulfonic acid sultone (III), and β-o-hydroxyphenylethanesulfonic acid sultone (IV) were studied in the presence of 14% acetonitrile at pH 7.0 by means of the proflavin displacement technique and by inhibition of N-acetyl-l-tryptophan ethyl ester (ATrEE) hydrolysis. Under saturating conditions of either I, II, or III, an enzyme intermediate was shown to accumulate using either the proflavin displacement technique or the ATrEE activity assay. The intermediates have characteristics of covalent enzyme-substrate compounds and are believed to decompose simultaneously by two pathways, one to give free enzyme and hydrolyzed cyclic ester, and the other to give the original cyclic ester and free enzyme. With α-chymotrypsin and III the observed first-order rate constant for decomposition of the intermediate by the two pathways was 0.19 ± 0.04 min^?1, while the rate constant for the hydrolytic pathway alone was 0.013 ± 0.0009 min^?1. These results indicate that the covalent-like intermediate with this sultone is not only capable of reverting to starting cyclic ester but prefers this pathway over hydrolysis. Sultone IV was found to bind to enzyme; but in contrast to the behavior of esters I–III, the binding did not result in accumulation of a covalent-like intermediate.     

Efficient high-performance liquid chromatographic assay for the simultaneous determination of metoprolol and two main metabolites in human urine by solid-phase extraction and fluorescence detection

An improved, more efficient method for the determination of metoprolol and its two metabolites in human urine is reported. The simultaneous analysis of the zwitterionic metoprolol acidic metabolite (III, H117/04) with the basic metabolites α-hydroxymetoprolol (II, H119/66), metoprolol (I) and guanoxan (IV, internal standard) was achieved employing solid-phase extraction and isocratic reversed-phase HPLC. The analytes were extracted from urine (100 μl) using C₁₈ solid-phase extraction cartridges (100 mg), and eluted with aqueous acetic acid (0.1%, v/v)–methanol mixture (40:60, v/v, 1.2 ml). The eluents were concentrated (250 μl) under vacuum, and aliquots (100 μl) were analysed by HPLC with fluorescence detection at 229 nm (excitation) and 309 nm (emission) using simple isocratic reversed-phase HPLC (Novapak C₁₈ radial compression cartridge, 4 μm, 100×5 mm I.D.). Acetonitrile–methanol–TEA/phosphate buffer pH 3.0 (9:1:90, v/v) was employed as the eluent (1.4 ml/min). All components were fully resolved within 18 min, and the calibration curves for the individual analytes were linear (r²≥0.996) within the concentration range of 0.25–40.0 mg/ml. Recoveries for all four analytes were greater than 76% (n=4). The assay method was validated with intra-day and inter-day variations less than 2.5%.     

p-Benzoquinone monoketals,novel degradation products of β-O-4 lignin model compounds by Coriolus versicolor and lignin peroxidase of Phanerochaete chrysosporium

2-(4-Ethoxy-3-methoxyphenyl)-3-hydroxymethyl-6,10-dimethoxy-1,4-dioxaspiro[4,5]deca-6,9-diene-8-one (III) and its isomer IV were identified as catabolites of 4-ethoxy-3-methoxyphenylglycerol-β-syringaldehyde ether (I) by the culture of Coriolus versicolor. Compound III was also produced from 4-ethoxy-3-methoxyphenylglycerol-β-syringic acid ether (II) by lignin peroxidase of Phanerochaete chrysosporium. An isotopic experiment showed that molecular oxygen was incorporated into the quinone oxygen of III in the degradation of II by lignin peroxidase.     

Computational investigation of the geometric structures of [(CN)5PtTl(CN)n]n− (n=0, 1, 2 or 3)

[(CN)₅PtTl(CN)_n]ⁿ⁻ (n=0–3, complexes I–IV) have been studied computationally using quasi-relativistic gradient-corrected density functional theory. Good agreement is obtained with previous EXAFS and Raman data for complexes II–IV, but calculations significantly overestimate the PtTl bond length and underestimate ν(PtTl) for complex I. The addition of co-ordinating water molecules to the thallium atom in complexes I–III has little effect on complexes II and III, but significantly shortens the PtTl bond in complex I, bringing it into excellent agreement with experiment. The bond length shortening is traced to intramolecular hydrogen bonding. The total molecular bonding energies of hydrated I and I′ (in which the axial ligands on the thallium and platinum atoms are interchanged) are found to be very similar to one another, suggesting that complex I might exist as a mixture of isomers in solution.     

Automated high-performance liquid chromatography method for the determination of rosiglitazone in human plasma

A robust, fully automated assay procedure for the determination of rosiglitazone (I, BRL-49653) in human plasma has been developed. Plasma concentrations of I were determined using automated sequential trace enrichment of dialysates (ASTED) coupled to reversed-phase high-performance liquid chromatography. Sequential automated dialysis of human plasma samples was followed by concentration of the dialysate by trace enrichment on a C₁₈ cartridge. Drug and internal standard, SB-204882 (II) were eluted from the trace enrichment cartridge by mobile phase (0.01 M ammonium acetate, pH 8–acetonitrile, 65:35, v/v) onto the HPLC column (a Novapak C₁₈, 4 μm, 100×5 mm radial compression cartridge) protected by a Guard-Pak C₁₈ cartridge. The compounds were detected by fluorescence detection, using an excitation wavelength of 247 nm, and emission wavelength of 367 nm. The lower limit of quantitation of the method was 3 ng/ml (200 μl aliquot) with linearity demonstrated up to 100 ng/ml. Within- and between-run precision and accuracy of determination were better than 10% across the calibration range. There was no evidence of instability of I in human plasma following three complete freeze–thaw cycles and samples can be safely stored for at least 7 months at −20°C. This method has been successfully utilised to provide pharmacokinetic data throughout the clinical development of rosiglitazone.     

Synthesis,antioxidant and photoprotection activities of hybrid derivatives useful to prevent skin cancer

Chronic ultraviolet (UV) radiation exposure is a major cause of skin cancer. A novel series of hybrid derivatives (I–VIII) for use in sunscreen formulations were synthesized by molecular hybridization of t-resveratrol, avobenzone, and octyl methoxycinnamate, and were characterized. The antioxidant activity values for VIII were comparable than to those of t-resveratrol. Compounds I–III and VI demonstrated Sun Protector Factor superior to that of t-resveratrol. Compounds I and IV–VIII were identified as new, broad-spectrum UVA filters while II–III were UVB filters. In conclusion, novel hybrid derivatives with antioxidant effects have emerged as novel photoprotective agents for the prevention of skin cancer.     

Separation of the stereoisomers of the main metabolite of a non-steroidal anti-inflammatory drug,flobufen, by chiral high-performance liquid chromatography

The major metabolite of a novel non-steroidal anti-inflammatory drug, dl-4-(2′-4′-difluorobiphenyl-4-yl)-4-oxo-2-methylbutonoic acid (flobufen, I), namely 4-(2′,4′-difluorobiphenyl-4-yl)-2-methyl-γ-butyrolactone (4-dihydroflobufen lactone, III), has four stereoisomers consisting of two racemic pairs of enantiomers. Of three chiral stationary phases tested, Cyclobond I β-RSP (Astec) (β-cylodextrin derivatized with R,S-hydroxypropyl) was best able to separate the (++)(−−) racemate, with a liquid phase containing acetonitrile as modifier and triethylamine acetate as buffer. Using the Box-Wilson Central Composite Design for three factors, an optimum combination of pH and concentrations of the modifier and buffer was eventually obtained. A chromatographic response function based on a combination of the Kaiser peak separation function, P_i, and retention time of the second eluting enantiomer, t_RL, served as a response criterion for the process of optimization. The optimum conditions developed for the (++)(−−) racemate were also found to be suitable for separating the (+−)(−+) racemate, for which earlier studies had shown the separation to be more facile. Separation of the four stereoisomers of III, for which the chiral chromatographic system optimized in this study is proposed as the second stage, is targeted at a biochemical study of the stereoisomeric metabolism of I.     

Comparison of structural features of three new cis-dioxomolybdenum(VI) complexes with 2-hydroxy-1-naphthaldehyde-S-methylisothiosemicarbazone: Possible role of intermolecular interactions on the geometry of the cis-MoO2 unit

Three closely related [MoO₂(L)(ML)] complexes, where L is the 2-hydroxy-1-naphthaldehyde-S-methylisothiosemicarbazone ligand, and ML is EtOH (I), Py (II) and DMSO (III), were synthesized, characterized by NMR and IR spectra, and their X-ray crystal structures were determined. The crystal structure properties of these three closely related complexes were compared. Two cis-Mo-O bond lengths were almost the same in the crystal structure of complexes II and III, while in complex I a significant difference between the two cis-Mo-O bond lengths was observed. At the same time, the geometry of L ligand in complex I is different, compared to II and III. DFT calculations on the isolated molecule I, as well as geometrical analysis of the complexes indicate that intramolecular interactions are not responsible for these structural differences. On the other hand, the pattern of intermolecular contacts in the crystal structure of I differs from those observed in II and III. Analyses indicate that differences in cis-Mo-O bond lengths and in the geometry of ligand L could be related to intermolecular interactions. These results suggest the possibility that in enzymes oxotransferases or in their model systems, the Mo-O bond length could be designed by the interactions of chelate ligands with the surroundings.     

Synthesis of modified fragments of fibrinogen and their effect on the activity of proteolytic enzymes

New analogues of the Gly-Pro-Arg and Arg-Gly-Asp fragments of fibrinogen were synthesized: Gly-Pro-Arg-Pro (I), Gly-Pro-Arg-Pro-Met-OMe (II), Gly-Pro-Arg-Pro-Phe (III), Gly-Pro-Arg-Pro-Asp (IV), Gly-Pro-Arg-Pro-Glu (V), and Arg-Asn-Trp-Asp (VI). Their effect on the activity of proteases of various types was studied with the method of lysis of fibrin plates. All the peptides were found to inhibit plasmin activity (by 60–85%) and the γ-subunit of nerve growth factor (by 55–93%). Tetrapeptide (VI) proved to be an effective inhibitor of tissue activator of plasminogen and the γ-subunit of nerve growth factor (by 96 and 93%, respectively). The peptides exerted practically no effect on the activity of urokinase and moderately inhibited the activity of streptokinase [(III), IV), and (VI)], papain [(I), (II), IV), and (VI)], subtilisin [(V) and (VI)], α-chymotrypsin [(III), (V), and VI)], and Bacillus subtilis metalloprotease (VI). They inhibit trypsin [except for (I) and (III)] when applied on fibrin plates at a concentration of 1 × 10^?2 M, while, at the concentration of 1 × 10^?3 M, (I) and (II) induced an increase in proteolytic activity by 35 and 47%, respectively.     

Development and comparison of high-performance liquid chromatographic methods with tandem mass spectrometric and ultraviolet absorbance detection for the determination of cyclobenzaprine in human plasma and urine

Sensitive assays for the determination of cyclobenzaprine (I) in human plasma and urine were developed utilizing high-performance liquid chromatography (HPLC) with tandem mass spectrometric (MS-MS) and ultraviolet (UV) absorbance detections. These two analytical techniques were evaluated for reliability and sensitivity, and applied to support pharmacokinetic studies. Both methods employed a liquid-liquid extraction of the compound from basified biological sample. The organic extract was evaporated to dryness ,the residue was reconstituted in the mobile phase and injected onto the HPLC system. The HPLC assay with MS-MS detection was performed on a PE Sciex API III tandem mass spectrometer using the heated nebulizer interface. Multiple reaction monitoring using the parent → daughter ion combinations of m/z 276 → 215 and 296 → 208 was used to quantitate I and internal standard (II), respectively. The HPLC-MS-MS and HPLC-UV assays were validated in human plasma in the concentration range 0.1–50 ng/ml and 0.5–50 ng/ml, respectively. In urine, both methods were validatedin the concentration range 10–1000 ng/ml. The precision of the assays, as expressed as coefficients of variation (C.V.) was less than 10% over the entire concentration range, with adequate assay specificity and accuracy. In addition to better sensitivity, the HPLC-MS-MS assay was more efficient and allowed analysis of more biological fluid samples in a single working day than the HPLC-UV method.     

High-performance liquid chromatographic assay for the determination of the novel etoposide derivative dimethylaminoetoposide (NK611) and its metabolites in urine of cancer patients

A simple, reproducible and specific urine assay for the novel epipodophyllotoxin derivative dimethylaminoetoposide (NK611, I) its picro form (III), the N-demethyl metabolite (II) and its picro form (IV) is reported. The method involves the addition of Pr-NK611 as internal standard, chloroform extraction and HPLC separation on a Nova-Pak C₁₈ column with a mobile phase of acetonitrile-0.05 M KH₂PO₄ (pH 6.4) (23:77, v/v). UV detection was used with absorbance monitored at 205 nm and the limit of quantification was 100 ng/ml. The intra- and inter-day precisions were within the ranges 1.1–3.4% and 1.9–2.4% for all analytes and the accuracy was 101–107%. The extraction recovery was more than 88% for I, II and IV and more than 83% for III. The assay is applicable to the urinary monitoring of I–IV in clinical pharmacokinetic investigations.     

A Comparative PET-study of five carbon-11 or fluorine-18 labelled salicylamides. Preparation and in vitro dopamine D-2 receptor binding

Five ¹¹C- or ¹⁸F-labelled salicylamides ([¹¹C]raclopride (I), [¹¹C]eticlopride (II), [¹⁸F]NCQ 258 (III), [¹⁸F]NCQ 134 (IV) and [¹⁸F]NCQ 135 (V)) were prepared. The total radiochemical yields of I–V from EOB were 3–30% (decay-corrected) with an overall synthesis time of 40–110 min. All compounds were isolated by semi-preparative HPLC and the radiochemical purity was > 99%. I–V were in separate experiments injected into Cynomolgus monkeys for PET-examination of ligand distribution in brain in vivo. I–V passed rapidly across the blood-brain barrier. With both analogs I and II there was a high uptake in the striatum, a region with a high density of dopamine D-2 receptors. With the ¹⁸F-labelled analogs III and IV, the uptake in the striatum was almost identical to that in the dopamine receptor poor cerebellum whereas the striatal uptake of V was clearly higher than in the cerebellum. Unlabelled I–V (raclopride, eticlopride, NCQ 258 (VII), NCQ 134 (VIII) and NCQ 135 (IX)) were also prepared and examined in vitro using [³H]raclopride and [³H]spiperone binding to rat striatal dopamine D-2 receptors. A significantly lower affinity was shown for NCQ 258 and NCQ 134 (5 times) compared to that of raclopride and eticlopride, respectively, whereas the affinity of NCQ 135 was similar to that of eticlopride.     

Some observations on the minor products of the reaction of 2,2′-dilithiobiphenyl with mercuric chloride

Reaction of 2,2′-dilithiobiphenyl (formed from 2,2′-diiodobiphenyl and lithium in diethyl ether) with mercuric chloride gives the ortho-biphenylenemercury trimer (I) with 2,2′-bis(iodomercury)biphenyl (II) as an isolatable intermediate. The mass spectrum of impure 2,2′-bis(iodomercury)biphenyl at high sensitivity shows ion clusters which are interpreted as the ions of a polyphenyl iodomercury complex [Hg₃(C₆H₄)₄I₂] (III) which is identified as a further intermediate in the production of ortho-biphenylenemercury trimer and several iodomercury cations of general formula [Hg_xI_y]⁺, where x, y = 1, 2, 3. A fragmentation scheme is presented to account for these unusual iodomercury cations. Reaction mechanisms are presented to account for the production of II and III.