Synthesis of [11-2H2], [8-2H2], [7-2H2], [6-2H2], [5-2H2], [4-2H2] and [3-2H2] cis-9-octadecenoates

Deuterated oleates have been synthesized by semihydrogenation of acetylenic intermediates. [11-²H₂]Oleate was prepared by two-carbon chain extension of the C₁₆ alcohol obtained from [1-²H₂]octyl bromide and 7-octyn-1-ol. [8-²H₂] and [7-²H₂]oleates were both prepared from dimethyl suberate, tetradeutero intermediate C₁₆ alcohols were synthesized from [1,8-²H₄] and [2,7-²H₄]octane diols by monobromination, conversion to deuterated 9-decyn-1-ols and reaction with octyl bromide. Oxidation gave [8-²H₂]-9-octadecynoate and [2,7-²H₂]-9-octadecynoate, after semihydrogenation of the latter, deuterons at C-2 were removed by exchange with aqueous alkali. [6-²H₂] and [5-²H₂]oleates were obtained from methyl 5-tetradecynoate, semihydrogenation, deuterium exchange at C-2 and two malonate extensions gave [6-²H₂]oleate; reduction with lithium aluminum deuteride, two malonate extensions and semihydrogenation gave the [5-²H₂] ester. [4-²H₂] and [3-²H₂]oleates were both obtained from methyl 7-cis-hexadecenoate, exchange of the α protons and chain extension gave the [4-²H₂] ester and reduction with lithium aluminum deuteride and chain extension gave the [3-²H₂] ester.     

Hydrolysis of [17,17-2H2]gibberellin A20-glucoside and [17,17-2H2]gibberellin A20-glucosyl ester by Azospirillum lipoferum cultured in a nitrogen-free biotin-Based chemically-defined medium

Azospirillum lipoferum strain USA 5b, a gibberellin producing bacterium, was cultured in a nitrogen-free biotin-based chemically-defined medium in the presence of the glucosyl ester or the 13-O-glucoside of [17,17-²H₂]-gibberellin A₂₀. The [17,17-²H₂]-gibberellin A₂₀ conjugates were added at both the stationary phase of the cultures and at the beginning of the growth curve. Metabolism of the conjugates was examined after 72 h of incubation using capillary gas chromatography-mass spectrometry, with identification by full scan mass spectra. Metabolites identified were [17,17-²H₂]-gibberellin A₂₀, [17,17-²H₂]-gibberellin A₁ and [17,17-²H₂]-gibberellin A₃. Also, in the Azospirillum cultures fed at the beginning of the growth curve, gibberellin A₅ and gibberellin A₂₀ were characterized as endogenous by mass spectrometry/full spectrum. These results support the concept that the growth promotion in plants that is induced by Azospirillum infection may occur by a combination of both gibberellin production and gibberellin-glucoside/glucosyl ester deconjugation by the bacterium.     

Tetrapyrrole biosynthesis in Anacystis nidulans; incorporation of [1-13C]-, [2-13C]-, [1,2-13C]- and [2-13C, 2-2H3]acetate

Labelling experiments with [2-¹³C]- and [1,2-¹³C]acetate showed that both photopigments of Anacystis nidulans, chlorophyll a and phycocyanobilin, share a common biosynthetic pathway from glutamate. The fate of deuterium during these biosynthetic events was studied using [2-¹³C, 2-²H₃]acetate as a precursor and determining the labelling pattern by ¹³C NMR spectroscopy with simultaneous [¹H, ²H]-broadband decoupling. The loss of ²H (ca 20%) from the precursor occurred at an early stage during the tricarboxylic acid cycle. After formation of glutamate there was no further loss of ²H in the assembly of the cyclic tetrapyrrole intermediates or during decarboxylation and modification of the side-chains. Thus the labelling data support a divergence in the pathway to cyclic and linear tetrapyrroles after protoporphyrin IX.     

Synthesis of esters of saturated and unsaturated sixteen-carbon acids deuterated at the terminal or penultimate carbons

General syntheses of saturated and unsaturated fatty acids, specifically trideuterated at the terminal carbon or dideuterated at the penultimate carbon, from ω-hydroxy esters, have been developed. Methyl [16-²H₃]hexadecanoate was synthesized from methyl 16-hydroxyhexadecanoate. The hydroxyl group was protected as the tetrahydropyranyl ether and the ester group reduced with lithium aluminum deuteride, first to an alcohol and then, by way of the derived mesylate, to a trideuteromethyl group. The new ester group was formed by oxidation of the hydroxyl group. Methyl 16-hydroxy[2-²H₂]hexadecanoate was prepared, from 16-hydroxy-hexadecanoate, by exchange of the α protons and, by the reductive route above, with lithium aluminum hydride, gave methyl [15-²H₂]hexadecanoate. Methyl 16-hydroxy-7-hexadecynoate was synthesized from 6-chlorohexanol and was converted, by means of the above reactions, to methyl [16-²H₃]- and [15-²H₂]-9-hexadecynoates. Lindlar reduction gave methyl [16-²H₃]- and [15-²H₂]cis-9-hexadecenoates. Overall yields ranged from 30% to 38%.     

Biosynthesis of monoterpene hydrocarbons from [1-3H]neryl pyrophosphate and [1-3H]geranyl pyrophosphate by soluble enzymes from Citrus limonum.

A soluble enzyme preparation from the flavedo of Citrus limonum transforms [1-³H₁]neryl pyrophosphate or [1-³H₁]geranyl pyrophosphate into β-pinene, sabinene, α-pinene, and limonene. The enzyme has been partially purified and stabilized by precipitation with polyethyleneglycol. The enzymic cyclization requires the presence of Mn²⁺, which cannot be replaced with Mg²⁺. The addition of reagents containing sulfhydryl groups is essential for optimal activity. Allylic C₁₀ monophosphates do not act as substrates, but they inhibit hydrocarbon formation. Inorganic pyrophosphate has a similar inhibitory effect. No interconversion of neryl and geranyl pyrophosphate has been observed. Possible pathways for the enzymic cyclization reactions are proposed.     

Method for quantitative analysis of PGA2 from plasma using deuterated carrier and gas-liquid chromatography-mass spectrometry

The preparation of [3,3,4,4,-²H₄, 17, 18-³H₂]prostaglandin A₂ (PGA₂) and [17, 18-³H₂]PGA₂ is described. These compounds have been prepared for use in quantitative determination of corresponding nondeuterated prostaglandin by gas-liquid chromatography-mass spectrometry. The method is based on addition of a known amount of carrier to the sample. After purification and derivatization, the ratio between the protium and deuterium form is measured in the mass spectrometer. Ions originating from deuterated and nondeuterated moleeules are focused intermittently on the electron multiplier using an accelerating voltage alternator. With this technique, 60 pg of PGA₂ can be determined with a precision of ±8.4%. The recoveries from plasma of added PGA₂ were about 97%. Basal levels of PGA₂ in human plasma were lower than 10 pg/ml.     

Metabolism of gibberellin A29 in seeds of Pisum sativum cv. Progress No. 9; Use of [2H] and [3H]GAs,and the identification of a new GA catabolite

The metabolism of GA₂₉ in maturing seeds of Pisum sativum cv. Progress No. 9 was further investigated, and the utility of ²H-labelled GAs in conjuction with GC-MS is illustrated. Using [2-²H₁]GA₂₉ as an internal standard, endogenous GA₂₉ was shown to reach a maximal level (ca. 10 g/seed) 27 days from anthesis, and to decline to ca. 1.6 g/seed in mature seeds. In a time-course feed the metabolism of [2-²H₁] [2-³H₁]GA₂₉ applied to 27 day old seeds, and of endogenous GA₂₉, was compared from the ¹H:²H ratios in the recovered GA₂₉. Although both [2-²H₁] [2-³H₁]GA₂₉ and endogenous GA₂₉ were metabolised to the same limited extent to a putative conjugate, in the main metabolic process endogenous GA₂₉ was preferentially converted to an untraceable (i.e. unlabelled) metabolite. In contrast, endogenous GA₂₉ and [1,3-²H₂] [1,3-³H₂]GA₂₉, derived from [1,3-²H₂] [1,3-³H₂]GA₂₀ in a time-course feed, were metabolised in an identical manner. In the latter case isotope loss precluded identification of the metabolite. The structure (8) has been assigned to a GA catabolite present in maturing seeds and seedlings of pea. The isotope data are consistent with this compound being the hitherto untraced metabolite of GA₂₉ in pea.Abbreviations GA_n gibberellin A_n - GC gas chromatography - GC-MS combined gas chromatography-mass spectrometry - GC-RC combined gas chromatography-radio counting - M⁺ molecular ion - Me methyl ester - R_T retention time - SICM selected ion current monitoring - TLC thin layer chromatography - TMS trimethylsilyl ether     

Internode length in Pisum sativum L. The kinetics of growth and [3H]gibberellin A20 metabolism in genotype na Le

The relationship between shoot growth and [³H]gibberellin A₂₀ (GA₂₀) metabolism was investigated in the GA-deficient genotype of peas, na Le. [17-¹³C, ³H₂]gibberellin A₂₀ was applied to the shoot apex and its metabolic fate examined by gas chromatographic-mass spectrometric analysis of extracts of the shoot and root tissues. As reported before, [¹³C, ³H₂]GA₁, [¹³C, ³H₂]GA₈ and [¹³C, ³H₂]GA₂₉ constituted the major metabolites of [¹³C, ³H₂]GA₂₀ present in the shoot. None of these GAs showed any dilution by endogenous ¹²C-material. [¹³C, ³H₂]GA₂₉-catabolite was also a prominent metabolite in the shoot tissue but showed pronounced isotope dilution probably due to carry-over of endogenous [¹²C]GA₂₉-catabolite from the mature seed. In marked contrast to the shoot tissue, the two major metabolites present in the roots were identified as [¹³C, ³H₂]GA₈-catabolite and [¹³C, ³H₂]GA₂₉-catabolite. Both of these compounds showed strong dilution by endogenous ¹²C-material. Only low levels of [¹³C, ³H₂]GA₁, [¹³C, ³H₂]GA₈, [¹³C, ³H₂]GA₂₀ and [¹³C, ³H₂]GA₂₉ accumulated in the roots. It is suggested that compartmentation of GA-catabolism may occur in the root tissue in an analogous manner to that shown in the testa of developing seeds. Changes in the levels of [1,3-³H₂]GA₂₀ metabolites over 10 d following application of the substrate to the shoot apex of genotype na Le confirmed the accumulation of [³H]GA-catabolites in the root tissues. No evidence was obtained for catabolic loss of [³H]GA₂₀ by complete oxidation or conversion to a methanol-inextractable form. The results indicate that the root system may play an important role in the regulation of biologically active GA levels in the developing shoot of Na genotypes of peas.Abbreviations GA_n gibberellin A_n - GC-MS gas chromatography-mass spectrometry - HPLC high-pressure liquid chromatography     

Dynamic Measurements of Cerebral Pentose Phosphate Pathway Activity In Vivo Using [1,6-13C2,6,6-2H2] Glucose and Microdialysis

Abstract: Cerebral pentose phosphate pathway (PPP) activity has been linked to NADPH-dependent anabolic pathways, turnover of neurotransmitters, and protection from oxidative stress. Research on this potentially important pathway has been hampered, however, because measurement of regional cerebral PPP activity in vivo has not been possible. Our efforts to address this need focused on the use of a novel isotopically substituted glucose molecule, [1,6-¹³C₂,6,6-²H₂]glucose, in conjunction with microdialysis techniques, to measure cerebral PPP activity in vivo, in freely moving rats. Metabolism of [1,6-¹³C₂,6,6-²H₂]glucose through glycolysis produces [3-¹³C]lactate and [3-¹³C,3,3-²H₂]lactate, whereas metabolism through the PPP produces [3-¹³C,3,3-²H₂]lactate and unlabeled lactate. The ratios of these lactate isotopomers can be quantified using gas chromatography/mass spectrometry (GC/MS) for calculation of PPP activity, which is reported as the percentage of glucose metabolized to lactate that passed through the PPP. Following addition of [1,6-¹³C₂,6,6-²H₂]glucose to the perfusate, labeled lactate was easily detectable in dialysate using GC/MS. Basal forebrain and intracerebral 9L glioma PPP values (mean ± SD) were 3.5 ± 0.4 (n = 4) and 6.2 ± 0.9% (n = 4), respectively. Furthermore, PPP activity could be stimulated in vivo by addition of phenazine methosulfate, an artificial electron acceptor for NADPH, to the perfusion stream. These results show that the activity of the PPP can now be measured dynamically and regionally in the brains of conscious animals in vivo.     

The combined use of selective deuteration and double resonance experiments in assigning the 1H resonances of valine and tyrosine residues of dihydrofolate reductase

Selective deuteration is a general solution to the resolution problem which limits the application of double resonance experiments to the assignment of the ¹H NMR spectra of proteins. Spin-decoupling and NOE experiments have been carried out on Lactobacillus casei dihydrofolate reductase and on selectively deuterated derivatives of the enzyme containing either [γ-²H₆]Val or (α,δ₂,?₁-²H₃]His, [α,δ₁,δ₂,?₁,?₂,ζ-²H₆]Phe, [α,δ₁,?₃,ζ₂,ζ₃,η₂-²H₆]Trp and [α,?₁,?₂-²H₃]Tyr. When combined with ring-current shift calculations based on the crystal structure of the enzyme, these experiments allow us to assign ¹H resonances of Val 61, Val 115, Tyr 46 and Tyr 68.     

The biosynthesis of trichothecin from acetate- [1,2- 13C2]

The coupling pattern of trichothecin biosynthesized from acetate-[1,2-¹³C₂] is in accord with previous enrichment studies. Multiple labelling was observed. Exogenous acetate has been shown to inhibit the utilization of glucose and the incorporation of radioactivity from pyruvate-[2-¹⁴C] and citrate-[1,5-¹⁴C] into the metabolites. Two pairs of ¹³C NMR assignments are interchanged.     

Studies with Differentially Labeled [11C]Cocaine, [11C]Norcocaine, [11C]Benzoylecgonine,and [11C]-and 4′-[18F]Fluorococaine to Probe the Extent to Which [11C]Cocaine Metabolites Contribute to PET Images of the Baboon Brain

Abstract: The psychostimulant drug of abuse, cocaine (benzoylecgonine methyl ester), is rapidly metabolized by cleavage of its two ester groups, to give benzoylecgonine (BE) and ecgonine methyl ester, and by N-demethylation, to give N-norcocaine (NC). The recent use of [N-methyl-¹¹CH₃]cocaine to image brain cocaine binding sites with positron emission tomography (PET) raises the question of whether PET images partially reflect the distribution and kinetics of labeled cocaine metabolites. We prepared [O-metty/-¹¹CH₃]cocaine by methylation of the sodium salt of BE with [¹¹C]CH₃l, and showed that PET baboon brain scans, as well as regional brain kinetics and plasma time-activity curves corrected for the presence of labeled metabolites, are nearly identical to those seen with [N-methyl-¹¹CH₃]cocaine. This strongly suggests that ¹¹C metabolites do not significantly affect PET images, because the metabolite pattern is different for the two labeled forms of cocaine. In particular, nearly half the ¹¹C in blood plasma at 30 min was [¹¹C]CO₂ when [N-methy/-¹¹CH₃]cocaine was administered, whereas [¹¹C]CO₂ was not formed from [O-methy/-¹¹CH₃]cocaine. Only a trace of [¹¹C]NC was detected in plasma after [O-methyl-¹¹CH₃]cocaine administration. Nearly identical brain PET data were also obtained when 4′-[N-methy/-¹¹CH₃]fluorococaine and 4′-[¹⁸F]fluoro-cocaine (prepared by nucleophilic aromatic substitution from [¹⁸F]fluoride-and 4′-nitrococaine) were compared with [N-methy/-¹¹CH₃]cocaine. In vitro assays with rat brain membranes showed that cocaine and 4′-fluoroco-caine were equipotent at the dopamine reuptake site, but that 4′-fluorococaine was about 100 times more potent at the 5-hydroxytryptamine reuptake site. The studies with positron-emitting 4′-fluorococaines thus support the lack of significance of labeled metabolites or of binding to 5-hydroxytryptamine reuptake sites to PET images taken with [N-methy/-¹¹CH₃]cocaine. [¹¹C]NC prepared by O-methylation of norbenzoylecgonine gave PET images with preferential uptake in striatum, but slower clearance from all brain regions than [O-methy/-¹¹CH₃]cocaine. [¹¹C]BE prepared by N-methylation of norbenzoylecgonine did not show brain uptake.     

Metabolism of ent-kaurenol-[17-14C], ent-kaurenal-[17-14C] and ent-kaurenoic acid-[17-14C] by germinating Hordeum distichon grains

Subcellular fractions from germinated barley embryos, chloroplast preparations and whole germinating barley grains are able to carry out the conversions ent-kaurenol → ent-kaurenal → ent-kaurenoic acid → ent-hydroxykaurenoic acid, the initial steps of the biosynthetic pathway to gibberellins. Whole grains, and chloroplasts to a slight extent, incorporate radioactivity from ent-kaurenol-[17-¹⁴C] and ent-kaurenoic acid-[17-¹⁴C] into materials with similar but distinct properties from the gibberellins GA₁, GA₃, GA₄ and GA₇.     

Incorporation of methionine-[methyl-2H3] and mevalonic acid-[2-14C,(4R)-4-3H1] into Phycomyces blakesleeanus sterols

Ergosterol, episterol, 4α-methyl-5α-ergosta-8,24(28)-dien-3β-ol and 24-methylene-24,25-dihydrolanosterol, isolated from Phycomyces blakesleeanus grown in the presence of methionine-[methyl-²H₃], each contained two deuterium atoms; lanosterol, however, was unlabelled. The ¹⁴C:³H atomic ratio of the following sterols isolated from P. blakesleeanus grown in the presence of mevalonic acid-[2-¹⁴C,(4R)-4-³H₁], was: ergosterol, 5:3; episterol, 5:4; ergosta-5,7,24(28)-trien-3β-ol, 5:3; 4α-methyl-5α-ergosta-8,24(28)-dien-3β-ol, 5:4; 24-methylene-24,25-dihydrolanosterol, 6:5; lanosterol, 6:5. The significance of these results in terms of ergosterol biosynthesis is discussed.     

Facile Preparation of Deuterium-Labeled Standards of Indole-3-Acetic Acid (IAA) and Its Metabolites to Quantitatively Analyze the Disposition of Exogenous IAA in Arabidopsis thaliana

[2′,2′-²H₂]-indole-3-acetic acid ([2′,2′-²H₂]IAA) was prepared in an easy and efficient manner involving base-catalyzed hydrogen/deuterium exchange. 1-O-([2′,2′-²H₂]-indole-3-acetyl)-β-D-glucopyranose, [2′,2′-²H₂]-2-oxoindole-3-acetic acid, and 1-O-([2′,2′-²H₂]-2-oxoindole-3-acetyl)-β-D-glucopyranose were also successfully synthesized from deuterated IAA, and effectively utilized as internal standards in the quantitative analysis of IAA and its metabolites in Arabidopsis thaliana by using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). The use of this technique shows that these metabolites were accumulated in the roots of Arabidopsis seedlings. Dynamic changes in the metabolites of IAA were observed in response to exogenous IAA, revealing that each metabolic action was regulated differently to contribute to the IAA homeostasis in Arabidopsis.     

Nature-inspired pyrrolo[2,3-d]pyrimidines targeting the histamine H3 receptor

Inspired by marine compounds the derivatization of the natural pyrrolo[2,3-d]pyrimidine lead scaffold led to a series of novel compounds targeting the histamine H₃ receptor. The focus was set on improved binding towards the receptor and to establish an initial structure-activity relationship for this compound class based on the lead structure (compound V, K_i value of 126 nM). As highest binding affinities were found with 1,4-bipiperidines as basic part of the ligands, further optimization was focused on 4-([1,4′-bipiperidin]-1′-yl)-pyrrolo[2,3-d]pyrimidines. Related pyrrolo[2,3-d]pyrimidines that were isolated from marine sponges like 4-amino-5-bromopyrrolo[2,3-d]pyrimidine (compound III), showed variations in halogenation pattern, though in a next step the impact of halogenation at 2-position was evaluated. The chloro variations did not improve the affinity compared to the dehalogenated compounds. However, the simultaneous introduction of lipophilic cores with electron-withdrawing substitution patterns in 7-position and dehalogenation at 2-position (11b, 12b) resulted in compounds with significantly higher binding affinities (K_i values of 7 nM and 6 nM, respectively) than the initial lead structure compound V. The presented structures allow for a reasonable structure-activity relationship of pyrrolo[2,3-d]pyrimidines as histamine H₃ receptor ligands and yielded novel lead structures within the natural compound library against this target.     

Synthesis of 3,4-13C2 steroids

A-ring enollactones $\text{1a}$, $\text{1b}$ or $\text{9}$ derived from 4-cholesten-3-one, testosterone benzoate or 3-oxo-4-estren-17β-yl benzoate were condensed with [1,2-¹³C₂]acetyl chloride to give intermediates $\text{2a}$, $\text{2b}$ or $\text{10}$. $\text{2a}$ and $\text{2b}$ were cyclized by acid or base to give 3,4-¹³C₂-labeled 4-cholesten-3-one and testosterone, respectively. [3,4-¹³C₂]4-Cholesten-3-one was converted via reduction of its trimethylsilyl enol ether to [3,4-¹³C₂]cholesterol. Acetyl enollactone $\text{10}$ was cyclized in acetic acid to [3,4-¹³C₂]3-oxo-4-estren-17β-yl benzoate followed by aromatization and hydrolysis to produce [3,4-¹³C₂]estradiol-17β. Alternatively, cyclization of $\text{10}$ with base afforded [3,4-¹³C₂]3-oxo-4-estren-17β-ol directly, which was then oxidized and aromatized to yield [3,4-¹³C₂]estrone. Ozonolysis of progesterone, conversion to the diketal ester $\text{16}$ and acylation followed by acid hydrolysis furnished [3,4-¹³C₂]progesterone.     

Halogenated rhenacarboranes: optoelectronic behavior of the iodinated rhenacarborane complex anion [3,3,3-(CO)3-8-I-closo-3,1,2-ReC2B9H10]

Treatment of the long-known compound Cs[3,3,3-(CO)₃-closo-3,1,2-ReC₂B₉H₁₁] with [N(C₆H₄Br-4)₃][SbCl₆] in the presence of Me₃NO in THF (tetrahydrofuran) has led to the formation of [HNMe₃][3,3-(CO)₂-3,3-Cl₂-closo-3,1,2-ReC₂B₉H₁₁] in good yield. Structural characterization of this compound has identified it as a four-legged piano stool half-sandwich complex anion resulting from oxidation of rhenium by both the aminium and hexachloroantimonate ions and CO displacement promoted by Me₃NO in the presence of by-product chloride ions. Direct iodination of Cs[3,3,3-(CO)₃-closo-3,1,2-ReC₂B₉H₁₁] has yielded [3,3,3-(CO)₃-3-I-closo-3,1,2-ReC₂B₉H₁₁], which undergoes iodide migration in donor solvents from the metal to the β-B vertex in the coordinating face of the cage. The resulting complex anion, [3,3,3-(CO)₃-8-I-closo-3,1,2-ReC₂B₉H₁₀]⁻, whose structure has been confirmed by X-ray diffraction, has been shown to be luminescent in MeTHF at 77 K (λ_em = 455 nm) and electroactive in solution at ambient temperatures, undergoing a quasi-reversible two-electron oxidation to a proposed Re^III cationic rhenacarborane species in MeCN solutions. By contrast, two fully reversible sequential one-electron oxidations have been observed in CH₂Cl₂ solutions.     

Synthesis of 2,6-difluoro-N-(3-[11C]methoxy-1H-pyrazolo[3,4-b]pyridine-5-yl)-3-(propylsulfonamidio)benzamide as a new potential PET agent for imaging of B-RafV600E in cancers

The authentic standard 2,6-difluoro-N-(3-methoxy-1H-pyrazolo[3,4-b]pyridine-5-yl)-3-(propylsulfonamidio)benzamide was synthesized from 2,6-difluorobenzoic acid and 3-amino-5-hydroxypyrazole in 9 steps with 1% overall chemical yield. Direct desmethylation of the reference standard with TMSCl/NaI gave the precursor 2,6-difluoro-N-(3-hydroxy-1H-pyrazolo[3,4-b]pyridine-5-yl)-3-(propylsulfonamidio)benzamide for radiolabeling in 70% yield. The target tracer 2,6-difluoro-N-(3-[¹¹C]methoxy-1H-pyrazolo[3,4-b]pyridine-5-yl)-3-(propylsulfonamidio)benzamide was prepared from the precursor with [¹¹C]CH₃OTf through O-[¹¹C]methylation and isolated by HPLC combined with SPE in 40–50% decay corrected radiochemical yields with 370–740 GBq/μmol specific activity at end of bombardment (EOB).     

[S2], [S3], and [N3] coordination modes of hydrotris(thioxotriazolyl)borato. Zinc, nickel, cobalt, and bismuth complexes

The ligand hydrotris(1,4-dihydro-3-methyl-4-phenyl-5-thioxo-1,2,4-triazolyl)borato (Tr^Ph,Me) was synthetized as natrium salt and the complexes [Zn(Tr^Ph,Me)₂] · 7.5H₂O · 1.5CH₃CN (2a), [Zn(Tr^Ph,Me)₂] · 8DMF (2b), [Co(Tr^Ph,Me)₂] · 8DMF (3a), [Ni(Tr^Ph,Me)₂] · H₂O · 6DMSO (4a), [Bi(Tr^Ph,Me)₂]NO₃ (5), have been isolated and structurally characterized by X-ray diffraction. In the zinc derivatives the ligand adopts different denticity and coordination modes, η² and [S₂] for 2a and η³ and [N₃] for 2b, depending on the crystallization solvent, giving rise to tetrahedral and octahedral geometry, respectively. In the octahedral cobalt and nickel complexes the ligand is η³ and [N₃] coordinated whereas in the bismuth complex the η³ and [S₃] coordination is exhibited.