Synthesis of [N-methyl-3H]-7-chloro-1,3-dihydro-5-(2-fluorophenyl)-1-methyl-2 H-1,4-benzodiazepin-2- one (3H-fludiazepam) by phase transfer catalysis

[N-methyl-3H]-7-Chloro-1,3-dihydro-5-(2-fluorophenyl)-1-methyl-2H-1,4- benzodiazepin-2- one ( [3H]fludiazepam) was prepared by phase transfer catalytic N-methylation of the corresponding nor-derivative with [3H]methyl iodide [407 GBq/mmol (11 Ci/mmol)] in a radiochemical yield of 34%. The specific activity was 271.6 GBq/mmol (7.34 Ci/mmol).     

Synthesis of a tritium-labeled, fipronil-based, highly potent, photoaffinity probe for the GABA receptor

3-[4-[1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazolo]]-3-(trifluoromethyl)diazirine is a fipronil-based (i.e. fiprole), high-affinity probe for the GABA receptor. For synthesis of the tritium-labeled version of this trifluoromethyldiazirinylfiprole ([(3)H]TDF) the required intermediate, 3-[4-[1-(2,6-dichloro-3-iodo-4-trifluoromethylphenyl)-5-iodopyrazolo]]-3-(trifluoromethyl)diazirine, was prepared in 10 steps from pyrazole and 3,5-dichloro-4-fluorobenzotrifluoride. One of the key transformations was lithiation and subsequent iodination of the 4-(2,2,2-trifluoro-1-hydroxyethyl)pyrazole intermediate. The last step involved reduction of the diiodofiprole with tritium, Pd/C, and triethylamine in ethyl acetate and afforded [(3)H]TDF with a specific activity of 15 Ci/mmol and 99% radiopurity.     

Tritium Labelling of Naltrindole,a δ-Receptor-Selective Opioid Antagonist via 1-Bromonaltrexone

The synthesis of [1,5′-³H₂]naltrindole ( 9 ) with labels at both the morphine skeleton and the indole moiety was carried out by catalytic tritiodehalogenation of 1,5′-dibromonaltrindole ( 8 ) resulting in a specific activity of 46.1 Ci/mmol (1705 GBq/mmol). The brominated precursor was prepared by the Fischer indole synthesis starting from 1-bromonaltrexone ( 7 ) and (4-bromophenyl)hydrazine.     

Preparation of substituted cinnamic acids labelled with deuterium and tritium at the ring positions

A series of substituted cinnamic acids labelled at the ring positions with deuterium or tritium has been easily obtained via the Doebner modification of Knoevenagel condensation reaction between labelled benzaldehyde derivatives and malonic acid in pyridine. The substituted benzaldehyde precursors were synthesized by isotope exchange method in deuterated or tritiated water at 80 °C in acidic medium. Ring-tritiated substituted cinnamic acids with specific activity ranging from 207 GBq /5.6 Ci/ mol^–1 to 4366 GBq /118 Ci/ mol^–1 was obtained using ca. 37 GBq /1 Ci/ of HTO.     

Synthesis of deuterium and tritium labelled phenyl glycine

A new method of synthesis of phenyl glycine labelled with deuterium and tritium was elaborated. Labelled phenyl glycine was obtained by isotope exchange method between phenyl glycine and deuterated or tritiated water at elevated temperature in hydrochloric acid medium using K₂PtCl₄ as a catalyst. 37 GBq /1 Ci/ HTO was used for the synthesis of tritiated phenyl glycine and labelled product with specific activity of 185 MBq/mole /5 mCi/mole/ was obtained.     

α-Melanotropin Labelled at its Tyrosine2 Residue: Synthesis and Biological Activities of 3′-Iodotyrosine2-,3′-125Iodotyrosine2-,3′,5′-Diiodotyrosine2-, and (3′,5′-3H2)tyrosine2-α-Melanotropin,and of Related Peptides

α-MSH was labelled at its tyrosine² residue with tritium and iodine. Several synthetic routes were investigated by preparing 13 precursor or mode compounds and 4 different labelled products (via about 40 intermediates). Their melanotropic activity was determined with an in vitro frog skin assay and, for some of the compounds, with a tyrosinase assay. The tritiation was performed on [Tyr(I₂)²]α-MSH by catalytic halogen/tritium exchange, yielding α-MSH of high specific radioactivity (34 Ci/mmol) and full biological activity. Iodination was studied in detail using five different techniques. An equimolar chloramine T procedure proved to be the most convenient and reproducible method, resulting in monoiodinated α-MSH containing 99% of the label in position 2. The biological activity was 50% that of α-MSH; the specific radioactivity, determined in a competitive binding assay with a highly specific α-MSH antiserum and [Tyr(I)²]α-MSH as competitor, was 1530 Ci/mmol. The labelling techniques and the bioligical results are discussed.     

Synthesis of Tritium and Deuterium Labelled Agmatine

Agmatine is a promising anti-opioid dependence and relapse drug1~2 discovered and developed by Beijing Institute of Pharmacology and Toxicology, but the physiological role of agmatine in inhibition of tolerance to and dependence on opioid are not well est…     

Preparation of tritiated fluorenone and fluorenol

Summary Tritiated fluorenone 2 was prepared from 2-iodofluorenone 1 by halogen-tritium exchange. The product had specific activity of 17 Ci/mmol. The product 2(after dilution with unlabeled congener) on reduction with NaBH₄gave the corresponding tritiated fluorenol 3.     

Fluorinated analogs and tritiated enantiomers of inositol (1,3,4)-trisphosphate

The total syntheses of 2-fluoro- and 2,2-difluoro-2-deoxy analogs of DL-myo-Ins (1,3,4)P3 are described. Resolution of a key intermediate followed by borotritide reduction and phosphorylation provided both D- and L-[1-³H]-Ins(1,3,4)P₃ enantiomers with specific activities 15 Ci/mmol.     

Design of A Metabolically Stable Tritium‐Tracer of the PI3Kδ‐Inhibitor CDZ173 (Leniolisib) as a Tool to Study Liver Metabolites

In this disclosure, we summarize the preliminary metabolic profiling of the PI3Kδ inhibitor CDZ173 (leniolisib, 1a ) obtained from incubations of the unlabeled compound and the synthesis of its metabolically stable tritium isotopologue 1b used for metabolite structure confirmation. Access to 1b was achieved when a halogenated precursor was subject to Hal/³H‐exchange. Hence, [³H]CDZ173 with specific activity 630 GBq/mmol, HPLC‐RA 97% and ee = 99.2% was obtained. Synthetic key to the precursor was using a bis‐halo‐pyridine in a Pd‐catalyzed mono‐amination of the tetrahydropyrido‐pyrimidine core. Stereochemistry of the synthetic precursors were confirmed by X‐ray analysis of the unlabeled bis‐halo‐pyridines and chiral HPLC of the tritiated material. The correct position of tritium label in the target, was confirmed by ³H‐NMR difference spectroscopy. Besides, we report on the validation of the radiotracer as a tool for pre‐clinical ADME in incubations with hepatocytes. Based on this data, we present a quantitative metabolite profile of leniolisib which was confirmed by independently synthesized metabolite references. The conformation of CDZ173 was investigated by NMR suggesting two different amide backbones each with specific pyrrolidine puckerings.     

Synthesis of dirhodium[3H]tetraacetate

Realizing a need for labeled dirhodium tetraacetate [Rh₂/OAc/₄] for binding studies by the equilibrium dialysis procedure, we have established a method for the preparation and purification of [³H]Rh₂/OAc/₄. This is obtained with a tritium label of a sufficiently high specific activity in the methyl group of acetate residues. The method consists of replacement of the existing acetate bridge by [³H]OAc^–. A typical preparation involves refluxing Rh₂/OAc/₄ with [³H]NaOAc in dry ethanol at 80°C for 6 h. The reaction time is critical for obtaining the product with a high specific activity. A simple purification of reaction products yields the compound of interest with a high specific activity, i. e., 315±10 Ci per mol of Rh₂/OAc/₄ and in satisfactory yield /87% of the starting material., This labeled material can be synthesized with greatly increased specific activity /of tritium in acetate groups/ by employing [³H]NaOAc without prior dilution. The labeled Rh₂/OAc/₄ is stable and yields a characteristic product with adenylic acid.     

Tritium Labelling of Cyprodime ( = (—)-17-(Cyclopropylmethyl)-4,14-dimethoxymorphinan-6-one), a μ Receptor-Selective Opioid Antagonist

The preparation of [1-³H]cyprodime ( 2 ), which has a specific activity of 31.6 Ci/mmol was carried out by catalytic tritiodehalogenation of 1-bromocyprodime ( 3 ). Bromination of cyprodime was performed by using chloroperoxidase, KBr, and H₂O₂.     

Hydrogen release from mixtures of lithium borohydride and lithium amide: a phase diagram study

We recently reported the synthesis of a new quaternary hydride in the lithium-boron-nitrogen-hydrogen quaternary phase diagram with the approximate composition LiB0.33N0.67H2.67 having a theoretical hydrogen content of 11.9 wt %. This new compound forms by the reaction of appropriate amounts of lithium amide (LiNH2) and lithium borohydride (LiBH4) and releases greater than 10 wt % hydrogen when heated. A small amount of ammonia, 2-3 mol % of the generated gas, is also released. We now report a study of hydrogen and ammonia release from the series of reactant mixtures (LiNH2)x(LiBH4)1-x, where x=0.667 corresponds to the composition LiB0.33N0.67H2.67. We measured hydrogen and ammonia release amounts as a function of composition and found that maximum hydrogen and minimum ammonia release do occur for x=0.667. We also present evidence for an additional new quaternary phase and for two possibly metastable phases in this system.     

Tritium-labeled 5-oxo-Pro-Arg-Pro

Conditions of tritium introduction into 5-oxo-Pro-Arg-Pro have been developed. Labelled 5-oxo-Pro-Arg-Pro has been obtained in 75% yield and molar radioactivity of 60 Ci/mmol. Tritium distribution over amino acid residues in the peptide has been determined. 5-Oxo-Pro : Arg : Pro ratio in the labelled peptide has been found to be 1 : 5.2 : 2.8. Nonterminal amino acid has been found to contain the major portion of tritium, about 35 Ci/mmol; i.e., arginine includes more than half of the label. Such a feature can be explained by the effect of readily protonated guanidine group of arginine. The influence of charged guanidine group of arginine seems to increase the shift of electron density in the neighboring C–H bonds of arginine and proton mobility, thus increasing protium–tritium exchange at these carbon atoms.     

Synthesis and pharmacokinetics of 1 alpha-hydroxyvitamin D3 tritiated at 22 and 23 positions showing high specific radioactivity

A novel synthesis of a radioactive compound of 1 alpha-hydroxyvitamin D3 (1 alpha OHD3) (1) and its pharmacokinetics are described. Radioactive 1 alpha OHD3 tritiated at 22 and 23 positions ([22,23-(3)H4]1 alpha OHD3) (5) was prepared via key reactions of the reduction of acetylenic side chain in the ketone (12) with tritium gas in the presence of palladium-charcoal and the subsequent Wittig reaction with the A-ring synthon (16). [22,23-(3)H4]1 alpha OHD3 (5) showed high specific radioactivity (111.5 Ci/mmol) and was used successfully in pharmacokinetics studies with rats. In the pharmacokinetics studies, the plasma concentration level of the active form of vitamin D3, 1 alpha,25-dihydroxy-vitamin D3 [1 alpha,25(OH)2D3], after oral or intravenous administration of [22,23-(3)H4]1 alpha OHD3 (5), showed longer half-life, lower maximum concentration, and lower area under the curve than those after treatment of 1 alpha,25(OH)2D3 tritiated at 26 and 27 positions (4). These results might suggest a beneficial therapeutic utility of 1 alpha OHD3 (1) over the treatment of 1 alpha,25(OH)2D3 (2).     

硼酸盐水溶液热力学研究II: H3BO3-LB(OH)4-LiCl-MgCl2体系

在278.15～318.15K下, 测定了无液电池(A), Pt, H2│B(OH)3(m1),LiB(OH)4(m)2, LiCl(m3), MgCl2(m4)│AgCl, Ag和电池(B), Pt, H2│B(OH)3(m1), LiB(OH)4(m2), MgCl2(m4)│AgCl, Ag的电动势。利用Debye-Huckel外推法和多项式拟合法确定了硼酸镁离子对[MgB(OH)4^+缔合常数pKt, 并得到了经验方程pKt=A1+A2/T+A3T以及缔合过程的其他各标准热力学量, 同时指出缔合熵是形成[MgB(OH)4^+]离子对的推动力。     

Synthesis of [D-alanine, 4'-azido-3',5'-ditritio-L-phenylalanine, norvaline4[alpha-melanotropin as a 'photoaffinity probe' for hormone-receptor interactions (author's transl)]

Synthesis of [D -alanine¹, 4′-azido-3′, 5′-ditritio-L -phenylalanine², norvaline⁴]α-melanotropin as a ‘photoaffinity probe’ for hormone-receptor interactions. The synthesis of an α-MSH derivative containing 4′-azido-3′,5′-ditritio-L -phenylalanine is described: Ac · D -Ala-Pap(³H₂)-Ser-Nva-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val · NH₂. This hormone analogue is being used for specific photoaffinity labelling of receptor molecules. The synthesis was performed in a way to minimize the number of radioactive steps and to introduce the radio-active and the photoaffinity label exclusively into position 2. The dipeptide N(α)-acetyl-D -alanyl- (4′-amino-3′,5′-diiodo)-L -phenylalanine was tritriated and transformed into the azido compound, N(α)-acetyl-D -alanyl-(4′-azido-3′,5′-ditritio)-L -phenylalanine which was then condensed with H · Ser-Nva-Glu(OtBu)-His-Phe-Arg-Trp-Gly-Lys(BOC)-Pro-Val · NH₂ to the tridecapeptide. The α-MSH analog displayed a specific activity of 11 Ci/mmol, and a biological activity of about 4 · 10⁹ U/mmol (10% of α-MSH).     

Radiolabelled peptide ergot alkaloids.

Paspalic acid ( 11 ), labelled at different positions with ³H or ¹⁴C and at specific activities up to 1 Ci/mmol (³H) and 2mCi/mmol (¹⁴C), has been prepared biosynthetically in a scale of 2–5 mmol in submerged cultures of a selected strain of Claviceps paspali by incorporation of DL -[5-³H]-tryptophan, DL -[6-³H]-tryptophan, DL -[alanine-2,3-³H]-tryptophan, or DL -[alanine-3-¹⁴C]-tryptophan. Radioactive lysergic acid ( 12 ) was obtained from paspalic acid by base catalysed rearrangement. The procedures for labelling the precursors at high specific activity arc described. The ergolene carboxylic acids 11 and 12 were used as key intermediates for tlie chemical synthesis of radiolabelled peptide ergot alkaloids 14 required for pharinacokinetic and metabolic studies. Linking of the aminocyclols 13 (peptide parts) of the ergotarnine (R¹ = methyl), ergoxine (R¹ = ethyl) and ergotoxine (R¹ =isopropyl) series with a reactive derivative of either lysergic acid or its mixture with paspalic acid was accomplished by standard procedures. l-Mctliyl-[13-³H]-ergotarnine (MY 25) ( 16 ) and 2-brotno-α-ergocryptine (bromocriptine, C73 154) ( 17 ), labelled with ³H at position 12 and with ¹⁴C in position 4, were obtained by alkylating ³H-ergolamine and by ljrominating appropriately labelled α-ergocryptines. Radioactive peptide ergot alltaloitls labelled by tlic present nietliotl proved suitable for the use in biological tracer studies.     

Tritiation of Peptides to High Specific Radioactivity. Part 1. Synthesis and Biological Properties of [13-(3H4)Norvaline]-α-MSH and of [2,23-Bis((3H2)tyrosine)]ACTH(1–24)

α-MSH and ACTH(1–24) were tritiated to high specific radioactivity (> 100 Ci/mmol) using a new tritiation apparatus with which the tritiation reaction can be performed at slightly elevated pressure. This allows short reaction times with the least possible damage to the molecule. The starting compounds for the tritiation were [13-propargylglycine]α-MSH and [2,23-Bis(3′,5′-diiodotyrosine)]ACTH(1–24). Both tritiations were quantitative and yielded products of high purity, full biological activity, and with a specific radioactivity of 115 Ci/mmol and 100 Ci/mmol, respectively.     

A radioanalytical technique to study the behavior of organic toxicants applied to a study of the photodegradation of 2,3,7,8-tetrachlorodibenzo-p-dioxin

A general method for tritium labeling of organic compounds by the use of thermal activation of tritium is described. It allows obtaining uniformly tritium-labeled organic compounds with high specific activity (up to 50 Ci/mmol) which permits tracing the majority of the biodegradation products of compounds studied. More than 40 compounds were labeled using this simple, rapid and inexpensive method. Separation of the biodegradation products is performed by thin layer chromatography. Quantification is performed by direct measurement of the radioactivity by liquid scintillation counting after transfer of the layer from TLC plates into scintillation vials, or by densitometry of autoradiographs. The technique is useful for a wide range of organic compounds, including ones with unknown structure, and can be applied to various in vivo and in vitro studies.