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 [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).     

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 [3H]-higenamine

The synthesis of [³H]-higenamine by a four steps reaction, namely condensation, cyclization, catalytic tritiation and demethoxylation is described. The acidulated product was purified by thin layer chromatography and the final component has a high specific activity and radiochemical purity.     

Palladium(II)‐Mediated C−H Tritiation of Complex Pharmaceuticals

Tritium‐labeled molecules are critical tools for elucidating the binding and metabolic properties of bioactive compounds, particularly during pharmaceutical discovery. Direct tritiation of inert C?H bonds with T₂ gas is an ideal approach for tritium labeling, but significant gaps remain for direct tritiation of structurally complex molecules with diverse functional groups. Here we report the first application of palladium(II) C?H activation chemistry for tritiation with T₂ gas. This practical transformation exhibits novel substrate scope and greater functional group tolerance compared to previous state of the art tritiation methods, and has been applied to directly tritiate 9 complex pharmaceuticals and an unprotected dipeptide. The isolated tritium‐labeled products exhibit >15 Ci mmol^?1 specific activity, exceeding the typical requirements for application in studies of molecular interaction and metabolism.     

Divergent Melanophore-Dispersing and Tyrosinase-Stimulating Activity of Synthetic Leucine9-α-melanotropin

Leucine⁹-α-melanotropin ([Leu⁹]α-MSH) was synthesized in homogeneous solution by a fragment condensation approach, and it was assayed for its melanophore-dispersing and its tyrosinase-stimulating activity with a reflectometric in vitro frog skin assay and with cultured mouse melanoma cells, respectively. In both assay systems, parallel log dose-response curves were obtained for ([Leu⁹)]α-MSH and α-MSH; however, in the frog skin assay the activity of the title compound was 1 middot; 10¹⁰ Units/mmol, i.e. 25% of the activity of α-MSH, whereas its tyrosinasestimulating potency was only 1% compared to α-MSH (EC₅₀= 2.5 · 10^?7M ). This indicates a major difference in the recognition/stimulation process of the receptors of the two cell types.     

O-alkylation de la Quercetine et synthese de la tetra o-ethyl-3,7,3′,4′ O-ethyl [3H]-5 quercetine

An efficient procedure is described for alkylation of quercetin with alkylhalides by use of tetraethylammonium fluoride in DMF or HMPT. The method is applied successfully to the preparation of 3,7,3′,4′,tetra-O-ethyl 5 [³H] O-ethylquercetin with a specific radioactivity of 45 Ci/mmol.     

Synthesis of diazipine and [3H]diazipine: novel dihydropyridines as photoaffinity probes of calcium channels.

Diazipine and [3H]diazipine were synthesized as new 1,4-dihydropyridine photoaffinity ligands containing a phenyldiazirine group. After simple high performance liquid chromatography separation, both compounds were purified in good overall yields. [3H]Diazipine (21.2 Ci/mmol) was synthesized in two steps from commercially available [3H]ethanolamine. Diazipine competitively inhibited [3H]PN200-110 binding to the calcium channel of cardiac membranes with high affinity.     

Modified synthesis of deoxyadenosine-5'-(35S)-thiomonophosphate [dAMP (35S)] with high specific activity: An important starting material for the synthesis of deoxyadenosine-5'-(&;#945;-35S)-thiotriphosphate [dATP (&;#945;-35S)]

Deoxyadenosine-5'-monophosphite was treated with excess of trimethylsilyl chloride. One equivalent of trimethylsilyl chloride treated phosphite in pyridine and one equivalent of elemental ³⁵S in toluene solution (specific activity > 1000 Ci/mmol) were stirred together with gradual removal of solvents under vacuum, over a period of one hour, to give deoxyadenosine-5'-(³⁵S)-thiomonophosphate [dAMP(³⁵S)] in high yields.     

N-[11C]methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine (MBDB): synthesis, quality control and biodistribution

N-[¹¹C]methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine ([¹¹C]MBDB) 3 was prepared by methylation of the demethyl precursor BDB with [¹¹C]CHI. The radiosynthesis was optimized with regard to temperature, reaction time and amount of precursor, best results (i.e., 84% radiochemical yield, based on [¹¹C]CH₃I activity) were obtained using 3 mg BDB at a reaction temperature of 130 °C in 8 minutes. With respect to a facilitated workup routine, productions were performed with 0.6 mg BDB at 110 °C for 10 minutes, yielding more than 50% of 3. The radiochemical purity of the final tracer solution was >98%, the specific activity was determined to be 300 GBq/mol (8000 Ci/mmol). Biodistribution, studies in rats showed two major metabolic pathways as indicated by an increasing liver uptake (9.1% ID/organ at 5 minutes to 21% ID/organ at 30 minutes) and a high urine activity (up to 16% ID/g). In brain tracer uptake was more than 1%, with a brain to blood ratio of almost 12 resulting from a very rapid blood clearance of 3.     

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.     

青蒿素生物合成的研究II. 前体[15-^2H]-和[15-^3H]-青蒿酸的 化学合成

青蒿酸甲酯(5)用NBS溴化产生的溴化物,经NaBD~3CN或NaBD~4氘解,生成[15-^2H]-青蒿酸甲酯(6),其结构由MS,^1H,^2H和^1^3C的NMR确定。(6)经水解生成[15-^2H]-青蒿酸(4),用同样方法以NaB^3H~4为氘化试剂与溴化物反应,合成了[15-^3H]-青蒿酸(1)。     

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.     

Synthesis of [Sar1, Val5, (4′-Azido-3′,5′-ditritio)Phe8] Angiotensin II,a Photoaffinity Label for the Isolation of Angiotensin II Receptors Communication 1

The synthesis of [Sar¹, Val⁵, (4′-azido-3′,5′-ditritio)Phe⁸] angiotensin II from a iodinated precursor peptide is described. The principal problems of this synthesis and their resolution are discussed: (i) The β-induced autophotolysis of the highly tritiated (73 Ci/mmol) and photosensitive label, and (ii) the absorption problems encountered during the purification of microgramm quantities. Such photoaffinity labels are being used for specific labeling and isolation of peptide hormone receptors.     

Radioiodination of 4-benzyl-1-(3-iodobenzylsulfonyl)piperidine, 4-(3-iodobenzyl)-1-(benzylsulfonyl)piperazine and their derivatives via isotopic and non-isotopic exchange reactions

A mild and simple technique for preparing of 4-benzyl-1-(3-[¹²⁵I]iodobenzylsulfonyl)piperidine, 4-(3-[¹²⁵I]iodobenzyl)-1-(benzylsulfonyl)piperazine and their derivatives, as sigma-1 receptor ligands, with relatively high radiochemical yields via nucleophilic substitution reaction by means of isotopic and non-isotopic exchange reactions is described. Some factors affecting the radiochemical yield were commonly studied in presence of acidic medium at elevated temperature. Unfortunately, the radiochemical yields were weak. Some attempts were carried out in presence of polar aprotic solvents to enhance the radiochemical yield. N,N-Dimethylformamide was proved highly efficient for preparing of radioiodinated 4-benzyl-1-(3-iodobenzylsulfonyl)piperidine (4-B-[¹²⁵I]-IBSP, 70 ± 5.7 %) and 4-(3-iodobenzyl)-1-(benzylsulfonyl)piperazine (4-[¹²⁵I]-IBBSPz, 72 ± 6.0 %) at moderate temperature (100–105 °C) within 8 h. The specific activities of 4-B-[¹²⁵I]-IBSP and 4-[¹²⁵I]-IBBSPz (6,534.2 and 5,927.4 MBq/mmol) were obtained respectively.     

Synthesis, NMR Characterization, and a Simple Application of Lithium Borotritide

LiBH(4) is a powerful and selective reagent for regiospecific reduction reactions. A simple synthesis of LiB(3)H(4) at near theoretical specific radioactivity is reported. We have treated Li(3)H synthesized from tritium gas ((3)H(2), approximately 98%) with BBr(3) to produce LiB(3)H(4) (specific activity = 4120 GBq/mmol = 110 Ci/mmol. The maximum theoretical specific activity of LiB(3)H(4) is 4252 GBq/mmol = 115.04 Ci/mmol; 1 matom of (3)H = 1063 GBq = 28.76 Ci.) The tritium labeling performance of the reagent was tested by an exemplary reduction of 2-naphthaldehyde to 2-naphthalenemethanol. LiB(3)H(4) and the reduction products were characterized by a combination of (1)H, (3)H, and (11)B NMR techniques, as appropriate.     

Synthesis of the methanesulfonates of α-(4-chlorophenyl)-α-[1-(2-chlorophenyl)emenyl]-1H-1,2,4-triazole-1-ethanol and α-[1-(2-chlorophenyl)ethenyl]-α-(2,4-difluorophenyl)-1H-1,2,4-triazole-1-ethanol,alpha styryl carbinol antifungal agents

The methanesulfonates of (α-(4-chlorophenyl)-α-[1-(2-chlorophenyl)ethenyl]-1H-1,2,4-triazole-1-ethanol and α-[1-(2-chlorophenyl)ethenyl]-α-(2,4-difluorophenyl)-1H-1,2,4-triazole-1-ethanol ( 1a, b ) are orally effective α-styryl carbinol derivatives developed for the treatment and prevention of systemic fungal infections. Practical new processes amenable for the large-scale production of these compounds are described. Of note is the selection of dichlorostyrene as a convenient precursor of the styryl portion, modification of a sensitive Grignard addition into a realistic preparative reaction and the use of 1,2,4-triazole simultaneously as a base transfer agent and nucleophile.     

A convenient synthesis of (z)-3-(α-alkoxycarbonyl-α-cyanomethylene)-2-oxo-1,2,3,4-tetrahydroquinoxalines and related compounds

(Z)-3-(α-Alkoxycarbonyl-α-cyanomethylene)-2-oxo-1,2,3,4-tetrahydroquinoxalines 3 and (Z)-3-(α-alkoxycarbonyl-α-cyanomethylene)-3,4-dihydrobenzo[g]quinoxalin-2(1H)-ones 5 possessing various alkoxycarbonyl groups were prepared in good yields directly from the reaction of dialkyl (E)-2,3-dicyanobutendioates 1 with o-phenylenediamine ( 2 ) or with 2,3-diaminonaphthalene ( 4 ), respectively. Furthermore, 2,3-diaminopyridine ( 6 ) and 3,4-diaminopyridine ( 7 ) were reacted with the diethyl ester 1b to give (Z)-2-(α-cyano-α-ethoxycarbonylmethylene)-1,2-dihydro-4H-pyrido[2,3-b]pyrazin-3-one ( 8 ) and (Z)-3-(α-cyano-α-ethoxycarbonylmethylene)-3,4-dihydro-1H-pyrido[3,4-b]pyrazin-2-one ( 9 ), respectively. The structural studies of 3, 5, 8 , and 9 were carried out by nmr experiments in some details.     

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.     

Synthesis of some derivatives of imidazo[1,2-a]pyridine,pyrazolo[1,5-b]imidazole,and 4-(3H)quinazolinone from α-ketohydrazidoyl bromides

α-Aroyl-N-arylhydrazidoyl bromides 1 react with 2-aminopyridine in ethanol and give 2-aryl-3-arylazo-imidazo[1,2-α]pyridines 2 in 60-75% yield. The reaction of 1 with 3-phenyl-5-aminopyrazole in ethanol leads to 2,6-diaryl-3-arylazo-1H-pyrazolo[1,5-b]imidazoles 3 in almost quantitative yield. Also, 1 react with anthran-ilic acid in the presence of triethylamine giving 3-arylamino-2-aroyl-4-(3H)quinazolinones 4 in 80-85% yield. The structures of the products were assigned and confirmed on the basis of their elemental analysis and electronic absorption, infrared and nmr spectra.